P200 Cylinder Head

Does anybody know the difference between the two cylinder heads listed for the PX200 on page 83 of the SIP Catalogue.

It describes one as being ‚Centred‘, I think this means that the combustion chamber and squish area have been machined?

Does anybody know, I do not want to order one if it is something different?

I am having problems with pinking above 60mph, the engine is standard P200 apart from a SIP Performance pipe, I have tried jetting, timing and using super unleaded but it still does it! I think the cylinder head needs modifying.

Any ideas???
[:drink:]

I have just changed the cylinder head for one of the latest PX 200 type (has raised bosses around stud holes).

The latest PX200’s have a lower compression ratio (probably because of the crap petrol we get now!) And the pinking appears to have stopped even in this heatwave.

I am running 19 Degrees ignition timing and a 130 main jet (may try a smaller one as it appears to be running really rich now).

Hope this helps!

[I)]

[:angry:] Hi there I also have a standard P200 but fitted with a Taffspeed Pipe
and I cannot stop it pinking I have tryed the timeing jetting even put a T5 carb on because it has a richer slide but nothing will stop its tinkleing I thought it could be the stand spring but I will try the pipe holding springs, if it is that what can I do to put it right? any body got any ideas.[:look:]

I think your scooter should already have the later type of head on.

Have you checked your timing with a strobe light as the standard marks are not always accurate, a couple of degrees can make all the difference.

Good luck!
[:drink:]

[:bounce:] Vespandy
thanks for the post, the pinking starts between half and three quarter revs I am not running an air filter on my standard T5 carb with standard air jet 160 BE3 atomiser 138 Main jet and 50/100 pilot jet. the pinking stops as soon as I shut the throttle off. I have done a plug test and it looks good not too wea. The timing is set to 19 Deg BTDC. I have also tryed useing Castrol Laed additive with octane boost but no joy.
What do you think?[:rotate:]

Have a look at the spring on the down pipe and exhaust which holds them together as it can rattle at high revs

[:bounce:] Hi Stringy
I’ve got a 2001 PX200 electric start do you know if it will have the type of head that you have just fitted or is there a newer one I can try?
Thanks[:dance1:]

the only way your’e going to stop the pinking is by changing your pipe, the SIP is just too revvy for a standard barrel and piston which is designed to pull at low revs. a mate of mine had the same problem with a Taffy pipe, he put a Sito Plus on and now it pulls through every gear and no pinking cos it’s designed to work closer to the original revs. If you are going to spend money on a machined head my advice would be to get it from Taffspeed or PM.
[:dance1:]

VespaPaulo2:

You have tried the most obvious options:

Where is the pinking in telation to rpm…maximum, somewhere in the middle, all over the rpm range, only when throttling off from a full throttle run?

You can adjust the carb further maybe to compensate…answers to the above may help establish where it needs adjusting.

Drilling out a hole in the heart shaped recess in the bottom of your air filter allows more air in, combine this with the biggest air corrector (smaller number ?) and main jet (bigger number) for more fuel to keep the mix correct and youget more cold air and petrol i the cylinder = better cooling = reduced pre-ignition (pinking)…you have to be careful up-jetting correctly or too much air to petrol will make matters worse. You may need to adjust the jetting several times to get this right.

Try retarding the timing a little as a last resort (ie. if at 21 degrees move to 20)

Before attempting any of the above, try running a colder plug (NGK BE8 or BE9) and make sure you are jetted rich enough by doing a plug-chop to check the plug colour.