Anyone consider mounting fan on their carbs?

[JTGS850GL]

I think fuel boils at about 170 degrees F; that will stall an engine. What temperature an engine's internals would have to reach to damage internals at idle is a good one, but carb boiling is no indicator of that.

At idle the fuel in the bowls sits for a long time and gets hot. The oil is still circulating pretty quickly, by comparison. The fuel got hot because the heat left the engine. Convection and radiation is still cooling it when stationary, although the center cylinders don't see much of that.

Any fuel that's "boiled away" will vaporize and leave the float bowl via the vent lines. As the fuel level drops is will be replaced by fuel from the tank which will be MUCH cooler then the fuel in the bowls. Even if the fuel is completely boiled off in the carbs, it will still be fed by they tank if put in the "prime" position. I can't see any way that the engine would be stalled and not be able to be restarted for a long period of time unless something else (probably electrical) is inhibiting it.

[Gorminrider]

The fuel got hot because the heat left the engine.

Heat rises on a stationary bike so I'm still wondering about A) just how hot it was where you live, Dmitri and then , how best to remove the hot air given it's a real nuisance. Air rises so your fan should not blow down. It should "assist" present circulation. Do you smoke ? watching where the smoke goes would help set up the airflow.

[tkent02]

I haven't timed it but it will run for at least 15 minutes in a hot garage before it has trouble. If I roll it out to the driveway and there's a little breeze it can go all day.

I can't imagine taking 15 minutes to synchronize carburetors. Hell, five minutes is a stretch.

[DimitriT]

I can't imagine taking 15 minutes to synchronize carburetors. Hell, five minutes is a stretch.

I was adjusting the idle mixture.. but yea what can I say I'm slow.

[DimitriT]

Any fuel that's "boiled away" will vaporize and leave the float bowl via the vent lines. As the fuel level drops is will be replaced by fuel from the tank which will be MUCH cooler then the fuel in the bowls. Even if the fuel is completely boiled off in the carbs, it will still be fed by they tank if put in the "prime" position. I can't see any way that the engine would be stalled and not be able to be restarted for a long period of time unless something else (probably electrical) is inhibiting it.

I think what could happen is that fuel boils in carbs and we get a bubble somewhere in the network of tubes and pipes which keeps it from spitting fuel into the airflow. At least that's my 25 cent theory.

[JTGS850GL]

Hmm. Thing is the plugs look fine. Not wet or fouled. I can get it to keep running a bit if I hold the throttle open. So it's probably not the coils. What else could it be.

Have you verified spark when it happens? Strong and blue? Have you tried to turn the petcock to prime?

Not saying that you couldn't have boiled the gas out of the carbs but it should be as simple as turning it to prime unless the heat is so high that the fuel vaporizes as soon as it gets into the carbs. That would be very unlikely since the inrush of cooler fuel should be able to get things back down below the boiling point.

I'm still a bit concerned about what other things may be getting MUCH hotter. Just seem to me that the engine temp would have to be WAY above normal operating temps if things are getting hot enough to boil and keep on boiling fuel from the carbs.

Anyone else have this happen?

[Buffalo Bill]

Just reminds me of my own 550 problems.
I think I traced a similar problem down to the electrical system, then on down to bad crimp connections, poor connection to the battery ground.
Once it stalled on the highway and that turned out to be the main glass fuse sliding sideways out of the holder.

[Gorminrider]

from the tank which will be MUCH cooler

but not so much on a hot day with sun beating down on a (black?) gas tank while the bottom is being warmed by the engine? I'm not saying Dimitri doesn't have a mechanical issue but can anyone say there is no viable scenario on these bikes that involves a hot day in desert traffic? True, I haven't heard it mentioned as a common issue but one wonders....
it seems to me... having a carb enrich itself (flood) bubble gas out of carb passages on a hot day has happened to me on old cars. And I'd have to floor the throttle to get her started.
Any smoke when your bike does start, Dimitri?

[DimitriT]

but not so much on a hot day with sun beating down on a (black?) gas tank while the bottom is being warmed by the engine? I'm not saying Dimitri doesn't have a mechanical issue but can anyone say there is no viable scenario on these bikes that involves a hot day in desert traffic? True, I haven't heard it mentioned as a common issue but one wonders....
it seems to me... having a carb enrich itself (flood) bubble gas out of carb passages on a hot day has happened to me on old cars. And I'd have to floor the throttle to get her started.
Any smoke when your bike does start, Dimitri?

No smoke. I let it sit for two hours and it started right up on the first crank.

[DimitriT]

Have you verified spark when it happens? Strong and blue? Have you tried to turn the petcock to prime?

Not saying that you couldn't have boiled the gas out of the carbs but it should be as simple as turning it to prime unless the heat is so high that the fuel vaporizes as soon as it gets into the carbs. That would be very unlikely since the inrush of cooler fuel should be able to get things back down below the boiling point.

I'm still a bit concerned about what other things may be getting MUCH hotter. Just seem to me that the engine temp would have to be WAY above normal operating temps if things are getting hot enough to boil and keep on boiling fuel from the carbs.

Anyone else have this happen?

I haven't verified spark but I did try to turn the petcock to prime. If this happens again I'll have a spare spark plug handy.

[John Park]

Any fuel that's "boiled away" will vaporize and leave the float bowl via the vent lines. As the fuel level drops is will be replaced by fuel from the tank which will be MUCH cooler then the fuel in the bowls. Even if the fuel is completely boiled off in the carbs, it will still be fed by they tank if put in the "prime" position. I can't see any way that the engine would be stalled and not be able to be restarted for a long period of time unless something else (probably electrical) is inhibiting it.

The vapour leaving the surface will go out that way; the fuel in the idle passageway will probably not head 'down and out'. It's going to take a lot of vapour leaving to make much draw of new fuel.

[DimitriT]

Any chance this could be a valve clearance thing? I checked the clearances and they were within spec but a few just barely. Do we know if the exhaust valves get tighter or looser as it gets hot.

[tkent02]

I think they get tighter, but I haven't ever checked them cold and then hot to find out. Are yours on the small or the large end of just barley?

[DimitriT]

I think they get tighter, but I haven't ever checked them cold and then hot to find out. Are yours on the small or the large end of just barley?

There were a few which measured .03 or .04 mm.

[JTGS850GL]

The valves clearances do close up as they get hotter. You might be onto something.