TS185 ER compression ratio

**jcarlin123** · #1 10 Mar 2009

Hello Hubbers,

I have a question about the compression ratio on my 1982 ts185. Stock it is 6.2:1. If atmospheric pressure is approx 14.7, i should expect to receive approx 91psi from a cylinder compression test, right?

When i test it though, i actually get 125psi. I've tested the compression gauge on an air compressor (it monitors the pressure leaving the tank), and it appears to be reading accurately. That would suggest that i have a compression ratio of approx 8.5:1.

Am i calculating this correctly, or am i missing out on something (a brain perhaps

)

Cheers, John.

**Nigel Marx** · #2 11 Mar 2009

That's a good question John. I'm going to cross post this on another forum and see if I can get any answers for you.

regards

Nigel in NZ

**jcarlin123** · #3 13 Mar 2009

Thanks Nigel

**EAnchak** · #4 24 Apr 2009

If its any help, my 74 ts185 gets 122 PSI on the compression tester, so it would seem normal to me.

As for the ratios, I haven't a clue.

Ed

**jcarlin123** · #5 24 Apr 2009

Yeah, it sounds like 120-130psi is a normal sort of reading. Thanks.

**AliBaba** · #6 24 Apr 2009

Calculate compression:
Compression=P0*C^^1.4
P0=Pressure at TDC (14.7 PSI)
C=Compression
1.4=Ratio for air

Your bike
C= 14.7 PSI* 6.2^^1.4= 189 PSI

But you will never get that high, parts of the stroke doesn't contribute to compression.

**jcarlin123** · #7 24 Apr 2009

Thanks AliBaba! There was more to it than I thought. It's reassuring to know that my engine hasn't been 'stroked' - if it were I'd be in all sorts of trouble with timing, jetting, lubrication etc. Thanks for the handy info!

**TS185** · #8 25 Jul 2009

Well im gettin 140 psi out of my 84 TS 185
John