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Old 07-13-2008, 02:12 PM   #1
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Questions?? VAPOR LOCK ?

I run a RB S3 L2G it's new just over a gallon thru her. She was on a XTM X2 with the stock XTM pipe. I recently bought a LOSI 8B with a Jammin JP2 pipe 2 days ago. When the motor was on the XTM vapor lock was rare and minimal even with running for 5-6 tanks straight after break in. Now in the LOSI once I get her started and run her for a tank vapor lock starts to occur. If it cuts off or I run out of gas it is a B*tch to restart. I send gas to the carb kick it over on the box and fuel starts back flowing away from carb. I know the carb is hot I can hear the nitro sizzle. My gas tank is new and so is the motor RB's come sealed from the factory. Any suggestions. No performance issues when engines running good smoke, good take off top ends good temps are good.

engine temps 220-250
byrons gen 2

p.s. If your only reply is don't let it cut off or run out of fuel keep it movin. Looking for some real answers or ideas from some real techies.
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Old 07-13-2008, 04:04 PM   #2
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Do you leave your gas in an open container IE leaving the lid off at night?

Is there condensation like droplets (but on the inside) on your tank ?

could be caused by water. thats why i ask
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Old 07-13-2008, 04:20 PM   #3
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Check the length of your pressure line from your pipe to the tank. You might also think about installing a pressure vessel.
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Old 07-13-2008, 04:27 PM   #4
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Try putting youre finger over the exsaust opening wile youre trying to start it. It will force the fuel into the carb.
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Old 07-13-2008, 04:32 PM   #5
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Try richening the bottom end. Never tune the bottom cold. It will lean out on the bottom when it gets hot and vapor lock ensues.
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Old 07-13-2008, 04:33 PM   #6
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Pinky I thought of that one even though the gas I was using was only a week old I went and bought new gallon it happened anyway thanks.


GhettoTeacher, When you say length of pressure line. Is there a specific length I should be using? Pressure Vessel whats that? Thanks

woodchuck, I've been trying that when I see it backing off I quickly cover the stinger. Still no luck. Thanks


Thanks keep the ideas coming
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Old 07-13-2008, 04:35 PM   #7
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Wing, I will try that. Thanks
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Old 07-13-2008, 04:37 PM   #8
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To get it to fire back up you need to cool the carb and crankcase. The quickest way to do this is to pour fuel from the fuel bottle on it. This is dangerous however. I have seen a fire from this technique but the motor will fire right up if you do it. If you know you might have the problem you can keep a little spray bottle of water with you to do the job.
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Old 07-13-2008, 04:41 PM   #9
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I've never tried it or nor seen it eather, but I've herd that some guys keep a can of compressed air (keybord cleaner) with them in the pits for this reason. They spray the carb to bring the temp down. I don't know if it works or if it does any damage, maybe others will weigh in on this. I've thought about trying this myself when this happins to me.
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Old 07-13-2008, 04:43 PM   #10
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That's not a bad idea. Safer then dumping fuel on it.
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Old 07-13-2008, 04:44 PM   #11
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Also, if you know any good .12 touring car racers in your area ask them. They are notorious for vapor locks.
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Old 07-13-2008, 04:49 PM   #12
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So you guys are saying its pretty common to experience vapor lock? I'm not a total idiot screwing up his ride. I just need to find ways to lesson the problem.
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Old 07-13-2008, 04:54 PM   #13
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Quote:
Originally Posted by vladconnery View Post
So you guys are saying its pretty common to experience vapor lock? I'm not a total idiot screwing up his ride. I just need to find ways to lesson the problem.
Yes it's common, I've found that if my engine loads up and shuts off, it'll generaly start right back up. But if I run it out of fuel, it will have the exact problem that you started the post about. So,,, don't run out of fuel
(I know you didn't want to hear that)
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Old 07-13-2008, 04:56 PM   #14
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It's a very common problem with .12's. They just don't have the mass to dissipate the heat when idling. .21's are no where near as bad about it but can still do it.
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Old 07-13-2008, 05:30 PM   #15
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Quote:
Originally Posted by jrwoodchuck View Post
I've never tried it or nor seen it eather, but I've herd that some guys keep a can of compressed air (keybord cleaner) with them in the pits for this reason. They spray the carb to bring the temp down. I don't know if it works or if it does any damage, maybe others will weigh in on this. I've thought about trying this myself when this happins to me.
It works. I had to do that with my Go 3 port to restart it.


Wait.... Doesn't the s3 come with a composite carb?
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