ThumperTalk.com's Decompression Plug

ThumperTalk.com's Decompression Plug

You've most likely heard all of the horror stories by now about the cheap rubber seal that Yamaha uses to plug up the decompression mechanism hole on the cylinder head of the 2004 YFZ450. The problem is that this poor-fitting "seal" can easily be blown out by normal crankcase pressure, causing engine oil to pour out like a faucet. Since this hole is right above the head pipe, stories of entire YFZ450s going up in flames doesn't sound so far-fetched. Yamaha fixed this problem with the 2005 YFZ450 by casting a new head and eliminating this hole completely. But what can 2004 model year owners do to prevent this from happening?

Here's the answer; The ThumperTalk.com Decompression Plug. We spotted it while surfing ThumperTalk.com, and instantly placed an order to prevent any mishaps during the next ride. This little life-saver is constructed from billet aluminum, and comes with a real lip seal. No instructions are provided with it, but you shouldn't need them anyway. It's very straight-forward. The plug itself has a notch cut out on one end, which the pre-existing 10mm bolt will "lock" into, making it impossible for this plug to fall or be blown out. Installation is simple; just remove the stock seal from the cylinder head with a pick or some other small instrument like a flat-head screwdriver, while making sure not to damage the head itself. We've actually heard from others that their's has come out by just using their fingernail (shows you how easily they can blow out). Once removed, unscrew the 10mm bolt completely from the head, and push the new ThumperTalk.com Decompression Plug/Seal into the hole where the old seal existed. The seal must sit flush in the hole, so you may have to tap on the plug itself slightly until it seats fully. To make sure you have it in all the way, look through the bolt hole and make sure that the notch that is cut out of the aluminum plug lines up in the center of the hole you're looking through. If everything looks good, you can re-install the 10mm bolt, but please use caution in doing this! There's not many threads in this hole, and the soft metal can and will "strip out" easily, so make sure not to over-tighten.

We've had the ThumperTalk.com Decompression Plug in our YFZ450 for several rides now and haven't had one problem, and don't plan to in the near future. This is a must-have for all 2004 YFZ450 owners. If you don't have one yet, get one! The price tag of $22.49 (which includes shipping costs) is a small price to pay to ensure the life of your motor, or your entire ATV in some cases. They come in regular aluminum color, or anodized blue and can be purchased directly from ThumperTalk.com. Make sure you get one before it's too late!

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Scale: 1=terrible, 2=poor, 3=fair, 4=very good, 5=excellent