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Post by devinchasteen15 on Jan 1, 2015 1:34:23 GMT -5
I think my scooter Is not starting due to low compression. Is there any way to fix it or am I screwed.
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Post by wilds on Jan 1, 2015 2:22:42 GMT -5
How many miles do you have on the engine? It could be the piston rings, the cylinder has gone bad, leaking valves.
First check the compression with a gauge, if you have one (remember to have full throttle when measuring).
You should have at least 100psi compression.
If it's lower than 100 psi, you can try and squirt a little oil into the cylinder and try measuring again.
If the compression got much better you should change the piston rings.
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Post by devinchasteen15 on Jan 1, 2015 2:31:55 GMT -5
It has 1707 km on it
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Post by hillbillybob on Jan 1, 2015 8:52:40 GMT -5
When did you adjust the valves last? With just 1050 miles, this scooter isn't fully broken in yet, let alone worn out. Something tells me, it has never had a PDI done on it. You can find lots of help with procedures (tune ups etc.) in other parts of this forum.
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Post by rcq92130 on Jan 1, 2015 11:03:50 GMT -5
Hi Devin.
Like HBBob, my very first gut reaction (you didn;t include very much info to go on!) was: valves need adjustment, which is simple as can be, free, and can cause non-start. You should have checked (and almost for sure adjusted) the valve clearance once or twice in the first 1,000km or so, so if you did not that's a good first thing to check. Problem is the valves seat in and the clearance set at the factory changes. Eventually there is no clearance and the valves never really close, and so .... low compression and non start.
Here is a video showing how to do this:
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Post by lain on Jan 1, 2015 14:01:42 GMT -5
Hi Devin. Like HBBob, my very first gut reaction (you didn;t include very much info to go on!) was: valves need adjustment, which is simple as can be, free, and can cause non-start. You should have checked (and almost for sure adjusted) the valve clearance once or twice in the first 1,000km or so, so if you did not that's a good first thing to check. Problem is the valves seat in and the clearance set at the factory changes. Eventually there is no clearance and the valves never really close, and so .... low compression and non start. Here is a video showing how to do this: When I first got into scooters, about a year and a half ago, I had this same problem. I knew nothing about mechanics at that point, it would always be really hard to start. Once I heard about valve clearances, sure enough I checked and there was no clearance. After setting the clearance I was surprised at how easily the scoot started! |
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Post by devinchasteen15 on Jan 2, 2015 2:07:45 GMT -5
When did you adjust the valves last? With just 1050 miles, this scooter isn't fully broken in yet, let alone worn out. Something tells me, it has never had a PDI done on it. You can find lots of help with procedures (tune ups etc.) in other parts of this forum. Don't have feeler gauges to adjust the valves  any other things to adjust valves with |
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Post by devinchasteen15 on Jan 2, 2015 2:10:08 GMT -5
Here is the valves and piston they don't look very good. Also there is no gaskets. Previous owner didn't take very good care of it. Probably why I got it for free   |
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Post by rcq92130 on Jan 2, 2015 2:36:35 GMT -5
Holy crap. You just forged ahead!
Valves look OK from what I can see in the photo.
Are you saying there was no head gasket? Seems to me it would never have started - ever - if that was the case.
Feeler gauge is maybe $3 or $5 at walmart, target, auto parts store, etc. And you WILL need it now that it's apart and needs to be put back together. Also need a gasket kit - about $5 from scrappy dogs or elsewhere.
Are you planning on getting a BBK, and that's why you stripped it down?
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Post by hillbillybob on Jan 2, 2015 4:54:51 GMT -5
No head gasket....for real? Guess that explains the lack of compression. It is rather odd that a scooter with only 1700km, would already have had it's head pulled at least twice. Wonder why it was off the first time, and then reassembled without a head gasket. Think you may have to talk to the person you got it from to find out what gives.
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Post by rcq92130 on Jan 2, 2015 12:38:54 GMT -5
If you look at the photo of the head you can clearly see the outline of where the head gasket was. he must be speaking about some other gasket(s).
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Post by JerryScript on Jan 2, 2015 16:56:05 GMT -5
Just FYI- Now that you have pulled the cylinder, you will either have to replace it, or re-hone it, and put in new rings. Most repair shops will hone it pretty cheap for you, but if they charge more than $50, you should just get a new cylinder for the same price (or less). If you want to BBK it, now is the time, and it's only $80 or so for a decent 50mm BBK.
While you have the head off, you should lap your valves as well, just to be sure they aren't part of the compression issue. Takes about a half hour to disassemble the valves and lap them, and reassemble. Check out youtube for videos of how to remove the valves without special tools (easy on a 50cc, the valve springs are not to strong).
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