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Old 11-15-2009, 01:43 PM   #1
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Default Motor won't start when hot!!!

Hey all
After running for around 8 min and running the tank dry I cannot start the engine till it cools down. Measured temps to be at around 95-97 deg C which I thought to be OK. It seems to not be pushing fuel through the line. I have checked for air leaks and don't seem to have any. Do I have a compression issue??
Any one got suggestions??
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Old 11-15-2009, 01:51 PM   #2
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running dry. i hope your priming the fuel hose. i bet your having problems getting fuel into the crankcase.

also, try not running dry. come back in 6-7 mins, and top it off. how do you typically shut down your motor? if you shut down (flywheel) and restarted, without running dry, im sure start ups wouldn't be nearly as difficult.
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Old 11-15-2009, 02:34 PM   #3
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Was doing distance trial to see how long I could get out of a tank! and yeah I had primed the fuel line. It also seems to happen if I have a flame out ( not often ). Tried new plug, new exhaust seal.
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Old 11-15-2009, 03:21 PM   #4
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Is your carb housing made out of aluminum ? I have issues like this with my Mach 427, which has a aluminum housing.
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Old 11-15-2009, 03:28 PM   #5
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It's vapor locked. A splash of fuel on the carb/crankcase will usually cool it down and get it fired up.
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Old 11-15-2009, 07:42 PM   #6
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Quote:
Originally Posted by builtb16a View Post
running dry. i hope your priming the fuel hose. i bet your having problems getting fuel into the crankcase.

also, try not running dry. come back in 6-7 mins, and top it off. how do you typically shut down your motor? if you shut down (flywheel) and restarted, without running dry, im sure start ups wouldn't be nearly as difficult.
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Old 11-15-2009, 09:53 PM   #7
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It could also be that the engine is just loosing compression. How much fuel have you run through it? And when you turn the engine over by hand, how much resistance does it have?
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Old 11-16-2009, 06:00 AM   #8
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Ive had similar problems with my RB H9. It seems if it flames out or stalls when its hot, getting it restarted is tricky. Instead of just holding it down on the starter box, ive got to bump it in short intervals until it fires. I think it has to do with the carb heating up and becoming vapor locked. I never had a problem with my GRP .21, but that motor ran way cooler than my RB.
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Old 11-16-2009, 11:41 PM   #9
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Yeah the carb has an allumin housing, the motor has had around 12 liters through it (5gal I think) and when cold it seems to have plenty resistance but when hot it does drop a bit but i thought it was Ok. Its sounding more like vapour lock. Is there any way to prevent this other than change carb?
Thank for ya help.
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Old 11-17-2009, 02:03 AM   #10
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richen the LSN so that your carb will run cold all the time. Run your engine for few min up and down with full speed and touch the carb. It should be touch able. If HOT then richen more.
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