I recently bought a used TT .46 Pro.
I disassembled, cleaned, reassembled and tried a bench run.
It starts easily but runs backwards, at very low rpm, with a regular tendency to pop forward yet never makes the transition.

The cylinder liner is pinned so it's not in wrong.

Any thoughts, notions, suggestions?

Thanks.

Terry

Check for and add an additional head shim, use a cooler plug, prime about 2 times then flip the engine over 10 times very fast to aerate the charge, then flip the prop backwards, it should fire front ways.
Are you running a carb or venturie?  nitro % ?  size of prop?

Randy

Add the head shim, or 2  that should stop it

Randy

Tnx Randy - do you know (or would you guess) the thickness of the head shim?
Don't have any, but can try making rather than wait.

Terry

You can make one anywhere from 5 to 10 thou, any of those should do it

Randy

Ordinarily that's a symptom of being badly flooded and is fairly normal with RC engines with the throttle at, or close, to idle even with just a bit of over priming. Try to ensure the engine is completely dry then prime with a few drops of fuel without the fuel line attached and see if it starts correctly. If so then make sure the needle valve is actually fully closing first before attaching the fuel line. I had one engine (brand new) that would run in a slobbering 4 stroke with the needle fully closed. Actually it was the barrel bottoming out on the threads, not the needle itself.

It's extremely unlikely to be a compression problem because I generally run mine at 12-13:1 with no problems.

OK, I'll make a couple .005".
Would you explain what's happening?
I assume timing?

Terry

It is VERY likely that compression is helping in causing this, The 46 is very high compressed and if you have  ZERO head shims in it, it can make it "diesel " and run backwards
What is most likely causing this is a combination of things ,too high compression,excess oil, afterrun or other oils  and /or excess amount of fuel charge inside the engine when you try to start it. the EXTRA COMPRESSION is making this much worse and aids in the running backwards. Sometimes with the very high compression the engine will start without a battery on it.
Try to clean out any excess oil, and fuel before you start it next time, and try one of the .005 head shims that your making.
You will also not blow as many plugs with a head shim in the engine, as with zero  shims.

If you start it again and it runs backwards, do not shut it off, instead pinch the fuel line to stop more fuel from going into the engine, it most likely  will pop back and run the other direction, even if it doesn't this will clean out the excess
Randy

  My Stalker .81 does just this. I believe it is very much over compressed. I added 1 head shim & it actually 4 stroked at a higher RPM.... 
  Work in progress, John

The weather is finally cooperative enough to get outside to play, so I ran the engine a bit w/2 .004" shims, cooler plug.
It took a good bit of prime (about a dozen) and didn't diesel but the NV has little effect.
Has to be ~6 turns open to run and won't lean or richen appreciably, 11.8K-13.3K range.
Recommendations for a decent venturi/NVA assy?

Terry

Hi Terry

I of course make them, let me know If i can help, but  did the engine run the correct direction?  and is the  TT ventuire NVA setup or aftermarket or carb?

Randy

It ran the right direction Randy.
It has a carb w/.295 bore, not sure if factory, marked DV-II, single needle.
It dies w/no leaning at less than ~ 4 turns, dies at ~8 turns w/little richening, when the needle unseals from it's body.

You mentioned excess oil in an earlier post - is 22% too much in this engine?

Terry

NO The oil content is not what is causing the poor needling   unless you have old fule, or fuel with water in it

Randy

Fuel is good - I was thinking of the high compression/dieseling issue.

Terry

Forcefully flush the spray bar from both the threaded end and the fuel nipple with your fuel syringe. 

Is there a funny shoulder in the needle like it was crushed in over tight?  Was there any trash on the needle?  Is the needle straight? 

Phil

Passages are clear, needle straight and tapered Phil.

Terry

PM sent Randy.

Terry