Old engine loses revs when at full throtle..
 

Ive got an old(ish) nitro engine in 1 of my cars, at low and medium speed it seems fine but as soon as i try to go at full speed the engine revs up to full and the seems to lose its revs and almost stalls, any ideas?

Sounds too lean to me on your main needle...

Does it "hesitate" when you hit full throttle almost like it wants to stop, if so it is too lean, I would imgaine it is running a bit too warm to as a signal of this

At full throttle it starts to go fast then when it reaches a certain amount of revs it backs down and seems like it wants to stall, at which point i back off the throttle. Its a .12 thunder tiger engine running on 30% nitro (ive been told by bolton model mart that this should be fine)

Open up the main needle.

What's happening when the engine revs up is that it asks for more nitro than the carb can provide due to it being too restricted by the main needle. You don't see it right away as it's probably not too far off.

30% in a .12 sounds a little overkill to me, but then each shop offers different advice and I have no experience of Thunder Tiger products, but any .12 that we would run would be between 16% and 20% as a rule.

tuning a nitro by from HPI

richen your top end mate, your starving it of fuel on the top.

When it finally gets to top end speed theres no fuel there basically.