low compression

N

Naples

Location
georgia
135 in both cylinders. Got a hone and put new rings, same #'s. Got a used whole topend that had 150 - 150. Installed it, now 135-135. WTF?

Checked my compression gauge on my other ski and its 150-150 so i know the gauge isnt broke. All tests done with a brand new battery.

Lets here your suggestions. Thanks in advance.
 
steveyz250fpilot

steveyz250fpilot

Banned
Location
Huntsville, Alabama
Did you ever have numbers higher than 135? You said you got a new topend that had 150... that means it wasn't new, but in another set of jugs. Your porting in your cylinders can affect compression to the best of my knowledge.
 
Waternut

Waternut

Customizing addict
Location
Macon, GA
Since the numbers are dead even, I find it hard to believe that something is wrong with the engine internally. If porting is stock, the other thing it could be is a really thick head gasket. If the gasket is roughly 0.015" thicker than whatever stock is, it will cause the 15psi difference you're seeing. No idea what stock is for you though since you didn't say what ski it was.

I'm a firm believer in fixing before it quits running because it costs less that way so a 168/154 is un-rideable in my book. If you fix it now it's rings and hone with the possibility of new pistons. If you wait until it blows up, you need your cylinder bored, new pistons, new rings, and possibly a new head and crankshaft if you're really unlucky.
 
Talsivar

Talsivar

X-
Location
oregon
it's been that way for a year now so i'm not worried about it. i know i need to go to the next bore to fix it but i'm at 85.5 now with a max of 86. so until it drops so much that it won't fire it's not an issue. really i seriously doubt it would take out the head or anything. worst that will happen is the compression will drop more from the bore being worn and i will have to take it up to the last bore.
 
Mouthfulloflake

Mouthfulloflake

ISJWTA member #2
Location
NW Arkansas
Not in my book.

I had a 650 SJ, proteck head, and pipe, made GREAT power.

130 in one cylinder and 185 in the other.

most folks thought it was a 701, it pulled hard.

I ran it for like 4 seasons without ever taking the head off of it.

stone cold reliable.

I guess i could have torn it down and spent $$$ on it, but why?

it ran great!

I think too many people get bored and want to tinker, and watch the compression guage like a soap opera on TV.



jfw432 said:
I'm a firm believer in fixing before it quits running because it costs less that way so a 168/154 is un-rideable in my book. If you fix it now it's rings and hone with the possibility of new pistons. If you wait until it blows up, you need your cylinder bored, new pistons, new rings, and possibly a new head and crankshaft if you're really unlucky.
Click to expand...
 
N

Naples

Location
georgia
Mouthfulloflake said:
Not in my book.

I had a 650 SJ, proteck head, and pipe, made GREAT power.

130 in one cylinder and 185 in the other.

most folks thought it was a 701, it pulled hard.

I ran it for like 4 seasons without ever taking the head off of it.

stone cold reliable.

I guess i could have torn it down and spent $$$ on it, but why?

it ran great!

I think too many people get bored and want to tinker, and watch the compression guage like a soap opera on TV.
Click to expand...

Yeah but I just spent alot of money to upgrade to 701 rather than 650 and the difference is dissapointing.
 
Mouthfulloflake

Mouthfulloflake

ISJWTA member #2
Location
NW Arkansas
you are lacking something in your overall setup then.

I could tell the difference, granted its not a GIANT leap.

thats the sort of reason, im saying that I prefer not to throw tons of money at it ( unless its a known fact/upgrade)

Id rather spend $10 and be dissappointe, than spend $500 and be dissapointed.
 
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