P2 Problems - pinking

I have a tuned P2 as follows:

Cut Crank, Opened inlet, shortened barrel, skimmed head, opened ports, crown of piston ground all done professionally about 8 yrs ago. Runs on std 24mm carb, 118 main jet and autolube - timing set to 20 degs.

It ran well for the last 8 yrs on a simonini exhaust with no probs, the exhaust fell to bits and I replaced it with a RZ evo RHS in stainless.

I upjetted the carb (122) to suit and the plug is a nice golden brown, it ran ok low to mid revs but pinks when i reach 70+. Tried retarding ignition to 18, ran better but still pinks, retarded further till its up against the stops and it still pinks.

Any suggestions would be gratefully received - could i damage it running it this far retaded?

Quick response appreciated - off to iow tmrw!

I have tried a 125 and it runs way too rich, it pulls really well all the way through the rev range but (pinks?) vibrates really badly at 70+.

I did wonder if the compression was too high but it ran really well with no probs with Simonini - may try changing the head for a standard one just to rule this out.

Many thanks for your suggestion

I had a similar set-up but with a Scorpian exhaust and T5 carb and was
experiencing bad pinking at high revs in 4th, I slotted the stator an
extra 3-4mm and it cured my pinking problems.



Not sure what to advise with regards the vibration though.  


Thanks Jonny

Any advice from others with regards to vibration would be appreciated.

RJ

TRY 125? cut cranks tend to need a big main, worth a try!(does it go when pulling choke out, when on full throttle?)
Also try running without petrol cap on to make sure its not restricting flow
might need a gasket on the head
none of this might help! but its all I think of!
good luck

Problem solved as follows:

Carb cleaned thoroughly, new carb box gasket, 120 Main jet, air screw 2 1/2 times, timing set to 18 degs, may need a fuel pump fitting now though![:D]

try 125 or 128 main jet with a stainless pipe and it must be set upwhile the engine and pipe are hot as the characteristics change as the pipe gets hot, also swing timing round to 16 btdc, if it still pinks youve got an air leak somewhere

regards

the doctor

Hi Everyone...

I have the same problem with similar set-up.

Malossi 210, Racing crank, HP4, RZ RH Pipe (Black), 24mm SI carb, Timing fully clockwise on Stator plate. Main jet 135 . 132 was slighly lean.

 Rode the scoot to Brighton for the Ace cafe run last Sunday and it pulled well through the gears. Same trouble though - at 70ish it pinks badly.. Ive had it before and holed pistons so i backed off straight away. I've been advised to slot the stator another 3 mmm to retard the timing even more. - Any comments please??

Also since fitting the RZ RH Ive got v bad vibration -  I've even fitted rubber grommits between the main engine mount and brackets but still the same.

Any advice on timing and how to stop the RZ vibating also appreciated.

RJ