Cylinder Questions

[Bad Ass Honda 250r]

i have a 86 honda 250r with a stroker crank and the spacer plate and a 86 piston... could i run the 88-89 cylinder so i do not have to use the spacer plate with the 86 piston???

[ky 2stroker]

you would still have to use the spacer plate with the 88-89 cylinder if your still using the stroker crank. the only way to ditch the spacer plate would be to get the head rechambered/cut for the extra stroke.

[EAT_A_450]

Originally Posted by ky 2stroker

you would still have to use the spacer plate with the 88-89 cylinder if your still using the stroker crank. the only way to ditch the spacer plate would be to get the head rechambered/cut for the extra stroke.

That is correct- both cylinders are the same height.

[Bad Ass Honda 250r]

i already have the head macined for the extra stroke... but for the longer rod... i am useing the spacer to take up space for the longer rod... not stroke... so all atc-trx 250r cylinders are the same heith???

[fiveOnick]

You can cut the head for the stroke increase but not the deck change due to the piston. That must be done with a plate.

[Bad Ass Honda 250r]

So if i had a stock 1989 honda trx 250r.... i put a stroker crank in it.... milled the head out for longer stroke.... would i have to use the spacer??? im kinda confuzed

[bean86]

Yes you would. All of the cylinders are the same height. The whole for the piston rod is lower on th 86 piston to accomodate for the shorter rod on the 86. In 87 they went to a longer crank and move the whole for the piston up to keep the same stroke. By running the 87 rod with the 86 piston you gain about 4 mill. so you have to use the spacer. If you switch to an 87 piston with the 87 crank you won't need the spacer then because everything will line up. However just run the spacer with 86 piston on the 88-89 cylinder and you will have the best of all worlds. A longer stroke with the best port layout of the stock 250rs.

[all250r]

Just to add my 2cents, and to clarify a common misconception, a longer rod does not make a longer stroke, at all. A 10 foot rod attached to the regular crank would still only travel 72mm, correct? What makes a longer stroke is the position of the crank pin. You can only "stroke" a motor by adjusting the actual distince the piston travels, no matter where in the bore that travel is occurring.

So, the common corrections made with a spacer plate have nothing to do with the stroke of the motor. If you're using an OEM crank, you're running stock stroke.

However corrections made with a spacer plate to accommodate an actual stroker crank has to do with stroking the motor, but only so far as the crank is creating a different stroke, not by the height the cylinder is above the crankcase. Typically porting is done to adjust and create the desired port timing. So if you feel you can just swap any 198X cylinder on your bottom end, you probably never finished your original design/build.