1jz Stroker

[Jon Levatte]

another long story short...dont take your motor to c-tech performance in grand rapids, Michigan...ruined the one good cylinder and then ruined the cylinder that was resleeved and refused to fix it.)

first off no one will give out port numbers to anyone. This is what separates jim-bobs porting service aside from f.a.s.t or herrjuggsracing. so if you needing porting done talk to one of the site sponsers they will help you out.

And then for the pipes thats on what kinda riding you do. Since you listed fmf toomy and dmc then I'm going to guess you ride in the woods for the majority. I wouldn't just limit to those 3 pipes I would also consider the pro circuit platinums.

i will be running a stock head...that is why i asked about cylinder porting. I was reading the post "spacer vs NO for 4mill" and they talked about having to port the lower portion of the port 2mill because of running the spacer plate.

Don't run a spacer plate. Also, if your builder is not familiar with 2 stroke porting, goes with out saying, don't take your motor to him for porting! You can assemble the motor with basic hand tools and a manual. Leave the port work to a competent builder if you want to do it right the first time. As far as case porting goes, I would recomend it. I would also suggest you call a builder and discuss your goals with him. Call Jeff for your motor work, 1-785-364-5325. This is his website.

speaking of builder, that's who you should really talk to. whoever is going to port it is going to need to know what kind of ridding, and what kind of power you need, and will need to know all the other mods, and/or suggest what will run best with the porting, including pipes, reeds, carbs, etc, you can get ideas on how the different bolt-ons will perform, but ultimately, the builder will know best how/what will work together best for you.

as for my suggestions, get your head rechambered for the stroke to the size the builder suggests. pro citrcuits will be awesome with a woods/trail port, boysen reeds, and 28-30mm carbs. and, i would also suggest wildcard as my favorite builder, but you should check out the different builders on the site and pick the one you like.

And for your motor builder I wouldn't listen to a 4stroke builder for tips on 2stroke power. If its a friend and you dont want to tell him you are going to someone else thats up to you. But porting needs to be left to the pros.

well i dont know if he builds 2strokes or not....i do know that he builds 4stroke ATVs and sprint car motor and drag car motors. He used to build snomobiles...which most used to be 2stroke right? anyway all i was having him do was bore my cylinders. he has a flow bench and said he could port my cylinders if i wanted to.

like i said idk if he does 2stroke (i havent talked to him much but i will) but he has build some pretty bad 4stoke drag bikes. he is well known in the area for that. he also invented some kind of chain tensioner for QT motors (winged sprint car i think). he has been doing motor work all his life and i trust him with it. but as far as porting...i need to ask him if he does it much on 2strokes...if not ill have to send the cylinders off to someone.

random memory...he also built the motor for the fastest honda...what was it...umm...650 (maybe 750?) motorcyle form the 70's i think...built it in the 90's sometime i think...the guy talks so fast its hard to understand him...but he has proof of it all.

if i opt to just go ahead and buy the cool head and 4mm domes...i wouldnt need to port the cylinder because i wouldnt be running the spacer plate correct? but i would theoretically want to port them anyways purely for performance and not functionality right?

$100 dollar port job makes me wanna cringe.. I think you'll get what you pay for. Just call a builder and talk it over. You may end up leaving it a stock stroke motor with a mx port job! Either way I wouldn't buy anything until you get a good clear direction for your build. I would use one builder through out the project. I wouldn't have one guy bore it, one guy port it and order my parts from another guy..

that is exactly why i got on here! $100 sounded too good to be true...and i know all about getting what you pay for (trust me) thats why i havent bought anything yet and havent done anything to the cylinders...they are at 64.5mm and need to be pushed to 65mm...and ported

On a 2 stroke your rasing the ports, and changing the angle of the ports. When you change the port hight and shape your changing how the engine breaths. Porting on a 2 stroke controls when the exhaust goes out, and the fresh air and fuel come in. It is like putting a cam shaft in a 4 stroke. I wouldn't trust my cylinders to a guy that does general 2 stroke porting, let alone one that doesnt have any experiance. Take them to some one who has there reputation built on building banshee engines. Just cause you have ported a chain saw doesnt mean you know how to port banshee cylinders.

