Made my Grand Dink 250 to a 300

Life Cars & Motorcycles
1

After finding out my my piston compression was low, I finally decided to make my 250 into a 300. Well, I know it’s not really a 300,
more like a 280, but it’s something I’ve wanted to do for a long time. For me the best thing of doing that was I did the work myself.
Sure, it cost a lot in parts, about 26,000 NT, but that because I went and bought everything new that was related to the job. I could
have re-used some parts, but the ones I could have re-used were cheap parts, why not buy new ones? Considering this is my first
engine rebuild, I was really surprised to have it run again for the first time today.

 A few surprising revelations in rebuilding the motor.  Damn, getting that piston into the cylinder was really hard.  You have to put

the piston onto the piston rod, and then slide the cylinder onto the piston. The problem, can’t use a piston ring compressor sleeve
to help do that. Well, maybe you could, if you can actually find one. Took me 4 hours the first time, and I say the first time because
I ended up having to do it again. The first 2 rings are easy, it’s the oil ring that’s the real biatch. The cylinder at the bottom beveled
to allow the rings to go in easier. That works well for the first 2 rings, but the oil ring is different. The oil ring is really made of 3 rings,
2 really thin rings, and one wavy ring. The 2 thin rings go on either side of the wavy ring. Anyways, it’s that last thin oil ring that
can really get in your way of getting the piston into the cylinder. Instead of going in smoothly, it would buckle out of it’s position
and wouldn’t go into the cylinder. Ended up using an e-xato like knife to help me put pressure on the ring as I wiggle the cylinder
on the piston. During those 4 hours, I thought why don’t I just put the piston itself into the cylinder, then put the piston pin in
and connect it to the piston rod and put the piston clip in? That doesn’t work because the last damn oil ring will slip out of the
cylinder when you have to put in the piston pin. I also found out after talking to a mechanic friend of mine it’s much easier if you
move the cylinder side to side and not up and down. Probably has to do with the fact that the piston will move up and down and
not side to side.

   Another revelation is that it's better to put in your coolant in first, if you have a water cooled engine, to check for leaks, than

put in your oil in first. I put my oil in first, then put in the coolant and began “burping” my coolant system for air as I was adding
coolant. After a few minutes of adding coolant and burping, I decided to take a look at my engine, and was shocked to see a
steady drip of coolant between my cylinder and crank case. Turns out that I put in my bolts that connect to the crank case
through the cylinder to the cylinder head in the wrong. There are 4 bolts, 2 are long and 2 are short. My friend suggested to
me I put the long bolts on the wrong side of the crank case. Even though I torqued the head down right, it didn’t apply the right
pressure, and so I had a coolant leak. Ended up having to drain the oil and replace the 2 gaskets for the crank case and cylinder
and cylinder and cylinder head, as I couldn’t be sure that they would work as they should. I guess the only positive thing for me
I can think about that is that I was able to teach my friend something, instead of always leaching information from him. Anyways,
since I never had read anything about what to put in first, oil or coolant, to a rebuilt engine, I just put in my oil and then coolant
and trusted that I had done everything right. I’m guessing that those of you who have way more experience in rebuilding
engines can get away with oil then coolant, but to me it isn’t practical. If you have a bad coolant leak, you’ll end up having to
drain the oil, and most likely not be able to re-use it.

   Anyways, just thought I'd share that with you guys.  Not sure if there are other 250 Grand Dink owners out there that want

to make their Dink into a 300, but if you do I can reply to this post with a complete parts list that you’ll need to do the job.

2

Impressive that you did it yourself, but I wonder you paid more for doing it yourself. 26,000nt seems a little high.

3

Ya, it does seem a little high, but then again, I had to buy a lot of parts. Top 3 big ticket items, crank shaft with piston rod and bearings, cylinder, and
cylinder head. I’d say the cylinder head was the most costly, considering I also had to buy all new parts to go with it. I couldn’t re-use the original
crank shaft, as the stroke is longer on the 300 and doing so would mean I’d lose compression. Actually, I was happy to replace the crank shaft, as
working on my transmission became a huge hassle. The ramp plate needed a gear puller just to get the thing off. That’s not a good thing, it should
slide off easily.

