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Rex P5 need help tuning, factory settings?

Rex P5 need help tuning, factory settings?

Old 10-29-2004, 02:41 PM
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Default Rex P5 need help tuning, factory settings?

I got a slightly used Rex P5 and am having big problems with it. It is still nice and tight and has lots of compression. When I first started it up and was making low speed needle adjustments I noticed the mid range screw on the opposite side of the carburetor was turning, Oh No! I believe this needle is factory set and is never supposed to be moved. I don't know where it's supposed to be set but I set it flush with the body of the carb and loctited it. I can not get this motor to run right and now I am suspecting this was not the correct setting. I got it to idle nicely so I think my low end is set close to correct. It idles smooth and doesn't drop down or speed up signifigantly after coming down from higher revs. Also if I can get it past about the mid range rpm range it wants to run like a raped ape, but here's the problem. If I give it more than about 1/4 throttle it stumbles, falls on it's face and usually kills the engine. It's like it just runs out of gas if I crack the throttle too much, either quickly or even if I gradually bring the rpm up. Just to be sure I put new o-rings on the low and high speed needles and sealed the carb to the motor with silicone seal. Does anyone know where the factory setting for this mid range needle is supposed to be? Do you think this is my problem? Does anyone have a manual showing factory settings on the needles or know where I can get some info on this motor. I can't find any useful info or manuals on the internet anywhere. Please Help! Thanks a lot, Mike.
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Old 10-29-2004, 05:03 PM
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The mid needle is set from the factory flush with the body of the carb.

It could be that your lsn is still a bit too rich. lean it out 2 hours. do a couple of full throttle passes and stop the car. let it idle for a few seconds and then pull the trigger to the max. if it hesitates a bit and then takes off like a "bat-outa-hell" , your lsn is pretty close.
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Old 10-29-2004, 05:23 PM
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Boy do I feel dumb. I decided to try a Hyper 7 carb and I got the same results which made me think it wasn't the carb but the motor, an air leak, crack, whatever. I then tried one more carb off of a RB S7 that I know runs awesome and still the same results. This piece of crap (Rex P5) was dieing so often as it sat on the starter box that I just left the glow ignitor on the glow plug as I farted around and HOLY COW, it stopped dieing! You gotta be kidding, I thought to myself. I've never had a glow plug go bad but would still start and idle the motor smoothly. I popped a new glow plug in it and it's all good now. Thanks for the response and this might be something to put away in the memory bank for the future. I guess you never stop learning. Thanks, Mike.
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