You could do the 4 mill, run a cool head with stroker domes, and leave the cylinders not ported. You will be missing out big time though. It will run and you might notice a little gain in power. It wont be near as fast as a stock stroke ported banshee though.

The stroker will raise your compression ratio to about 13.1:1. Its not typically a problem. What you'll find is it makes a lot of pull your arms out power. You dont need to do anything regarding the balance or the piston etc other than do a mock up and makes sure everything is going to clear. If you need a cylinder, you can go to 511cc by using the Cylinder works big bore and the Hot Rods 3mm stroker. I did one with a ported head and it was impressive. Its only money, right ?

I built the engine for a customer. He'd got quite a bit of time on the crank. When I pulled the motor down, the crank measured perfect. Its a hot rods piece. You can buy replacement parts for it too (the rod is shorter than stock to make up for the stroke) At 13.1:1 you dont need race fuel. Peak Hp probably isnt too dramatic. But from idle to about 8000 rpm, it pulls way harder. For MX or trail/play, its a great mod. If you were racing SuperMoto or flat track, there are better ways to make power. Raw numbers on the power with the crank alone, I really cant hazard a guess. Like I said, the one I did was 511cc with a port job on the head. The compression ratio came to 12.6:1 with the big bore and stroker combo, a stock cam and a Yosh pipe (heavy friggin pipe too) Id guess it was an honest 55+ hp. It was fast, really fast.

The power unbelievable but not unmanageable. It pulls and pulls throughout all the ranges and seems never ending. And look out when you hit 4th gear. It's like the legendary little race horse Seabiscut in the final stretch. Looks around and says it's time to go...

This is a cool thread - very pertinent. From this and other threads, I've picked up that switching to a high compression piston [13.5:1] and a stroker crank both add low-to-mid power without grenading the engine.

Since I've always chickened out when trying to find the rev limiter on my 450R, I am thinking I can do the stroker and 13.5:1 together with the switch to stainless intake valves and matching springs/retainers while still maintaining engine integrity and longevity.

With a 13.5:1 piston and a 65mm stroke crankshaft, you're looking at over 14.1:1 compression. I doubt 91 octane could cope with that. 93 might be able to, but from what I understand, 93 is pretty rare in the west.

I wouldn't do a stroker if I wanted maximum reliability. Stroker cranks by their very nature increase piston speed/acceleration. They increase the force the piston skirts put on the cylinder walls, and they're harder on the crank and rod bearings due to the higher piston accelerations. The fact that most CRF450 stroker cranks use shorter rods just compounds all those issues. If you want more displacement on a 450, I'd go big-bore over stroker any day.

People often stroke to increase the displacement and compression ratio of the engine. You have to be careful of the resulting increase in maximum piston speed and the corresponding forces accelerating and decelerating the piston. Engines are destroked for for the opposite results. Lower piston speed may allow a higher maximum RPM resulting in more power at high RPMs -- compression ratio losses are compensated for with different piston dimensions.

Some engines have a poor rod-stroke ratio, and a shorter stroke and longer rod can reduce side-loads on the bores, or the changed piston acc'ns work better with the engine's breathing characteristics.

*Back in the day, the small block Chev' engine was made in 8 different engine capacities, from 265 to 400CID. Seven of which used the same crank main bearing bore and the 400 could with the other's cranks with special "spacer" bearings, or the crank mains turned down for a long stroke crank in the others. With at least 5 different OEM bores, and at least 4 OEM crank strokes, one could mix and match for many different capacities. The 302, 327, and 350 all used a 4" bore but with different wrist pin heights to work with the 5.7" connecting rods all but the 400 used. This sort of thing also meant different rod lengths could be used with 'off the shelf' pistons.

If you are operating without any form of capacity limit, generally the bigger capacity the better. If you want to stay with you current block and can't bore it out any further, stroking is the only option left to increase capacity. Bigger capacity will lead generally increase to more torque over a greater RPM range.

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