Gremlin in da MOTOR

[brraaaAA]

(xr50 Take 88s 18mm Keihin 95main clip down one from center big gun pipe stock head) OH...MY...GOD! I read and understood all the jetting help sites suggested. Please understand the bike runs great at times. I brought it to THE shop. THE "MAN" took it for a many spins and tweaked the air fuel screw a little and said,"who ever built your 88 kit did a great job, and the jetting seems right on." ? Five guys around him agreed, me too. Now here I am 30 minutes later, and it's sputtering under throttle and backfiring when I let off! ? ANY ideas why it keeps running great then shitty, then great, then shitty, then..... ? HELP! You beat the pros if you solve this one.

P.S. The problem exists with the big gun pipe. The stock pipe and 85 main has no problem.

[Jetster220]

Im not thinking your problem is jetting, as it wouldnt run great one minute then crappy the next. I would suggest checking your grounds, as that sounds more like the symptoms you are describing.

[brraaaAA]

Im not thinking your problem is jetting, as it wouldnt run great one minute then crappy the next. I would suggest checking your grounds, as that sounds more like the symptoms you are describing.

you say ground(s). :excuseme:I only know of one ground wire on my bike, and it's secure. Am I missing something? Should I replace ALL wiring in my bike? I'd like to. :smashpc:I agree that the electrical is suspicious.

[Jetster220]

May want to try checking the kill switch as sometimes they can short out. I dont think replacing all the wiring is nessassary. But I do think that electrical is your problem, not entirtely sure where though. I would suggest just going through it and checking everything.

[ThumperMX113]

Couldn't a bad rev-box also be the cause? Just a thought.

[Jetster220]

Good possibility, didnt really think of that. What are you running for CDI, Stock?

[brraaaAA]

I went from stock rev box to the TB box during this problem, hoping it might help. No luck. I have an update on my problem though. I went back to my stock pipe and jetting for a long ride today and the studdering although mild was present EVEN with that setup. Something is getting worse! Could an air leak in my manifold cause this????

[DIRTBIKES987]

Check your kill switch. Disconnect it at the plugs. My kill switch got smushed in between the triple clamps and the gas tank, and it still worked but my bike would run, and then die. Then it would run die etc.

The kill switch wires might not look damaged, but they could be damaged still.

PETER

[MINIACT]

BACK FIRING ON A FOUR CYCLE WHEN YOU LET OFF IS AIR GETING IN THE PIPE TIGHTEN THE PIPE TO THE HEAD GET A GOOD SEAL. OR THE PIPE IS CRACK

[brraaaAA]

is there a gasket or seal of some sort between the pipe and head? If the pipe isn't sealed well to the head, could THAT caus the studdering/hesitations??? By the way, my friends removed my key and kill switch. I guess they were thinking of that problem also.

[Jetster220]

Yea I think a airleak could be a cause possibly. This is getting wierd lol. Check around your manifold for air leaks then.

[brraaaAA]

Ok I put the good pipe back on so I can hunt down the problem(s) that you guys are mentioning. The first thing I did was squeeze gasket maker at the head/pipe, and head/manifold connections to eliminate the air leak theory. After a little drying time the bike is running like a champ...I don't buy it. It has done this before. Then I ride it for a few minutes and here comes the studders. I'll post again in an hour or so. I'm gonna take it to the trails to give it a beat down.

[Jetster220]

Hmmmm. I just realized that you havnt really described the sputtering in great detail, like exactly what does the sputter sound like, at what throttle increments does it do it or all of them. Im really scratching my head hard on this one man, cant think of what is causing your problem.

[brraaaAA]

Well I guess it's solved. ? I hesitate to say that since it has acted fine in the past too, but not this long. Someone mentioned an air leak possibility. So I used liquid gasket goop on the head/pipe and head/manifold connections. Suddenly everything seems fine. ? Go figure?

[Jetster220]

Just one thing is you might want to replace the liquid gasket around the pipe with the regular exhaust gasket that goes there, something tells me that liquid gasket wont hold up long to the temperatures coming from the header.

[brraaaAA]

well it says safe to 700 degrees. But it does kind of feel riged having liquid stuff down there. I'll go grab one. Thanks for all your input jester. ?

[Jetster220]

No problem man, just glad its working good now. And since you know that it must have been a air leak bewteen either the head or the pipe, since you putting the gasket in the pipe might as well redo the ones for the intake so they dont look ghettoed either ? :cry: