Author Topic: cylinder compression  (Read 309 times)

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snowcross

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cylinder compression
« on: February 11, 2018, 08:18:34 PM »
Hi,

just wondering what the proper cylinder compression should be ?.....I used after market pitons with single ring. I'm only getting 116-120 lbs ... 

any suggestion would be appreciated.

mswyka

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Re: cylinder compression
« Reply #1 on: February 11, 2018, 08:40:31 PM »
I think that compression will vary by the gauge.  Our experience with these sleds, and our gauge, has seen compression between 120 and 160.  When we have found compression around 120 the sleds are pretty hard to start.
Intruders:  1978, 1979, 1980, 1981 Custom
Invaders:  1979 340, 1980 440, 1980 440 TOC Custom
Projects:  1979 Invader 340, 1980 Invader 340, 1979 Intruder 440, 1982 Intruder 440, 1980 Drifter 340 F/C, 1972 Panther 303 ...

Interceptor398

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Re: cylinder compression
« Reply #2 on: February 12, 2018, 07:53:47 AM »
Has the engine been run enough to seat the rings?

gixxer6

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Re: cylinder compression
« Reply #3 on: February 12, 2018, 08:11:44 AM »
Do you have a history with the tester?  I just have a cheapo tester when I first got it, it seemed to read correctly.  After a few years it seems to read about 10psi low. 

I say anything over 110 is good.  The FSM says the minimum is 90psi... 

kawhead

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Re: cylinder compression
« Reply #4 on: February 12, 2018, 08:28:25 AM »
your compression sounds fine

snowcross

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Re: cylinder compression
« Reply #5 on: February 12, 2018, 11:09:56 AM »
Thank you for the comments ..
now wondering where the problem is .....sadly the carbs (mikuni ) sat for the summer with untreated gas .....in the end the mains (350) were varnished and burned one piston...
when tested the other piston (stock pistons ) read around 130 psi . the burned one around 65psi  (snap on gauge)....
The cylinders were honed and new single ring pistons installed  (Image Enterprises).... at best now only  116- 120 psi. , starts extremely hard.
Thoughts? pistons or carb settings ? the carb settings worked fine until I  burned a pistons so I'm thinking its lack of compression ??

gixxer6

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Re: cylinder compression
« Reply #6 on: February 12, 2018, 11:26:08 AM »
Compression should go up slightly once the rings seat in.  From my experience 115 is plenty, I thing the issue is with the carbs. 

snowcross

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Re: cylinder compression
« Reply #7 on: February 12, 2018, 04:12:47 PM »
I want to agree but the carb settings worked fine before the mishap.... only thing that has changed is the pistons ...any concerns that the single ring piston can't produce enough compression ? ...my stock piston with 2 rings produced 130 psi.  could it be  because it has lower compression i need to adjust the carb setting ie pilot main ect. ?

Teherr

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Re: cylinder compression
« Reply #8 on: February 12, 2018, 07:39:00 PM »
I have a new but inexpensive tester, but I have 6 sleds and all but one is kawi.  they all test 130 to 150. 
2 440 Invaders
440 LTD Monohead
Liquifire
80' 4/6 
250 & 340 Enticers

kawhead

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Re: cylinder compression
« Reply #9 on: February 13, 2018, 10:13:39 AM »
I've never used a single ring piston in an invader,any one else?

gixxer6

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Re: cylinder compression
« Reply #10 on: February 13, 2018, 11:18:10 AM »
I assume he is talking about an Interceptor?  I have not tried the single ring pistons, but I know it is common to run the modified single ring jet ski pistons in the 550's. 

snowcross

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Re: cylinder compression
« Reply #11 on: February 13, 2018, 03:35:27 PM »
yes they are in the interceptor ....the pistons and ring set came from image enterprise ..........I tested my stock interceptor last night 132psi and 130 psi.
I'm staring to believe its the pistons and rings ? Has anyone else had luck with these aftermarkets?
 

gixxer6

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Re: cylinder compression
« Reply #12 on: February 14, 2018, 06:50:31 AM »
Stock chrome cylinders?  From what I hear the rings Image sells are made for steel sleeves or nicasil ONLY.  Trying to run chromed rings in a chromed bore will end in disaster very quickly. 

Interceptor398

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Re: cylinder compression
« Reply #13 on: February 14, 2018, 07:40:27 AM »
Stock chrome cylinders?  From what I hear the rings Image sells are made for steel sleeves or nicasil ONLY.  Trying to run chromed rings in a chromed bore will end in disaster very quickly.

True!!

snowcross

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Re: cylinder compression
« Reply #14 on: February 14, 2018, 11:42:46 AM »
well not really getting anywhere with this ...they are stock chrome  cylinders..image claims the ring set is compatible ..i think the answer is going back to stock piston and rings ....now to find them ?
anyone have a suggestion? is there another piston and ring set with 2 rings ....any other company?