Gp racing

[L111amo]

Hi all, my gp( casa185) kit been on about 15 years has started to hold revs up a bit when hot, changed ex gasket, inlet gasket & rubber, no difference, any ideas, thanks in advance

[Toddy]

Do an air test

[hullygully]

check your ring gap?

[Warkton Tornado No.1]

If the leak test includes inlet & exhaust manifolds & proves the engine to be air-tight, the ignition strobes up to be as desired setting, then there could be a carbon build-up causing pre-ignition. Spark plugs also can have a whisker or build-up to cause that. Fuel flow issues can also cause the problem so that includes tank, tap/filter, fuel pipes & carburettor.

[L111amo]

Gonna get a leak test done on it first, it holds up for 30 seconds or so then drops to normal, been to jersey & back( from Brum) in april with no issues apart from the high idle

[Warkton Tornado No.1]

On the additional information: after the leak test - I often just use a cycle inner tube cut opposite the valve with one end stretched over inlet manifold, t’other over exhaust manifold/‘U’ pipe. You don’t need a gauge or even soapy water spray as deflation is obvious - I’d suspect carburation. Very likely a sticky float bowl/needle which may vibrate into working properly as soon as the engine is running.

[L111amo]

Hi, when you say once it’s running? It alwayscstarts first kick & runs fine then after a couple of miles hangs up, then drops down, samecevery journey etc, ??