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Old 12-16-2011, 06:49 PM   #1
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Default Anyone "Give Up" on An Engine That Won't Run Right?

I know the answer has to be yes...or at least I think so!

I got this OS .12TR used as part of a sale. It was supposed to be lightly used and the pinch was really tight. It always gave me problems with flaming out. I took it apart and everything looked good. I sealed everything up (neck, carb bolts, backplate, fuel inlet) and there were no leaks. I pressure tested it and all is good.

When I got the tune right it would run awesome...but at times it started flaming out. I finally solved that problem with a new tank, or so I thought. New tank, new fuel lines, sealed engine, tight pinch, no internal signs of trauma, bearings were good, crank had no signs of wear and fit tight, no issues with the piston or sleeve, they looked new...and it ran great for a short while...

Temps were good, it would run great for a short while, then just when I thought I had it down, it would act up again. I am positive the HSN and LSN were dialed in as all the indicators of a good tune were solid.

Then same old crap. Would flame out at random. I gutted the thing and looked at every needle and seal, air filter, glow plugs and my underwear. I sacrificed a couple of chickens and still nothing.

My motivation was not to save money on a new engine, but to beat this thing! In the end I got so frustrated it was replaced with an engine that runs flawlessly every time, with the same tank, fuel lines, clutch, drivetrain...you get the picture.

So it beat me down. And it still sits on my workbench mocking me because for some reason I can't throw it away...LOL

Anyone have one of these?

Last edited by Jake C6R; 12-16-2011 at 07:26 PM.
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Old 12-16-2011, 07:55 PM   #2
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Sell it to me lol. I love my 12tr.

My novamega sx12 is like that but i cant find anything on that motor. Funny. My 12tr will run for days without problems. Only changed the plug twice even.
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Old 12-16-2011, 07:58 PM   #3
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Sell it to me lol. I love my 12tr.

My novamega sx12 is like that but i cant find anything on that motor. Funny. My 12tr will run for days without problems. Only changed the plug twice even.
This one has a turbo head and the rotary carb - you want it?
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Old 12-16-2011, 08:19 PM   #4
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while i was reading your description of the motor problem, i see that you might have a buyer. i just wanted to say try 1 more chicken (crispy) and maybe a new front bearing/seal. i'd be thinking of leak after motor heats up, you've pretty much covered all other bases.

formerly of Sunnymead.....
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Old 12-16-2011, 08:55 PM   #5
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while i was reading your description of the motor problem, i see that you might have a buyer. i just wanted to say try 1 more chicken (crispy) and maybe a new front bearing/seal. i'd be thinking of leak after motor heats up, you've pretty much covered all other bases.

formerly of Sunnymead.....

Sunnymead! I grew up in O.C. and spent a lot of time in the inland empire! Had a good buddy in Moreno Valley. Thanks for the tip, it's a good a theory as any at this point! If I keep this turd it might be worth a shot because I can't let a little engine win! LOL

If Valk wants it, I will send it to him for $5 express shipping in a padded USPS envelope or small box - maybe I can learn something when he figures out what is wrong with it!
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Old 12-16-2011, 09:04 PM   #6
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Found a front bearing for $16 on eBay...
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Old 12-16-2011, 10:08 PM   #7
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$5 for the engine? yes please! what you want for it though? my spare is the sx12 that i cant keep running. mine is a slide carb non turbo, but i bet the crank is all the same.
mine has a busted carb insert. the one that goes into the crank case between the carb and the motor. i tore a chunk out of it, flipped it around and it works, but i doubt it seals right. dont have money to buy a new motor, but the 12tr isnt slower than the newer novas at our track. track is too small for those cars to really sing, and my 12tr with massive low end is easily able to keep up to them.
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Old 12-17-2011, 02:21 AM   #8
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Jake, i'm hoping you tame the gremlin in that little motor just for the principle of the thing! I had a used motor i bought and did the best i could to clean it out and reoiled before firing it. The motor had moments of brilliance but i had to start chasing needle valve settings and then it went berserk......front seal.
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Old 12-17-2011, 04:10 AM   #9
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Quote:
Originally Posted by Jake C6R View Post
I got this OS .12TR used as part of a sale. It was supposed to be lightly used and the pinch was really tight.
This with all the problems does raise me a Question: you are sure it has the original piston and/or sleeve?

Mixing piston and sleeves from different brands or production series can cause bad running/adjusting engines.
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Old 12-17-2011, 05:17 AM   #10
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A few questions that haven't been asked or answered:
  1. What plugs are you using?
  2. What's the head clearance of the engine?
  3. Have you tried a different carb on it?
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Old 12-17-2011, 07:51 AM   #11
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Thanks everyone for trying to solve this. As to the questions. I am not 100% sure it is the original piston and sleeve but based on the diagrams they look right to me. The piston is tight in the sleeve and has plenty of distance from the top when you push it inside the sleeve. Maybe you can tell from the pix is it looks right to you.

I am running OS RP6 plugs and 20% Byrons Race Gen 2. There is the one head gasket. I have not tried a different carb as I don't have access to one, but if all else fails I may try that.

You guys have inspired me not to give up on this thing just yet! I tore it down completely and took some pix. Before I did I tested the front bearing again and there is a small air leak. It is almost nothing but who knows when it heats up maybe it is getting worse. At this point I think I will find some new bearings, clean and reseal everything and see what happens! It is just not in my nature not to figure things out if I can!

I will post some pix in case anyone sees anything. Honestly I inspected it carefully and the only potential issue I think is left is the bearings. They are not completely smooth spinning, but no worse then bearings I have used with no problems in other engines. At this point I think that must be it based on process of elimination. Edit - OK that rear bearing is $62!!! We won't be replacing that one LOL, the front I can get for $16 so that one is good to go.

Last edited by Jake C6R; 12-17-2011 at 02:59 PM.
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Old 12-17-2011, 07:58 AM   #12
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Default Here Are The Pix...




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Old 12-17-2011, 05:14 PM   #13
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Ordered the front bearing and also the carb gasket and HSN and LSN o-rings just for good measure. I'll still seal everything up. Added a couple glow RP6 glow plugs as well, so I can try it with a brand new one.

Cleaned every little part and then dried them with the compressor, so just need the bearing and gaskets and we will see.

Any other ideas after looking at the pix?

Last edited by Jake C6R; 12-17-2011 at 07:36 PM.
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Old 12-17-2011, 06:08 PM   #14
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Default Front Bearing

Front bearings in onroad engines do not have an airtight seal. If you get a new bearing wash it out and hold it up to the light, you will see what I mean and the ones with the biggest gaps are the metal sealed.

Last edited by fairgo; 12-18-2011 at 02:20 AM.
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Old 12-17-2011, 07:07 PM   #15
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Damn traxxas 3.3 engines. Such a piss off. Make it half way across the track, flame out. Take it off the track, try to replicate the issue, wont do it, throw it back on the track, flame out.

A picco .26 solved that issue. And when that kicked the bucket I just went brushless.
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