use a competition heater or aluminum foil around the cooling head to keep the temp up , as the prop will cool the engine quickly. 1/10tire foams work well too

You have to turn the carby around so with the blades on check that it wont strike the carby, Make sure all bolts are secure. I use a old towel and keep it under the exhaust to collect all the fuel and oil.I also make a template out of cardboard and place it in between the carby and head the amount of air that the blades turn out cools the engine to much...all my engines get the first 800ml to a liter on the bench where i can keep watch and heat into the engine... Then in the car..

Yea, sounds like your engine ingested the glow plug element. If the scratches go all the way up the piston past the oil rings, it will cause the problems you are describing. Im suprised the #6 plug did this. this has hppened to me twice with #5 plugs.
If the engine ate the element there is a good chance that it got into the rear bearing and damaged the races as well.

The engine performed just great during the race yesterday. 10ºC ambient temp and the engine was approx. 100ºC (made only one temp measurement). 9901 pipe, 41001 header and 5,5mm venturi. When I drag raced down the straight alongside a Ninja JX21-B02 engine with 6,5 mm venturi, my car had the same acceleration and topspeed . I don't know if the 41021 header would have made similar performance. Didn't have time to make an comparison during this one day race.

BTW: just got my 4,7 mm venturi... I guess it will test my tuning skills to get the settings right... . Its so different how different engines reacts to venturi sizes: I've no problem tuning Novarosssi engines and my sons old Sirio (Novarossi carb) engine with a 5,5 mm venturi. On my practise engine (STS D21T with Novarossi carb) anything smaller than a 6,5 mm is impossible...

Be sure to check your pipe as someone has already suggested. If the pipe has any restriction , the restriction will be at the smallest point, most likely at the exhaust press port. When your tank has more fuel in at, like at the first of the run, it may not take as much press to push fuel to the engine. 4 minute is you have less fuel, more air, fuel may require more pressure. Exhaust port on the pipe may not be completely closed, but may be clogged enough to reduce your pressure and cause a problem. Just a theory, but I've cleaned a lot of pipes and you would be surprised what comes out!

Yep, I thought of that. Ran it on 3 pipes. An OFNA 086, Nova 9886, and a brand new never ran before OS 2090. Did it on all 3 pipes. Other 3 buggy engines will run all day and night with all the same parts. I am getting ready to tear it down here in 30 minutes actually. I will take pictures tonight or tomorrow morning.

Did you try the P5 carb?

I have not had time tonight. I am tearing the carb on hte plus-4btt apart right now and trying to see of I see anything. Will post pics in a little bit....

ok, so I took everything apart and have some pictures. Everything looks really clean. The carb looked good and the orings look brand new. Flushed the whole carb out with denatured alcohol and some air. No dirt came out and looks as good as new. The piston and sleeve looked pretty good, no signs of cracks, sleeve is really smooth, etc.... I have a picture of the farthest i could push the piston up the sleeve and is really tight at the top still.

The only thing I saw that might cause a problem is one of the shims on the head button was a little rough looking. I had some shims so I put new ones on it and at .80 for now as I do not have the shim to go .70 right now. Maybe not sealing good and the top of the sleeve is a little nicked but it ran fine for 3 race weekends like that. I am going to put it back together and go to the track Wed. night and bring the carb on the P5 and see if it does it or not and switch to p5 carb if it does.Pictures are not the greatest but hopefully it helps.

You may need to resurface the top of the sleeve. Looks like there are a couple deep scratches there.

Yeah that is what I was thinking after looking at it but all is well for the most part.

Well, I believe I have found the problem...... What is the chance of getting a bad 17011 bearing from the factory. I looked at things a lot closer after I put the engine back together and i noticed some play in the bearing. I am not talking the crank moving front to rear a little as that is normal. I can take the crank and move it up and down to speak in the bearing. I can turn the crank and the inner race does not move. Like the crank has wore down or the race is too big in the bearing. As soon as I put it in I did the motor clean test and it passed. I noticed oil on the bottom of the engine while tearing it apart but I also had a fuel guy spill fuel while "playing" with this engine at the track. The crank looks fine and perfectly smooth feeling and looks fine but does not begin to fit correctly in the inner race of the bearing.

I went and looked at the CRE P5 I have and the new bearing in it is super tight and I have none of that play and it runs fine and never flames.

What are the chances of getting a new bearing that is out of tolerance bc I think I might have.

I honestly have no more than 10 minutes on this bearing since I had to pull the engine and put something in that would run for the mains.

Coincidence or not?


What should the measuremant of the crank be at where it meets the front bearing? I would like to measure just to check if it is the crank?

Bingo! 17011's got really crappy. They were really good, then got really bad. Our local hobbyshop has a huge track that draws many racers and can't give those bearings away.

I had heard grumblings about this, but at the same time I have heard these are still the best bearings on the market. It sucks to be out $30 but sometimes the hassle is not worth it trying to get them to do something about it. I think I will roll with a $14 TKO. Put one in my Speed and has been very good!!!!

Well this sucks.....

At least you found the problem, I have TKO ceramics front and rear, they are excellent bearings, long life and high quality.