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Post by gingel on Apr 19, 2015 4:54:21 GMT -6
Hi,
I have a SYM scooter with a 125cc engine (air cooled).
I'm after an engine rebuild, and i also replaced the cam chain and the tensioner.
A few days ago i finsihed the engine break in, and i checked the valves clearence,
and i noticed that the cam chain have free play to the sides.
I turned the tensioner about a 1/4 of a turn counter clockwise, and i guess it
made the chain more tensioned, and the free play is much less.
Is it a bad tensioner, or sometimes do you need to "help" the tensioner ?
Here is a video of the chain before i turned the tensioner:
(you can hear the "tic" sound from the chain moving)
This is a video after i made the chain more tensioned:
Thank you for helping.
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Post by dmartin95 on Apr 20, 2015 14:52:17 GMT -6
I hope you get an answer, I'm curious too.
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Post by cyborg on Apr 20, 2015 15:45:36 GMT -6
it's correct in the second video,,,but it should have been clockwise to push the shoe into the chain more but it is good now,,,it was a little loose before but it wasn't bad,,,it would have made noise but i don't think it would have jumped ,,,,but cam time would have been in and out a bit,,,nothing radical
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Post by gingel on Apr 21, 2015 1:00:30 GMT -6
Thank you for the answer. Maybe the SYM tensioner is a little different  , because clockwise is making the tensioner to be loose, and counter clockwise making it more tensioned. It's like that also in the old tensioner that i have. Do you think i should replace that tensioner, or that manually adjusting it is not so bad? What will happen during the life time of the engine, will it adjust the chain automatically? |
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Post by cyborg on Apr 21, 2015 7:29:32 GMT -6
there is a spring that keeps tension on the chain but it is a manual adjuster so periodic adjustment is needed ,,,i did not know myself that they were left handed threads,,,but you have it adjusted correctly by the second video i saw
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Post by gingel on Apr 21, 2015 16:24:57 GMT -6
I always thought that these tensioners don't need any adjusting, just install them and forget about them. Btw, here is a picture of the old tensioner:  |
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Post by dmartin95 on Apr 22, 2015 20:55:40 GMT -6
I always thought that these tensioners don't need any adjusting, just install them and forget about them. I think you're correct. They're self adjusting. Check out this video: |
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Post by cyborg on Apr 22, 2015 21:01:28 GMT -6
To a point they are,,,,,it's spring loaded ,,,but you have to preload them
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Post by Alleyoop on Apr 22, 2015 21:07:27 GMT -6
Yes they adjust by themselves To retract the plunger you turn it clockwise and you actually have to hold it in that position if you let go the plunger will extend to its fullest all by itself due to the spring inside.
Also when you put on a chain on the cam sprocket you always have it tight on the bottom side and the slack side of the chain on top toward the tensioner. Then then tensioner pushs the chain down on the top to tighten it up. If you don't then you do have a chance of it jumping a tooth because the chain is loose on the bottom and the top would already be tight and the tensioner is doing nothing for you.
Alleyoop
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Post by gingel on Apr 23, 2015 3:13:07 GMT -6
So what do you think i should do? Alleyoop, do you also think it's tight enough in the second video? Do you think i should replace the tensioner? Also, why it was ok when i closed the engine, and after 600 miles it's suddenly became too loose? |
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Post by Alleyoop on Apr 23, 2015 10:46:47 GMT -6
Yes it is tight in the second video,
As far as becoming loose over some miles two things can cause that.
A. Chains stretch and or the tensioner spring has weakened and no longer strong enough to keep it tight.
Just get a new Tensioner.
Alleyoop
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Post by gingel on Apr 24, 2015 6:19:10 GMT -6
Thank you guys with helping me with this issue.
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Post by dmartin95 on Apr 24, 2015 10:03:32 GMT -6
Yes it is tight in the second video, As far as becoming loose over some miles two things can cause that. A. Chains stretch and or the tensioner spring has weakened and no longer strong enough to keep it tight. Just get a new Tensioner. Alleyoop I thought the whole point of of a CAM tensioner was to deal with the chain stretching.... Will a GY6 chain stretch to the point the tensioner no longer works? I've never put enough miles on these scoots to get a chain to that point but always just assumed the tensioner would handle any stretching.  |
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Post by Alleyoop on Apr 24, 2015 11:22:32 GMT -6
The chain tensioner is not only for chain stretching but if you notice a new chain IS ALREADY LOOSEY GOOSESEY. And the stretching really is the wearing of the rollers and pins on the chain. So the longer the chain the more pins and rollers to wear and the longer the chain may get. But I have yet heard of a chain getting so long as to jump out of timing UNLESS the tensioner is not working at all. Also if enough slack has occurred it will retard the timing and you may start to see loss of power and harder
starts etc..
But on these scoots not likely just change the oil dirt and grit is what causes chain wear.
Alleyoop
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, 
..BAD TO THE BONE..
