Compression Test ?

[zewcrew]

I'm about to do a compression test on a 99 CR125 I purchased recently. The bike runs awesome, but I was told the piston/rings have never been changed, there just weren't many hours on the bike. So, I wanted to make a comparison between old/new before changing it out.

My question is this... I know the regular process of performing the test, open throttle with kill switch, and kick till the pressure reading tops out (preferably on a warm engine). Does anyone actually remove the air filter too? I wouldn't think it would be that necessary, but the compression tester manual directs people to do that.

and...
separate question, but thoughts?
Is anyone rubbing down the air boot itself with some filter oil just as an extra preventative measure against sand getting past the filter?

Thanks!!

 

[Oldman125]

I'm about to do a compression test on a 99 CR125 I purchased recently. The bike runs awesome, but I was told the piston/rings have never been changed, there just weren't many hours on the bike. So, I wanted to make a comparison between old/new before changing it out.

My question is this... I know the regular process of performing the test, open throttle with kill switch, and kick till the pressure reading tops out (preferably on a warm engine). Does anyone actually remove the air filter too? I wouldn't think it would be that necessary, but the compression tester manual directs people to do that.

Kick it hard, it'll tell you what you need to know.

and...
separate question, but thoughts?
Is anyone rubbing down the air boot itself with some filter oil just as an extra preventative measure against sand getting past the filter?

Thanks!!

Wouldn't Filter Skins be much less messy? Just a thought.

 

[biglou]

Is anyone rubbing down the air boot itself with some filter oil just as an extra preventative measure against sand getting past the filter?

Thanks!!

Don't do that! That oil will eventually work its way through the intake system and clog every possible jet and passage in your carb and you'll play hell getting things right again!

 

[zewcrew]

Don't do that! That oil will eventually work its way through the intake system and clog every possible jet and passage in your carb and you'll play hell getting things right again!

I wasn't thinking that much oil, but rub it on and wipe off the excess just to make it tacky. I definitely see your point about having the oil pulled in to clog the carb.

 

[biglou]

If everything is sealed properly, I think that is unnecessary.

Also, I've read of over-oiled filters letting enough oil into the intake and beyond to cause problems with clogging the carb. I say, clean the filter often, and make sure everythings sealed up, and it should be good to go.

 

[darringer]

I'll bet if you look close enough at your intake boot, it already has a very light film of filter oil that has been drawn through the filter. As biglou stated... it's overkill, and will probably do more harm than good.

No need to remove the filter for compression testing. And fwiw, I have done compression checks back-to-back on a cold engine and then warming it up and have found very little difference in the readings.

 

[zewcrew]

Thanks for the posts guys. I got 143psi on the old piston/rings cold which doesn't seem bad. I'm planning on doing the disassembly tonight or tomorrow morning (depending on how cooperative the wife and kids are) to see what everything looks like.