Compression test and Leak Down Test ?'s

[Eddiesanders250]

First I just did a compression test on my R and came to about 135psi. I am running the thick (stock type i think) head gasket. The one with 3 metal plates two thin one thick. Anyway I was wondering if the compression is too low. And if it is what to do.

Second i did a leak down test and lost about 3psi in ten minutes after pressurizing the motor to 10psi. Is that ok?

[norcalduner]

This might help.

http://www.duncanracing.com/techfaq/Tech_2-stroke-pressure-testing.phtml

[C-LEIGH RACING]

When you presure tested, did you spray soap water around the gaskets & intake to find the leak.
In the old days, kart engine builders would pump the engine up & put the whole engine under water, a leak would show up real quick if it had one.
Neil

[Aceman]

Originally posted by Eddiesanders250
Second i did a leak down test and lost about 3psi in ten minutes after pressurizing the motor to 10psi. Is that ok?

I wouldn't be happy with that.

Get out the soapy water sprayer and check your leakdown setup first to make sure you're not causing the leak. After that start spraying down the whole engine. When mine dropped pressure, it was a small base gasket leak and an intake leak. Had to live with the base gasket leak(I'm not tearing the cylinder off!) but orange hi-temp silicone fixed the reed gasket leaks. I think it only dropped half a pound or so when I was done.

[Eddiesanders250]

I was deffinately going to look more into the air leaking out and trying to find a leak. I think i might try submerging the whole motor. ( Also my exhuast block off may not have worked. going to do that a better way too).

No one answered weather or not 135psi is too low for my compression. Ive tried searching for this but the search does not allow the word low to be entered. So help on this would be appreciated.

[st8jacket]

135lbs. is an ok number for a stock engine..If your engine was a built engine,I would look into a top end..But for a stocker 100-110 is top end time..You did hold the throttle wide open when kicking it right??

[Eddiesanders250]

Ya i had it wide open.


Also i believe i may have found the leak. I submerged the whole motor and the only place i could find bubbles was from the two wires coming from the stator. I pulled the stator cover off and there was a long bolt that was broken that holds the balancing holder bearing in place. i dont know what to do now. The bolt is broken way inside the case.
Ive had a lot of problems with this motor. Does anyone think this may be why?

[Rich250RRacer]

Originally posted by st8jacket
135lbs. is an ok number for a stock engine..If your engine was a built engine,I would look into a top end..But for a stocker 100-110 is top end time..You did hold the throttle wide open when kicking it right??

175 is factory spec, anything more than 10% under means it's time for a rebuild. 135 is more than 20% down.

[trx250rider]

Originally posted by Rich250RRacer
175 is factory spec, anything more than 10% under means it's time for a rebuild. 135 is more than 20% down.

wow...i was thinking more like 150psi - 160psi on a stocker...but even then 135 psi is a little low..

[86 Quad R]

at this point with the longer bolt being broken, the leak could be coming from a number of places to include the stator side seal. i personally preferr to do a leakdown test with both staor and clutch cover removed. that way i have a visual of ALL potential leak spots.

depending on the year, 140 to 160 psi is about average for stock compression. use a common sense approach and inspect the piston, rings and cylinder walls for wear. :cool:

[st8jacket]

180 psi is pushing the limits towards race fuel..Factory honda wouldnt run that high of compression stock..Messing with base gasket and head gasket thickness could possibly bump it up that much...

Do you have a pick of your leak down plugs? I was gonna make some over the winter for a cr80..