Karting1.co.uk

[superhans88]

Hi guys, I've been having a little engine trouble recently and was hoping some of you would know more than I do!

My 100cc Lynx was stripped down and rebuilt at the end of last year but it is only recently that I've managed to get the thing fired up. Now that it starts (albeit on a very lean mix) it will tend to idle for so long before the revs start to spike, after a short period of this the engine will then start to rapidly accelerate - requiring me to hit the kill switch.

I've tried all sorts of carb adjustments (with a brand new carb) and it still experiences this even when the high and idle speed screws are set to a lean mix. It's fairly obvious that it's a fuel/air supply problem and I was thinking there may be an air leak somewhere. Would this be consistent with the symptoms?

Thanks, Steven.

[Taylor58]

Well the obviously would speak to the builder

Like most engines if you run them lean on mixture they will increase revs themselves, when on stand, (watch any cadet dad trying to set their carbs!)
i always run around 1+1/4 = 1+1/2 and never have starting issues, little bit of choke when cold and make sure blwo fuel through as normal, check obvious like petals are undamaged and the gaskets back on properly the correct way round
just cause a carb is new doesnt mean it will be perfect (spoken from experience)

[poddy]

Hi

I've just gone through exactly the same thing. Had a full rebuild then took to Hooton to run in. My son got half way around and kart conked out. I had found it very difficult to start, didn't seem to want to suck through fuel but got it going again eventually, then did another half lap.

Also had exactly the same problem with the engine running away with revs, without any throttle input, then it would scream and I'd panic to swtich it off.

Took me ages to find out the problem, which is a small mistake by the engine builders, which of course is impossible to prove!

Anyway, it was the gasket between the reed block cover (the blue plasic cover between the carb and engine. The gasket has a hole that must line up with the hole in the crankcase and the reed block cover. Mine was on the wrong way around, blocking the hole.

Refitted it and started straight away and then ran fine.

Sounds exactly the same with yours and hope this helps as I was at the point of sending the kart to someone to fix as I couldn't work it out.

Who did the rebuild by the way?