Total Motorcycle Community Forums

This bike has been sitting for a while. It's an '89 with only 13,000 miles on it, so it's had some time sitting about. The previous owner said he rebuilt a set of carbs and threw them on and it ran worse, so he rebuilt the ones on the bike and put them back on. It still runs pretty strangely.

First, cold starts are really cranky. Either the bike runs at about 3,000 RPMs or it will idle slower and slower until it eventually dies. This depends on where you have the choke set, but there's no middle ground.

Second, when you jump on the throttle and let it go, such as revving the engine with a quick flick of the wrist, it will shoot up to a high RPM (about 5,000 or so) and then drop to 3,000 quickly, then take a full two seconds or so to get back down to idle at 1,500 RPMs.

Finally, when you get on the throttle, it shoots smoke. My buddy in the car behind me didn't see what color it was, but snapping on the throttle to get the engine speed up shows white smoke. I'm not too sure what this is.

My only lead are the Mikuni carbs are of the CV (constant velocity) variety and I've never ridden a bike with one before, but I assume these are not normal running conditions. I have a spare rank of carbs that were included with the bike, but apparently they were rebuilt and I don't want to shell out $20 a carb for a rebuild kit that looks like a couple of gaskets.

Any help or places to start looking will be greatly appreciated.

Anyone?

You might try adjusting the idle air screws, if you can get at them. At a wild guess, it sounds like the pilot(low speed) jets are too big or the idle air screws are set too rich. If there wasn't a puff of smoke on accell under load, I might guess an air leak. Are the carb boots to the heads connected properly and sealing?

BuzZz wrote:You might try adjusting the idle air screws, if you can get at them. At a wild guess, it sounds like the pilot(low speed) jets are too big or the idle air screws are set too rich. If there wasn't a puff of smoke on accell under load, I might guess an air leak. Are the carb boots to the heads connected properly and sealing?

This was just suggested to me on another forum, as well. Sounds like a good place to start, I'll see what I can do tomorrow after work and Spiral Highway. Friend of mine will let me take her Ninja 250 up and down Spiral, oooh baby that will be nice.

Thanks for the help!

"Help" might be pushing it, but it's worth a shot. I hope it works out.

Troubleshooting on the internet is crapshoot at best.... it's like selling parts and having people come in with 'my car is making a grrr-pop-grrr-ping noise.... what is the problem?'... but without the hand gestures and sound effects.

Skier wrote:First, cold starts are really cranky. Either the bike runs at about 3,000 RPMs or it will idle slower and slower until it eventually dies. This depends on where you have the choke set, but there's no middle ground. Second, when you jump on the throttle and let it go, such as revving the engine with a quick flick of the wrist, it will shoot up to a high RPM (about 5,000 or so) and then drop to 3,000 quickly, then take a full two seconds or so to get back down to idle at 1,500 RPMs.

All symptoms of a lean condition

Finally, when you get on the throttle, it shoots smoke. My buddy in the car behind me didn't see what color it was, but snapping on the throttle to get the engine speed up shows white smoke. I'm not too sure what this is.

Could just be the funk of 5,000 years filtering thru the system. Alot of bikes do this for a while after sitting. Or could be the rings ... the results of much hard running. Have you done a compression test or a leak-down test?

My only lead are the Mikuni carbs are of the CV (constant velocity) variety and I've never ridden a bike with one before, but I assume these are not normal running conditions.

Your carbs are probably the issue for your start/idle problems. How does the bike idle when it's warmed up? There's probably something screwy going on in the idle circuit - either the jet is clogged or your idle screw is set to far out. Is it popping out of the carbs? Does it backfire on deceleration?

Well, this is how she sits now (large image): http://screaming3d.com/pics/Kat/work/IMG_0500.JPG

How should I go about checking for vacuum leaks? I tried letting the bike idle a bit and spray in a large amount of water via a spraybottle, but I only found once place where that did anything, and that was on the intake side of the carb, which means it can't be the problem.

how does she idle when warm?

Need more info.... make some bigger hand gestures and louder engine sounds, please.


No, I am not serious....

BuzZz wrote:Need more info.... make some bigger hand gestures and louder engine sounds, please.


No, I am not serious....

Don't tempt me, I have a camera that can take video and lots of space left on my hosting.

(edit)

If I don't respond for a few days, it's because I'm on vacation. Need to get some much needed-R&R in!