Freshman Rider
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Joined: May 14, 2013 22:50:01 GMT -5
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Post by chihuahuas on Mar 17, 2013 10:06:02 GMT -5
at 9000 miles the crankshaft bearing came loose, (bearing was loose on variator side of crankshaft).
Replaced crankshaft with used one, alls fine ran to 14000 miles and it did the same thing.
On inspection the bearing comes loose at the press fit. This is just odd. Something wrong with the hardness of the steel. I don't know.
This time I noticed it early and ordered a new crankshaft. Split the case and replaced the crankshaft and it ran fine but wouldn't idle.
""there was an alignment issue with the cam timing, it looked to be 1/2 a tooth off retarted""
Next (Came in the mail late) the 44mm oversize BBk. I installed the 44mm cylinder and piston. Ran strong but would not idle.
Replace the cylinder head and this fixed the idle problem for 2 days and now it's back. Won't idle. Slows down cuts off.
It appears the cam sprocket is pressed on the crankshaft wrong. It's 1/2 a tooth off.
It appears this is the cause of the idle problem.
Has anyone seen this before?
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Post by JR on Mar 17, 2013 14:45:16 GMT -5
Is it too late to return it on a warranty?
Seems really strange, Is this on a 150? a gy6 B?
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Post by tvnacman on Mar 17, 2013 14:52:14 GMT -5
What type cdi are you using .
Could the timing chain not be seated on the crank correctly ? I have heard of the chain sitting between the gear and bearing on the crank shaft .
was the scooter down for more than 3 weeks could you have jelled the pilot jet , I ask because I find the timing marks and aligment sloppy , maybe stretched chain ?
John
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Post by wilds on Mar 17, 2013 15:40:52 GMT -5
If the idle was fine for two days, I don't think that it depends on the cam not lining up.
But you can try to move the cam one tooth on cam sprocket, so it gets to be 1/2 tooth advanced instead?
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Post by alleyoop on Mar 17, 2013 15:40:52 GMT -5
Take a picture of the Flywheel timing mark when the cam is aligned with the 2 little holes even with the top of the head as if your going to adjust BOTH VALVES.
Alleyoop
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Post by tvnacman on Mar 17, 2013 16:23:51 GMT -5
If the idle was fine for two days, I don't think that it depends on the cam not lining up. But you can try to move the cam one tooth on cam sprocket, so it gets to be 1/2 tooth advanced instead? You can then play with cdi's to play with timing returd and advance . John |
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Post by wilds on Mar 18, 2013 4:11:30 GMT -5
I always start the alignment of the cam by verifying that the piston is at TDC.
I then install and align the holes on the cam with the cylinder head and finish it off by checking the valve clearance.
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Freshman Rider
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Joined: May 14, 2013 22:50:01 GMT -5
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Post by chihuahuas on Mar 18, 2013 11:28:46 GMT -5
When I run at 1/2 tooth advanced the power is way down and it coughs back through the carb. When it runs 1/2 tooth retarted is has great power and runs really well although the idle fissels out. Here is what it should look like.  Alleyoop Here is where TDC lines up on the flywheel  |
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Post by alleyoop on Mar 18, 2013 11:43:19 GMT -5
That is TO retarded move the chain 1 link forward. Normally the Case pointer when the cam is lined up IS BEFORE THE "T".
Don't forget the "T" is when the piston is as far as it will go up so it is fireing on the downstroke. It does make a little more power but your crank bearings will not last. It has to fire just before TDC don't forget that even though it fires before top dead center the piston will still go up a little more before the explosion actually forces it back down.
Alleyoop
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Post by triker on Mar 18, 2013 12:11:05 GMT -5
I think you have something else going on in the engine. If the bearings came loose on two different crankshafts. When you had the case apart did you check where the bearing seats in the case? If so did the crank bearing fit snug in the case? You stated that it ran fine for two days after a new head was installed. Have you checked the valve settings? I don't think the cam is your problem. It may be a stretched chain or bad tensioner. I am just throwing out some ideas here and may be wrong.
Roy
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..BAD TO THE BONE..
