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Old 02-02-2011, 03:10 PM   #1
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Default Hyper .12 overheating during break-in

Looking to get some advice from you guys...

I've got an OFNA CD3 I picked up used. Bought a brand new Hyper .12 engine for it, and other goodies go get her up and running.

Today was my first day trying to break in the engine. After much fussing, I finally got it to run. I couldn't even get through one tank without it overheating... I mean, it would start up, idle for a bit (from cold, it was 0 degrees here today) then idle along... I'd check the temps as the idle seemed to increase, and they would climb, and climb. I'd shut it down as soon as it hit 275.

Checked for fuel leakage around the head/carb/backplate... nothing, clean.

Fuel lines are good, no cracks, etc...

HSN setting is at 4 turns out. Factory is 3.5 but I figured I'd take it out an extra 1/2 to compensate for the cold...
LSN is at 2 turns, factory is .5 -- I had to richen it up a bit, just to keep the idle down a bit.

I'm thinking maybe an air leak in the fuel tank??? I didn't see a lot of bubbles in the fuel lines though... So, I'm kinda stumped... Any help would be appreciated!
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Old 02-02-2011, 05:35 PM   #2
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Originally Posted by Dadic 78 View Post
Looking to get some advice from you guys...

I've got an OFNA CD3 I picked up used. Bought a brand new Hyper .12 engine for it, and other goodies go get her up and running.

Today was my first day trying to break in the engine. After much fussing, I finally got it to run. I couldn't even get through one tank without it overheating... I mean, it would start up, idle for a bit (from cold, it was 0 degrees here today) then idle along... I'd check the temps as the idle seemed to increase, and they would climb, and climb. I'd shut it down as soon as it hit 275.

Checked for fuel leakage around the head/carb/backplate... nothing, clean.

Fuel lines are good, no cracks, etc...

HSN setting is at 4 turns out. Factory is 3.5 but I figured I'd take it out an extra 1/2 to compensate for the cold...
LSN is at 2 turns, factory is .5 -- I had to richen it up a bit, just to keep the idle down a bit.

I'm thinking maybe an air leak in the fuel tank??? I didn't see a lot of bubbles in the fuel lines though... So, I'm kinda stumped... Any help would be appreciated!
Hmm, that is strange
Have you checked that the head is sitting on the case correctly, and there are no leaks on the engine itself? That could cause major problems.
What kind of fuel are you using to break it in?
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Old 02-02-2011, 06:22 PM   #3
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I did check the head/block seal. At first, I could see a little bit of fuel leaking out from the top of the block, and noticed that the head was on a slight angle... I took it inside, inspected everything, piston, etc looked OK, so I re-bolted the head in the "X" pattern, and it seems sealed.

Inspected it once I had it running, and no fuel leak anymore.

I'm running byrons 20% which is the recommended fuel for this engine...

Odd part is that it's running PIG rich, and still getting crazy hot! I mean, at idle, I've got a crazy amount of exhaust smoke, and it's got that pig-rich idle sound...
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Old 02-02-2011, 09:07 PM   #4
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hahaha, that's really weird then!
Try running it on the road for a little and see if it just needs the passing air over it to cool it off.
The last motor Ive broken in and the current one I have now, I have a layer of cloth around the head and its not even reaching 190F on my temp gun.
Maybe 20% is too much for that engine, normally .12 race engines run on 16% and that's plenty of power for it, but then again a Hyper .12 is not a race engine so 20% might be OK for it.
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Old 02-03-2011, 08:24 AM   #5
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Well I think I've got this odd problem solved...

I took out the engine last night to (at the very least) seal the thing up. After sealing it up, I inspected the flywheel/CB. One of my clutch springs broke... Odd, never had that before... So, I take it all apart, and after much fussing, realized that the brass taper-cone that the flywheel sits on was about 2mm too long. When I tightened up the bolt that holds the flywheel down, it wasn't exactly holding the flywheel in place rigidly. With a load on it, the flywheel would spin freely. This caused a lot of friction generating a ton of heat, not to mention the "no load" effect it had on the engine.

So, fixed it up, and I'm looking forward to getting it broken in today. Another 2-3 degree day today. Perfect!

Thanks for the help DJ.
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Old 02-03-2011, 05:27 PM   #6
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Originally Posted by Dadic 78 View Post
Well I think I've got this odd problem solved...

I took out the engine last night to (at the very least) seal the thing up. After sealing it up, I inspected the flywheel/CB. One of my clutch springs broke... Odd, never had that before... So, I take it all apart, and after much fussing, realized that the brass taper-cone that the flywheel sits on was about 2mm too long. When I tightened up the bolt that holds the flywheel down, it wasn't exactly holding the flywheel in place rigidly. With a load on it, the flywheel would spin freely. This caused a lot of friction generating a ton of heat, not to mention the "no load" effect it had on the engine.

So, fixed it up, and I'm looking forward to getting it broken in today. Another 2-3 degree day today. Perfect!

Thanks for the help DJ.
AHHHHHHHHHHH!!!
I hate that!! I had to do that to my cone as well!!! I don't know why they do that, but it sure is annoying!!
That would have caused alot more problems then just overheating: it should affect your idle as well because you have to keep it high enough for it not to shut down on you!
Ahh well, at least you solved your problem, without my help actually! When I was reading it I thought it was a broken gasket causing it to overheat - it happens, dont really know why.
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