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Post by bnz on May 2, 2007 9:41:04 GMT -5
Does anyone know the range of what it should be when checking?
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Post by wireburn on May 2, 2007 9:59:34 GMT -5
213 psi according to the Tank service manual.
-Mike
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Post by bnz on May 2, 2007 12:57:42 GMT -5
Thanks Mike!  |
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Post by bnz on May 2, 2007 15:23:11 GMT -5
Uh oh, just ran up to the local cycle shop to do a compression test on my scoot and it only read 100 psi.  Can someone verify for me whether or not it is supposed to be 213? If it is I may have to get the shop I bought it from to just send me a new engine, or go ahead and upgrade to the 59mm cylinder and piston.  |
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Post by 12string on May 2, 2007 16:07:51 GMT -5
That 213 sounds high. 120-150 psi is normal for most automotive purposes. The higher compression ratio the higher the compression test readings. 100 psi would be about right for an engine with a 8 to 1 compression ratio. your engine should run fine with that reading. It might down a little on power, but the valves may need adjusted to bring up the readings , valves that are too tight may bring down your readings.
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Post by bnz on May 2, 2007 20:32:12 GMT -5
Yeah, Stan at oregonvintage said the limits should be between 140 (normal on a warm engine) and 170 the high range. If a few drops of oil brings low compression up, there's a ring problem. Otherwise it's a valve problem. He really went o ut of his way to look it up for me. Karma points for him! |
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Post by randy on May 3, 2007 6:12:34 GMT -5
Make sure you hold the throttle in the wide open posiiton while cranking it over. I have seen guys do a compression check with the throttle in the idle positin and it doesn't get enough air in to compress thus it is not accurate. Also if the reading is low you can put some oil in the cylinder and see if the compression goes up. If it goes higher then you have bad rings if it stays about the same the problem is probably in the valves or head gasket.
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Post by wireburn on May 4, 2007 6:08:32 GMT -5
I thought it was high too. I thought maybe they inverted the numbers, but they also list a metric value of 15 which is equivalent to 213psi. It is strange that they would make that big an error in a factory service manual. It IS China, though.
Sorry if I gave bad info.
-Mike
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Post by randy on May 4, 2007 6:31:45 GMT -5
Mike I agree 213@ pounds of compression is an awful lot.
I would venture to GUESS that 125# would be with in specs. and 100# would be boarderline. with 213# I don't believe that you would be able to kick it over or for that matter the electric starter could spin it.
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Can someone verify for me whether or not it is supposed to be 213? 
