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Can a bike sound tappety even when tappets are fine?

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mistermentali...
Two Stroke Sniffer



Joined: 30 Apr 2013
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PostPosted: 17:06 - 16 Apr 2018    Post subject: Can a bike sound tappety even when tappets are fine? Reply with quote

I did a top end rebuild on my hn125-8 replacing the piston barrel and cylinder head and the piston rings. I had to helicoil one of the two holes that the piston barrel bolts go into as one was dethreaded.

When doing this the drill went straight through while drilling very slowly. I got the drill bit out but couldnt remove any swarf as the hole bottomed out, no way to get into the bottom of it. I had to helicoil and break the tang of the coil off.

The bike runs fine and has had an oil change and I cant find any signs of metal or swarf in the piston area nor in the oil removed nor in the area where the pushrods go but the bike sounds very tappety even though I have made sure the valve clearances are set spot on.

I am hoping that where the drill went through was a hollow area as there's no sign of any metal debris in the engine that I have found but I am wondering if the tappety sound could be metal debris in the engine somehow maybe trapped in gear cogs etc. Can an engine sound tappety even when the valve clearances are set correctly?

Dave
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Pete.
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Joined: 22 Aug 2006
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PostPosted: 17:42 - 16 Apr 2018    Post subject: Reply with quote

How can you have a bottomed-out through hole? Either the drill wnet through or it bottomed out, it can't do both.

First thing to check is for exhaust leaks BTW. They sound just like noisy tappets. Did you use a new crush gasket on the exhaust?
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mistermentali...
Two Stroke Sniffer



Joined: 30 Apr 2013
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PostPosted: 18:09 - 16 Apr 2018    Post subject: Reply with quote

Sorry, poor choice of words on my part. I meant that I drilled and the drill bit went right through and there was nothing underneath the drill bit to stop it going further, I didnt explain that well as I meant it had nothing at the bottom of the bit.

I did put new exhaust gaskets on, there seems to be no leak of any air from the exhausts where they sit in the engine but thats a good point I hadnt considered. I could put some exhaust seal paste around them and see if it makes a difference.

Thanks for the quick reply and advice, it is very much appreciated.

Dave
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MCN
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Joined: 22 Jul 2015
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PostPosted: 22:03 - 16 Apr 2018    Post subject: Reply with quote

We use NDT dye penetrant Developer spray to find subtle gas leaks on manifolds etc.
The spray leaves a fine white residue when it dries. Any gas leak blows the developer away.
A dry deodorant spray can do the save thing.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.
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Rogerborg
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Joined: 26 Oct 2010
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PostPosted: 22:25 - 16 Apr 2018    Post subject: Reply with quote

As above, but it's not a refined engine, it will buzz and clatter a bit. It's if it goes quiet I'd start to worry.

Also, the clearances on those cheese metal locknut tappets can go off pretty quickly, like round the block quickly, so even if you set them spot on, it's worth checking again.
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WD Forte
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Joined: 17 Jun 2010
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PostPosted: 14:37 - 17 Apr 2018    Post subject: Reply with quote

Don't know if it's OHC or OHV but have known rocker arm bearing wear on older bikes to cause tapping despite careful tappet setting.
I know yours isn't an oldie but if it isn't the aforementioned and you've set them on the right stoke not the overlap. it might be that
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stinkwheel
Bovine Proctologist



Joined: 12 Jul 2004
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PostPosted: 15:06 - 17 Apr 2018    Post subject: Reply with quote

Don't use exhaust paste, use plumbers silicone to seal exhausts.
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