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Old 11-17-2006, 12:53 AM   #1
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Default Pinched Nitro Motors???

I had a p5x and a s7II, they both started to get tired so i had them pinched, by a pro, break in using heat cycle method, i had both motors brand new and always ran them about 220 degrees, the problem is now they both wont run right, they will not clear out on straight away unless there running at 280 and up, by then it ruins the glow plug, i have several .21 motors and they all run fine expect the two that i had pinched, any else have this problem?
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Old 11-17-2006, 05:36 AM   #2
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are they definately fully re-broken in?
i repinched my os vspec and had similar problems, until i reaised that i had given it a bit more pinch back than i first realised. keep running it ever so slightly rich on low end and top end needles, and dont go full-on with the throttle till it starts to free up just a fraction. you'll feel it as it gets run-in.

also my needle settings changed after the repinch, perhaps yours have too. put everything back to factory settings and do the usual from there.

are u running any shims? were you before the pinching was done, when the motors were still good?
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Old 11-17-2006, 08:05 AM   #3
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Did you replace the rods after break in? If not there may be excessive rod bushing play which will cause you to go through glow plugs quickly.
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Old 11-17-2006, 10:43 AM   #4
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Try leaning out (turn clockwise) the low speed needle about an 1/8 to a 1/4 turn and see if it helps with the bogging situation. Pinching the cylinder restores lost compression and can make you have to readjust the carb.
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Old 11-17-2006, 01:12 PM   #5
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simonr23 yea i had another guy at the track tell me they take longer to free up, i have about 4 full tanks of heat cycles, then another couple of tanks on the race track for tuning, oh i did reset the settings to factory settings before the break in, i did add 1 thin shim in both motors for %30 nitro.
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Old 11-17-2006, 01:16 PM   #6
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Davidka, i did not replace the rod, i was being cheap, i guess thats what i get, it does have alot of play. in the p5x, the s7II seems fine.
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Old 11-17-2006, 01:19 PM   #7
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Sport10, i tried riching,and leaning, the bottom, still same thing, i think simonr23 is right just needs to be broken in more, even though i think 6-8 tanks is enough,
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Old 11-17-2006, 01:21 PM   #8
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Thanks for all your guys help, any else have more experience with pinch motors?
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Old 11-17-2006, 10:19 PM   #9
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Old 11-17-2006, 10:36 PM   #10
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Who did it for you? I would not send a P/S anywhere but OSrocket or Ray-A-racing. If it's really tight it is a good idea to preheat the engine with a heat gun to get things going more easily.
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Old 11-17-2006, 11:59 PM   #11
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I've had excellent luck using rayaracing for .12's and one .21
They all ran like a top. I just put a few easy tanks on em and then went racing. Like said above, who did your sleeves and how tight a pinch did you ask for?
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Old 11-19-2006, 02:44 AM   #12
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There is a local guy at the track that does the pinch, I check his pinching machine out it is the same one that OSrocket or Ray-A-racing use, is it ok to have it pinch that much that you would have to heat it up with a heat gun, i notice some companys offer light,med, and tight pinch, what do you guys order? and the local guy that does the pinching probally has done 70% of the people there, havent really heard any complaints.
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Old 11-19-2006, 09:33 AM   #13
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Your engines probably need new front bearings. Ask any motor guys they'll say the same thing. They will run hot because they have an air leak into the crankcase. Every 1-2 gallons replace the bearing. I oil them with quality synthetic oil and use inner and outer seals.
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Old 11-19-2006, 10:40 AM   #14
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Quote:
Originally Posted by schmelme
Your engines probably need new front bearings. Ask any motor guys they'll say the same thing. They will run hot because they have an air leak into the crankcase. Every 1-2 gallons replace the bearing. I oil them with quality synthetic oil and use inner and outer seals.
Thanks for the reply i am going to get new bearings.
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Old 11-19-2006, 01:41 PM   #15
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Quote:
Originally Posted by schmelme
Your engines probably need new front bearings. Ask any motor guys they'll say the same thing. They will run hot because they have an air leak into the crankcase. Every 1-2 gallons replace the bearing. I oil them with quality synthetic oil and use inner and outer seals.
you dont want inner seals. If you seal the inside, how will it get any lubrication from the fuel?



Replace the rod first, then possilby bearings. Those pinched motors really need a new rod after they have been broken in most of the time.
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