What's this bolt for


17 replies to this topic
  • Goosedog

Posted October 29, 2006 - 05:08 AM

#1

As I'm re-assembling since installing my new piston and valves I noticed this bolt was stripped (or I stripped it) and all it says in the manual is that it's a "bolt".....duh. It appears to be a stop point for the decomp mechanism or maybe a seep bolt. I'm either gonna Heli-coil it or just JB Weld it if it's not nessesary to remove it again til the next overhaul. Anyone know?

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  • Fastest1

Posted October 29, 2006 - 05:19 AM

#2

It sits in a recess in the decomp arm and keeps it from falling out. You could go with an auto decomp cam and then install the plug and seal it up or just tap it to the next largest size and grind the tip of the bolt to fit the recess.

  • Goosedog

Posted October 29, 2006 - 05:33 AM

#3

It sits in a recess in the decomp arm and keeps it from falling out. You could go with an auto decomp cam and then install the plug and seal it up or just tap it to the next largest size and grind the tip of the bolt to fit the recess.


If I go with an auto-decomp cam do I remove the present decomp arm or just the cable and lever and leave the arm in the head? Is this what you're refering to as the "plug"?

  • 02YZ426

Posted October 29, 2006 - 06:05 AM

#4

If you go with the auto decomp cam, you can get the TT decomp plug and remove that arm. As for the bolt, I would just get a 6mm heli coil and fix it properly. You don't really want an ugly blob of JB weld there do you? Plus if the JB fails, your going to have a nasty mess on the trail.

  • Goosedog

Posted October 29, 2006 - 06:35 AM

#5

If you go with the auto decomp cam, you can get the TT decomp plug and remove that arm. As for the bolt, I would just get a 6mm heli coil and fix it properly. You don't really want an ugly blob of JB weld there do you? Plus if the JB fails, your going to have a nasty mess on the trail.


I see now where I can get the plug at the TT store but what's the best way to go on the exhaust cam? Is it a simple exchange with an '03 part or is there anything else to do besides removing the arm, cable and lever?

  • 02YZ426

Posted October 29, 2006 - 06:44 AM

#6

Well, your going to have to shim the new cam up, and time the engine properly... other than that its a straight forward job. You might need to pick up a few valve shims, but you will have to wait untill the new cam is installed to figure out which ones to order.

  • grayracer513

Posted October 29, 2006 - 08:13 AM

#7

Here's the camswap instruction sheet:

http://www.thumperta...078#post3706078

If you use the TT plug, you will need to repair the threads in that hole, or rethread to the next larger size and make custom bolt by grinding the nose of one.

You can also use an 18mm freeze plug (cup plug, expansion plug), and any ordinary bolt.

If you decide on the more expensive Hot Cams cam, set the cam timing justlike the stocker, not as done in the instruction sheet.

You should have a sheet of plastic wrapped aroung that frame to keep any of that funk from dropping into your engine, too :mad:

  • Goosedog

Posted October 29, 2006 - 01:27 PM

#8

If you use the TT plug, you will need to repair the threads in that hole, or rethread to the next larger size and make custom bolt by grinding the nose of one.

You can also use an 18mm freeze plug (cup plug, expansion plug), and any ordinary bolt.


So, you're saying the TT plug requires that bolt (in it's original form) to hold it in as well?

I might go the freeze plug route then and just tap the stripped hole to a size up and use an ordinary bolt. Where can I get the 18mm plug and do I need to remove the head again to have it pressed on?

  • grayracer513

Posted October 29, 2006 - 01:44 PM

#9

So, you're saying the TT plug requires that bolt in it's original form to hold it in as well?

Yes.

I might go the freeze plug route then and just tap the stripped hole to a size up and use an ordinary bolt. Where can I get the 18mm plug and do I need to remove the head again to have it pressed on?

Any reasonably good auto parts store should have one. You don't need to take the head off to install it, but they can be tricky to install, especially when you don't have a straight shot at the bore to drive it in. You can use a pair of pliers like this to push it in place. Use a socket that fits loosely in the cup of the plug as a driver.

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  • Goosedog

Posted October 29, 2006 - 06:18 PM

#10

Should I put a little oil on the plug first to ease the install? And thanks GR, you da man! :mad:

This engine rebuild has been quite an experience for me. I've learned a lot about this bike and mechanicing (new word) in general. I can't wait to ride it soon with a new top-end and the decomp mod that I've always wanted to do but was chicken to try. Between my neighbor mechanic and the wealth of knowledge from all the cool TT guys it's been a real pleasure and worthwhile challenge. Thanks to you all.:mad:

  • grayracer513

Posted October 29, 2006 - 06:36 PM

#11

Should I put a little oil on the plug first to ease the install?

Use a non-hardening sealer such as #3 "Aviation" Permatex on the sealing surface. Don't use silicone RTV. Second choice would be telfon thread sealer, and last choice, a light smear of grease or oil.

  • Goosedog

Posted October 29, 2006 - 06:39 PM

#12

How about Yamabond #4?

  • grayracer513

Posted October 29, 2006 - 07:22 PM

#13

I'm not familiar with it. It should be more liquid than paste, and be non-hardening, even to the extent that it never realy quite dries. If that describes YB#4, then it should work. I'd use nothing before I'd use anything like a silicone sealer. They have their place, but this isn't it.

  • ONLY4STROKES

Posted October 29, 2006 - 07:34 PM

#14

Ever consider washing your bike before opening it up?

  • tnl

Posted October 29, 2006 - 08:24 PM

#15

Yes.

Any reasonably good auto parts store should have one. You don't need to take the head off to install it, but they can be tricky to install, especially when you don't have a straight shot at the bore to drive it in. You can use a pair of pliers like this to push it in place. Use a socket that fits loosely in the cup of the plug as a driver.

Posted Image


I just safety wired mine. Read somewhere on here where someone noticed oil spitting out of their engine as a result of the plug/bolt ejecting itself. Think I got a picture of it wired if you want it?

  • Goosedog

Posted October 30, 2006 - 04:18 AM

#16

Ever consider washing your bike before opening it up?



On the page before I mentioned this was my first time ever doing something like this and yes, I've made some mistakes. I did wash the bike beforehand however the dirt in the picture was on the frame under the tank and I missed that. I really do appreciate your hindsight though and I'll remember it for next time. :mad:

  • Goosedog

Posted October 30, 2006 - 04:19 AM

#17

I just safety wired mine. Think I got a picture of it wired if you want it?


Sure, thanks.

  • grayracer513

Posted October 30, 2006 - 08:25 AM

#18

It should only be necessary to safety wire the plug if you use Yamaha's inadequate original equipment plug. Properly installed, an expansion plug or the TT plug will stay in without help.





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