Bike Stops running after about 15 minutes!

[granny_rocket]

Hey Folks,
Heres the situation...this happened about a month ago and I just haven't had time to play with it.

I started the bike up w/ choke on and it fired right up. Runs for about 10 minutes and blows smoke out the tail pipes (i know what the smoke problem is. Its an incorrect mixture...a set of the carb jets are off somewhere - a completely different problem in itself. This should have no effect on the problem im having now). I rev the motor up a little bit to help clear some of the smoke out and *BANG* the motor backfires and stalls. Tried to restart with no luck.

I let the bike cool and tried again. Started right up ran for a bit then shut off once it hit a certain point. Im not sure if its temp related or what....

I left the bike for the night and tried again a week or so later and i still have the same problem. Bike will start up, run for about 15 minutes then stall. (It didn't backfire...that only happened the first time)

Any ideas on where to look? The clymer/haynes manuals are useless in this case and im familiar with cars and such, but not as familiar with bikes...just because I simply haven't worked on them enough. For what its worth, I just replaced the R/R last year and im 95% positive the electrical connections are tight. Although, i almost feel as if this could be an ignition problem...

Anyone have input???? PLEASE!!!! :roll:

Thanks Much,

[Anonymous]

I can't tell ya about ignition, but I think it's carburetion so I'll give it a shot.

A couple more questions for you:

What size, model, year is the bike in question?

What color is the smoke that comes out? Your choices are black, blue, or white.

Are you really leaving the choke on the whole time?

Pull all the spark plugs after it dies. What condition is each in? Use the chart here to tell us: http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html I hypothesize that they will be wet with gasoline. The cylinders are numbered left to right as you sit on the bike, 1 to 4, (or 2 if it's a twin) Tell us each one.

After it dies, feel which of the exhaust pipes are hot by placing your hand near enough to feel the radiated heat. Don't burn yourself.

Always work with a good fire extinguisher within reach!

Michael

[daveo]

the electronic ignition(ignitor) can fail this way, when they heat up, they open, so can coils, I'd put my money on the ignitor though, which model bike do you have? I think i have a stock ignitor for an 81 750EX if it will work you can have it,...if you choose to replace the unit with new, the Dyna III, is about 1/3 the cost of the stock unit

[granny_rocket]

Wow, sorry forgot to post what the bike is:

its an 85 GS550 L

As for the carburetor, the bike has been running fine* (and by fine i mean its been running with the smoking exhaust) prior to this problem. The smoking exhaust smokes a whitish/grey color which to me means incorrect mixture - what happened was the previous owner used a set of carbs off of an '83 GS550 LD instead of cleaning the ones on the bike (at least im assuming since all the jets in the bike are the jets listed for the LD and not the LF)

If you aren't confused yet, I did change the main and idle jets to the correct specs listed for the '85 LF but the bike still smokes white during the warm up. Once its warm the smoke disappears but I do stink like exhaust when I come back from riding - which still means something isn't right....

Aside from this mixture problem, the stalling started and I haven't been able to ride the bike. I'll have to start 'er up and check out what you all suggested.

Any other input is greatly appreciated!
Thanks Much,

[Anonymous]

Well, white smoke usually means that an engine is burning coolant. But since ours are air cooled, I'm gonna think that you're talking about a very thin bluish color. That would be oil burning. Improper mixture/rich makes a black smoke. Now, it's going to be a thin black smoke, but it is black, not blue or white.

As for the exhaust getting into your clothing, that is not an issue of mixture but an issue of airflow. Does your exhaust system leak? How about the gaskets up at the headers?

Michael

[Wingnut]

Have you tried running the bike with the fuel cap off (or loose)? Sounds like it could be a plugged vent hole in the cap. The backfire you had could be common to running lean as the carbs ran out of fuel. Could be several things but this is quick and easy to check.

bob

[granny_rocket]

well, the smoke is definately not oil. I know what oil smells and looks like!

As for the "smelling bad" after riding part, there is a leak at the bottom of the exhaust, but the exhaust coming out of the tail pipes also smells bad like my clothes so whatever is getting into my clothes is coming out of the pipe either place...

Anyway, thanks for the suggestions! I'll give them a try tomorow (hopefully) and see what I can find out!

Thanks Much,

[earlfor]

I would say your fuel consumption rate is exceeding your fuel flow rate.
Have you, when the bike died at the ten minutes, removed your float bowl drains to see if there was fuel in the bowls in sufficient quantity? If there is less than about 1 1/2 Oz. in the bowl, it isnt going to run. Also, do you have one of those itty bitty inline plastic tonka toy inline fuel filters installed? If so, get out your slingshot and send it as far away as you can. they aint worth doo doo.

Earl :-)

[granny_rocket]

Also, do you have one of those itty bitty inline plastic tonka toy inline fuel filters installed? If so, get out your slingshot and send it as far away as you can. they aint worth doo doo.

Earl :-)

Define "tonka toy" fuel filter...yes, i have an inline filter and yes, its plastic :P but its one of those clumpy brass balls or whatever you want to call it (it looks like a fish tank air stone) 8O What is your suggestion for a fuel filter?

Thanks Much AGAIN!

[earlfor]

The fine mesh screen on the petcock pickup in the fuel tank is more than sufficient as a fuel filter. Come to think of it, thats what it is. :-) :-)
Run a plain length of fuel line between your petcock and carb nipple.
I think all your problems will go away. Those inline tonka toys have caused grief to everyone that has been tricked into using them. I can guarantee you that a stone type filter will not flow enough fuel for a bike bigger than 50 cc. :-)

Earl

Define "tonka toy" fuel filter...yes, i have an inline filter and yes, its plastic :P but its one of those clumpy brass balls or whatever you want to call it (it looks like a fish tank air stone) 8O What is your suggestion for a fuel filter?

Thanks Much AGAIN!