As others said, inspect fuel lines, exhaust gaskets, retight every bolts.

After 4 minutes, your fuel tank is about half, fill it up and see if it solves temporarily the problem until the tank gets half again. Might be a fuel tank issue

All gaskets are new... New lines also.we ran a20 min main say with it and pitted twice it only got worst thruout the main..

It almost seems like the lsn is working its self in...but the Carb has all new o rings in it..I thought about putting a dab of lock right on the lsn to seal it and making it harder to adjust..

Faulty tank ^^ i had the same problem as you yesterday.

+1. i've had the same problem. sealed tank and all good.

i just bought one of these and i'm hoping for good things i have it in a mp9 tki and have a 2035 pipe on it. idled 1 tank took like an hour lol. then i ran a tank at 1/4 throttle let it cool and did this for about 4 tanks till i started leaning it out and getting in the throttle. so far engine sounds and runs well. i havent read what the different venturis are for yet and havent raced it yet if anyone has any info they would like to share id appreciate it. thanks and happy racing

What head shims are you running? Found my buddies with a similar problem and he had the wrong shims in it.

Did you solve your problem?

A smaller venturis will reduce power and increases runtime the opposite is also true

The engine comes stock with a 8mm installed. I run mine with the 7mm and I like how the engine performs.

thank you is there any particular glow plug you would recommend, think i'll be trying to race it this weekend with a p3. i ask because i read on here the that this engine likes to be run hot.

OS P3 is exactly what I use with my Reddy engines, works great,

With my Reedy I have tried the O'Donnell 97 T, OS P3, and the Reedy R3. Info like the R3 just a little better but any of them work. Richard Saxton generally uses the OD97T plugs for what that's worth.

I used OD77T in the past, until their price get higher, I then switched to OS P3

thanks guys. youve been a huge help to me.

just got back from the odonell race where i ran my new reedy and all i can say is this engine rips. richard saxton took 5 minutes of his time to tune my engine and it was awsome after that. definetly would recommend this engine to people looking for a new engine

3/4 gallon in my 121VR ST and it started to show all its power....Woohoo I love this engine !