harsh accel to decel, decel to accel?

[MyYz400]

I'm thinking it might be the cush drive, but even when trying to slightly accelerate from a decel, it will snap hard then goes. And when slowing down, (cut the throttle) it snaps hard into decel (seems to have alot of engine breaking on this bike). This makes it difficult at times when cornering. You have to be just right with you throttle and make micro movements with the throttle to keep a smooth turn. Otherwise you can get into a nasty bucking with the bike between acel and decel that can really get you into trouble!

I know the carbs need a good servicing, and I'm still questioning the cush drive's health at this point, but I'm sure rolling on or off the throttle should cause this much bucking. Thoughts?


David

[blensen]

How's your chain tension? If there's too much slack, the bucking could be the chain pulling taut. Get the carbs sorted out, adjust your chain and report back.

[MyYz400]

Chain was slack, Lubed her up good (gigidy), and took the slack out (but still left enough). It helped a little, but only by a small fraction. This weekend I'm tearing the bike down and going to inspect the cush, and carbs. Is it not advised to convert over to a cushless drive/hub system? Also, I would like to get a good set of filters (possibly remove airbox) and a good exhaust here soon, so I might tackle the carbs when I do a jet kit. I was hoping for a "I had the some problem, this is how I fixed it", but I guess I wont know more until I get her apart.

[blensen]

You could go cushless, but it's not recommended for the street. Without the rubber dampers there to absorb some of the shock, your transmission will quickly take a beating. I wouldn't be surprised if a good chunk of your problem is just your bike running poorly (no offense intended).

[pnbell]

yea. don't go cushless..
*Replace rubbers if worn.;TEST: (Grab the rear sprocket with your hand and try to twist it; if you can move it back and forth pretty easily it is likely worn and should be replaced) Replacement parts are about $40 and 30 minutes to an hour. very Very easy.

Chain slack will cause similar issues. Check that this is in spec.

^ This stuff will all help, but if the Carbs are not operating correctly this will also cause low end jerkiness. Sync the Carbs, and Tune the Pilot Screws.

i am Currently dealing with this same issue... It can be pretty annoying when trying to go the speed limit around town, or in traffic... I'll be syncing my carbs and playing with my Pilot Screws soon. (I replaced the Chain and Cush Drive; both really helped.)

[Clanky]

Had something similar with rapid deceleration after rebuilding my carbs but adjusting the mixture sorted it out. I'd check the carbs as recommended above.

[MyYz400]

Ok cool. I wasnt worried about having to replace, just dont like cush drives (dont ask way, ). I do know for a fact the carbs need some loving, evident when it will bog at mid rpm and full throttle, but and runs better with the choke on. I'm not ready to do a carb rebuild right now, but was thinking maybe I can 'fake it' for a bit by adjusting the pilot screw a bit to see if it helps for the time being.

Is there a good carb wiki or thread out there? One that tells you how to tune, 'sync' (new term for me), and setup? I found one, but it only goes into the differences between years. I'll keep looking tho!


Thanks everyone!

[pnbell]

Cush Drives are great, do not hate! ... Almost every Motorcycle, Car, and Truck has them...

Anyway, for setting the pilot screws I like this guys info
http://www.angelfire.com/md/fzrmofo/tech.html#pilots

Syncing the carbs is not new, and is actually very important..
-* Basically the Air being pulled through each carb (especially from Zero to Half throttle) into each cylinder is controlled by Butterfly Valves. These butterfly valves have to be adjusted so the vacuum being pulled by each carb is the same. If they are not the same then each cylinder will get a different Air/Fuel mixture and run differently. i.e. One Cylinder will be stronger than another, causing uneven power, idle, and acceleration.

To adjust the butterfly valves properly and sync the carbs you need a sync tool. Adjusting the Pilot Screws is a fool's errand if the carbs are not sync'd... haha