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Discussion Starter · #1 ·
If you've installed Cudney pistons, can you post your compression
with the Doo pistons when the sled was new and with the Cudney pistons new?

For example when my sled was new with doo pistons and rings compression was 137 ish. With the Cudney's using the same guage, its 150-152 using 5 good pulls on a cold motor.

I want to see if there is a trend that the Cudney's are giving you higher compression. Thus if they are, there may be more of a concern to run good gas with Cudney's or jet a little richer. I'm heading to Canada in two weeks and will
probably jet up from 380's to 390's to be safe anyways.
 

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smgunning said:
If you've installed Cudney pistons, can you post your compression
with the Doo pistons when the sled was new and with the Cudney pistons new?

For example when my sled was new with doo pistons and rings compression was 137 ish. With the Cudney's using the same guage, its 150-152 using 5 good pulls on a cold motor.

I want to see if there is a trend that the Cudney's are giving you higher compression. Thus if they are, there may be more of a concern to run good gas with Cudney's or jet a little richer. I'm heading to Canada in two weeks and will
probably jet up from 380's to 390's to be safe anyways.
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My BM has the stock pistons, and the compression shows 150 lbs. I've run the stock 380 mains to way below zero, I think you'll be fine
 

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Discussion Starter · #3 ·
You can't really make that statement. My guage on your sled could show
135 which could be the same as my sled when it was stock. Its a relative
term.

I'm really looking to see if Cudney's increase compression over stock
pistons & rings. Then I can decide if the jetting is safe.

I do agree with you, the sled with 380s is safe with stock pistons. But the
plugs are a light tan brown which is much different than what Doo usually
puts in for stock jetting. You know those black oily plugs you get with stock jetting!
 

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TT670 said:
Youre Ok, tan to almost white plugs are the norm the last couple years. On my 600HO cudneys pistons picked up about 8 lbs.
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Tan or white plugs? I keep hearing that but my Power TEK's plugs have went from Tan to a little black...lol...I burn a lot of oil...about 1.5 litres to every tank of fuel. My pump is in spec.
 

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Discussion Starter · #9 ·
Bill, I understand regarding the pistons, but I include your rings when I'm mentioning pistons. Sorry for the confusion.

11c, I was thinking about that on the way home. I thought stock was a 5 holer but never checked for sure... Can you tell me the 6 holer was the stock base gasket? I did install a 5 holer and that would explain everything.
 

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loots-42 said:
Yes, does anyone know for sure what the stock base gasket is for an 03 800?
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My guess is that there is not a stock gasket persay.. some might come with a 5 hole and some with a 6 or even more..

I suspect like automotive engines that they air gage the piston heights from wrist pin hole.. and they air guage the heights of the cylinders... and air guage the stroke.. and they do a selective gasket pick based on a machine stack up of the numbers...

And like all things .. they can make mistakes and put the wrong part in.. Thus you should always measure your squish before you disassemble and then measure it again with the new componets.. making sure they did it right to begin with.. and making sure you do it right when you put it back together..

Saying that it had a 6 hole and going back with a 6 or a 5 hole based on the original number of holes is not a good idea...

New pistons may not be exactly the same height.. and particularly if you had a cylinder fixed and renicked.. they may no longer be the same height for a number of reasons. But lots of us are in a hurry and slap them back together with out measuring anything.. some are lucky and some burn down again..

Just my two cents........ education can be costly!

I will now get off the soap box.. for the day.. good night..
 
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