Info on "Stroking"

Blaster250 · #1 (**permalink**) 12-01-2004

I have been thinking about "Stroking" the motor on the next quad I get. I dont know alot of specifics on how this is done. Shortening the stroke specifically.

1. When you change parts , is it a shorter rod, or a different crank, or both?

2. Does the jug need to be shaved down to match the new TDC?

3. What performance difference is in the low end, mid, ad high end RPM range?

4. Assuming you are going to increase the compression ratio, how much compression can you get thats normally done, and what compression ratio is common for alky engines, and how much smaller are the aftermarket domes sizes compared to the stock (avg cc)?

5. What is the average displacement lost in lets say a yz250.

If anyone would like to enlighten me on the world of stroking I would appreciate it.

Flattrack · #2 (**permalink**) 12-01-2004

Short version :When you stroke a engine you are increasing the the length of the stroke not shortening it. This is changed by relocating the pin in the web of
the crank. Changing he length of the rod is not necessary but but going with a longer rod is beneficial to reducing rod angle and reducing wear on the Cyl.and piston. The jug dose have to be modified with base spacers and port work to benefit from stroking to get the proper port timing for your particular needs. You will see a great gain in power through out the rpm range ad a substantial gain in low end torque. As far as CCs we run a head set of 15cc down from 22cc stock on our Flat track blaster this puts us in the 210 lbs range but the Cyl is also decked. Sorry this is so short I have to get to work.

Banshee · #3 (**permalink**) 12-01-2004

WOW that just sounds like a bad title, I guess "help with stroking" could be worse.

blaster2000 · #4 (**permalink**) 12-01-2004

Yeah I was thinking the post was going to be just a little different lol. At least it's not what I thought it was going to be :p

370banshee · #5 (**permalink**) 12-01-2004

Quote:

Originally Posted by Flattrack

Short version :When you stroke a engine you are increasing the the length of the stroke not shortening it. This is changed by relocating the pin in the web of
the crank. Changing he length of the rod is not necessary but but going with a longer rod is beneficial to reducing rod angle and reducing wear on the Cyl.and piston. The jug dose have to be modified with base spacers and port work to benefit from stroking to get the proper port timing for your particular needs. You will see a great gain in power through out the rpm range ad a substantial gain in low end torque. As far as CCs we run a head set of 15cc down from 22cc stock on our Flat track blaster this puts us in the 210 lbs range but the Cyl is also decked. Sorry this is so short I have to get to work.

you beat me to it!!!!!!!! damn you