stroker help??

[jokester]

currently my quad is bored to a 254 and I was wondering what it would be if I dropped in a 4mil stroker. Also I've heard that using a spacer plate isn't a good idea, is this true?

[methyman]

The porting needs to be adjusted for the stroker. It would need to be lowered 2mm's.

[jokester]

I understand what needs to be done with the porting, I was just wonderin what the displacement would be and also if using a spacer plate would be fine or should I just get the cases trenched?

[wilkin250r]

254 is a 67mm piston.

Add the increased stroke with the same 67mm piston, displacement becomes 268cc.


To verify, use 67mm bore, the stock stroke is 72mm, so the 4mil stroker would be 76mm stroke. How to calculate engine displacement (http://www.exriders.com/vbb/showthread.php?s=&threadid=196569)


Not to be a jerk or anything, but you have all your mods listed in your signature down to the grips. Do people really care what grips you're running? And does that last line for the 400ex mean that you don't even own it anymore? You've got a long list of mods for a quad you don't even own anymore?!?

[jokester]

ight thanks for answerin that first part, wilkin250r. but ya I hear what your sayin, I'll edit it:o

[86 Quad R]

wilkin is correct on the displacement. if your going to go with a 4mm strkr then i'd suggest that you do run the 2mm spacer. it makes for less port adjustment. a 4mm strker can be done without the spacer but there are many things that need to be addressed and modded of which i wont get into.

[kiesta00]

ahh, the good ol stroker threads!!

Make sure whoever is doing your engine work knows how to correctly setup a stroker motor. I went through hell with my first build when the guy didn't know squat about 250r motors. There are many different ways to set it up, just make sure he has done one of them before, and had no problems with it.

[86 Quad R]

lol kiesta00 is correct but there are plenty of guys out in oregon that build.......... just make dayum sure you shop good. :)

[wes350x]

Tell me if you guys have heard of this.
I bought a 89 250r and the guy told me this about the motor.
Its a 265 stoker done by Curtis Sparks. It has a YZ250 piston in it and also the spacer plat at the bottom. Could this be? new to 2 strokes so Im not sure about a few things but i know I have to run 100+ octane.

[Buttermilk]

I've heard of people doing that in my part of the country.

One reason that is done is simply because piston sizes run out on the 87-89 yrs. at 0.080" over (68mm) if I remember correctly. The YZ250 piston allows you to continue using your current cylinder w/o having to resleave. The spacer plate is used in conjunction with the YZ250 piston since the piston deck height is different (much like using an '86 style piston on a newer cylinder with a spacer plate...). '86 style pistons are available up to 72 or 73 mm's, I believe.

One thing you have to consider when going with a stroker crank on the 250R is making sure that the piston clears the crank lobes. I personally haven't checked, but I've been told that the 87-89 pistons will not clear on a +4 mill crank on the 250R.

On my motor, I do know that if you run an '86 style piston, with a +4 mm, 130.3 rod, combined with a spacer plate that measures 0.200", you will have zero deck height. My motor is an '87 bottom and '87 cylinder. The piston skirt just clears the crank lobes.

[jokester]

ok, so we've already established that it needs work done to the exhaust port, have it done at a good company(obviously), and it won't clear in stock form. So once again what I want to know is (will I be fine and get good reliability out of using a spacer plate, or should I have the cases trenched instead)???? and if I go the second route is there anything else that needs to be done?

[86 Quad R]

go the spacer plate route. its the most practical way. case trenching isnt called for on a 4mm strkr.

[Buttermilk]

Spacer plate is the way to go, as mentioned by 86 Quad R.

The spacer plate shouldn't cause any reliability issues. I've ran one for years with no problems.

In fact, most aftermarket cylinders such as the ESR, Pro-X variety require the use of a spacer plate if you run the long rod.

If you go with a +4 mm stroker, then you'll also want to run the 86 style piston to eliminate contact between the crank lobes and the piston skirt. Other wise, you'll need to remove material from the piston skirt to eliminate contact.

Whether you run spacer or no spacer, the 4 mm crank doesn't require trenching of the cases. Trenching is only required when the stroked crank causes the connecting rod to make contact with the case. The +4 crank does not.

As far as porting goes, the porting needs to be matched to the +4 mm crank. Both transfer and exhaust timing are affected by the longer stroke.

[jokester]

awsome thats what I needed to know! thank u guys for your help