I bought an 05 636 last week. It runs normally 90% of the time, but will sometimes stutter terribly.

Without warning, it will suddenly lose power, then surge, to the point that it is not possible to maintain a consistent speed.

It is definitely not a low gas issue, and the air filter is OK. There is an aftermarket pipe (yoshi rs-5) on it, without power commander, but it seems a more serious problem than that, since it isn't a consistent stutter (but when it does happen, bike is more or less unrideable). The plugs did show a bit of gray/white color (I guess showing it is running lean, or rich, which I forget)...

Any help would be appreciated. I searched previous posts, some suggestions about possible bad coils, plug issues, etc...hopefully someone here will have some more insight.

The previous owner did drop the bike, severely enough to have cracked some of the fairings. A friend of mine hypothesized that maybe a cracked piece is blocking the fuel at times, causing the stuttering...any thoughts?

Thanks in advance.

 

Are you running the full system or just the slip on? Either way, put it on a dyno and get it tuned with the dynojet or similar. The plugs sound like you are indeed running lean. Also wrap your ecu (mentioned in KF) to block the exhaust heat from frying the ECU.

Keep us informed. Welcome to KF and good luck.

 

+1 on the overheating ECU, if the aftermarket pipe isnt sheilded enough it could cause you problems on a long ride. Does it get better after the bike cools down?

 

is it a stock air filter??? Had the bike been stitting for any length of time??? a PC3 could help smooth it out if that's the problem of it running too lean...

 

Power loss and surge sounds like it's more than just running lean. Agree^ on the ECU and circuit wizardry issue. (My two cents.)

 

hey boss i have a 2002 zx6r just had that prob well i drained all the bowls and had some crap come out then i seen i tube on the front of the carb so i ran it down and it wasnt hooked up it hooks up to two lil tubes that come from the front air port on the front of the bike have u checked it i hooked mine back up and she runing great hope maybe that helps u out a lil if not srry for the post

 

The 02 and the 05 are a little different, 05 is fuel injected. But yes checking the vaccuum lines could definately help, good call.