hey all,

If you shave a little bit of metal off of the head where it seals to the cylinder, you can raise the compression ratio.

I remember doing some calculations on HC pistons and cylinder volumes, but I couldn't find that post.  Anyway, if one were to shave 0.1" off of the head (not necessarily a good idea, but maybe 1/2 as much?) the compression ratio would increase to about 10.2:1 (compared to stock ~8.5).

To do this... take off the head.  get some grinding compound (e.g.  alumina dust), and some oil, as well as a large piece of flat glass.  Run the head around on there in figure 8s until you have removed as much material as you want.

All that being said (typed), I have not done this.  It was suggested to me by a gear head friend of mine.  keep in mind he wants to split the case and balance my flywheel, too...

In this post, there is a link,

http://suzukisavage.com/cgi-bin/YaBB.pl?board=RubberSideDown;action=display;n...


In that article, an 80+ page pdf file, will be a section on shaving the head/getting more compression. According to that fellow, it gets quite a bit more complicated than just tightenning up the squeeze on the air & geiing more BANG outta the power stroke. But, if I was just the least bit more determined to get more outta the engine, that's where I would go to look for it. He said clean up the intake port, the exhaust, n ot as important. Eliminate steps between flanges & ports. Can't get the exhaust too straight cuz the ex valve spring pocket encroaches in the top of the port.

Have fun.

If a guy has the savvy to get the thing apart, mod it, & put it together, getting some slack to line the hoes up won't stip him. Aww, heck, I would gpo back & fix rthat but Im pooped,, lol

The article by Tumi points oout the change in cam timing from shaving the head. He says it is retarded & that is good because it somehow allows the cylinder to fill better. IF I read it andIF I remember it as he intended. If I was messing with my engine at that level I would certainly read it agagin & most likely ask a few folks, too. I am not so sharp as to be able to see exactly WHy retarding the cam would allow a better charge. From where I'm sitting, the cam duration hasn't changed so the time the valve is open stays the same. NOW, what I can see is the piston has dropped further before it opens & may create a bigger vacuum & cause a strong rush of incomming air/fuel charge that will continue to pack itself into cylinder even after the piston starts back up. Since I don't know where the piston is when the valves operate I can't even hazard a guess at to how the cam timing will affect the running. The most comforting thought is provided by Ed, using common sense, noting the caM timing retards naturally & the bike runs & runs & runs.

Me? I just want one spare engine.& a few extra hundred $$$ , owell,, I've never had anything like this bike. It's fun to mess with. It's fun to ride. It has me associated with a bunch O folks who enjoy the same things, Dang folks, it's just good all around..

BTW, just started raining & it sounds GREAT!

Whatever you choose VRoom, I've done all I know for ya, that's give ya the link to that article. I know it's long, but there's a ton O stuff in there.

Rockin_John wrote on 12/31/69 at 16:00:01:



I've been wondering if a 94mm high compression VW piston would work.

Don't know, it was just an idea I thought of when I found out that the Savage piston was 94mm. I have never had the opertunity to see the Savage piston and a VW piston side by side.

yeah, I've been thinking about other things that could go wrong.  It had not occured to me about the slack in hte cam chain...  a large shave would be 0.1", as I suggested, effectiely lengthening the cam chain by 0.2", or 0.2"*25.4mm/inch = 5.8 mm.  

Too much.  Another issue I thought up:  I don't want my piston to hit my valves.  Depends on timing...  and how much you shave off...

as implied above, there are no after market HC pistons presently available...

I read that article a year ago, and forgot most of it...  

At any rate, I'm just trying to figure out CHEAP performance mods....

If you're gonna replace the piston, replacing the connecting rod or machining the current one to ensure it fits wouldn't be that big a deal.  Any local machine shop should be able to handle the job.  If you got a VW or Camry aftermarket piston, you'd want to take careful measurements to be sure.  The last thing you want is an untimely (pun intended, you know it's about valve timing) contact between valve and piston.