Stroke engine yourself

[Knips178]

I'm just wondering how hard it would be to stroke the crank yourself 4mm or 6mm? I know a good shop that could do it, but then i have to find the right sized connecting rod and where can I get that? Other than that what else would i have to do? I just seized my motor up and like most people, i'm on a budget and want to stroke my crank while i got it out.

[AndrewRRR]

Originally posted by Knips178
I'm just wondering how hard it would be to stroke the crank yourself 4mm or 6mm? I know a good shop that could do it, but then i have to find the right sized connecting rod and where can I get that? Other than that what else would i have to do? I just seized my motor up and like most people, i'm on a budget and want to stroke my crank while i got it out.

If the shop is reputable it might be worth a try. You just move the pin out 3mm for a 6mil stroker. Make sure to true and weld it. The size of the rod should be the same, might want to get an aftermarket one that is a little stronger than OEM. I'm not sure what kind of case clearance 400EX's have, but on Banshees and 250r's at 5mm you have to start trenching the cases. Since it's a 4 stroke your compression will probably change dramatically.

[Knips178]

:confused:
When you say weld it, what do you mean? I understand one way of stroking is to machine down the crank pin where the rod connects to then use a connecting rod that has a smaller diameter hole for the machined pin. But where does the welding come in? or is the whole crank pin cut and rewelded 3mm farther out?

[Knips178]

here is a pic of what i'm talking about.
http://domino.newvisionnet.com/Joey/atv/stroker.bmp

[AndrewRRR]

Originally posted by Knips178
:confused:
When you say weld it, what do you mean? I understand one way of stroking is to machine down the crank pin where the rod connects to then use a connecting rod that has a smaller diameter hole for the machined pin. But where does the welding come in? or is the whole crank pin cut and rewelded 3mm farther out?

Yes the proper way to do it is move the pin 3mm further out. Also on 2 strokes and I assume 4 strokes it's a good idea to weld the counterbalancer because they can rotate and bend the crank and cause vibration. My R did it and threw the crank 8 thousandths off true. Banshees do it often too. I'm not sure if 4 strokes do as much.

[Knips178]

you mean add weld on to the counter balance to balance the crank right? because if you move the pin out it will make the crank shake due to the counter balance not being setup for the extra stroke weight.

[AndrewRRR]

I've never heard of adding weight. It does put increased strain on the crank and rod. But what i was talking about is welding or pinning the counterbalancer so it doesn't rotate on the crankshaft causing the crank to be very unbalanced.

[Knips178]

but if you take the counter balancer off the crank i would think it make the balance even worse, but your saying it will actually help it balance out?

[AndrewRRR]

I'm not talking about taking it off. They are pressed on. You simply weld it so it can't move because in high hp engines they can slip.

[INFANTRY RACING]

see the welds

http://www.powroll.com/images/P_W_16096-00288.jpg