Dirtbike Brad

Wr450f big bore?

6 posts in this topic

Alright guys it's almost tax return time so that means it's almost motorcycle upgrade season! The current situation is an 08 wr450f sitting on warp9 17's street legal hooligan beast with a 150+ hours on the top end, she's toast. Full fmf powerbomb /powercore4 exhaust & jd jetting. So my question is what do I do with a budget of $1000-1500? Do I go big bore or not? What's the 478cc gonna do to the bottom end & overall reliability of the bike? Primary use is as a 2nd vehicle/ weekend toy not a race bike. What would you do?

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Big bore = lower rpm limit, more torque at lower rpms, more vibration, runs richer, and accelerates slower....

 

Kind of all bad things for Sumo bikes.

 

Head work and a better pipe and jetting would be a much bigger improvment.

 

The stock WR head is super restrictive.

The FMF PC pipe is rudimentary at best. ProCircuit for race pace.

The JD jetting is very middle of the road. Go with an NCVS needle 4th or 3rd clip, and upgrade the accelerator pump with the 2008 crf450 upgrade kit and Tokyo mods linkage spring.

 

All of the above mods will improve power and throttle response at all rpms, add hp, and make the bike run cooler.

 

A big bore is going to make it feel more like a diesel.....

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Alright guys it's almost tax return time so that means it's almost motorcycle upgrade season! The current situation is an 08 wr450f sitting on warp9 17's street legal hooligan beast with a 150+ hours on the top end, she's toast. Full fmf powerbomb /powercore4 exhaust & jd jetting. So my question is what do I do with a budget of $1000-1500? Do I go big bore or not? What's the 478cc gonna do to the bottom end & overall reliability of the bike? Primary use is as a 2nd vehicle/ weekend toy not a race bike. What would you do?

 

I'm not sure you need a top end rebuild unless it was out of or too low on oil. I would go by mileage if it's being used as a street bike.

 

Big bore should give you more bottom end and torque for taller gearing or use a cam, porting and get more power. The ones I tried worked fine. Just like the DRZ big bore's.

But I would probably just keep the money in my pocket.

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Spend the money on a used 12 with FI  :jawdrop:

 

Why nuting wrong with the 08's especially with some mods. gytr277_zps7889ed6a.jpg

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Thanks all for the replies. Since the op I've torn her down to have a good look & honestly I'm surprised. The way they were going on at the dealer it sounded like everything was going to be a total loss but I don't believe that's gonna be the case. I think I'll be able to get away with a cylinder kit and a few gaskets. Ohh and btw that 08 is partly my inspiration. I've got the same graphics but on black radiator shrouds, tail, & sumo fender w/ a new front headlight/ number plate. Should be sick! Just wish I could afford those marchesini's

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