Rebuilding wasted 06 WR450F HS bike, but how big? Need input....

As of Memorial Day weekend, my WR450F suffered severe engine damage for the SECOND TIME in its life. The repair operation is on hold pending the discovery of a large sum of money. It could be worse, I suppose. My connecting rod s/e went poof and let go of the piston right at the wrist pin. The rod then proceeded forward through my cylinder and got a breath of fresh air. Somehow the case, valves and cylinder head are okay.

In an impulse purchase fueled by the despair of losing my prized Yamaha, I found a :banana: gangsta deal :banana: on a pair of Italian TM Racing dirt bikes. If you haven't heard, TM is the Ducati of dirt, Lamborghini of leaping, Ferarri in the forest, something like that. Check them out on the web. One is a 1999 125 EN, the other is a 2001 300 EN. Just say no to valves, they are hand-built 2-strokes. Trick looking baby-blue plastics, Ohlins suspension, Chromoly oval-section perimeter frame, billet wheel hubs, blue ano'ed Excel rims, fatbars, Grimeca hydraulic clutch. Neat stuff, and its not a freakin' orange KTM, I digress. I have been able to satisfy riding cravings with these bikes, but its not the same on a pinger. I need deep blue boom back in my life!!!

I am still deciding what to do. Should I make it faster? Should I make it slower? Since I have to replace the crankshaft and the cylinder, I have the opportunity to build a big-bore / stroker. I can go all the way to a 565cc with a kit from Falicon for about $2500.00. I can also do a cheaper ($800.00) 502cc (yfz450 quad bb/stroker from hotrods/cylinder works) setup thats not nearly as good, but if I build a lower compression low-rev / easy-going chugger it shouldn't matter. I can also rebuilld it completely stock for about $700. Falicon makes some stuff in between thats cheaper too. I also heard to stay the hell away from wiseco crankshafts.

I realized that I dont need a modified 450 for more power in harescramble racing, since guys on much smaller bikes go much faster than me. :busted: Mind power and Body power wins endurance races, not horsepower. I'm not out to break world records here, and I'm most likely going to get my ass handed to me on the track no matter what I ride. I just want something thats less hassle than a 14:1 race-gas-bonging monster that hates getting hot and bounced off of trees. I want to stop breaking stuff. What should I do? Reader poll!!

go oem. if it is the cheapest way for you then why change the motor if no more power is needed. im not sure how reliable the other kits are either so oem would proboly be the safest way to go. when you split the cases i would be careful about removing the bolts from the crank cases. if you strip one just drill the head off of it. also you will need all new lock washers, gaskets, and i would replace the seals as well in the motor. where are you buying the parts from? 700 sounds like a deal for a new crank and cylinder. hope that helps with your decission.

I have been thinking about what upgrades I would make in your situation. Since I like to ride technical trails and open desert. I think I would go with the OEM crankshaft for reliability. Then I would use a big bore kit for more power and better low speed chug factor. Then when having the head rebuilt I would have it ported by someone who knows what they are doing. Meaning they have a flow bench and know how to use it and the majority of their research is done already. I think the critical part is porting in the throat near the valve seat. Then I would use the a piston that resembles stock compression. The increase in displacement will in itself raise compression. This way I do not need to deal with race gas. I believe this would be a little more powerfull than stock and very reliable. It would be a hill climbing machine and still reasonably priced.:busted:

You did say you really don't need more power:moon:

if I had to re do my 06 wr, it would be as GCannon says.. but i probably would not do a big bore. My 06 runs very well as is... And reliable is important to me.

on a side note, how do you like the 300 tm ? I have a gasgas 300 that i really like also, but as you said, it is not the same...

2 different bikes and different usages !!

If it was me, I would go OEM all the way around :busted:

@ jhendr3702

(damn i need to log in more often)

Actually I cant stop riding the 125en!! It has a heavy flywheel and pulls hills like a 450 4stroke once it's on the pipe. The hydraulic clutch plays a nice role in keeping it there too! But now my fiancee fell in love with the smoothness and took it over, so i need to start riding my own stuff...

The 300 started as a basket case and is now at least seeing the light at the end of the tunnel. It was apparently someone's stupid custom engine idea left undone.... I tracked down 1 of 8 pistons left in the country to fit the big-bored cylinder. Now my latest issue is finding out that a +8mm long rod was not part of the guy's recipe. It's always cool finding this stuff out afterwards, like when the piston comes up and says "hello there" out the top of the cylinder. I have a few lines on a custom jug spacer and longer studs, so I think I can get it running at least by summer time....

@ all--

I appreciate all of your input very much! It helps to have like-minded maniacs as well as normal people to talk me through things. I am now leaning more toward just fixing the wr450 instead of upgrading it. I think i will save energy in racing by keeping power soft and smooth. Although it would be cool to have the biggest cc yamaha of anyone i know, I will save the "billy badass" routine for the TM300en practice-bike, since the more I learn about TM, the scarier they sound to ride.

I am still saving cash, and that will dictate what I do ultimately. If anyone can find a free stroker/bb kit from falicon laying around, I am game for that I guess. I'll even advertize on a t-shirt. I mean, who wants to put their name on the fast guy, anyway? It's too hard to focus on the sponsor decals. I roll by nice and slow and give everyone plenty of time to read!!

As always, i'll keep you guys posted with maybe even some pix/vids.

Edited by elcubeo

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