Help with a decompression assembly


14 replies to this topic
  • fmx09

Posted July 29, 2014 - 02:20 PM

#1

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.

 

YA6715_10.gif


Edited by fmx09, July 29, 2014 - 02:21 PM.


  • grayracer513

Posted July 30, 2014 - 06:59 AM

#2

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.



  • fmx09

Posted July 30, 2014 - 10:33 AM

#3

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. 



  • mercer137

Posted August 01, 2014 - 04:36 AM

#4

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)

  • grayracer513

Posted August 01, 2014 - 07:10 AM

#5

A week?  That's real longevity right there. 



  • mercer137

Posted August 01, 2014 - 12:32 PM

#6

Lol well not that it only lasted a week ... It's just only been a week

  • grayracer513

Posted August 01, 2014 - 02:48 PM

#7

I give it 3 weeks, tops.



Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • mercer137

Posted August 01, 2014 - 05:11 PM

#8

Well I guess I'm buying a 450 exhaust cam in 3 weeks cuz that plus the frost plug is about what they want for a heli coil kit up here

  • grayracer513

Posted August 01, 2014 - 08:08 PM

#9

Imported tools are pricey, eh?

 

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



  • mercer137

Posted August 01, 2014 - 08:10 PM

#10

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 ?

  • grayracer513

Posted August 01, 2014 - 08:43 PM

#11

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.



  • mercer137

Posted August 02, 2014 - 06:57 AM

#12

.. ok I understand ... It's crazy how the cheaper option is to upgrade lol

  • Yz400f Jeff

Posted August 04, 2014 - 05:52 AM

#13

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 .

  • mercer137

Posted August 04, 2014 - 06:55 AM

#14

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.

  • Yz400f Jeff

Posted August 04, 2014 - 01:42 PM

#15

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.





Related Content

Forums
Photo

100 hrs on 2014 yz450f, shim valves or replace them? by ttr230rider6


Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • Hot  79 replies
Forums
Photo

First Hare scramble tips by dhend8


Dirt Bike   General Dirt Bike Forums   General Dirt Bike Discussion
  • Hot  33 replies
Forums
Photo

Michigan Motocross Tires by 288yz450


Dirt Bike   Dirt Bike Regional Discussion   North
  • 1 reply
Forums
Photo
Motocross

Thinking about Yamaha 250... by Arctic Pride


Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  491 replies
Forums
Photo

Is it worth it? (Cam and High compression piston) by macgi77


Dirt Bike   Make / Model Specific   Honda   CRF 150/230 F/L
  • Hot  36 replies
 
x

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.