If I didn’t feel the need to replace my flywheel and one-way clutch, I could have saved about 2,000NT or more. I probably didn’t need a new one-way
clutch, but I wasn’t so sure about the flywheel. My alternator wasn’t generating enough power to handle the power draw of my stock HID headlight.
I had already changed the coil a few years ago, and I noticed something fishy at the time with my flywheel. The steel liner on the inside of the flywheel
would spin. I didn’t think it should do that, but since I didn’t have a flywheel puller at the time, there wasn’t much I could do about it so I just finished
the job. I visited my friend after that and happened to see a flywheel sitting there in the shop and I checked to see if the steel liner moves or not, and
it didn’t. I mention this to my friend and he thought it was strange that my liner moves. In fact he questioned if I had really seen it move or not, as he
found it hard to believe. When I was working on my engine and this time around I got a flywheel puller and a cheap car battery powered impact wrench
I sent my friend a line video of the liner moving.

4

Just for fun, I listed all the parts I ordered. I’ll comment on things that could be transferred over, or for practical purposes unneeded.
Edit The list I entered goes as follows - E01,02,03 etc. is the heading for the different sections in the parts manual. Following that the
list is divided as this - part number, part description, how many parts needed. Edit

Edit3051A-LEK1-E01 Ignition Coil 1 The 250 spark plug cap and short wire make it very hard to put on/take off. Saw the 300 coil is a little bigger,
the wire is longer, and the cap is smallerEdit*

E01

11341-LHG7-E00 COVER L CRANK CASE 1 *These parts are unneeded, they are parts to cover the transmission, you can use the original covers.
11343-LHG7-E00 RR COVER L COVER 1 *These parts are unneeded, they are parts to cover the transmission, you can use the original covers.
11345-LHG7-E00 DUCT L COVER 1 *These parts are unneeded, they are parts to cover the transmission, you can use the original covers.
11346-GFY6-901 BAND L COVER DUCT 1 *These parts are unneeded, they are parts to cover the transmission, you can use the original covers.
11391-LHG7-E00 PACKING L COVER 1 *These parts are unneeded, they are parts to cover the transmission, you can use the original covers.

** I forgot to order these parts, they’re very important

90031-KEBE-900 BOLT A STUD 8MM 2 ** This goes on the cam chain side, it is shorter
90031-KKA7-900 BOLT STUD 8MM 2 ** This goes opposite the cam chain, it is longer
11192-KHE7-980 GASKET CRANK CASE @A 1
91202-KKC4-90B OIL SEAL 27X42X7 1 ** If this is in good shape reuse. If you had to take it out, because the crankshaft bearing got stuck, replace

E02

12200-LHG7-E00 HEAD COMP CYLINDER 1
12205-KHE8-301 BOLT SEALING 12MM 1 ** this part is unneeded, it’s included with the head
12209-GDB4-68B SEAL VALVE STEM 2
1221A-LDB2-E00 HOLDER COMP CAM SHAFT 1
12251-KHE7-901 GASKET CYLINDER HEAD 1
12310-LDB2-E00 COVER COMP CYLN HEAD 1 ** could be reused, but it’s gas recycle functionally will be lost as the cylinder head doesn’t support it
12391-LDB2-E00 GASKET HEAD COVER 1 ** could be reused, if using original cylinder head cover
14100-LFG2-E00 SHAFT COMP CAM 1
14150-LDB2-E00 PLATE COMP STOPPER 1
14431-LDB2-E00 ARM VALVE ROCKER 2
14450-KEBE-900 SHAFT COMP IN ROCKER ARM 1
14452-LDB2-E00 SHAFT EX ROCKER 1
14711-LFG2-E00 VALVE INLET 1
14721-LFG2-E00 VALVE EXHAUST 1
14751-KHE7-900 SPG VALVE OUTER 2
14761-KHE7-900 SPG VALVE INNER 2
14771-GDB4-680 RETAINER VALVE SPRING 2
14775-MFA6-001 SEAT VALVE SPG OUTER 2 ** could be reused, they’re for holding the valve in place
14781-MFA6-001 COTTER VALVE 4 ** could be reused, they’re for holding the valve in place
90012-3C33-001 SCREW TAPPET ADJUSTING 2 ** could be reused, it’s the valve adjustment screw
90033-GFY6-900 BOLT STUD 832 2 ** could be reused, for holding the exhaust pipe to the cylinder head
90206-0A01-001 NUT TAPPET ADJG 2 ** could be reused, needed for holding the valve adjustment screw in place
90465-MDC4-001 WASHER 8MM 4 ** could be reused, needed for being under part 94050-08080
90478-7L00-001 WASHER A 6MM 2 ** could be reused, needed for being with part 96001-06110-06
92900-06050-0B BOLT STUD II 650 2 ** could be reused, needed to hold the air intake manifold in place
94050-06080 NUT FLANGE 6MM 2 ** could be reused, needed to hold the intake manifold on
94050-08080 NUT FLANGE 8MM 4 ** could be reused, needed to hold the cylinder head on
94301-10160 DOWEL PIN 1016 4 ** could be reused, needed to guide the cylinder head and cam shaft holder
95701-06025-06 BOLT FLANGE 625 4 ** can be reused, these are bolts for the cylinder head cover
95701-06028-06 BOLT FLANGE 628 (G) 1 ** this bolt is for the cylinder head cover. it’s longer for some reason, not sure why. not needed
96001-06110-06 BOLT FLANGE SH 6110 2

Most of the parts I commented on being able to be reused here are really cheap, and I’d recommend using new ones instead.
Also, with the cylinder head cover, the gas recycling function will not work, as it’s not supported in the cylinder head. You’ll
need to find something to plug a hole in the intake manifold, as it acts as a vacuum for the gas recycling pump. In fact, with
this modification, you can just take the gas recycling pump out, it’s not needed.
Edit If re-using the cylinder head cover, I recommend not doing so. You’ll need to plug a hole that leads to a chrome pipe
and plug a hole that leads to the vacuum pump. The job is much easier and faster to use the 300 cylinder head cover. It’s
around 500NT with a new gasket.Edit

E03

12100-LDE9-E00 CYLINDER COMP 1
12191-KHE7-910 GASKET CYLINDER 1
13000-LFG2-E00 CRANK SHAFT COMP 1
13011-LHG7-E00 RING ASSY PISTON 1
13101-LHG7-E00 PISTON 1
13111-LDB2-E00 PIN PISTON 1
14401-LDE9-E00 CHAIN CAM 1
14510-LDE9-E00 TENSIONER CAM CHAIN 1
14520-GFY6-90C LIFTER ASSY… TENSIONER 1 ** could be reused, if original is in good shape
14523-KED9-900 GASKET TENSIONER LIFTER @A 1 ** could be reused if original is in good shape
14531-KHE7-900 PIVOT CAM CHAIN TENSIONER 1 ** could be reused, it’s to hold part 14510-LDE9-E00 in place
14610-LDE9-E00 GUIDE COMP CAM CHAIN 1
15441-1K49-001 OIL THROUGH 1 ** this part can be reused, very important DON’T LOSE
15447-1K49-001 SPG OIL THROUGH 1 ** this part can be reused, very important DON’T LOSE
90001-GBHB-661 BOLT FLANGE SH 622 2 ** this part can be reused, it’s to hold the cam chain tensioner in place, part 14520-GFY6-90C
90005-KED9-900 BOLT SPECIAL 66 1 ** this part can be reused, it’s part of the cam chain tensioner
91306-1E05-691 O-RING 1.59.5 1 ** this part can be reused, it’s part of the cam chain tensioner
94301-10160 DOWEL PIN 1016 2 ** this part can be reused, it’s for guiding the cylinder in place
94401-25140 WOODRUFF KEY 2514 1 ** unneeded, this part comes with the crankshaft, or can reuse
94601-17000 CLIP PISTON PIN 17MM 2
96220-20118 ROLLER 211.8 1 ** unneeded, this part comes with the crankshaft

