Any combination of parts that would get my 491cc to 450cc

torque monster · Post by **torque monster** » February 11th, 2009, 10:54 am

I want to run in the 450 Supermoto class, has anyone made their 500 smaller to fit in the 450 class.

Some of you race guys must run into displacement issues in respective classes. As it stands the 500 would be runnable in the Unlimitted class in our race series but I would really like to be able to run 450 & unlimitted.

Would like to do it without braking the bank with stock parts if possible.

Any ideas?

Cheers
Chris

MICK · Post by **MICK** » February 11th, 2009, 11:03 am

Gonna be hard not to break the bank when you're looking atleast a new top end and resleeve.

I think you would have to resource a 250 big bore piston and drop atleast $350 into a custom sleeve. I'm thinking it would be a $500-$700 project.

torque monster · Post by **torque monster** » February 11th, 2009, 11:58 am

That isn't too insane. Still open for other ideas?

http://www.youtube.com/user/500bigbore · February 11th, 2009, 12:04 pm

I find that hiding the bills from yourself or dooing it all cash so you cant remember helps you justify dooing things like that

dannygraves · Post by **dannygraves** » February 11th, 2009, 1:45 pm

wasn;t the cr480 and cr450 the same bore different stroke? I know the kicker was on the other side on the 450, but I do wonder if you could flip a cr450 crank or find some way to adapt it to fit.

torque monster · Post by **torque monster** » February 11th, 2009, 1:49 pm

That is exactly what I was thinking about, if that would work you may be able to mill the cylinder down to the correct height. Anyone got a 450 crank and a 500 crank they could photo?

dannygraves wrote:wasn;t the cr480 and cr450 the same bore different stroke? I know the kicker was on the other side on the 450, but I do wonder if you could flip a cr450 crank or find some way to adapt it to fit.

dannygraves · Post by **dannygraves** » February 11th, 2009, 1:51 pm

I'd bet the rod length would worht fine with an '85-'86 jug. those had a really steep rod angle because honda kept stroking it w/o raising up the jug.

http://www.youtube.com/user/500bigbore · February 11th, 2009, 2:10 pm

my 450 shortblock is stil together, but i can take a pic down the case

dannygraves · Post by **dannygraves** » February 11th, 2009, 2:12 pm

is the 450 an 89mm bore?

MICK · Post by **MICK** » February 11th, 2009, 2:58 pm

I can't think of a more difficult way to go about it then start flip flopping cranks...Now we're talking about having to mod the entire engine to fit

I'd much rather my sole obstacle be piston pin diameter.

Check it out, you drop a KX500 piston into the motor as is and you get 458.89cc!! Pretty damn close if you ask me. How far off do you think the piston pin diameter could be? I'd say they're no more than a britincali hair. You either bore the rod's small end out, or shim it to size. Install KX500 top end kit, resleeve and be fucking DONE!! I bet this could be accomplished for less than $500. That's nickles and dimes really...

I think I'm going to do this when I rebuild my bike. Too easy...

http://www.youtube.com/user/500bigbore · February 11th, 2009, 3:22 pm

Mick its easier than you'd think, hone the kawi piston pin area 1mm larger and slip your honda 500 pin in it.
you'd better check the room in the piston for width tho, the bearing is 5mm wider

http://www.youtube.com/user/500bigbore · February 11th, 2009, 3:25 pm

do you know if the pinheight is the same in the pisotns?

MICK · Post by **MICK** » February 11th, 2009, 3:40 pm

Roostius_Maximus wrote:do you know if the pinheight is the same in the pisotns?

good question...that could be a bit of a show stopper fo sho. I have extra KX pistons but not here with me in FL. I could ask my Dad to measure the ones I got in ID. I think I'll do that.

So bore the piston pin dia 1mm, maybe machine the piston pin area a bit, and cut the head or add gaskets IF necessary? This does not sound hard at all.

