How do i convert compression ratio to puods of compression?

[Hoosier_Daddy]

I can't find how many pounds of compression my engines are supposed to have in my Tecate or 350X repair manuals. I can find compression ratios but that means nothing when i do a compression check and it reads in lb/ft. How do i know how many pounds of compression my bikes are supposes to have? What's low? What high, etc?

[Dirtcrasher]

?? AS far as the 350X it gives a PSI value and says it should be within 10% I believe.............

Or I'm smokin crack :D

Thats the service manual, not Clymer or Haynes..............

[Hoosier_Daddy]

?? AS far as the 350X it gives a PSI value and says it should be within 10% I believe.............

Or I'm smokin crack :D

Thats the service manual, not Clymer or Haynes..............I'll recheck my 350X repair manual. I may be looking in the wrong place for it.

The Tecate manual doesn't say jack. Apparently that info is suppossed to be memorized my the mechanics of the day? I might just be looking in the wrong section.


I have found that these manuals are like grocery stores. When you're looking for refried beans, you won't find them with the canned beans and vegetables. You have to go to the Mexican isle for them. know what I mean?

[Hoosier_Daddy]

What else kinda cracks me up is, I've seen many threads asking how many lbs of compression a certain engine should have and i have never seen an answer. Nobody seems to know. Even if you do a search something like "how much compressiojn should a 350x have" the results come up, "no thread found". Same if you words it with tecate. It's mind boggling haha

[fire1]

my 350x service manual say 178 psi + or - 14.2 PSI

[JohnR.]

2 things need to be mentioned here.

1. There is no way to correlate compression ration to a compression number in PSI. The camshaft (port size and timing on a 2 stroke), carb, exhaust, and other things will effect the compression gauge readings so you cannot calculate one from the other.

2. Since the 350X has a compression release attached to the kickstarter you will need to disconnect it before you can get an accurate reading on your compression test gauge.

John

[Dirtcrasher]

Cylinder compression 178 PSI plus or minus 14.2 PSI

In the BIBLE....or known as the HONDA 350X Service Manual.......

I'm pretty sure that I also posted in your 176 Topics (:lol:) that it will run (maybe not so well) with about 120PSI, and Twilight said about 100PSI - I think thats somewhere in - DA BALLPARK!!

WHAT-ZA-MATTA-U????!!!!

[ThinktwiceZ71]

mine ran with 30 !!! lol , but BARELY!! sure as .... wouldn't move tho.

[Hoosier_Daddy]

I haven't checked the compression in my 350x. I didn't have the 12 mm adapter before i tore it down. I found an adapter now though. it should have good compression when i get it rebuilt and back together though. My tecate has 160 lbs. i'm not sure if that's on the low side or not. The T3 is getting rebuilt anyway so it doesn't matter.

[fabiodriven]

My tecate has 160 lbs. .

That doesn't sound bad to me. Obviously you're holding the throttle open when you check it?

[Gag_Halfront]

1 bar at STP is about 14.5 PSI (not lb/ft that's torque)

10:1 compression, therefore, would be 145 PSI. That ignores only about a million variables (ambient temperature, barometric pressure, humidity, etc) , but is a good yardstick so long as you leave wide margins. As indicated earlier in this thread, dynamic compression is almost always higher than static (listed) so if it was me, and my bike was supposed to be 10:1, I'd go ahead and assume that I should see something around 160 PSI or better but I wouldn't tear the motor down for anything over 130.

Of if I was being lazy I'd just go look at http://www.3wheelerworld.com/1986HondaSpecpage.shtml and see that my tree-fiddy should sit around 178 PSI. :-D