Well, I have my bike all apart and removed the engine from the frame today. Going to do the big bore / high comp kit from lancer and was wondering this: Has anybody tried to stroke one of these engines?? If so, what is needed to do this? I am looking to enhance the performance as much as possible...looking to make it a true "Super Thumper" hence my handle   P.S. I had a dream about my bike the other night....my "Super Thumper" specs from the dream......750cc, 75hp, 80 ft. Lb Torgue. 1/4 mile....12.8 @ 115mph  

750 cc is 45 cubic inches, implying about 45 ft-lbs of torque unless you use a serious blower and some mighty high-octane fuel. Based on the Savage engine, probably 7000 or so rpm and lower if you stroke it. If you can get the high torque at max rpm (unlikely) you might be looking at 60 horsepower. I'd bet for more like 50 hp. But, I wish you luck.

The old rule of thumb says piston speed should be kept under about 4500 feet per minute for reasonable engine life. With a 94 mm stroke that comes to about 7300 rpm, about 15% above Suzuki's red line of 6500. Suzuki may have other reasons for the lower red line, or they could just be a little conservative on an engine simply not designed for maximum power.

arteacher wrote on 12/18/12 at 08:16:47:


Stroke usually means additional i.e., 94mm increased to 97mm
De-stroke means less i.e., 94mm reduced to 91mm

longer stroke means more displacement.

I've never been that involved in engine modifications, but I understand that a crank throw can have metal added to it on the outside by some variation of welding, and then the throw can be turned or ground with its center slightly further out, thus increasing the crank throw and the stroke. I would guess the cylinder could then be moved out by, perhaps, adding a brass spacer to the cylinder base gasket. Other factors would no doubt crop up, including cam chain length. Sounds like an interesting, and expensive, project.

Charon wrote on 12/18/12 at 17:13:11:

That is an offset grind of the same size.  You can also go with an offset grind at a smaller size if you are willing to change the rods.  (Which you may have to do anyway.)

I was looking at doing this on a Marauder.  Now I have not been deep inside a Savage motor, so this may not apply, but the same guys designed both so...

With more throw, you have the rod going down into the case more.  There was insufficient clearance in the Marauder case to do this without clearanceing the case.  And the case walls are kind thin, so that made me nervous.

Also, with more throw, you have sharper rod angles.  I was looking at potentially having clearance problems with the side of the rod and the bottom of the jug.

And if you solve all that, you had best calculate the deck height right.  Shorter desk heights mean more cam chain to take up...  And it also retards the cam as it takes it up...

I decided to look at other places than displacement.  Specifically raising compression, cam advance and timing advance.