A 2-smoker GS.  I've been thinking about this a tremendous amount lately.  A stupid amount.  I can pull it off, too...that's what pisses me off.  Real easy, even.  All I need are two RM125 jugs, pistons and caps.  I'll have to machine the pistons to fit the GS con-rods, and the jugs and caps will probably have to shaved some to fit the GS block...but I don't think so.  I'll also have to build a 3/8" plate that will adapt the now 12-bolt jugs to the 8-bolt GS block.

Now I'd much much much rather build this using RM250 stuff...I mean jesus...115hp at the wheel off the line with a potential of 185hp (I've seen 95rwhp RM250's)...just can't do it with the GS crank.  As it is we'd see right around 80rwhp out of the box with a good exhaust (not that I'd really know where to put THAT).

This could be a fun project.  If the GS had a 72~ish mm stroke I'd already be ordering parts.

oops this was supposed to be in odds/ends.

so you are going to use a gs crankcase but rm cylinders and head?

2-strokes don't have heads...but essentially, yeah.

or actually I'm not because I can't use RM250 stuff...

Quote from: makenzie71 on October 22, 2006, 08:26:17 PM
2-strokes don't have heads...but essentially, yeah.

Since when? lol 

Sounds cool, don't get your hopes up that this is going to work but good luck anyway.

I'd be "IMPRESSED"    if you could pull it off.

heads ..jugs ..... all the same there just made diffrent when you talk dirtbikes there normaly talked about the "topend"  if you have ever raced or hung around  racers

It would take some Major Work to make it happen.You will have to seal Both (Chambers) off from the Transmission,Each Other (or Have both Pistons Traveling at the Same time) and the Ignition and Clutch Cases.Or just use a Two Stroke Twin bottom End of Some Sort.I've often wondered About putting RM250 Watercooled Cylinders on a T500 but the Draw back is the liquid Cooling.Sure they Done it with the TR500's but those Cylinders are Super Rare and I would Have to Find a Water Pump ETC. from a TR too.

Nah gotta skip watercooling.  It's too complicated for such a simple project.  If I were willing to take on that kind of hassle I'd just find an RGV motor.

As said, the jug will be seperated from the bottom end by a 3/8" plate.

But you will have to have Separate the Chambers down the Middle or the Incoming Charge will be Blown out by the Exhaust Stroke on the Other side.Having Both Pistons Traveling on the Same Stroke though you would have them on the same Intake and Exhaust stroke.

Actually my plan would be to use a set of watercooled jugs and merge all the cooling ducts and use them as fuel suply chambers.  Yeah but I'm not too sure how I'd do it...

There's some company that took an SV650 block and stuck two CR500 jugs on it.  I guess I should ind out how they did that.

There is a lot of issues to overcome, all relate to the bottom end and crankcases. First thing that crosses my mind is the most important, lubrication.

Maybe a cross section of a two stroke motor in action would help us all understand the unique challenges involved.

Alright, let me be the first to say...

...this isn't going to work.

No offence, I like the idea, it would be a sweet project, but it isn't going to work. Not without tens of thousands of dollars. You're better off finding an RZ350 engine and trying to put that in.

The two cylinders would have to be independent, the cases would have to be sealed off from the transmission then you have to find a way to get power from the crank to the transmission. Two-cycle engines are case inducted, so there's just no way it will work. The rod length would seriously mess up all the port timing and it would run like garbage, if you got it to run at all. Good luck machining a piston to fit a different crank, too. Or running a high performance two-cycle engine with no water cooling. The list goes on and on, you have to take it from somebody who is inside 2-cycle and 4-cycle engines every single day.

It's not going to work.

Install a blower, machine a new head with rotary valves, grind some new camshafts, and change out the signal generator.  Modify the cylinder block to accomodate Nordberg through scavenging.  Forge a new crankshaft and block/transmission housing.  Forge and machine new aluminum connecting rods ala Hispano Suiza aero 3-piece.  Replace all the gearing with case hardened / lightened gearing.  Drill all the shafting.

Ought to sound good anyhow.