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fmx09

Help with a decompression assembly

15 posts in this topic

I have a 2001 Yz426F and the bolt that holds the decompression assembly into the motor is leaking oil. I still have the bolt but it won't tighten down, it just keeps turning and oil is seeping out through the hole. By looking at the bolt I'm pretty sure that the threads on the motor side are stripped. So I'm thinking that I may have to re-tap the hole and replace the bolt and gasket with a bigger ones. Anyone have any suggestions on how I would go about doing this and finding a bigger bolt that would still do the job afterwards? Thanks.

 

On the OEM parts diagram for the Crankshaft - Chain the bolt and gasket I am talking about it part #13 and 14.

 

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Edited by fmx09

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If you have the bolt, you will notice that there is a guide pin extending from the end of it, unless it's the wrong bolt.  You cant just oversize it.  Instead, you need to Heli-Coil or Time-Sert repair the threads in the head, get a copper washer on the OEM bolt, and replace it.  Bear in mind that the pin on the nose of the bolt has to run into a groove in the decomp shaft.  If the groove isn't lined up with the hole as it screws in, it will become "tight" while only the first one and a half threads are in contact, and you'll strip it again.

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If you have the bolt, you will notice that there is a guide pin extending from the end of it, unless it's the wrong bolt.  You cant just oversize it.  Instead, you need to Heli-Coil or Time-Sert repair the threads in the head, get a copper washer on the OEM bolt, and replace it.  Bear in mind that the pin on the nose of the bolt has to run into a groove in the decomp shaft.  If the groove isn't lined up with the hole as it screws in, it will become "tight" while only the first one and a half threads are in contact, and you'll strip it again.

Okay thanks a lot. I was wondering how I would going to get a larger bolt because I know its a specialty bolt. 

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I just got my bike and it had the same problem ... Along with the drain pug being stripped ... I just used rtv on the bolt sealing surface but just enough so it wouldn't get forced down into the threads ... Has worked alright for me up to now ( about a week)

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Imported tools are pricey, eh?

 

Then you can use any bolt you want in the hole for the anchor pin/bolt.

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Well I'm just in Canada so I don't even know if it's imported lol but the last kit I looked at was over 100$ and doesn't the anchor bolt have to have the narrower part at the end ?

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Not if you remove the decomp lever/shaft, no.  With that gone, there isn't anything for the pin to anchor.  It's just a threaded hole into the cam box then.

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Go to part source or another car parts store, they sell knock off heli coil kits, comes with the tap and tool plus 3 or 4 coils for about 15$ they work great .

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I'll keep my eye out for one but it seems pretty unrealistic that I'll find something lol ... I'm a bit of a pessimist.

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I could only find whole heli coil sets which were expensive. But I was looking at the wrong places like brafasco or fastenal which are industrial companies, try any car parts store I bet they have small individual size kits.

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