E04

11394-KHE7-980 GASKET.R COVER @A 1

E05 ** I forgot to order these parts, you’ll need them for your transmission to work

22105-LHG7-E00 BOSS DRIVE FACE 1
22110-LFG1-E00 FACE COMP MOVABLE DRIVE 1
22131-LBA7-900 PLATE RAMP 1

E06 ** These parts are unneeded, and in fact the flywheel will not work, use the original flywheel for the 250

28120-LDB2-E00 ONE WAY CLUTCH 1
31110-LHG7-E00 FLYWHEEL COMP 1
96600-08015-16 SOCKET BOLT 8*15 3

The most important thing that I almost forgot to mention is that the stock exhaust system will not work with
this modification. I have an after market exhaust system with clamps that hold the exhaust canister to a
mounting bracket. I had to loosen the clamps and readjust them in order to get the exhaust system on.

5

Big job.

Some questions:-

Where did you source the parts?

Given your recently bumped thread enquiring about parts sources, it seems this is still an issue for you, as it is for me.

Where’s the serial number?

I thought it was usually on the crankcase, which it seems you’ve replaced, though you didn’t have to. Any potential legal issues with that?

Do you notice any measurable difference in performance?

This gets uncomfortably close to the "Was it worth it? question, Wouldn’t be for me, (the upgrade aspect, not the repair) but I can understand taking satisfaction from the process as much as the end result.

Well done anyway.

6

  1. Where did I get the parts?
    A Taiwanese friend mentioned to me how he orders them through a guy on ruten. This guy on
    ruten is based out of Kaoshung. My friend helped me contact him, and then my wife talked with
    him to finalize the transaction. If you’re interested, I can ask my friend for his ruten page, as this
    guy can order anything. I could have ordered them in Jubei, but sometimes the shop tells me they
    can’t get something, as the local distributor doesn’t have it, or won’t sell it. Why won’t they sell
    something, either it’s too cheap, or they save those parts for the warranty shops, I don’t know.

  2. Where’s the serial number?
    The serial number is on the left crankcase. I didn’t have to replace that, as the the crankcase on
    the 250 and 300 are exactly the same. If you look a little more carefully, you’ll see I didn’t order
    the left crankcase. I know the parts list is a little hard to read, as I couldn’t format the list to make
    it more readable, it’s too cramped. Actually, one thing that surprised me is that I could have put
    in a even larger cylinder into the crankcase. I figure I had at least 1-2mm or more clearance
    between the cylinder and crankcase. I’m not sure if you need that clearance, but I’m sure it makes
    assembly a lot easier.

  3. Do you notice any measurable difference in performance?
    To be honest, I haven’t had the opportunity to test that yet. I’m waiting on getting transmission
    parts, which I ordered in Jubei, and I’ll get them tomorrow. Even when I get that, I’ll be going
    slow on the break in. I won’t be driving slow, I’m going to rev the hell out of it, making sure to
    vary the rpms a lot. I’m just not going to let my engine get too hot, just go for 5-10 minute rides
    for the first 100KM. After that, I can go for 20 minute rides for the next 400KM, and then after
    that ride normally. This is to (hopefully) insure that the rings are worn in smoothly.

  4. Was it worth it? (May as well answer this one)
    I guess I could have made the job a lot cheaper and just replaced the piston and cylinder, as I
    would have to do both in order to fix the compression problem. I mentioned that I felt a need
    to replace my crankshaft, as it was making transmission work tedious to say the very least. I
    felt if I’m going to replace the crankshaft along with the piston and cylinder, why not just go
    for a complete upgrade? Adding the cylinder head probably added another 30% or more to
    the job. The cost didn’t bother me so much, as I’d still be putting in the same amount of time.

