CRF 510 stroker


7 replies to this topic
  • link812

Posted December 15, 2011 - 02:49 PM

#1

I recently bought a CRF450 motor that needs rebuilt for my hybrid project quad. I was debating on putting the plus 3mm hot rods stroker crank in with a cylinder works cylinders and a CP 12.5:1 compression piston. I was wondering if anyone has ran the stroked and bored CRF motor? I wonder how long the well taken care of 510 motor would last and how it will run.

  • thecayub

Posted December 15, 2011 - 03:31 PM

#2

I have a similar set up, but not quite whatt you're talking about. I just did a 13.5:1 Je piston (stock bore) and +3mm stroker crank. This things a monster! If your cylinder is in good shape, i would recommend running stock bore piston with the stroker crank. And a 12.5 or 13.5:1 piston. you wont regret it. My bike rips now! Just my 2 cents.

  • link812

Posted December 15, 2011 - 06:42 PM

#3

the cylinder looks pretty torn up. I have had big bore motors and stroker motors but never both. Just seems like if im getting a new cylider and piston i might as well go big

  • Lead Head

Posted December 15, 2011 - 11:58 PM

#4

Theres already multiple threads going on about big-bores. Without a Stage 3 Cam and a lot of port-work, your engine will not make any more power. You will just shift the entire power-band down for more low end torque, but the engine will sign off early.

The piston and rod in a CRF450 already experiences G-forces similar (or even exceeding) those of an F-1 Racing engine. A stroker crank increases average piston speed, increasing those G forces. A big-bore forged piston hanging on the end of a stroker crank will just multiply the forces trying to tear the rod and piston in half even more.

Either do a stroker, or do a big bore. Don't do both if you value reliability, and without a cam and portwork, a big bore will not actually get you any more power.

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  • Shawn_Mc

Posted December 16, 2011 - 11:47 AM

#5

What the engine really needs is a longer connecting rod. But unless you hit up Crankworks and get a custom rod, I dont know anyone doing that.

You'd need a longer cam chain too, along with a spacer under the cylinder. If you were +5 on the con rod, with the +3 crank and the big bore, it may run ok if you had the head done big. Like a flat track head.

This can be done. How much money you got?

  • Ron Hamp

Posted December 16, 2011 - 04:44 PM

#6

the rod in the early 450 quad was nearly 3/8" onger than a crf i built a 490 motor with stroke and bore that made nearly 70 hp with over rev past 10500 rpm i beleive the rod length frees up some friction reduction.

  • Shawn_Mc

Posted December 16, 2011 - 11:55 PM

#7

i beleive the rod length frees up some friction reduction


Ya, and it will reduce the piston speed too so the thing can rev again. And that reduction in piston speed will calm the intake pulse at the opening event too.

Long rods are good. At least that's what she told me LOL...

  • link812

Posted December 17, 2011 - 04:04 PM

#8

I found a complete rebuild kit that includs the cylinder, piston, crank, stage three hot cams, kibble white black dimond dimond plus one mm valve with ti valve springs and retainers. I intended on doning a post and polish also.

I have had a big bore motor that felt like it signed off early on a suzuki I had. I really want to avoid that. I hated the way it felt. I had a stroker yamaha YZ426 that ran liked a raped ape.

I was planning on spending around 1500 or so on the motor (not including little stuff such as new bearings and gaskets) to push out the most power as possible. Thank you for all of the advice and i apoligize if there are many threads like this one.





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