HELP! Where to begin?
 

Hi everyone. I'm just bought a 2003 636 and am having a weird issue. I'll try to be as specific as I can. First off, here's the aftermarket parts on the bike: Yosh TRS slip on and a 520 conversion. It still has the stock air filter. So here's what's happening: it seems to run good for about 30 minutes of riding but all of a sudden it will start acting up. When I give it throttle it will severly bog down to the point it almost dies. I replaced the spark plugs thinking that was the issue and it ran good again for about 30 minutes then the same problem reoccurred. Also, even when it runs good, I could not get above 10000 RPM. It felt like it hit revlimit at 10K. To me, this seems like fuel starvation but I'm not sure where to begin. Has anyone else had this problem? Thanks.

RE: HELP! Where to begin?
 

Oh Yeah! When it happens, the FI light is NOT on.

RE: HELP! Where to begin?
 

Sounds like a tank vent hose may be kinked. Take the spare key with you and next time it happens, immediately open the fuel cap to see if it has created a vacuum. If this is the case, you should see an immediate improvement.

RE: HELP! Where to begin?
 

Wow! It worked! Thanks meanstrk. So how do I prevent this from happening again?

RE: HELP! Where to begin?
 

You need to see where the vent line is kinked or pinched. If you lift the tank, you can probably see where the hose routing is screwed up causing a kink.

RE: HELP! Where to begin?
 

Now that I cleared all the obstructions from the tank vent hose I found that I cannot rev past 9K rpm in ANY gear. The plugs and coils are good. I'm thinking thatmaybe I need a new fuel filter and tank cleaning since there's a bunch of rust inside the tank. What do you think? BTW i just discovered it a CA bike and it's got all the emission crap on it too.

RE: HELP! Where to begin?
 

OH yeah, once i get to 9000 rpm, if feels like a fuel cut like the motor is not getting enough fuel. It idles fine and accelerated fine. It only happens once I hit 9K rpm and It won't go any higher. Has any one you know ever had this problem?

RE: HELP! Where to begin?
 

few things. clean the carbs lately?

has the bike been sitting all winter, and you just started riding again? if you didn't winterize the bike properly (stable in the tank and such), that could be part of the problem. that happened to me last year. clean the carbs, empty the tank, and put fresh gas in.

RE: HELP! Where to begin?
 

Well the bike is fuel injected. No carbs to clean. I think I'll try to clean the tank this week. Clean the tank, the pump and the air vent again and see what happens then. What's the name of the chemical stuff you put in the tank to remove rust?

RE: HELP! Where to begin?
 

Well tonight I removed the tank and fuel pump and holy $H1T! The fuel pump was caked in rust particles which leads me to believe my lack of fuel was the problem (from being clogged with debris). I halfway disassembled the pump to clean it and tomorrow I'm going to see about removing the tank rust. I plan on buying the Yamaha tank rust remover. Has anyone used this product? Does it work well? Once I finish the tank and reassemble, I will let you guys know if it fixed the problem.

Any comments, or advice? I enjoy tech talk:eek: