I think I mentioned before that I swapped the FZ150 for a BWS100. It’s going well in general. There’s an annoying little glitch, though. It happens after the engine speed returns to idle. When I open the throttle again, right at the start of the throttle’s travel there’s a little “blip” then a flat spot (idle again) then gradual acceleration as normal.
It only does this once each time. So for example if I’m at a red light and I open the throttle a little to get that “blip” then close it, when the lights go green and I open the throttle normally, everything is normal.
It doesn’t feel at all like the kind of “bogging-down” that you get from the mixture being too rich.
The problem just started after I had the original handlebars and instrument cluster put back on the bike (it had other ones before but wasn’t comfortable). However, I don’t really see how it could be a throttle cable problem as the throttle action is smooth and the problem only occurs in the specific situation I mentioned.
Any ideas? Of course I’ll take the bike to Eric, but I’ve taken up quite a bit of his time recently so would like to have an idea of possible causes of the problem before I take it to him.
Agree with DM that an off-idle bog is usually a lean mixture problem. It’s a two-stroke, so the carb doesn’t have an accelerator pump to worry about. Because it’s so easy, I’d start by removing the idle mixture air screw (count the position first) and give that orifice a blast with carb cleaner. You could drain the float bowl as well since I had the experience before where some water in the bottom would get sucked into the main jet, but only when snapping the throttle open from idle. First time you get water and it bogs, the second time you get gas and it doesn’t. Took forever to figure that one out.
Since this only came up after moving the controls around, I’d also look in behind the plastic for a kink or tight bend in the throttle cable. It might also be that the cable is displaced in the throttle slide. Pull the carb top off and take a look.
Thanks for the replies. I know what “bogging” sounds and feels like, though, and it’s not that. The engine, carbs, spark plug etc are all in very good condition. And it only happens after returning to idle, and that only the first time I open the throttle after returning to idle.
Redwagon’s suggestion to look for a kink in the cable sounds sensible. It certainly sounds more like a throttle cable problem than a carburettor one. It just seems so strange that the glitch only happens in the specific situation I mentioned. And the throttle doesn’t feel stiff or rough and doesn’t jam.
Perhaps I can explain what happens a bit better. I open the throttle smoothly. What the engine does is as if I had blipped the throttle, returned to closed throttle for 1/4 second, then opened the throttle normally. The intensity of the blip depends on the speed with which I open the throttle, though it’s never enough to make the bike lunge forward.
It’s not easy to describe so I made these crude graphs:
As you can see, when the glitch happens it takes slightly longer to start the normal engine acceleration, which adds to the disconcerting effect.
I have seen so many cocked up things done to vehicles here it’s impossible to list. I would just go through everything and see that it’s all good. Start by removing the airbox and watching the throttle slide come off the stop and how it comes down again. Does the bike do the same thing whether you let the throttle off gently, or let it snap back on the spring? Check the cable run is okay. Open the splitter box and check that’s assembled correctly. The device that splits the one cable from the twistgrip into one each for the carb and the oil pump. Those can do some odd things if assembled incorrectly.
Make sure the carb top is fitted correctly. Check the carb itself is fitted correctly into the intake tube, there’s a notch there to align the carb properly, but I’ve seen them shoved in any old way.
Then check for dirt and water as I mentioned earlier.
This is due to the elastic band holding the chewing gum onto the gnumphenstat regulator. Ask Greasy Chen to replace the chewing gum at the next oil change. Ah. It’s a two-stroke. Er, put more oil in the petrol tank. Dunno. Oops. Have you tried painting little red and yellow dots onto the bodywork?
The problem started when changing handlebars so I think it’s definitely a throttle cable issue. Sounds like when you turn the throttle, the cable sleeve is also moving. The rev goes up until the sleeve is popped back into its proper position and then the rev goes back down to a normal operation. When you release the throttle at a red light, the sleeve pops out of place and you have to turn the throttle to pull on it for it to slip back into it’s groove. I think that the cable sleeve may be tied too tight at the top end near the handlebars and it’s pulling it out of place. More or less what redwagon mentioned here: [quote]The device that splits the one cable from the twistgrip into one each for the carb and the oil pump.[/quote]I doubt the device is faulty because you didn’t touch that when replacing the handlebars.
Here’s the part, notice that one one side you have a single cable coming from the twistgrip and it splits into two cables running to the carb and the oil pump.
picture one(properly mounted)
picture two(sleeve is pulled out of place)
I think that when installing the handle bars, the single cable coming from the twistgrip is tied or kinked and keeps popping out of place. Re-routing the cable and inspecting it to make sure it’s mounted right into the above illustrated part will fix it.
[quote=“bobepine”]The problem started when changing handlebars so I think it’s definitely a throttle cable issue. Sounds like when you turn the throttle, the cable sleeve is also moving. The rev goes up until the sleeve is popped back into its proper position and then the rev goes back down to a normal operation. When you release the throttle at a red light, the sleeve pops out of place and you have to turn the throttle to pull on it for it to slip back into it’s groove. I think that the cable sleeve may be tied too tight at the top end near the handlebars and it’s pulling it out of place. More or less what redwagon mentioned here: [quote]The device that splits the one cable from the twistgrip into one each for the carb and the oil pump.[/quote]I doubt the device is faulty because you didn’t touch that when replacing the handlebars.[/quote]Thanks for the clear and detailed explanation and the pictures! I think you’re right and I’ll look at the cable as you suggest.
Eric did a superb job of renovating the BWS for me and it is in excellent condition. As usual, he wouldn’t let me pay him for all the time he spent on it and I ended up buying him a gift to say thanks.
The glitch is very small and you have to be riding the bike for a while before you notice it.
[quote=“joesax”]
Eric did a superb job of renovating the BWS for me and it is in excellent condition. As usual, he wouldn’t let me pay him for all the time he spent on it and I ended up buying him a gift to say thanks.
[/quote]This Eric guy sure sounds like a nice and knowledgeable fellow. I wish I had found a mechanic like that in Kaohsiung. The ones I know are either knowledgeable but pricy and not overly friendly or very friendly but unable to fix difficult problems.
[quote]The glitch is very small and you have to be riding the bike for a while before you notice it.[/quote]Makes sense because if the cable sleeve was pulled out of place a lot, the bike would rev high all the time.
Hope that solves it for you. Glad you appreciated the pictures because it took me a long time to pull that out of my BWS.