You’re right about the satisfaction. Working on an engine like that was one of the few things
I haven’t done yet, and I really wanted to “pop that cherry”. I’m no trained mechanic, but I
used to do computer repair for a living. What’s similar between both fields is being able to
recognize problems, perform tests to accurately diagnose problems, then test solutions to
see if that fixes the problem at hand or not.

7

Got my transmission parts in, took my Dink for a little test ride today. First problem I noticed is that
I forgot how sticky my throttle can get after sitting for a while. My ride is over 10 years old, and I’ve
had to take a file to my throttle side handle bars to clean up rust on it… guess I’ll have to do that again.

As to the responsiveness to the extra power, can’t say I feel the difference, but then again, I haven’t
taken it out for a full out ride. Obviously I can’t right now, the engine is too new.

Right now my only concern is the noise I hear from the head. Are the valve clearances set right? I
think they are, but I want to double check to be sure. At least my coolant system seems to be doing
OK. Gave it a little burp test today when it was cold before I took it out for a ride, and no big bubbles
came out, only very small, small bubbles. The coolant level after the burp did drop a little and that
makes me worry that the coolant is going somewhere it shouldn’t. At least it’s not leaking on the
outside, but is it on the inside? I’ll know when I change my oil…

Something tells me I’m just being a worry wart. I’ll check my valve clearances and they’ll be right
where they should be, and when I change my oil after 100KM, I’ll see no coolant in there. I
guess these are just normal doubts on one’s own work being done for the first time.

8

[quote=“johnledoe”]1. Where did I get the parts?
A Taiwanese friend mentioned to me how he orders them through a guy on ruten. This guy on
ruten is based out of Kaoshung (Gaoxiong). My friend helped me contact him, and then my wife talked with
him to finalize the transaction. If you’re interested, I can ask my friend for his ruten page, as this
guy can order anything.[/quote]

Thanks, that might be useful. Kaoshiung is pretty close to Tainan and I sometimes buy tools there, but don’t now know of a parts outlet. Can’t see me doing anything on this scale, but I’ve got a bit of basic fettling to do and will need new forks eventually.

Supplementary question: Where did you get your information? Workshop manual availability (in English?) for Taiwan models seems to be patchy at best, and this was an upgrade rather than a standard service operation. I suppose the Dink is sold in other markets which might help.

9

So here’s the ruten page - class.ruten.com.tw/user/index00.php?s=bill5984
For some reason I tried to copy paste this to double check in another tab and his
page didn’t show up. If you know how to look for sellers, look for bill5984.

He has a Line ID, it’s the same as his phone number that he posts on that page.
I found this seller to be really professional, and honest. When I ordered all my
parts, I found out that one part was the wrong one. The proper part was a few
hundred NT dollars cheaper, so I looked for other parts I needed to make up
the difference, but including the right part and the other parts he would still
owe me money. I had my wife tell him that the money still owed wasn’t a
problem, but he still sent me the money he owed with the replacement part.

As to where I got my information, I got it from 2 sources. One, I have an
English manual for my scooter. Had to order that from the US. Two, I have
a Taiwanese friend who does warranty repair for Kymco. Since he works
for Kymco, he can easily tell me what engines are similar. He gave me the
parts manual sections I needed for ordering the right parts. Also, I can
talk to him about how to do a job and he’s able to help me understand
what to do, as the service manual doesn’t explain everything.

If you need a parts manual for a Kymco product, I should be able to
ask my friend for it. Though, I wouldn’t be surprised if you were able
to google search for it and find it faster than asking me.

10

A little up date on my baby, damn she’s running fine! The stickiness with the throttle seems to have
gone away, which is great, I don’t like having to deal with taking the 2 throttle cables off just to look
at my handle bars and grip to see if they are clean/rust free enough. I’ve done enough sweating in
my first floor undercover parking space this summer.

The power and acceleration, and how smooth it feels, was it ever that good? I’m having a little
trouble remembering, but I don’t think so. Riding something different for a while makes one forget.
It seems to me that before with the same acceleration I would be surprised that I’m already doing 80,
but now when I take a look I’m doing 100, and my baby is ready to give me more. In my short rides
I’ve managed to get my baby up to 120, and the acceleration doesn’t climb so quickly at that point.
I need an expressway to really see what she can do, but she’s not ready for that yet.

Doing a hard brake in with a CVT (constant variable transmission) is hard. Sure it’s easy to bring
the RPMs up, but bringing them back down hard is not so easy. There’s no engine braking on a
CVT, so I end up letting my engine rev down at it’s own rate, without using brakes. I’ll rev my
baby up, be doing 110 at maybe 7000 RPM, then let off the throttle, and when it’s down to 4000
RPM, she’s still going at 70. At that point I give her more gas, because my baby needs a good
workout, but I feel a little bad she’s not getting a proper workout.

Put in the 300 ignition coil in today too. It’ll make working with the spark plug/spark plug cap/
spark plug wire a lot easier. Took it on a short break in ride, and it seems to be working fine.
I’m a little bit concerned that the spark plug wire is too long, and may give me a weaker spark,
but I’m going to have to live with that. I should have looked closer at the 300 ignition coil
when I saw it before, as I would have seen how it was made cheaper than the 250 coil. The
250 coil has a cap that the spark plug wire passes through, and you screw that cap on to
the coil. The 300 coil doesn’t have that, the wire is just held on by glue… What bothers
me is that I want to trim that wire a lot, but I’m not sure what glue to use to hold it in place.

Finally, at least my baby doesn’t fart so loud when I let off the throttle. With my aftermarket
exhaust, she used to sound like gun fire when I let off the throttle. Now, no where near
like that at all. Taking off that “gas recycler” as I called it before, which really is a gas
after-burner, which burns the gas that doesn’t make it into the combustion camber and leaks
past the intake valve and floats above the cam shaft. How it does that is that it pushes that
gas into the exhaust system, just past the exhaust valve. I think now that gas is going to
the same place where the oil vapors go from the top of the cylinder head, and in to the oil
catcher.

11

[quote=“johnledoe”]So here’s the ruten page - class.ruten.com.tw/user/index00.php?s=bill5984
For some reason I tried to copy paste this to double check in another tab and his
page didn’t show up. If you know how to look for sellers, look for bill5984., so
.[/quote].

Thanks, could be useful. I see one or two car items on there, so might try and get some Skywing parts off him.

Incidentally, IIRC one recommended substitute for a piston ring compressor is to use a large hose clamp. Think I tried it and it didn’t work, so I bought a purpose built one (in the UK, many years ago) but it was still difficult. Think the problem might have been a wear ridge at the top of the cylinder (on BL B series 1800, the only engine I’ve done this on) bypassed by adding/removing the piston from the bottom, which you could do on that car with the engine in.

More recently I’ve heard of cable ties being used, but havn’t tried it

12

[quote=“Ducked”]Incidentally, IIRC one recommended substitute for a piston ring compressor is to use a large hose clamp. Think I tried it and it didn’t work, so I bought a purpose built one (in the UK, many years ago) but it was still difficult. Think the problem might have been a wear ridge at the top of the cylinder (on BL B series 1800, the only engine I’ve done this on) bypassed by adding/removing the piston from the bottom, which you could do on that car with the engine in.

More recently I’ve heard of cable ties being used, but havn’t tried it[/quote]

From what you’re talking about, it seems like you’re able to put the piston into the top of the cylinder, because the piston rod isn’t attached to the crankshaft, and
so you’re able to slide the piston down from the top of the cylinder with the piston rod attached. On scooters, the piston rod is attached to the crankshaft and
there is no way you’re going to change that. It would be next to impossible to try and take the piston rod off, connect it to the piston, slide the piston into the
cylinder, then connect the piston rod to the crankshaft. Why? Because there are 2 huge bearings on either side of the piston rod. At a guess I’d say the
bearings are at least 2x the diameter of the piston, and 3cm wide. Also, since the crankcase is split in half vertically, and not horizontally, you’d have the cylinder
only connected to the crankcase by 2 points, and not 4. To top it all off, you’d have to either try and connect the piston rod to the crankshaft with the bearing
in the way, or even worse, take the bearing off and figure out a way of putting that bearing back on when the crankshaft is in half the crankcase. Oh, I forgot to
mention that the piston rod doesn’t have a nut and bolt connecting it to the crankshaft, not sure how that have that on there for now. So the only way the piston
gets into the cylinder on a scooter is to slide the cylinder onto the piston.

