Survey Viper Compression

Automed

Automed

New member
Joined
Oct 18, 2004
Messages
101
Location
Edmonton, Alberta
Hey all you Viper guys I need some help on Viper engine compression.

Can you tell me what the compression is on your viper!

Mine is 100psi (pto) 121psi (center) 119psi (mag) sled has 350miles
 
I am using Megapower Heads with SRX domes mainly for the cooling benefits, running 2 .010 Cometic head gaskets so compression is still kinda mild at 120/125 on all 3..
 
120, 143, 143, Two layers removed out of the head gasket. Measured on a cold engine at WOT. Stock head gasket, was 110, 125, 125.
 
Took my sled back to the dealer and they said there is nothing wrong with my compression.

They tested a brand new 2004 viper mountain and got 120/130/130
My compression is 100/120/120 they indicated on the invoice "compression is within 10% and this is acceptable"

What bites my *** is I've only got warranty till Jan 19/05 and the sled only has 400 miles on it.

Not to mention that a new sleds compression should go up after break in not down...Right?!?

Does anybody know how I can contact Yamaha motor company and talk with them directly? Like their customer service department or something...
 
when checking compression if you use a guage with a hose on it you will see 10-15lbs different reading compaired to a screw in short guage. with a long guage the volume in the hose is added to the combustion chamber. so when you see someone giving a measurment ask what kinda guage they use to get the reading.
 
My dealer must be using the same gauge with the hose as I have because we both came up with the same compression amounts everytime we did the tests. So I would assume that my dealer also used the same gauge with the hose to test the new viper's compression...
 
This hole thing is really starting to piss me off everybody here seems to have better compression than me with only 400 miles on my sled.

And my dealer wont do a thing about it under warranty.

Come on Yamaha what's up with this...
 
Automed, you think your pissed, I have 02 viper with megapower heads and my compression is low. Gary at maxx perf says comp should be 135 and mine is 125,125, 123 with .051-.053 squish. I have more invested in mine and have no availabilty to different domes that will correct my problem. Maybe race domes cut but that could get expensive. Greg
 
why all the bother over compression? you should be more concerned that all three cylinders are within 10 lbs of each other...ridin a sled with 135lbs compression vs one with 125lbs compression would hardly be noticeable...if your that concerned try this...take your test with the cylinder dry then put in 1/2 teaspoon of oil...any difference?
 
Oldcat, I want to boost my compression to 140-145 and your saying that I won't gain much, I think differently.
 
Will higher compression always be faster?

The reason I ask is my buddy has a Pro-X 600 with a set LRM Hicomp cheater heads, We have had the heads on the sled a half a dozen times & the Pro-X is always quicker when tested against a test mule 600 for say 600' vers the stock heads but the lower compression stock heads run better on topend than with the Cheaters on, Its like the sled will squirt out 600' quicker than chit & then quit pulling like it hits a wall. It's got us stumped!
 
yamaviperGS30 said:
I want to boost my compression to 140-145 /QUOTE]

One of the tricks by Rotax buddys used back when MSDRA was worth running was to run a .010 over ring on a stock piston & file the endgap down to bump compression. Not recomended on a trail sled though.
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