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Post by scott7 on Jan 20, 2016 13:41:09 GMT -5
Ok guys so some of you might remember the scooter I got the other day for working on someone's scoot. Remember I did a compression check and it came up with 60 lbs compression . I also had a spare engine that had 150 lbs compression. Well I took apart both engines, the one that's still in the scoot is the one with 60 lbs compression. Here's some pics of it. The cylinder and piston look great but I noticed when I took out off the cylinder that the compression ring gaps were in almost the same place. Now I might have accidentally moved them a little but Mabey not. The piston is a lot larger than the oth motors piston. So I think this is a bbk. So by looking at the cylinder ,valves and piston ,do you guys think I should just put some gaskets on ,place the rings in the correct positions and see what happens.
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Post by scott7 on Jan 20, 2016 13:42:49 GMT -5
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Post by scott7 on Jan 20, 2016 13:43:31 GMT -5
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Post by cwazywazy on Jan 20, 2016 14:01:47 GMT -5
If you can't feel any grooves in the cylinder, I say put the rings in the right places and throw it together to see what happens.
It does look like a 50mm BBK but I could be wrong.
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Post by scott7 on Jan 20, 2016 14:21:26 GMT -5
I only have a ruler, I thought the bottom of ruler was mm
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Post by scott7 on Jan 20, 2016 14:25:07 GMT -5
Here is piston from engine in scooter compared to piston from spare engine
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Post by scott7 on Jan 20, 2016 14:26:24 GMT -5
Also this is the exhaust they had on the scooter
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Post by scott7 on Jan 20, 2016 14:44:58 GMT -5
Ok so the one cylinder in the scoot is 1and 3/4 inch diameter . The one in spare engine is 1 and1/2 inch diameter , so what mm size are they?
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Post by 90GTVert on Jan 20, 2016 15:23:44 GMT -5
1.5 x 25.4 = 38.1, so prob a stock 39mm piston. 1.75 x 25.4 = 44.45, so perhaps a 44mm. Those were stock on some scoots to make 63cc. If 1 3/4 is just an approximation, maybe it's 47mm.
You could try measuring again to the absolute nearest fraction that you can, if you haven't already. Multiply inches by 25.4 to convert to mm.
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Post by cwazywazy on Jan 20, 2016 17:40:35 GMT -5
You should put the rings where they should be and throw it back together to see if it's got good compression that way. If not, swap over the top end from the spare engine or buy a BBK or whatever.
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Post by katastroff on Jan 20, 2016 18:02:17 GMT -5
Also this is the exhaust they had on the scooter One can only gaze in admiration over the patina of this epic piece of the scooter exhaust system.
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Post by scott7 on Jan 20, 2016 18:47:05 GMT -5
90GTVert thanks it is exactly 1and 3/4 diameter so is that a 44mm ,just want to make sure before I order gaskets, cwazywazy I can't use old gaskets can I to check compression? , I mean I don't know . I would like to check before I buy some, although the cylinder seems really good.
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Post by scott7 on Jan 20, 2016 18:49:21 GMT -5
Now there is a lot of carbon build up,on the valves , could it be the valves that are leaking causing low compression. How do,I check them?
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Post by cwazywazy on Jan 20, 2016 19:04:58 GMT -5
Now there is a lot of carbon build up,on the valves , could it be the valves that are leaking causing low compression. How do,I check them? I think the proper method is to have the valves installed with the springs, then put the head upside down and fill the thing with WD40 or gas or whatever then see if it leaks through. If it leaks, lap the valves. Also I think that pipe looks pretty cool. I'd use it as is.
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Post by scott7 on Jan 20, 2016 19:43:17 GMT -5
Cwazywazy thanks I'll try that in the mornin.
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