My friend just picked up a '99 banshee and we can't get it to run right. The left cylinder has a bad miss and it only runs on the right cylinder most of the time. The bike won't really come up in ban, maybe for like a split sec here and there. The left cyl also smokes alot more than the right. Plugs are new, carbs are clean, and when it's running it sometimes pops like a backfire or something. Is it a carb problem? Bike is stock except for FMF pipes and silencers. If it was mine I would throw away the stock carbs and get a 2 into 1 setup, but he wants to keep the stock crap. It seems like a simple enough problem but I have no experience working on Banshees. Thanks guys

 

First thing I would do is check the compression. If the rings are shot, then it would do everything you described. If compression checks out, check the carbs.

Colby

 

Like mentioned above...plus. .....check that the carbs are in sync with each other. This can be done by removing the air filter and looking into the throats of the carbs. Move the throttle a couple of times and look where the slides come to rest. there should be about a toothpicks thickness at the base of the slides.


But my guess would really be in the compression area...sounds like you got yourself a low cylinder. You can get a compression gauge at Sears for like $40 or less. If you have lower than say..100 pounds in each cylinder then you can bet it's time for a rebuild. (my banshee ran right down to 90 on one side before I really needed a top end.)... You should see anywhere from 120lbs and up on a stock bore depending on wear and tear.

 

I thought it was the compression at first because the one pipe was barely blowing any pressure then someone told me that since it's not firing really on that cylinder it would not have as much exhaust pressure. I'm going to have a look at the carbs again, because every now and then it will pic up the dead cylinder for a second or two and rip, then back to popping and moaning. The carbs being out of sync could totally be the problem I guess I just had no idea how to fix it with that electrical crap on top. Whoever came up with this dual carb setup should have their b@!!s cut off. How do I go about adjusting them back in sync? Thanks for all the help, it's greatly appreciated

 

When my friends Banshee was still stock(quite some time ago [img]i/expressions/face-icon-small-wink.gif[/img] ) If you were running rich, or if you loaded the cylinders up too much it would sometimes foul one plug and not the other. Causing it to run on one cylinder.(It would run like crap) Sometime you could get it to come back in and it would scream again, then it'd go out again and back to running like crap. [img]i/expressions/face-icon-small-smile.gif[/img] I would say carburation could very well be the culprit. I wouldn't over look throwing a compression tester on there like others have said as well though.

 

Think about the fun that ALL of the street bike riders go through..... Consider yourself lucky its only two carbs and not 4.....or even 6 on some now...... [img]i/expressions/face-icon-small-shocked.gif[/img]

 

Yea I hear ya, 4 carbs would be a nightmare. But carb problems are easier on a 4-stroke IMO anyway. Most new street bikes have primative FI that is easy to work on. Hopefully atv's will have FI soon. And I guess the compression test is a must. Maybe I'll get lucky and the top end is still good. I think the bike was running good then it sat for a little while and ran ok for 20 minutes then here's where we stand with it. WHat about electrical problems? I had a cr80 back in the day that as soon as it hit ban it would fall on it's face and it ended up being a bad coil. How are banshee electrics? should I look at all that stuff as well?

 

Some money well spent would be to get rid of the TORS on the top of the carbs. Motion Pro (I believe) sells the cable and caps...then just unplug the tors from the harness. Makes getting to the carbs a breeze as well.

As far as getting the carbs in sync...It really is as easy as looking into the throat of the carbs and making sure that the slides are moving at the same time and resting in the same spot. On my ninja750r, I use a mercury vacuum syncronizer....but that is not the best way on a two stroke that pulses so much.

The dual setup really is not that bad once you get your jetting right. I have ridden banshee with the single carb mod...and, Yes it was easier to tune...but you loose a bit on the top end.

Don't give up...it will run. When it does..you will be a happy rider.

One important thing to check is that there is a little black hose from one carb to the other...if this is unhooked..it will make the carbs do strange things. (It is located right in the middle of the bike between the two carbs)

Double check that there are no leaks on the carb boots as well.

 

I agree with sAyIt_fmf if you do everything he said and it still aint right it has lost compression.