GS425 does not sound right (Link)

[bjones]

I am trying to help my son with his GS425 which he purchased last fall. He purchased in on his own, no experience and without any help (kids). As soon has I heard it running I was alarmed by the racket it was making.

He has been riding it but I cannot help but think that he should not be until this is resolved.

The noise seems to be coming from the top end and is marginally worse on the right side. I have checked valve clearances and they are fine. Turning the motor over by hand I cannot detect any interference. When the oil was changed I did not detect any metal filings.

https://www.youtube.com/watch?v=X62aGRHuBow&feature=youtube_gdata_player

Any suggestions?
Thanks!

 

[Guest]

Sounds like a couple of things to me...

Something is loose and vibrating in time with the engine pulses. See if the cam end caps are loose and vibrating or something else on the right side.

It also sounds like one thing our bikes can get which is cam walk, where there's enough play to allow them to "walk" left to right while moving. Typically you can ignore this as it only seems to be annoying and mainly only at idle.

I think there is more than one thing making that noise...

 

[earlfor]

I've only heard that sound once before and it was due to loose cam caps which were allowing the cam shafts to jump up and down with every revolution. I would remove the valve cover and check the cam cap bolts and then start the engine with the valve cover off and listen and watch.

 

[bjones]

Two votes for loose cam caps. I'll pull the valve cover and check them ASAP.

 

[bjones]

Finally got a chance to pull the valve cover today and found that the cam caps were tight. No joy there.

I did notice however that the cam chain was awfully loose as I turned the motor over by hand.

Long story short, I found that the cam chain tensioner was in the retracted and locked position. PO must have removed the tensioner, retracted and locked it, reinstalled but did not release the plunger after reinstall.

Problem solved.

Not sure how long it has been running this way. Probably a few hours run time since son bought it. No idea before that.

Any potential damage due to this condition? I'm assuming I probably ought to verify the cam timing as the chain could have skipped a tooth being so loose?
Though it has been running fine other than the natty engine noise.

Any comments on potential fallout I should look for before buttoning up?

Thanks!

 

[Guest]

Good news that you found it!

If the chain is loose, pretty much the only consequence can be skipping a tooth or three on the chain.

However the results of that can be quite disastrous (bent valves etc.) so definitely check the cam timing before buttoning her back up.

Your son may have dodged a bullet if it's still timed right...

 

[Guest]

Its hard to get them to skip but if the guides are worn enough It can definitely happen.

As pete says. If its timed right and runs you should be good. If it was timed wrong by more than 1 tooth it would not run and more than that would damage valves.