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ty151

what is this hole??

39 posts in this topic

I noticed this hole and i really dont know what it is...its right above where the header bolts to the engine. Can someone tell me what it is??

bikehole.jpg

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It's where the decomp lever used to go. If it's an actual hole , you had better put a plug ( freeze plug or tapped plug ) in there or you will lose all of your oil. WR Dave.

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its a 2003 wr450.

I believe it is an actual hole because there is some liquid sitting in there. Would this have anything to do with leaking coolant at the bottom of the radiator?? Because i had the rad. checked and there are no holes and all the clamp and hoses look okay. Any ideas??? Thanks for the quick replies..

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It's where the decomp lever used to go. If it's an actual hole , you had better put a plug ( freeze plug or tapped plug ) in there or you will lose all of your oil. WR Dave.

What he meant by an actual hole was that the older WR450's like yours had the spot for the decomp lever machined but covered with a rubber plug that liked to fall out. The later ones didn't get machined but the boss was still cast in. As he stated get it plugged a 18mm freeze plug will work well and cost about a buck.

Steve

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Do not put a freeze plug in that hole. Go on ebay and get the right plug for about $10. The little bolt will retain the billet alumininum plug. It is also a flashy upgrade.

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Not bolt, plug on ebay. Search yzf 450 plug and you get a decompression plug in 4 colors that is $10.99 with $2 shipping. The 10mm head bolt in the pic holds the plug in.

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ok thanks...

do you think this has anything to do with coolant dripping from the bottom of the radiator?? Thanks

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No, the coolant could be from something as easy as spillage from filling or poping the cap off. Hose it off and run it and keep an eye on it. My hose softened up over time and no amount of tightening could get it to stop dripping. I replaced the lower cross-over hose and clamps and that fixed it. Fix the head plug before hosing it down.

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As stated above, the decomp. lever for the 426's went through there. The small bolt on the outter part held it in place. If the breather hose that comes off the top of you valve cover gets kinked then the motor can build pressure, internally, and blow the plug out. You can buy the aluminum plug w/ seal from TT store. The small,outer, bolt then retains the plug. To remove the plug, remove small bolt, use small allen wrench, or something else that is rigid with a 90 degree angle, to pop it out from the inside.

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No, the coolant could be from something as easy as spillage from filling or poping the cap off. Hose it off and run it and keep an eye on it. My hose softened up over time and no amount of tightening could get it to stop dripping. I replaced the lower cross-over hose and clamps and that fixed it. Fix the head plug before hosing it down.

hose what off??? Im confused, because it doesnt look like the cap or any hoses are leaking...

When you say the lower cross-over hose, do you mean the one that goes to the water pump??

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Here is a picture of the plug on the TT store. I'm not sure why the hole is even still there from 03 up. I guess Yamaha had a lot of 426 heads in inventory and didn't want them to go to waste. :banghead: A word of caution. Be careful when you tighten the bolt, it strips fairly easily.

http://shop.thumpertalk.com/Decompression_Plug_p/qmr-03dpb.htm

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its a 2003 wr450.

I believe it is an actual hole because there is some liquid sitting in there. Would this have anything to do with leaking coolant at the bottom of the radiator?? Because i had the rad. checked and there are no holes and all the clamp and hoses look okay. Any ideas??? Thanks for the quick replies..

Check the line to the overflo. The first time I took my gas tank off and put back on, I snipped the overflo line with the bolt that holds the tank on. Its on the right side. Maybe there is a small cut in the line and its running to the rad.

Just a thought.

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the overflow tube comes right out of the rad. cap neck right? Would a little hole in this tube cause coolant to run down the radiaot and collect at the bottom??? Thanks

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its a 2003 wr450.

Would this have anything to do with leaking coolant at the bottom of the radiator??

Are you sure it's coolant? The oil that's lost through the decomp plug is mostly discharged as a fine mist, which hits the back side of the radiator then runs accross the fins and drips off the front. (At least that's what mine [an '04] did.) This was before I know about TT and I cleaned off my radiator two or three times before I figured out what the heck was going on!

:banghead:

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Are you sure it's coolant? The oil that's lost through the decomp plug is mostly discharged as a fine mist, which hits the back side of the radiator then runs accross the fins and drips off the front. (At least that's what mine [an '04] did.) This was before I know about TT and I cleaned off my radiator two or three times before I figured out what the heck was going on!

:banghead:

yea thats what i was thinking and somebody told me that couldnt happen...once you got that hole plugged up, it never happened again??

Was yours collecting at the bottom of your rad. and dripping onto the header??? Thanks

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yea thats what i was thinking and somebody told me that couldnt happen...once you got that hole plugged up, it never happened again??

Was yours collecting at the bottom of your rad. and dripping onto the header??? Thanks

That is exactly what my 04 did, the fact that oil was burning off on the header pipe is what tipped me off to the problem.

Steve

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