I'm helping a buddy build a nasty LT250R and I was hoping you guys could give me a few piston options. He's sending the 86 RM 250 Cylinder (LT500 Intake & better Port Layout and Mapping) out to have the sleeve pushed out, the voids filled, bored, honed, nikisil plated, and honed again. He wants to go as big as possible with the bore. What is the biggest piston you guys have ever heard of anyone using in a LT250R?

If he has to get Wiseco to custom make him a piston (What I expect we will have to to do) he wants to go with a 80mm Piston. By using a custom Wiseco Pro-Lite Piston the wrist pin location will be in the correct location which will eliminate the need for a spacer plate or head modification.

He's having Crank Works stoke, true, balance, and weld a Hot Rods Crank 4mm and install a billet rod. K a N Powersport's will be the shop that does the case mods, machine work, porting, and assembly. He's shooting for a 377cc Trail Ported Motor that runs off 100LL Av-Gas!

He's going to have a lot of money invested in this LT250R but it should be a reliable screamer when he's done. He's going to run a Chrome FTZ Super Fat Pipe w/ Oversize Alloy Silencer, LT500 V-Force V3 Reed Cage, Pro-Design Billet O-Ring Cool Head w/ Custom Hand Cut Dome, FTZ PVL Digital Ignition, Dynatek Coil Kit w/ 10mm Spark Plug Wire & NGK-IX Plug, 40mm Mikuni TM Pro-Series Carburetor with Intelajet Fuel Induction System, K&N Air Filter Pod w/ Outerwear's Pre-Filter, Custom Made Aluminum Air Filter Splash Guard, Micro Polished & Cryogenic Treated Transmission, Magnum Billet Clutch Basket w/ Tusk Heavy Duty Clutch Kit, New Hard Anodized OEM Inner Clutch Hub, new OE Gearbox Bearings, Bushings, Seals, O-Rings, & Gaskets, and few other things.

He's having the Cylinder, Billet Head, Clutch Cover, and Stator Cover Show Polished by Race Refections and the Center Cases will be Powder Coated Mirror Black.

This should be one BAD LT250! I know CP Industries doesn't make a Aftermarket Big Bore Kit for the LT's but his motor should be as close to a Power Valve Sphinx as anyone has ever gotten on the LT250 using the 250cc motor platform.

The Frame on this 1989 LT has been sand blasted, gusseted, and powder coated, the suspension consist of a hybrid LTZ-400 Aftermarket front A-Arms, Spindles, Hubs, Re-Valved/Re-Sprung Dual Rate LTZ-400 Shocks, LTZ Front Brakes w/ SS Braided Brake Lines, LTZ Steering Stem & Flag, and he has a custom +4 Heavy Duty XC Arched Latter Swingarm on the Rear with the LTZ-400 Hybrid Rear Shock, Custom Built Sprocket/Rotor Guard, Aluminum Belly Skid Plate, and OMF Bend Ring Aluminum Wheels w/ New XC Tires.

He's got new Maier Replacement Plastic, 91 LT Seat w/ Gripper Cover,  Fly XC Woods Handlebars, Anti-Vibe Handlebar Mount, ASV Break Away Levers, Moose Throttle Assembly, New Grips, Nerfbars, Aluminum Front Bumper/Rear Grab Bar, Yamaha Blaster Headlight Assembly, and the list goes on and on.

If we're able to get the 86 Nikisil Plated RM 250 Cylinder to a 80mm with a matched Piston he should have a LT250R that's capable of competing with the TRX250R with the big Rotax Power Valved Sphinx Cylinders on the trails and in the 300ft Dirt Drags! This LT should blow minds!

Let me know what you think and any input a piston and rod option we can use for this LT build would be greatly appreciated.

Thanks 

Sounds like a good build but how ya plan on gettin a 80mm piston in somethin that comes what like 67 stock? Anything over 76 in a stock Cyl/modified is pretty much impossible or gonna be a complete catastrophic failure..

Have fun sealing the head and water passage to cylinder. Your asking for way too much bore from that cylinder. I'm not saying it can't be done, just that your exceeding the capability of the parts you want to use, you will spend less money and be further ahead to use a sled cylinder and get the cases welded up to work with it.
I've done all the homework with this setup from 302-344 and I know anything beyond that is not going to be a reliable daily rider.
As much as I like Suzuki, your not going to compete with a properly set up CP cylindered Honda, the Transfer layout of the Suzuki can't support the flow necessary to make the same power.

Sounds like an energetic project. Keep us posted with progress pics & notes on this. As far as a piston goes, check with JE or Mahle.
A few years back, I remember MHR & Mat Shearer both talking about filling & machining the cases to accept a Puma or Sabertooth  cylinder. But I never heard anything more about them. Maybe the builder can look into this?

Do you by chance have a link to CP Cylinder Swap MHR and Matt Shearer did? Did you ever see any pictures of the transplant completed or hear how it ran?

I would LOVE to check that out!

Thanks man,

It was on the now defunct 2strokecentral.com forum.   
However, Iceracer has done all the homework with his 302+ engines. I am all for innovation to do something different but it's also hard to argue with something that is already race proven. Do your research & let us know what you come up with.

Just yank the 250 out and put in a lt500 motor and make it a hybrid and be done with it. Will be a lot less money and a lot less headache.

I agree with this. However there is something nice about lots of cc's & a 6 speed.

Okay, thanks guys, I'll do some more digging and get back with you and let you know if come up with something. Has anybody ever done a heart transplant using the new RM 250 Cylinder? There's a abundance of big bore and stroker Setup's for them.

I wonder if its possible to counter balance the newer RM 250 motor and use it in the LT? Anyway thanks for all your input, if you come up with something please let me know.

Where you putting the reed cage cylinder or case the new RM cylinders worth using are all case reed set ups?

Problem is cp will never do that cuz they would sell about 10 total and I remember calvin saying he would have to sell like 50 for it to be profitable. Hence why there are no aftermarket lt5 cylinders just no market. I understand if there was a bolt on kit it prob would sell some more but especially for drag racing ure further ahead with the trx nate mccoy offers the billet tranny and 3-4 diffrent cylinder options. Seeing how calvin passed recently I highly doubt u will see anything other than 4 stroke or banshee stuff being produced.