problem with losing cylinder

[thebottle]

If I launch hard from a dead stop my bike loses the number one cylinder... the exhaust on number 1 was cooler than the other three pipes. It stops firing but if I keep driving it on three cylinders eventually it will come back and start working again. It doesn't drop out at any other time, only when I launch hard from a stop. I checked the plug and it was white. I'm not sure what I should be checking first, electrical or fuel? Any advice is greatly appreciated.

[TopCatGr58]

With 1 pipe cooler than the other 3 points more to fuel problems. White plug sounds like it's lean. Starting off from low rpm is using the pilot circuit, and it's probably clogged, but once you are actually riding it, you're getting some into the mains, and it's finally getting some fuel and kicks back in. The pilot circuit actually provides quite a bit of fuel a ways into the use of the mains.

If you're not into wanting to tear into the carbs....get a bottle of Sea Foam, pour about 1/2 bottle into a tankful, run the bike a few minutes, to get the sea foam into the carbs, then park it overnight to let it sit and soak, then fire it up the next day, run that tankful thru, fill up and put the other half of the sea foam bottle in it and run it some more. IF it's a mild amount of gum and varnish clogging the pilot jet, this can sometimes cure it. IF no joy, then you'll know you need to get into the carbs more thoroughly!

T.C.

[thebottle]

Thanks for the advice, greatly appreciated. I'll try the seafoam and if that doesn't work then I will clean the carbs, .

[thebottle]

Well, that didn't work and something else happened today that confuses me but maybe will provide more insight for you guys that are more knowledgeable.

After I launched hard the same thing happened where it loses a cylinder, loss of power, sounds wrong... came to a stop and it completely died. Tried to start it up and smelled gas. Looked down and there was gas coming out of the bottom of the airbox. It was turning over really hard (the starter was having problems with it) and sort of acting like it was flooded. I opened the throttle and turned it over and gas really started pouring out of the bottom of the airbox. I left it sit for 20 min and it started. Ran like it was really rich... a lot of smoke or moisture came out of the left pipe and once it burned off started running good again.

So this is confusing to me. Why would a clogged jet cause this? And if it was the pickup coil then it should mess up two cylinders, right?

[James England]

The flooding and gas dripping out of the airbox is caused by the float valve(s) not closing properly. It's probably only one valve that's not working (the cylinder that's been giving problems possibly). The float valve may not be working for several reasons. Dirt in the needle valve seat. A damaged float (leak or dented). Wrong float needle height (but carb would always have flooded if this were the case). Float sticking in the carb bowl.


You began your post "well that didn't work"... what? Seafoam? Or cleaning the carbs. It sounds like you need to do a complete carb strip and clean in order to be sure there is no contamination in there. No additive or product will do this properly.... you need to strip and clean everything. It sounds to me like you had a clogged jet and then developed a float valve problem. These are both symptomatic of dirty carbs

[thebottle]

Alright, well, I will clean them again. I did go through them all and completely cleaned them one month ago... there was a lot of **** on the screen under the float needle on all four carbs. I have in line fuel filters though so I don't know how it would get dirty so fast.

[DGXSER]

Unfortunately, James is correct you need to get hose float valves sealing and that will take carb cleaning.

As to how the junk got there, well, what is down stream of your filters? Fuel line. If your using the double wall soft inner rubber type lines, I had a bad problem with those type of lines where the soft rubber was getting scraped off by the Ts in the fuel system and it woudl get to those floats and make them stick open. Could also be what got into your pilot circuit. Just another thing to consider.

[thebottle]

Yeah, those are the kind of lines I have... and the stuff that was under the float needle did look like flaky black rubber so I do have to consider changing the lines. I will see what I have when I take them apart again. Thanks for all the advice.

[natemoen]

Also, did you replace the o ring on the float seat?

[thebottle]

I did on only one of the carbs (#2) because only one leaked. That was the reason I had them apart and cleaned them in the first place. Now I will rebuild all of them and go over them more thoroughly.

[DGXSER]

Yep, I always recommend that when you pull them off the bike, just take the time to go through all four and clean them, if you replace the o-ring on one, replace all four cause the other three can not be far behind in failing.

[cywelchjr]

In addition, small bits of rubber smaller than the screen openings can get through that will hold the needle valve open and cause just what happened, and will work just like you saw. You can get the inexpensive clear line for gas lawn mowers that is single wall and won't do that to solve the problem as most auto supply stores and many hardware stores in the lawnmower section. This can get so bad that it can fill the crankcase with gas DAMHIK, but it's not good for the bearings in the engine, so check the oil after that happening.

[thebottle]

Well, I cleaned all the jets and replaced all the o-rings on the float seats. Put gas in carbs and #1 still leaked. Switched floats between #1 and #2 and problem moved to #2. Replaced the float and now all is good, thanks for the help everyone.