Engine cutting out when it gets up to temp

[Rick]

Whilst running the truggy this weekend we had problems completing a heat.

The engine starts OK and ticks over, there is blue smoke from the exhaust and it accelerates OK.

The problem is about 3 mins into the race it cuts out, we retrieve it and it restarts OK and then lasts till the end of the 5 min heat. During the 10 min final however it cut out again after about another 3 minutes.

At the end of the heat we check the temp at around 120 degC.

Engine - Novarossi N21B
Plug - Novarossi C6S
Fuel - Byrons Gen2 25%

NB
It ran Ok last time out, the only change being fuel. We ran Byrons 25% before (just changed to Gen2).

Any ideas?

[bigred5765]

sounds like piston and liner needs a change, when it gets hot it expands and losses compresion it then stops, classic piston and liner change time.

[Rick]

Surely not, its only a few months old and was run in as per instructons. We have only just started to lean it out.

[bigred5765]

get someone that realy knows how to tune your engine to have a look first

[Rick]

Had a look at the instructions that came with it, thought I would put it back to factory settings and try again.

BUT

It says:

High flow rate - screw fully in and then out 3.5 turns
Low flow rate - screw fully in and then out 5 turns

Now this may seem like a stupid question, what do they mean by a turn?

Is it a full 360, or just 180?

The reason I ask is that if I turn the low end screw out by 5 * 360 turns it seems too far, its well out of the casing. The top end is not as bad, whereas if I use 180 as a turn they look better.

[James]

Turn = 360


I think its going to be pretty hard to tune your engine via a forum, they're temperemental even when face to face with one , I would try to find someone who knows what they are doing at a race meeting and ask them to have a look, sorry to be of no use but i really think you need the engine infront of you to tune and diagnose...