However, the idea of using cable ties may work, if you were to file half the length of it to fit the bottom taper of the cylinder. You would only really need just
one cable tie, for the final oil ring. That last ring is like, no more than a shim, it’s so thin, and it likes to buckle, rather than slide in. If a cable tie could keep it
compressed enough to get pass the taper where it would buckle, it might just work.

13

Cylinder onto piston probably isn’t possible (or at least would be very difficult) for most car engines because the cylinder is part of a fairly massive multi-cylinder block with so you’d give yourself a hernia and probably drop it and break something.

Suppose it might work for some air-cooled engines with separate cylinders, such as VW beetle or 2CV engines.

14

Of course on a car it would be near impossible, or on any multi-cylinder engine, to fit the cylinder onto the pistons when
the cylinders are all in a block. If the cylinders can be put on separately, then that’s another thing, but I think we both
understand that.

On another note, just changed the oil after my first 100km break in. The oil had a golden hue, much like it looked like
when I put in in there. Didn’t see much material on my magnetic oil drain screw, that’s a good thing. However, on the
oil screen, there was this material that was covering the screen that I’ve never seen before. Not sure what it is, maybe
bits of white glove material, though I thought I was more careful about how I handled my engine to allow something like
that to get in there. I think I’ll change my oil again after another 100km to see if there is anything else still floating around,
rather than after 400km.

The other tricky bit that bothers me at the moment it getting my carburetor tuned right. I have an air/fuel meter installed,
and at least that’ll give me an good idea if I’m running rich or lean. It’s easy to see if things are OK when I’m at idle, but
I’m not so sure about the main jet, as it reads rich when I apply full throttle, which I expect, but is it really? I guess I have
to go old school and keep looking at the spark plug.

Damn it, it’s late, and I forget for the moment what the name of that thing is that provides a bit of back pressure in the
exhaust that would quiet or eliminate any backfiring noise in a muffler. I only mention that as my muffler doesn’t have
that. Took that out to ensure that my exhaust is as loud as possible, as people are less stupid around me when they hear
me. Anyways, at least my backfiring from before my engine rebuild doesn’t sound like gun shots when I back off from
hard throttle to no throttle, but there is still some there. I suspect it’s a lean condition in my carburetor setup, but I’m
not sure if it’s my main jet or pilot jet I have to adjust, as I don’t have acceleration problems.

15

[quote=“johnledoe”] I have an air/fuel meter installed,…
[/quote]

Quite sophisticated for a carburretted scooter. How’s it work?

I’ve heard of people making them from scrap oxygen sensors from catted cars, hooked up to an LED output voltage display. Didn’t look like a trivial job though.

Slightly surprisingly, you can still apparently buy the Gunson Colortune new (though almost certainly not locally) and IIRC it did sort of work, though I’ve only used one once, when I borrowed my brothers.

I was tuning ultra-lean to get my Lada through the emissions test, but overdid it and got failed for high idle. Can’t remember what I did after that.

gunson.co.uk/item.aspx?code=G4074

ebay.com/itm/Gunson-Colortun … 0758004248

I’m not sure if you can use it for high speed operation (might break) , but if you can position a small camera you could probably get info on the mixture while moving.

