A10 SR Wont better 74mph

[Rob_Roy]

hi folks

I have an A10 SR, It hits a brick wall at 74mph.  Gets to this speed on half throttle, but won't rev beyond it.
The engine is fitted with an auto advance magneto, my guess is that this could be an ignition timing problem, or potentially plugs or the magneto.
Hot restarts are quite difficult and the engine will not tick over once warm - I believe these are potential pointers to the mag.

Any thoughts would be welcome

Regards

Rob

[G/F DAVE]

Hi, Rob sounds like your SR is running a weak fuel mixture, best to remove spark plugs & check colour on electrodes for fuel mix should be a chocolate brown colour, if white then you have a weak mix. Also check for retarded ignition timing which also can cause the problems you describe. Good luck G/F DAVE...

[snowbeard]

what does it do when it hits the wall?  stutter?  stall?  just not run any harder, no matter the twist on the throttle?

could it be as simple as your fuel delivery?  maybe it's pulling all it can as fast as it will flow?

[A10Boy]

Could be starvation, have you checked the fuel flow, sometimes the banjo filter blocks up, or it could be something as odd as the fuel tank breather.

 I had a once harley that if you filled it to the brim, would do the same until the tank level dropped.

If its missing when it reaches the wall, it could be a broken valve spring.