Compression rating

[nudedaytona]

I just did a compression test on my Aprilia RS250.

The top left cylinder read 122-125 psi dry after 4 kicks. The bottom right cylinder was 118-120 dry after 4 kicks.

Is this good, or OK? Does anyone know what the reading should be? I just replated the bottom right cylinder and put in a new piston and rings. Shortly after doing that, I was cruising along the northern motorway at about 7,000rpm, just thinking of changing up, when the motor lost power and felt like it was siezing up.

Then, the power came back straight away and I was off again. It's been riding fine since. I thought I'd do the compression test to see if there was any problems. I don't really want to open up engine again at moment, especially as its been going fine. I haven't been revving it hard or trying to fang it as I've been warming it in.

[The Pastor]

aparantly with the 2 strokes you cant cruise at a constant rpm with them, you have to to be working them up to redline all the time etc.

What does your manual say the compression should be?

[nudedaytona]

Can't find it. I've heard that about the rpm but that's overplayed I think. And even on the motorway its not like I was at a constant rpm for ages, I was just about to shift up.

I thought someone would know about compression tests?

Anyone know what the compression should be on a nissan primera? 1.8L?

[Ixion]

120 odd on a two smoker is excellent. 100 + is all good, under 70 means time for refurbishment. Ideally not more than 10% variation between cylinders, though that's often a bit of an ideal world especially on a multi. (this is for road machines, race bike is probably another matter )

[nudedaytona]

120 odd on a two smoker is excellent. 100 + is all good, under 70 means time for refurbishment. Ideally not more than 10% variation between cylinders, though that's often a bit of an ideal world especially on a multi. (this is for road machines, race bike is probably another matter )

That's a relief, gives me a bit of confidence when I'm riding it. I haven't been riding all that much so have lost a bit of feel, and always worrying whether its going to blow up again.

I didn't really want to open it up unless it was necessary because there goes $100 worth of gaskets every time I do that.

[Mr. Peanut]

If you're constantly worrying about your engine, get something cheaper, and enjoy riding again. Like you did on your first bike :)

[nudedaytona]

It is my first bike! I'm sweet, wouldn't sell it to you for a million$

[Mr. Peanut]

Good to hear. Stop worrying :niceone:

[gixxer-king]

readings seems good. nice and high. its the variation more than anything. why gaskets upon wide open throttle? should be able to take a fair bit before damage occurs, good old 2 smokers.

[more_fasterer]

The difference between the two isn't enough to worry about.



Anyone know what the compression should be on a nissan primera? 1.8L?

160-170

[nudedaytona]

The difference between the two isn't enough to worry about.



160-170

It came out at 165psi. The timing chain is stretched, but it looks like the enging itself is ok. I asked because a timing chain kit and a used engine were about the same price.

[TygerTung]

readings seems good. nice and high. its the variation more than anything. why gaskets upon wide open throttle? should be able to take a fair bit before damage occurs, good old 2 smokers.

I think he mean open up the motor to do inspections.