LOVEMYCR500 · Post by **LOVEMYCR500** » February 11th, 2009, 4:33 pm

the easiest way would to have a sleeve made and then find a 85 mm snowmobile piston that uses a 20 mm wrist pin. I looked around once at this and found a few. This would put you at 448 cc's. It would cost more to do (call crankworks to see of possible) but I personally would destroke from a 79 mm stroke to a 72 mm stroke. You would have the same 448 cc's but a motor that would live all day with a 2.00 rod/stroke ratio. This motor could be ported to rev and it would live a long life. You would have to deck the bottom of the cylinder down which depending on the port timings wouldn't be that big of a deal. If crankworks will do that much destroke, this would probably be the way to go since I think it's going to be hard to find someone willing to make a 85 mm cylinder sleeve. Maybe I'm wrong.

MICK · Post by **MICK** » February 11th, 2009, 5:21 pm

Custom cylinder sleeve $325 quoted by Advanced Sleeve. Steel or aluminum your choice...

The snowmobile piston is a good idea. Give you more options to look for. The KX piston just kinda popped in my head

Shoot if you could find a snowmobile piston that fit you would indeed come in at under $500 in parts. But a re balance should be done to complete the project the right way. That'll set you back a few hundred bills.

100hp honda · Post by **100hp honda** » February 11th, 2009, 6:14 pm

resleeving it for 85mm would definatly be the easiest way and cheapest im sure. i wonder how it would run ?

MICK · Post by **MICK** » February 11th, 2009, 6:58 pm

So do I? I serisously think I might try and find out. Drop 50cc and port the shit out of it

90cr500guy · Post by **90cr500guy** » February 13th, 2009, 7:47 am

dannygraves wrote:wasn;t the cr480 and cr450 the same bore different stroke?.

no, the 480 and the 500 are the same bore. the 480 has a 3mm shorter stroke than the 500. The cr450 is actually only 430cc

LOVEMYCR500 · Post by **LOVEMYCR500** » February 13th, 2009, 8:25 am

I think I would see what destroking that crank would cost first.

CR480R · Post by **CR480R** » February 14th, 2009, 3:45 am

dannygraves wrote:wasn;t the cr480 and cr450 the same bore different stroke? I know the kicker was on the other side on the 450, but I do wonder if you could flip a cr450 crank or find some way to adapt it to fit.

Those cranks have 4-stroke style crank wheels that would drastically lower crankcase compression ratio... especially when combined with the reduced displacement.

Roostius_Maximus wrote:Mick its easier than you'd think, hone the kawi piston pin area 1mm larger and slip your honda 500 pin in it.
you'd better check the room in the piston for width tho, the bearing is 5mm wider

that would mean every time you replaced a piston it would need costly or time consuming modification... I would use a KX500 rod since the crank needs altered anyways for legal displacement...

LOVEMYCR500 wrote:the easiest way would to have a sleeve made and then find a 85 mm snowmobile piston that uses a 20 mm wrist pin. I looked around once at this and found a few.

That would definately be the cheapest route... Although the sled pistons may not have a long enough skirt for a 79mm stroke and could possibly free-port the exhaust at TDC.. the piston would also need to be wide enough to support the bridged exhaust port of a cr500..

LOVEMYCR500 wrote: It would cost more to do (call crankworks to see of possible) but I personally would destroke from a 79 mm stroke to a 72 mm stroke. You would have the same 448 cc's but a motor that would live all day with a 2.00 rod/stroke ratio. This motor could be ported to rev and it would live a long life. You would have to deck the bottom of the cylinder down which depending on the port timings wouldn't be that big of a deal. If crankworks will do that much destroke, this would probably be the way to go since I think it's going to be hard to find someone willing to make a 85 mm cylinder sleeve. Maybe I'm wrong.

keeping the stroke closer to stock would keep the ports alot closer to where they need to be and would probably work much better with the available CR500 pipes... Since such a thick sleeve is needed for a de-bore for maximum weight reduction, heat dissapation, and friction losses I would use a plated aluminum sleeve... If cost wasnt an issue I would use a 86.25mm KX piston... a CR500 cool head with a custom KX dome insert.. and a CR crank destroked 2mm for 77mm with a 145mm KX rod... displacement would be 449.88cc... and once the crank, head dome, and sleeve were made the bike could be easily maintainted with off the shelf parts...

BannedCR500Riders.com

Any combination of parts that would get my 491cc to 450cc

Any combination of parts that would get my 491cc to 450cc