Compression Testing

[Haydock2542]

Question for the tech bods out there. What is good compression PSI for a sport or Strada ?
My bikes have always run well but never been as quick as the performance figures and media would suggest. Carbs are balanced, mixture is good, valve clearance set, plug gaps set and the electronic ignition is original. The only thing I can think of now is the compression. Having tested both bikes compression I get readings between 130-135 PSI for both cylinders and with a drop of oil added it rises by approx 10 PSI. The local bike shop suggested anything over 120 PSI is good. Does anyone have a view as to what a good test reading might be.

[smotorboy]

Two Questions: Are you holding the throttle open when kicking over the motor, and do you continue to kick till the pressure stops going up on the gauge ?

I saw 175 psi on my stock 1985 K2...

Robert in California

[Haydock2542]

Hi Robert, yes throttle fully open and kick it hard about 6 times. Can't make it go any higher. I did see an old post stating 170 PSI although I don't know how achievable that it is normally. 175 looks good. Didn't mention the valve seats in the first post, its not many miles ago I had the heads off for a clean up and took time to grind the valves in.

Thanks for your reply.

Geoff

[mgelder]

My bikes have always run well but never been as quick as the performance figures and media would suggest.

I don't think *any* bikes have ever been as quick as the media of the 1970s and 1980s suggested.

If they run well, I wouldn't worry.

[mad muller]

you have to get the engine spinning to get the best out of them, plenty of revs and let them howl, If you sit on them in top gear doing 30mph it can feel a bit gutless unlike jap bikes of the era which were more forgiving ,I find fifth gear is the one to go for, 7 or 8 grand no probs and its a flyer, in fact it just keeps climbing up the rev band , for a push rod 350 there not bad I must admit it took me a while to get the hang of them, I had an 1957 enfield bullet now that was slow, as for compression test I use the tried and tested thumb over the plughole crude but effective. not so mad muller.

[Haydock2542]

Oh we can make it sing alright as you say 5th gear is favourite and they do rev cleanly into the red line. Will be at Cadwell again this year, will wave to you Martin as you glide past assuming you going again. I will be the one with my head on the tank. Priced pistons at NLM just as guide, Pistons + gaskets + the "dreaded VAT" your looking at around £250 + re-bore. Think I will make do for now.