To stroke or not to stroke

Mwrunt · Jan 17, 2015

I am in the process of building a new engine. I am starting with 62t ported cases and have a ported 850 blowsion non powervalve cylinder with cr500 pistons
46 mm taper bore carbs.
I big question is do I buy the 5mm stroker crank or stay with stock.
The cost to stroke the motor is a difference of about $500. And time to trench the case. Figure out deck height.
So probably another 20 hours plus in extra time to stroke the motor.
So is 62 cc worth 500 dollars more and the time.
How much extra power will it produce.
This will be going into a square for now until I get funds freed up for a hurricane hull

Dartman · Jan 18, 2015

adding a stroker crank might make the porting way to much for freeride/freestyle even with a stock base gasket

Mwrunt · Jan 18, 2015

That has been a thought for me to. I was planning to cut the domes deeper to allow the pistons to travel farther into the head. This will allow the port timing to stay pretty close to stock.

Dartman · Jan 18, 2015

adding the stroker crank will increase the porting even staying with stock gasket and cutting the domes
usually adds about 3-4 degrees

Mwrunt · Jan 18, 2015

I have done this with stroker cranks on bikes before. But you can work with the powerband moving up a few hundred rpm when u have a clutch.
Will a few degrees make that much of a differnce

Mwrunt · Jan 18, 2015

Any one have any input. Has anyone ridden both a 908 and a 850. Was there a big differnce.
Please share your input.

Dartman · Jan 18, 2015

adding more port timing will depend on where you are now with timing durations
imo 50cc can be made up with a really good setup on the 850
programmable ignition timing, highest compression ratio the setup will take, skatrak setback mag and correct prop setup, matched carb and exhaust system-tuned
i don't think there many 5mm strokers/w CR piston setups around

XJCrawler · Jan 18, 2015

Dartman said:
adding more port timing will depend on where you are now with timing durations
imo 50cc can be made up with a really good setup on the 850
programmable ignition timing, highest compression ratio the setup will take, skatrak setback mag and correct prop setup, matched carb and exhaust system-tuned
i don't think there many 5mm strokers/w CR piston setups around

The Jetworks 900r is the only one I know of