3.5 slow turnover when hot

[teamidris]

I wish it was, but it is a cheap aftermarket unit which is smaller and lighter than the lucas shunt wound.
I've had a good think about this and I think a solid state motor that was noticably weaker when hot would have to have a a bad earth or somthing else wrong with.

Although current is reduced with temperature in metal, I've never heard of it having a noticable effect on wire wound motor speed. Ours always got faster as the oil got thinner and we had it so hot the fuel in the carb boiled? But it is scarily close to the exhaust system on an RV8 (especially mine).

[DaveEFI]

There's a thread on here about this happening to a Lucas unit, and I've experienced it myself. No idea what the theory is as to why. Both on SD1s where the manifold goes very clse to the starter.

[DEVONMAN]

Just heat soak from the engine block will also affect the starter output.

If it's a rebuilt engine then it could be stiffer when hot due to tight initial tolerances. Not good though.

Denis

[shaunod]

Just a note from the previous comments about timing and detonation. The instructions given to adjust the timing until you get the maximum possible just before it 'pinks' is a little dangerous IMHO. There are a number of things that will cause detonation in an engine but the points of primary concern are Air Fuel Mixture, Cylinder pressures, Cylinder temperatures, Ignition advance and finally fuel quality / octane. On a standard 9.35:1 RV8 with a suitable AFR for the given engine load, we generally see the peak power output at around 28 degrees at 4000 rpm. But if the compression is higher, the AFR weaker or the fuel quality lesser, this may have to be pulled back to as low as 20 degrees to prevent 'pinking'. More fuel certainly helps to mask the issue by reducing cylinder temperatures and softening the combustion process .. but will not help with power output. So .. to stop me from rambling! .. if you want to set you timing properly .. first make sure of the mixture get that right, adjust the timing for best response, power and driveability .. then re-check the mixture (it is likely to have changed as the combustion improves) then check for pinking and get a solid reading for the advance at idle and at 4000 rpm with the vacuum off. Only my opinion and I am not criticizing anyone else's opinion, but the physics and experience tells me that it makes sense!
As regards the starting .. I agree with almost everyone (shock horror ) The starters do suffer badly from overheating and get worse with time. The heat soak in the engine can cause fuel to vaporize in the carb which makes hot starting tricky. The starting advance can cause problems as well. If I were asked to place a bet I would start with the starter and ground connections. Try putting an air line on the starter when the problem occurs to cool it down quickly then try it again and see if it spins faster.