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Post by 90GTVert on Feb 20, 2012 23:16:13 GMT -5
When you look over that summary I posted (bottom Page 4), there is actually a lot of stuff that hasn't been addressed or at least if it was the results aren't clear to me.
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Post by Fox on Feb 20, 2012 23:17:18 GMT -5
Yeah I thought that he posted that it would run for a short time and then stop but I guess not.
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Post by 90GTVert on Feb 20, 2012 23:18:30 GMT -5
He did, he said he can't get it to run under 4000RPM though usually. Sorry I didn't include every detail in my summary, mainly tried to make a list for sctrdawg to go over and address. We can think ourselves to death, but it will get us nowhere if the OP doesn't check and report with as much detail as possible. It's hard enough to fix stuff in person, we need all the help we can get on the forum.
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Deleted
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Post by Deleted on Feb 20, 2012 23:19:16 GMT -5
Yes agreed. If compression is low however it would not run even if all those things were good. In my view it is time to check the most basic fundamental of internal combustion engine operating principle. Usually the proper diagnostic flow is to check compression first.
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Deleted
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Post by Deleted on Feb 20, 2012 23:34:40 GMT -5
actually mechanical timing is the very first thing then compression.....thats the way i was taught anyway. Line the crank pulley up with the 0 mark and check to see if #1 cylinder is TDC then check compression on all cylinders. Point is its time to go to basics IMO. If this was a known good running engine that suddenly started cutting off hot then maybe going another direction would be ok but this engine has not cranked easily since the top end was done. Larry, 90GTVert and I both have had scooter engines that have had the keyway on the crankshaft machined in the wrong spot making in my case mechanical timing a tooth off when the marks were lined up. I have made the mistake of assuming things were good or correct when I did not verify them, hell I still do that sometimes. Just trying to help you not make the same mistakes I have made  |
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Post by rocketdog on Feb 21, 2012 19:52:49 GMT -5
actually mechanical timing is the very first thing then compression.....thats the way i was taught anyway. Line the crank pulley up with the 0 mark and check to see if #1 cylinder is TDC then check compression on all cylinders. Point is its time to go to basics IMO. If this was a known good running engine that suddenly started cutting off hot then maybe going another direction would be ok but this engine has not cranked easily since the top end was done. Larry, 90GTVert and I both have had scooter engines that have had the keyway on the crankshaft machined in the wrong spot making in my case mechanical timing a tooth off when the marks were lined up. I have made the mistake of assuming things were good or correct when I did not verify them, hell I still do that sometimes. Just trying to help you not make the same mistakes I have made I agree. Start from square one. Check all your work, I know it's a pain. The worst I have had the crank timing off was 3 degrees, not as bad as you guys. If it's getting spark, at the right time, and it's getting fuel and has compression, it will run. RD |
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sctrdawg
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scooter bum
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Post by sctrdawg on Mar 13, 2012 19:50:06 GMT -5
ALL right guys had a bent valve! hence not enough compression changed both valves and lapped them ! no liquid comes thru! now no compression! it turns over toooo fast wont suck my hand to the carb! head gasket? i usually can reuse those metal ones but it just wont seal ! scotchbrited all the paint off head and cyl. even repainted the gasket! THINK ITS TIME FOR A NEW MOTOR AND ANOTHER 50mmBBK!
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Deleted
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Post by Deleted on Mar 13, 2012 21:17:59 GMT -5
cracked piston from hitting the valve?
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sctrdawg
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scooter bum
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Post by sctrdawg on Mar 13, 2012 21:32:53 GMT -5
no cracks in piston!
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sctrdawg
Scoot Enthusiast
scooter bum
Posts: 149
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Post by sctrdawg on Mar 13, 2012 21:33:14 GMT -5
no cracks in piston!
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Post by Fox on Mar 13, 2012 21:59:19 GMT -5
Is there a spark plug installed?
Sorry, had to ask...
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Deleted
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Post by Deleted on Mar 13, 2012 22:05:45 GMT -5
I am for hire. Bring it to Cary |
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sctrdawg
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Post by sctrdawg on Mar 14, 2012 7:29:27 GMT -5
yes bro!plug is installed! did i mention the case has arnd 2o,ooo miles on it ! the crank arnd 15,ooo! bbk kit,arnd 300 miles!
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Deleted
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Post by Deleted on Mar 14, 2012 9:32:42 GMT -5
valves dont bend on their own. you have a habit of saying its not something we say it is ...then it turns out to be what we said. piston to valve contact bends valves and that usually breaks the piston too. Seems i recall someone said it was low compression.....and it was.
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sctrdawg
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scooter bum
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Post by sctrdawg on Mar 14, 2012 18:48:40 GMT -5
yes ! i have put 3 base gaskets to raise deck height, thus stopping that prob! rode it couple hundred mi. . obviously with a bent valve ! it cut off at work in my parkn spot ! wouldnt crank back til coupledays later! then this thread started!! and now ive fixed the valve problem now no compression! No cracks anywhere ! i'm thinkin it's gotta be something where the head n cyl. meet used head gasket w/ bout 300 miles on it! hoping a new one will remedy the no compression issue!
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