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Stalling when hot

  • Thread starter Thread starter Hooptie
  • Start date Start date
H

Hooptie

Guest
This just reared its head since its finally getting warm out here. When coming to a stop and the clutch is in, it died and didn't really care for starting right back up. If it sits for a bit and cools off, it will start back up, and even bump start.

I parked it in the driveway and let it idle for about 10 minutes and it finally coughed and died again. It starts with starter fluid, so its back to a weak fuel supply again I guess. Is there a hot idle circuit screw or is this an internal issue?

I bumped up the idle from 900-1000rpm to about 1200-1300rpm and it seemed less inclined to crap out. Outside of that, the bike runs phenomenally. Much harder than I expected a 572cc bike to run.
 
The factory manual states something above 1000rpm.

A secondary issue is a slightly stretched throttle cable. Any way to take slack out of them?
 
Forgive my newness. Is that a barrel mount at the grip or on the carb rack?

I guess I could get off my narrow butt and walk out and look. But its hidden behind the Mustang.
 
Could overheated coils cause this? I may start the bike and park it in the driveway after work today to see if it acts up.
 
Well,

the 550's were known to have faulty ignitors, and that could show up as the symptoms you are describing. However, because it starts up hot with starter fluid I would lean away from that at first and think that you have idle circuit issues to deal with.

Yes, you could also have other electrical issues, including a weak coil(s), but from what I have gleaned from other people's experiences, the coils are less likely. How is your R/R situation? I have had occasion where my 550es would run at idle if I kept it above 1100rpm, and die below 1000rpm. Turns out the R/R was fried, and I had cooked the battery. Swapped it (R/R) out, with n'er a repeat of the problem.
 
My 550 was doing that. It would stall and would be super hard to start when hot. It would fire right up and run cold but i would have one heck of a time getting it running again when it was hot. Have you checked the voltage at your coils? If you have excess resistance in the wiring somewhere or in the kill switch it will get worse the longer you run it as the wiring heats up. Your stator is not really putting out much power at idle so if your voltage to your coils is low it will tend to show up more at idle speed. What you need to do is run the bike for 15-20 minutes and return back to the house. Then you need to unplug both of your coils and check the voltage to both of the coils. If you don't have within about a half a volt of battery voltage you need to do the coil relay mod.

On my bike the coil voltage would start out the same as battery voltage and would steadily decline to around 9 volts after it had ran for a while. I did the relay mod and haven't had a problem since. I would doubt that it is a fuel problem. The reason it would start easier on ether than on just gas is because ether has a super low flash point compared to gasoline. If the voltage is low to your coils you would still have spark but maybe not not enough to get the gasoline to burn. Shooting it with some ether would be enough to get the engine speed up enough to get it to hit and run.
 
Last edited:
Hooptie said:
Forgive my newness. Is that a barrel mount at the grip or on the carb rack?
Click to expand...

It should have both. You can just loosen up the jam nut at the throttle (same basic setup as a clutch cable) and take some of the slack out of the cable. If it won't adjust enough you need to loosen up the adjuster at the carbs and take the slack out then do your fine adjustment at the throttle barrel.
 
You might try a set of plugs that are one heat range colder. ;) They are listed in the factory service manual.
 
Hooptie said:
If I had to guess, RR and coils are exactly 1986 vintage.
Click to expand...

Sorry, Hooptie...

I was subtly asking what electrical maintenance and tests have you run so far to determine the state of your RegRect, coils, and stator.

There is much baseline information missing to really help in more than general terms.

D
 
I've done none at this point. It was the first time it acted up and i ran out of day/week to play with it.
 
I played with the bike today. It seems like when hot, it isn't pulling enough fuel to stay running. Vacuum issue at the petcock? Is it possible that its vapor lock? If I shoot starter fluid in it, It catches and runs great. If it sits for about 40 minutes, it fires up fine too.

It idles great, revs great, pulls cleanly. Actually, the only time it doesn't is when it is just fired back up with string fluid. If it idles for a minute, the stutter goes away. Its like is just isn't drawing enough fuel in.
 
Did you try to run it on prime? Put a piece of clear plastic tube in place of the fuel line so you can see if fuel is getting there or not. Although if it was a petcock or fuel issue you would have other running issues as well not just hard starting.

Have you checked compression yet? What about valve adjustment? Carb sync? Voltage at the coils? All are important.
 
Fuel line is new and clear. Prime makes no difference.

Carbs are great. Valves are great, compression is great.

I know the petcock has to see vacuum to start pulling fuel in the "on" position, so maybe once its running it is able to pull harder than while cranking?
 
Shouldnt matter. Once its been running you have to assume the carbs are getting fuel to them on PRIme. Its afree flow when in prime, so one would have to think fuel would be free flowing regardless of the petcock being good or bad and whether the bike is cold or hot.

This makes me think theres a flow problem within the carbs themselves. Be it wrong float hts, partially cogged jets, whatever. but the problem is in nthe carbs if you ask me.

If the petcock is flowing a good stream in the prime position, the next place downstream is the float seats and float needles. So, take a rag and loosen all the float drains to see how fast they are draining. Gonna be messy and lots of gas but you need to verify that the bowls are getting good flow and are filling at a rate that is sufficient.
 
Don't forget air-venting too...the tank cap has a vent -You could crack the gas cap and ride that time period to check...and the carbs have a vent too...
 
Gorminrider said:
Don't forget air-venting too...the tank cap has a vent -You could crack the gas cap and ride that time period to check...and the carbs have a vent too...
Click to expand...

Its funny you mention this. There was definitely pressure built up inside the tank. But even after I opened the filler, it still didn't want to start.
 
When I bought my bike it had a similar problem and it turned out that their wasn't oil getting to the head. This would make the aluminum expand around the steel camshaft which would seize the engine. It would make it seem like a loss of power once warm. If the bike idles under 1,000 RPM then you may be affecting the oil circulation resulting in similar results. Does it lose power if you're riding it around or just if you let it sit idle?
 
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