The N2001bf i think is a 3 port. Does it have a black head on it? If so it is a great little engine, good runtime, decent bottom and a little lacking on the top. A couple guys at my track ran them as there backup motors they ran good with them. The 21-5kt however I dont know alot about but if it is missing shims that might be why you cant turnover with your hand, I would def get the right shims in there before you run it.

The bf does have the black head on It ! I normally run the p5xlt and these will be for back up engines !

They are both good backup motors. Just make sure you install the correct shims in the 21-5t.

My opinion
 

It aint the bearings, those things will outlast the engine times 2. That engine makes insane rpm's thus it wears out the piston sleeve quickly. I recommend just taking the engine apart, and cleaning it really good, especially the bearings, and sending off the piston sleeve to Ray to have it resized. I will bet he will tell you it was low on compression thus the very rich change after the pitstop. Put the resized piston sleeve bak in the engine and try lowering the head shimming from .80 stock to .60. remove the copper or brass shim and leave the two silver shims in it for .60. Put the top end back to flush and retune the bottom end and put the idle at .60 mm. I think the bottom end should be set to where you are, but most likely it likes to be a little out from flush or it runs on.

Downloaded the Manuel for the 21-5kt and it shows 3 shims ! But there's no reference to size of all 3 ! 03001x1 03005 x2 Anyone no what the finale measurement is?

Yes final measurement is .70mm, 03001 is .10mm and 03005 is .30mm. You can buy them at amainhobbies in packs of 5.:)

thanks maddog ! I went ahead and took them off my old P5 ! its 2 aluminum and 1 brass ! Thanks

Wow a 4.7mm venturi, that would be fun to tune.
http://www.novarossi.it/eng/news/read.php?newsid=191

engine damage regardless... Who needs lubrication when you have that kind of fuel eco. lets run 4mm worth of head shims, a short header and A fuel eco pipe. Heck we may only get a gallon of fuel and no power out of it but it will get 12 minutes. :D

if you ran the new carb with the 5.4 inserted you may think differently.. no power loss.. temps were the same.. but only a slight increase in runtimes.. nothing to warrant getting the new carb.. these inserts maybe only intended for the new carb.. which become standard on nova engines soon...

Guys whats the pipe combo for the p5 in a truggy. I don't need a lot of top end. I prefer bottom end....Thanks

9901 pipe/021 header

Or, 2096 pipe/ 41021 header , either one you can't go wrong. By the way, these are Nova Rossi pipe/header as are 9901/41021.

I really look forward to try one. An OS 5,5 are just great on a Nova with a significant powerloss. The tuning window are narrow but I really likes it, because you "easily" can hear, when the tuning has changed e.g. during a race day.

Many Danish drivers runs 7 mm in their RB and SH engines and gets +9 min of runtime - the same as I do with my Nova Plus 4 Team with 5,5 mm venturi.

I'm gonna try try both 4,7 and 7 mm venturies to see the difference :tire:

9853ss/41021 :nod: