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Discussion Starter · #1 ·
Hello!

It's mr paranoid speaking here. I've done my first engine rebuild on my beloved ST4. I've noticed the engine ticking a bit louder than usual when idling after the rebuild. The ticking noise is mainly coming from the exhaust side on the left of the bike on both cylinders. Though it's running really well. Specs for those valve were (I followed the workshop manual) :

Exhaust :
Opening : 0.21
Closing : 0.11

Intake :
Opening: 0.16
Closing 0.16

Rebuild included :
  • 8 new opening rockers
  • New valve seals
  • New head gaskets and base gaskets
  • New piston rings

I've tightened the timing belt a bit too much at the beginning but loose it up 5 miles after the first start (belt was whistling in the revs).

I think the valve clearance hasn't been done for at least 20K miles (at least) so maybe everything got quite tight in there that's why I didn't hear it that much.

I'm a bit of a maniac don't forget this, but that's my first rebuild so I take extra attention to everything.

Thanks
Tom
 

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Try and compare noises with a stethoscope (screw driver to the ear works as well) to pin point the noise. As it is nearly impossible to diagnose something over the internet I default to checking important things first. Check the cam timing again to make sure you are not one tooth off as I have seen this far too often and it gives you a ticking noise at idle when the valves are hitting the piston and bad things happen at higher rpms.

Once you know you are not about to grenade your motor then start listening to each area with the stethoscope to pinpoint where the noise is coming from.
Missing circlip on piston.
incorrect shim size ( I have seen mechanics mis-read a measuring tool and be off .5-1.0mm)
incorrect seating of 1/2 rings (more often happens on MBP collets)
incorrect squish setting - thickness of base/head gasket change causing the piston to hit the head.

You are not admitting any of these are wrong by checking but if you are wrong bad things can happen. In the end a loose clearance will make noise and exhaust openers run looser than intake or any closer. You are the mechanic though and it is all on you to verify you have or do not have a problem. Slow down double check your work and think this through, if in doubt trust your gut until you probe it to be right.
 

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Discussion Starter · #3 ·
Hey @ducvet ,

Thanks for your reply.

So I've done about 80miles so far with it, mostly city ride with hot running temps. I guess if something was really wrong, it would have happened already.

  • Timing has been thoroughly checked and is completely right
  • I re-checked the clearance on the vertical cylinder exhaust side yesterday and it didn't move so nothing wrong there (though it's at 0.21 gap on the opening so quite loose, I can hear the noise just but moving it with my finger. I didn't check where it was when I pulled it apart).
  • Circlips were in place in the gutter when I put back the pistons
  • I've probably triple checked that all the shims where seating properly and measured the gap twice

The only thing I didn't measure is the gasket thickness assuming they were the same, though they are aftermarkets ones. I'll measure my old ones. New base gasket was 0.4mm, the same as the OEM.

I'll let you know, but as you said exhaust side is running loser so that should be it.

Tom
 
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