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FOG this is probably directed to you. Is there any place to get larger slugs? How big an over bore is safe on this motor? Does anyone make cams for the EX? I saw something you wrote about race prep and figured I don't have to live with in the rules of any sanctioning body so why not over bore. I have an extra motor, well whole bike to play with so I may just do some internal mods also.
 

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I have only built 1 Oversize engine. That was 2mm oversize. It seemed to work OK. It produced 59 HP with the stock Cams. The owner was going to replace them with Cams from Megacycle. But I don't know the results of that.
Since the EX is already a Bored and stroked 454 making the bores much bigger it a risky business. Even the 2 mm mentioned above is risky. The stock bores don't even stay round.
The better way is to get a kit with new cylinders and pistons then you can get up to 640cc I think. With a Megacycle cam that combo with the stock CR should produce 62-3 HP. Those kits usually bump the CR too but get a lower set if you can. Going much over 11:1 is death. Can you say grenade? And under no circumstances rev it past 10 grand. SO don't bother with any valve lightning stuff to raise the revs.

Do a google search for ex bits and see what you can find.

FOG
 

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i've seen two kits thus far:

540cc (bored stock sleeves)
600cc (Replacement sleeves, bored case)

both made by Engine Dynamics. Last i knew, they will tune the engine before they ship it back to you for either race or street applications.
 

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Spears makes a 1mm over (512cc) piston kit with 12.5:1 CR. Wouldn't the engine be fine with high compression as long as u get high lift/duration cams, springs, retainers, adj. sprockets, and some head work?
 

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This engine as I have said many times is a very poor candidate for hot rodding. It has already been Bored and Stroked to within an inch of it's life. The problem/s are the cases are too weak, the crank it too long and wippy. The whole thing is cut in half down the middle by the cam chain gallery, so it squirms and distorts like a bowl of jelly. When you raise the CR you put extraordinary strain on all the systems that are unable to handle it.
All that valve work is designed to allow increased reves, which is a bigger No No. The valves are operated by rocker arms for who knows why, instead of the more conventional shim under bucket system that almost everybody else uses. The big ends of the rods open up at 11.500 RPM and the bearings will spin the rods also stretch and allow the pistons to hit the head.

Make it bigger is the best thing but don't try to make it make a lot of HP. All you'll get is a Box of bits.

Remember this is a 60s design using thirties technology.

FOG
 

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FOG said:
I have only built 1 Oversize engine. That was 2mm oversize. It seemed to work OK. It produced 59 HP with the stock Cams. The owner was going to replace them with Cams from Megacycle. But I don't know the results of that.
Since the EX is already a Bored and stroked 454 making the bores much bigger it a risky business. Even the 2 mm mentioned above is risky. The stock bores don't even stay round.
The better way is to get a kit with new cylinders and pistons then you can get up to 640cc I think. With a Megacycle cam that combo with the stock CR should produce 62-3 HP. Those kits usually bump the CR too but get a lower set if you can. Going much over 11:1 is death. Can you say grenade? And under no circumstances rev it past 10 grand. SO don't bother with any valve lightning stuff to raise the revs.

FOG
So I guess putting a small turbo to it would be a bad idea... :( Damn. So much for that idea.

Mark
 

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FOG said:
The valves are operated by rocker arms for who knows why, instead of the more conventional shim under bucket system that almost everybody else uses. T
FOG- Would this be to increase the lift on the valves, again a reprofiled cam can do this as well complete with less moving parts. From my limited experience with early 80's japanese cars (Most of the cars in NZ are japanese) they loved the rocker configuration, it does not seem a big stretch to shift to the bike.
 

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art1989-

would suggest saving $$$ you'd spend on mods and put towards a late model 4 cyl. kaw, suz, honda...whatever. it'll run circles around the EX (sorry, guys ::) ) after time, $, experimentation , $, failure, more $ you'd be better off with a higher performance bike from the get go.

hey, FWIW.................duc 8)
 

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ducatiman said:
art1989-

would suggest saving $$$ you'd spend on mods and put towards a late model 4 cyl. kaw, suz, honda...whatever. it'll run circles around the EX (sorry, guys ::) ) after time, $, experimentation , $, failure, more $ you'd be better off with a higher performance bike from the get go.

hey, FWIW.................duc 8)
This is just my track beater... I wanted something uber cheap that I could throw off a cliff and laugh about. Although I probably should just reconsider and get something better. I figured if I could learn to ride the 500 fast, I would probably be faster/safer/better on my 1000cc street bike (SV1000) which is a bit more powerful than the 500R. I just love tinkering is all... and I like turbo's. The nature of the SV1000's design is decidedly non turbo friendly, the 500R, looks like it needs... no wants, a turbo.

Mark
 

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turbo ?

nah, just go for a smaller displacement bike with skinnier tires. screaming around a 1000cc behemoth is pretty cool in my book :)
 
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