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For getting the air/fuel meter installed, I just bought the cheapest O2 sensor that Kymco sells, had
a hole drilled into my exhaust pipe and a nut welded to it, so I can install the O2 sensor, and bought
an A/F meter and had it hooked up to the O2 sensor. I don’t have the O2 sensor heating wires
powered, as it’ll get hot enough after the engine is running long enough for the A/F meter to take a
reading. The A/F meter gets its power from the ignition key wiring, so it’s only on when it’s the
ignition switch is turned to the ON position. In fact, I had to tell the shop who was installing the
meter to NOT connect the O2 sensor heating wires to the battery. I know that the O2 sensor only
gets heating power when the computer that controls the ignition for fuel injected engines says it
should get power. Which to me means, the O2 sensor is not heated up all the time. Since I don’t
have a computer on my scooter like that, I chose not to have the O2 heating wiring hooked up.
Sure I have to wait a minute for the meter to start giving a reading, but I can live with that, since
I have to wait for the engine to warm up anyways to make any adjustments to the carburetor.

That Gunson colourtune product looks interesting indeed! Unfortunately, that e-bay link says it won’t
ship to Taiwan.

Made a change to my carburetor setup, had a 38 slow jet and a 105 main jet, and I changed it to a 45
slow jet and a 112 main jet. Adjusting the pilot screw is a lot more touchy, as an 1/8th of a turn shows
up on my meter. I’m happy that having the pilot screw turned all the way in doesn’t read as rich on
my meter, it’s about 1 and 1/2 turns out and the manual says it should be 3 to 3 and 1/2 turns out, so
it shouldn’t be too big. I’ll have to take a look at my spark plug to see if the main jet is big enough
after taking it for a 10 minute ride doing mostly 6,000+ RPMs to see if that’s right. The setup seems
a lot better after taking it for a ride. It’s has much more bass to the sound of the exhaust and the
backfiring is almost gone. You only hear a little when going from full throttle to no throttle, the kind
you’d expect from having an exhaust without a baffle (I remembered the word, YAAA!).

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That seems to be pretty standard, not sure why. I could probably get one forwarded from the UK or Australia, but of course it puts the cost up.

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I’m interested in your mixture monitoring setup. Could you post details of the parts and where you got them?

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I use this meter for my A/F ratio - koso.com.tw/products-detail. … =en&id=314
They are made for scooters, so there one for Kymco, and one for SYM. If you know wiring, I’m
sure you can modify either one to suit your needs for something else. I bought it in a “famous”
scooter mod shop in Hsinchu for 1,000NT at this place.
google.com.tw/maps/@24.8039 … 6656?hl=en
It’s the shop right of the bakery. I’m not sure if that link will give you the street view image I’m
looking at. Just looked at my link, and it should. I think the name is Wei-Lun, not so sure.
I just know the boss, from my son, and his English name is Micheal. The boss does speak
English, so if you call for him, he’ll be able to talk to you.

As for the O2 sensor, I used the one for the Grand King motorcycle from Kymco, the farmers
motorcycle. Like I said before, it was the cheapest O2 sensor that Kymco has. I’m not so
sure if it’s good enough for the A/F meter, as the readings I get on the A/F meter varies a lot
at idle speeds, at +/- 0.5-1. However, I’m not positive about that, as it may be do to the fact
that I have a carburetor, and that may not give me a consistent fuel mixture.

I suppose I could take my O2 sensor from my old Quannon muffler, and see if that makes a
difference in the readings, as it’s more expensive. I left it in there when I got a new muffler
and bought a new O2 sensor for it. The old muffler was looking very rusty, and I didn’t want
to take a chance on it not coming out cleanly to transfer it to the new muffler. I wanted to
keep the old muffler intact as much as possible, in-case I had to take a stupid EPA test from
whiners who didn’t like the sound of my new muffler. Which was smart in my case, as I’ve
already had some whiny douche-bag complain like a little biatch to the EPA about my
Quannon. So I put the old muffler on and passed the stupid EPA test. Man, I really wish
I knew the legalese to challenge those EPA fucks, as I’d really like to know who’s the victim,
and who’s damaged by the sound of my scooter for them to be able to tell me I can’t have my muffler as it is…

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Thanks. Interesting, and the meter’s not as expensive as I expected. There’s an abandoned car on a soon-to-be-construction site I was going to get the sensor off, but someone else has taken the wheels, which makes it probably more trouble than its worth.

Re the EPA, ALL modifications are illegal, so they’re covered, as you might expect.