Hitchcocks Forum

Good evening to all aficionados. Since it’s my first post let me introduce myself. I am almost sixty, living in Poland and tinkering with classic or simply old vehicles since my teen years. Enough said my 1934 NSU 500 bike has been with me since high school.
Anyhow for whatever reason I’ve got myself Royal Enfield. I guess for a while I will be frequent customer here.

My question for a start, what is the acceptable piston pressure in twin 700. I have measured 7 bar on each cylinder cold and hot. It’s same on both which is good but according to compression ratio is should be in 10-11 bar region (compression pressure in bar = compression ratio x 1,25).

What is your experience? Or perhaps listed compression ratio of 8,5 is just wishful thinking.

In my experience, enfields run on wishful thinking.

I'd say if it is running well, pulling properly and not burning loads of oil, it's good. What would be more of a worry would be if the two sides were significantly different.

I was always told cylinder compression readings in and of themselves are relatively meaningless except compared to previous readings on the same motor. So if you are keeping a log of the compression readings and it's dropped significantly between services, you may have a problem.

Hi, during its production the Connie had different compression ratios depending on the spec for that year , so unless you know what pistons are fitted its rather academic. Vince

Measuring cylinder pressure cannot give you the compression ratio, only the cylinder pressure, which could become higher or lower just depending on valve timing and cam profile, before anything else is taken into consideration. I have probably used a compression tester less than half a dozen times in my entire life, tbh.