Cylinder Heads

[St George]

What is the basic difference between a 225 and standard 200cc SIL head. Is the combustion chamber smaller on the 200cc or bigger. I have just fitted a new 200 head from AF and don't seem to have the same power or revs. Cheers.

[Knowledge]

Have you fitted a new 200 head to a 225 (70mm bore)?

[St George]

No I have a Yammy 60 mm con rod, AF crank and a 3 mm spacer and cut down piston. I think they call it a stroker. The heads looked the same. I might just advertise for a bog standard 200 engine. Just want to plod about at 55 mph. Shame it's just run in.

[Knowledge]

You are describing a good selection of parts there George, but the tone of your reply is that you're a bit disappointed.

What problems are you experiencing? Why are you looking at the cylinder head? What barrel and bore are you currently running?

With a bit more info, we might be able to offer some useful advice.

[St George]

Standard size barrel which has been nicely ported to stage 4. Piston is new and cut down on inlet. Just don't rev or pull that well in 4th gear. May put the 48 mm AF Clubman back on despite the noise. All input welcome. The plug is the right colour. I know that this engine can push out the BHP. Thanks.

[Scooterlam]

Sounds like a possible gearing issue.
What pipe are you using at present.

[CHRIS in MARGATE]

What pipe and gearbox ?

[St George]

Hi Chris, How are you mate. I think it is the bog standard Sil 200. It used to fly with a 30 delly and JL 4. I used to have a standard GP 200 and that was quick ? My current exhaust is a new GP 200 system I bought from AF and the carb is a new Jetex 22 SH. I have jetted it up and down in all departments. I will probably SORN the old girl and play with it over winter. Thanks for the reply Chris.

Colin