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Cylinder compression

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Hunter
Nitrous Nuisance



Joined: 01 Mar 2002
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PostPosted: 18:11 - 13 Jul 2002    Post subject: Cylinder compression Reply with quote
Hey Guys

Have you tried testing the compression on your bikes? I have an NSR RK and get a reading of about 8 bar (approx 112 psi) which seems a little too low! Confused But the bike seems to run okayish and Its been like that since I bought it (have done 10000 miles). Wonder If I could get away with just changing the piston + rings?

Cheers for any help!
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Hunter
Nitrous Nuisance



Joined: 01 Mar 2002
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PostPosted: 17:31 - 15 Jul 2002    Post subject: Reply with quote
Nobody checked their pistons for compression rates? Confused

Just put all things back together again on my bike.. and its actually started the first time around.. heheh.. sorted!
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Robby
Dirty Old Man



Joined: 16 May 2002
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PostPosted: 17:46 - 15 Jul 2002    Post subject: Reply with quote
the nsr has a relatively low compression - they had it a while back in superbike with a 125 test, the NSR was about 8.4 and the RS was about 9.6 i think. which is part of whys RSs pop more.
your reading is fine, so dont open the engine up its an expensive process.
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Hunter
Nitrous Nuisance



Joined: 01 Mar 2002
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PostPosted: 18:06 - 15 Jul 2002    Post subject: Reply with quote
Cheers Robby for the response! I was a little concerned though cause the work shop manual says 10 bar (+- 2 bar), and mine was just 7.75 to 8 bar. hmmmm.. well it is an old engine (about 9 years old) and the mileage is 10000 miles!

Anyway.. I thought i'll keep the engine intact until something else crops up.

I was a little worried that too much piston slap can cause the nikasil plating to get wasted. Just don't have much experience with performance bikes or 2 strokes yet! Any ideas? :)
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 22:40 - 15 Jul 2002    Post subject: Reply with quote
robby wrote:
the nsr has a relatively low compression - they had it a while back in superbike with a 125 test, the NSR was about 8.4 and the RS was about 9.6 i think. which is part of whys RSs pop more.


Hi

Honda and Aprilia quote different types of compression ration. Honda quote an effective compression ratio (ie, using the cylinder volume after the ports are closed) while Aprilia quote a theoretical compression ratio (ie, using the full cylinder volume). You cannot compare the 2 directly

Basically the higher the compression the more power you produce, but go too high and you will get detonation, and to avoid this you need to run higher octane fuel or retard the ignition timing (which looses you power)

All the best

Keith
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