Looking on feedback from guys using big bore kits


8 replies to this topic
  • CanadianWR450

Posted March 28, 2010 - 04:08 AM

#1

I'm doing the top end, and I'm contemplating a big bore kit in the process.
Bike is a 04, with all free mods, FMF Ti PowerCore, Hotcams, and JD Jetting.

I'm looking for torque.
Right now the bike is very hard hitting, big power, but major wheel spin, not overly "tractable".

Best way I can describe it is a comparison to the inline 4 street bikes like a CBR, versus a big V-Twin...I like the big V-Twin power over the inline 4 power....
The old XR 600 kinda power.....

The HotCams is a love/hate thing for me....love the power gains, don't love the wheel spin....

For the guys with big bore's, pro/cons?
What did it do to the power delivery?
How did it affect jetting?

If I stick with OEM piston/cylinder, I'm going to play with gearing, going from a 14/51, to a 14/48 combo...

Also thinking of a stainless Megabomb....that help me get to where I want, or make it even worse?

  • ArcticWR400

Posted March 28, 2010 - 10:15 AM

#2

While i don't know for sure, I think a supercross header (as opposed to a motocross) will help with the low end grunt. Also, an exhaust that more trail-tuned than race-tuned may help also.

The biggest difference you might find, and the cheapest option, might be to bring the front sprocket down to a 13t... that combined with perhaps keeping the 51 or perhaps only going down to 50 or 49 might also help get that low end grunt that you're looking for.

Any other TT'ers here have more experience than myself (that should be just about everyone) and want to give some input?

PS: what about a heavier flywheel?

  • Birdy426

Posted March 28, 2010 - 11:54 AM

#3

I went from a 426 to a 444, with Hot Cams and a YZF exhaust. I also went 13.5:1 compression. With stock gearing, first gear was absolutely useless, as all the bike would do is dig trenches. I went up one tooth on the front, and love it. Still a big hit inthe mid range that carries thru all the way to over rev, but the power is usable in all gears and all RPMs.

  • CanadianWR450

Posted March 28, 2010 - 12:17 PM

#4

I've thought of a heavier flywheel, and think this would also help me get what I'm looking for.

Gearing down, I do not think will get me where I want it, and would make it even more "explosive".

I'd like to stretch the gears out more so to speak.

I'm kinda in a catch 22 situation, I like the power gains with the hotcams, I'd just like to change the delivery of it.

I still consider myself a newb with these new style 4 strokes as well, but I have some guys who are long time, hard core hare scramble guys, and this is how they describe it:

"too much, to soon - lights up way to quick, and way to hard"

They would take the hotcams out, and put in the stockers. If I was a pure single track/HS/ rider, I'd consider that, but, I'm not one of those riders...lol

I do a lot of ATV/Snowmobile trails, pretty open...old survey, and fire roads, etc. and overall, I like the bike with the hotcams better then without them.

I guess I'm looking for the best of both worlds, and wondering if the big bore / hotcam setup will give me what I'm looking for.

I DO think a heavier fly wheel, and dropping a few teeth in the rear will also help get me what I'm looking for.

Since I'm doing the piston/cylinder now anyway, if there is ever going to be a big bore on the bike, it's now or never...:thumbsup:

Anyone know what the weight is for a stock 04 flywheel is btw?

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  • CanadianWR450

Posted March 28, 2010 - 12:20 PM

#5

I went from a 426 to a 444, with Hot Cams and a YZF exhaust. I also went 13.5:1 compression. With stock gearing, first gear was absolutely useless, as all the bike would do is dig trenches. I went up one tooth on the front, and love it. Still a big hit inthe mid range that carries thru all the way to over rev, but the power is usable in all gears and all RPMs.


Hey Birdy, thats one of the tracks I'm on...gear it up....make the pull/gears longer.....

Any insight on what the big bore alone had on your bike though?

  • CanadianWR450

Posted March 29, 2010 - 10:26 AM

#6

Well, there was less then a $70 CDN price difference between OEM and the Anthena 480 big Bore kit....sooo...I couldn't pass it up.

I'm going to go from the 14/51 to a 14/48 combo and see if that gets me in the direction I want to go.

  • redhurricane

Posted March 29, 2010 - 02:23 PM

#7

What tire are you running? If you want to get the bike to be more tractable, maybe another style/size tire would connect the dots so to speak. Increased rotating mass (either at the crankshaft or at the wheel) will slow the "snap" of the engine. You've already got enough HP, trick the bike into believing it has more mass to spin. I've always found myself going a bit higher than I first thought on gearing and riding smoother.

BTW, 2006 WR450 with minimal mods(ais /grey wire/airbox/intake/exhaust) and a 120/100/18 Maxxis Desert IT and I love it.

  • CanadianWR450

Posted March 29, 2010 - 04:51 PM

#8

It has a 120 Maxxis Desert IT on it now, before that a 110 Michelin S12, and now I have a Michelin 110 M12 going to go on (Michelin sizes converted to 'normal). Honestly did not find a huge difference between the desert IT and the S12....
I think my key here is going to be in gearing......the big bore shouldn't be to bad either as I'm figuring more mass, and it won't build rev's quite so fast, not to mention better able to pull taller gearing

  • Birdy426

Posted March 30, 2010 - 10:15 PM

#9

Hey Birdy, thats one of the tracks I'm on...gear it up....make the pull/gears longer.....

Any insight on what the big bore alone had on your bike though?


No...I put it all on at once...

Higher compression will also tend to slow the power delivery a bit, but it is more intense, if that makes any sense...




 
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