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View Full Version : i think my compression tester is lieing to me


troy
06-10-2007, 06:55 PM
Said in one other post I made about 2 days ago I was having problems starting my Honda 200ES. And when I would get it to start it ran badly. And a 5 year could pull it over:lol: . I did the compression test heres the results..

With no oil in the cylinder (tested the way she stopped):

- 60psi closed throttle
- 120psi WOT

With oil in the the cylinder (added by me)
-90psi closed throttle
120psi WOT


Now of course with those results I was not happy as most of you wouldn't be. So off with the head and wall and away I went. I replaced the rings with newer ones I bought for a older projected the ended up cancelled, and (don't yell at me) reused the old gaskets of course after cleaning them up and inspected them closely. I clean up the head and wall (where the two meet) and put it all back together. Set the timing which may or may not be right. I match the 0 of the cam sprocket to the top of the valve head, and the T on the fly wheel was showing dead in the middle of the timing window. NOW where I think the tester is lying. When I did the test heres the results.

120 psi WOT.....BUT the bike is ten times harder to pull over then before.

So any ideas what’s going on? I haven't got the bike completely together because it was getting late and work calls for me tomorrow.

thanks
i58829
06-10-2007, 09:12 PM
If you're a tooth or two retarted on one or another the fire will be late enough that it will combust as the piston starts to return to the top causing it to be harder to pull. On a car this would be the 'kicking' the starter thats often refered to when trying to set time the 'quick' way...
troy
06-10-2007, 09:35 PM
If you're a tooth or two retarted on one or another the fire will be late enough that it will combust as the piston starts to return to the top causing it to be harder to pull. On a car this would be the 'kicking' the starter thats often refered to when trying to set time the 'quick' way...

LOL....heres the thing. I just pulled it over, there no cdi or any ignition setup on it yet. Just the carb and exhaust and spark plug with nothing hooked up to it
i58829
06-10-2007, 09:39 PM
Well it could be way out of time, a V8 will still act the same way because the compression is in the cyl. and will be trapped there due to bad timing whether its firing or not. If the air is getting compressed by the piston and the valves aren't open when they need to be the pressure will be felt by the starter (your arm in this case). Try it without the plug and see what happens...
troy
06-10-2007, 09:43 PM
see thats the thing every thing match's the service manual spec's. T in the timing window and 0 mark on the cam sproket at the top. but like you said and i did notice with my ERN 1 tooth makes for a problem
Erics350x
06-10-2007, 11:42 PM
You should check compression on a warm engine otherwise your #'s will be low. And crank it over a few times.
Rustytinhorn
06-11-2007, 01:19 AM
MY '81 ATC200 (185) has 120psi with WOT. I cant remember if it was warmed up or not though, I think it was. However, I am 5280 feet above sea level and my bike smokes quite a bit.
It says you should have you bike at an operating temperature to get an accurate compression reading. This is becuase when hot, the rings will expand and create a tighter seal. 120psi is enough for a bike to run on. You should be fine with this compression.
cr480r
06-11-2007, 03:38 AM
120 psi WOT.....BUT the bike is ten times harder to pull over then before.

So any ideas what’s going on?

You may have the exact same ring seal as before.... and the extra drag you feel is just the added ring tension from the newer rings.... But most likely your guage just has a bad valve.... that can only trap 120 psi... most testers just use a standard schrader valve core... a simple fix...