Compression #^$@$&%*@$*($ !!!!!!

[tor*p*do]

So I buy a cheap compression gauge and confirmed it was accurate at work.
My '88 WR500 had both cylinders at 130 - 135. OK.
My '90 650 SN w/porting had 150-152. Good!
I put on the extension for the Kawi and then . . . .
My 750sx had 110 - 115. WTF??????? :frown:
Is the reading affected by the ES plug extension?
Is that why it is tough to start sometimes?
At what PSI do you rebuild the top end of a Kawi 750?

I will re-check with the engine hot, but dont expect much difference.

Thanks!

 

[Matt_E]

Seems stock Kawi motors run 120ish low compression. Is that right?

 

[sjetrider]

I thought Kawi's ran higher OEM compression, at least they do on the SXR like 170/175 OEM. I think the prob. may be the GA.

 

[Mark44]

So I buy a cheap compression gauge and confirmed it was accurate at work.
My '88 WR500 had both cylinders at 130 - 135. OK.
My '90 650 SN w/porting had 150-152. Good!
I put on the extension for the Kawi and then . . . .
My 750sx had 110 - 115. WTF??????? :frown:
Is the reading affected by the ES plug extension?
Is that why it is tough to start sometimes?
At what PSI do you rebuild the top end of a Kawi 750?

I will re-check with the engine hot, but dont expect much difference.

Thanks!

You don't you trade it in on a super jet. O was that not a quiz?

Mark44

 

[njfl]

So I buy a cheap compression gauge and confirmed it was accurate at work.

You didn't confirm it was accurate in the same way you used it (with the extension).

Reconfirm at work using the extension before you blindly go chasing problems.

 

[tor*p*do]

I have a SN and actually prefer it over a RN
The 750 is my sons toy
The adapter adds a couple cc's to the volume of the received but at ~370 ccs per cylinder the additional volume is less than 1% error.
Local shop said to check the reeds, but that makes no sense as the ports are closed during the compression cycle.
Anyone know what an old small pin 750 compression should be?

 

[Dustin Mustangs]

One ski or the other should be able to be safely tested both w/ and w/o the extension. Do both and see if there's a diff.

 

[tor*p*do]

So I got home, pulled off the ES adapter and tried that.
I now I get 115 - 125.
One time the PTO hole almost hit 130.
I will take it out tomorrow and have my son run it if he is around.
Also will try the comp check warm.
Piston wash was a little lean so I richened her up a bit.

Time to start scouting 750s, dont want the downtime of a rebuild. :banghead:

 

[pyro723]

By any chance is it one of them cheap compression gauges off ebay? I think there like 30 bucks. :banghead:

 

[tor*p*do]

By any chance is it one of them cheap compression gauges off ebay? I think there like 30 bucks. :banghead:

Nope, Harbor Freight for $29!

Then verified on a $5000 NIST traceable calibration setup at work (I work in high tech semiconductor manufacturing).

Surprisingly, it was right on the money!

 

[pyro723]

Oh ok just checking. I bought one of them cheap ones on flea bay. It tested at 150 on my ski. Then when I checked it with a snap-on gauge it came out to 190. :bigeyes:

 

[sjetrider]

Oh ok just checking. I bought one of them cheap ones on flea bay. It tested at 150 on my ski. Then when I checked it with a snap-on gauge it came out to 190. :bigeyes:

I bought that POS off ebay to, the guy knows there junk because when I emailed him and told him I would posted bad feedback he sent my $$$ in 10 mins. flat. LOL

 

[pyro723]

I bought that POS off ebay to, the guy knows there junk because when I emailed him and told him I would posted bad feedback he sent my $$$ in 10 mins. flat. LOL

I should have done that. I did not even think about it I was so pi$$ed off. :banghead: