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Message started by ThumpinSquid on 12/20/06 at 19:34:43

Title: Engine mods?
Post by ThumpinSquid on 12/20/06 at 19:34:43

I know there's some hot-rodders on here and this question is aimed particularly at them. Have any of you guys gone with a taller piston or offset ground the crank to bump up compression to about 10:1?

There's nothing wrong with my engine, and it proved it's mettel plenty. But, we all know at highway speeds it could use a little more umph. I'm kicking around the idea of rebuilding a second engine to swap in next winter. I've built a few small blocks (here's a pic of the one I'm building now)
http://img.photobucket.com/albums/v406/Wagothing/rollerrockers1.jpg

And I'm fully aware of the advantages of increased compression (and 91 octane gas ain't that expensive when you buy it 3 gallons at a time, and E85 is 110 if that becomes available up here) I'm just not aware of the side effects to an air-cooled single piston engine. Will this cause any problems with over heating, and is there a way to adjust the "transistorized" ignition system (that I don't really understand what that means yet)?

Any insight would be appriciated!

TIA
Matt

Title: Re: Engine mods?
Post by klx650sm2002 on 12/21/06 at 00:14:18

IMHO the best single mod you can do is sort out that horrible exhaust port.

Clive W :D

Title: Re: Engine mods?
Post by barry68v10 on 12/21/06 at 03:59:15

I did a search of this site, and it seems the general consensus is "there are no sources for high compression savage pistions." However, I'm quite sure you could find an auto parts supplier that has 3.7 inch bore pistons. You probably have to measure deck height, wrist pin placement, etc. to get the correct fit. It may also require some "eye-balling" or complex calculations to figure out what your compression should be with the "new" piston. Mahle piston makes a few 94mm bore pistons for the VW, and I think any performance piston from a Toyota Celica should work. There may be other options, but some of these engines are getting close to 1hp/10cc's in a track config. If the ol' Savage had that, we'd be talkin' 65 HP! Yikes!! That's about what an SV 650 has with 11.3:1 compression and 8 valves.

To combat overheating, look at the oil cooler threads. (Yes, if you're increasing HP, you'll want to address the added heat.) I've got one for my Savage, it's just a frame rail tranny cooler I've mounted vertically to the Savage frame behind the front tire. Just waiting til my riding season is over to install. As long as there's no snow on the ground, I'll keep riding. ;D

Title: Re: Engine mods?
Post by lancer on 12/21/06 at 05:49:29

There are 2 possible solutions which are relatively easy.
1. shave the cylinder of head surface
2. During the mid-ninties the LS650 Savage and DR650 shared a common piston and wrist pin. It may be possible that one of the aftermarket DR pistons will be workable on the Savage.

But in my way of thinking, why go to all the trouble of playing with the pistons when a simple shave will do the trick.

Another possibility would be to use a single piece copper head gasket in place of the multi-piece stock item. Cutting that thickness in half would add a little to the comp ratio.

Title: Re: Engine mods?
Post by azjay on 12/21/06 at 06:42:11

the problem we have found with high performance air cooled motors (vws in the desert), as the heat increases from the greater energy being produced, it becomes more difficult to control the heat dissipation, and thermal run away can become an unwelcome participant. very large or dual oil coolers are not uncommon, water cooled motors will encounter the same problem at some point, which is why hi-vol water pumps, t-stats, and radiators exist. i believe an oil cooler should be a part of any hot rodding of this motor.

lancer, thanks for the DR650 tip, i was surprised when i found out that suzuki built two different 650 singles, at the same time? who missed that at the board meeting ???

Title: Re: Engine mods?
Post by hutch on 12/21/06 at 07:26:23

I agree with Lancer completely.In my hot rod years, I always went with flat top pistons and shaved head/block. You are increasing compression over by only taking a little off(20 thow) versus a big bump in the piston, and then worry about valve clearance. It's cheaper, especially when dealing with 8 pistons

Title: Re: Engine mods?
Post by Ed_L. on 12/21/06 at 08:24:29

Head work would probably be the way to go for easy horse power. The exhaust port really needs major work for the engine to breath easier. Just dropping the exhaust pipe and going to work with a dremel on the high spots would help. Shaving the head will kick up the compression but changes the cam timing so you might loose instead of gain by doing it. If you have the time to tinker I would think you could cut an offset key for the cam or keyway in the cam but that's just an idea, don't know if it is pratical or even do-able. So far Lancer's engine seems to be the most modified with a coated piston, reground cam and aftermarket carb and exhaust. The DR piston has come up a lot but I haven't heard of anyone trying it. I'm interested in the spark advance mod but haven't got up the time or nerve to try it, don't want to fix it broke.

Title: Re: Engine mods?
Post by Dynobob on 12/21/06 at 08:55:49

Raising compression, by using a domed piston or shaving the head is a fine way to raise horsepower. That and adding some more ignition advance will yield some impressive results. I'm not so sure the bottom end of these engines is up to the task though ???

Check out Wiseco for motorcycle pistons. They should help you cross reference another piston.

http://www.wiseco.com/default.aspx

Title: Re: Engine mods?
Post by hutch on 12/21/06 at 13:21:53

Ed_LT
Thanks for the reality check. Just to many years with pushrod motors. Shaving would only cause more problems.

Title: Re: Engine mods?
Post by ThumpinSquid on 12/21/06 at 13:33:31

Thanks for all the replies guys, and the links to sources for a piston. I was planning on getting the measurements off the stock piston when I dissassemble the donor engine (that I do not have, this is all dream time right now, lol) and send the specs to KBS. I had to have them custom make .060 12:1 forged pistons for the AMC 401 pictured above. It was close to a $K for those, so I figure just buying ONE custom piston would be a lot more reasonable, haha! But if Wiseco has 'em off the shelf, that'd definitely rock.

On all of ya'lls recommendation, an oil cooler will definitely be part of the build. MOTO points like that, that'd I've have missed if left to my own devices, are why boards like this rock!

I avoid shaving decks to get compression. It may be fine for flat-head V-8s and may be fine for this little thumper I'm still getting intimate with, but on a short stroke American V-8 (typical small block from any maker) it means PITA maching work to the intake manifold and even bigger PITA rocker geometry correction that usually results in lots of new parts just to get everything to fit. It's been my experience that taller pistons are the easiest and most reliable means to increase compression without throwing everything else out of whack. All you have to do is make sure your valve reliefs are placed right and deep enough ( I don't like interferrance engines, broken valve spring = need new motor) and if you got the time and inclination, you can incorperate some quench pads for a super fast flame pattern, cooler burn and over all internal combustion goodness. Stroking the crank is a close second( this is entirely just my opinion), because that not only bumps up compression, but it increases displacement too! But it reduces con-rod journal size weakening the crank, or it means beaucoup bucks for a completely custom crank. I guess I'll be better prepared to figure this all out once I get to know the engine better. Keep the ideas coming, and pics of what my fellow engine twisters have done, particularly in this new-to-me realm of motorcycle engines, would rock!

Thanks again everybody!

Title: Re: Engine mods?
Post by Ed_L. on 12/21/06 at 19:05:44

Just a quick followup on the oil cooler on my '02, clocked about 500 miles on the engine since the mod with no problems. Short trips when the engine is cold the cooler barely gets warm, think the oil is circulating thru the block, not the cooler. Seems to take 15 miles or better to get the cooler warmed up and get a good flow thru it. The top end of the engine, cylinder and head still gets hot which was expected but there is a noticable temp difference between the inlet and outlet of the cooler. After 40 miles the cooler gets too hot to touch. I still need to figure out how to measure the inlet and outlet temp of the cooler but it seems to help a lot. If you are planning to squeeze the big single for power I would recommend an oil cooler of some sort.