Best engine for swap

[solo2racr]

Hello all. I have been looking into stuffing a XS650 into a '88 FZ600 chassis. Is there any particular year model of 650 that is better or would be more suited for this type of thing?

Thanks,

Ken

[aero]

I real terms the XS engine was always the same.

In detail it varied between the early and late models. We're talking gudgeon pin sizes, gear box shaft clearances and cam chain spocket differences.

Use an engine from a late model as its easier to get parts for. Ideally liberate an engine from a low mileage Special, ('fug ugly custom). Perferably one that has been garaged,looked after and polished for 20 years of its 30 year life.....with low mileage...then give it some real use in a proper frame!

Halco tuning in the UK had a 840cc big bore kit and some good gear box mods...unfortunately Tony died a couple of years go and with him much of the info. Personally I think a decent 750 conversion is better, but I'm working on the gear ratios he used.

[solo2racr]

First....sorry to dig up this old thread. Marcus, (or whomever) what year models constitute "early" and "late" I'm a bit fuzzy on this as it's been YEARS since I messed with these bikes. I'm thinking in the '78-'81 year range was the change.

[5twins]

'73 and older are known as the "256" motors. They have different pistons, cam chains, rods, among other things, and parts are harder to come by. '74 and up are the newer "447" type motor. Parts are much more available and cheaper. '80 saw a factory electronic ignition installed but with the aftermarket Pamco ignition available now, that's not such a big deal any more. I would stick with a '74 or newer motor. If you're buying a "roller", I'd try for '76 or newer, you'll get better carbs.

[solo2racr]

Thanks for that 5twins. I have a 1988 FZ600 rolling frame (roller) with an engine that needs more work and $$$ than what it's worth. I figure it would be a good frame to tuck a 650 into. Fabricate a 2-1 exhaust and either Mikuni VM or Keihin PWK carbs.

[grizld1]

Even on the stock frame, 2-1 systems ground on the XS650. Also, the off-the-shelf 2-1's have oversized collectors that give a small increase in power when you're almost at redline, at the expense of a big hole in the midrange (and please, don't refer me or anyone else to Jerry Heiden's dyno charts; if you have a sales pitch to deliver, you can tweak a dynamometer to print out about any kind of encouragement you want it to).

I started a project with XS650 motor and FZ600 frame years ago; didn't get past a crude mockup with gutted cases and empty barrels and heads when I ran out of motivation, and passed it along to Jack. The way the 650 engine covers fit the curve of the FZ frame was truly beautiful.

[solo2racr]

Here's an idea for the exhaust...... Have the head pipes meet in the center, under the engine and run parallel on out the right hand side. As they go rearward, they will start to separate for a pair of mufflers.

Also, You wouldn't happen to have any pics of your mock-up, would you?

Kinda like this...

[grizld1]

Sorry, didn't take pics--didn't have a digital camera at the time, it's been awhile! Jack may still have that project; I think he's a member here and he may chime in.

Re. exhaust, you need to keep that second bend as high and close in as you can; it's hard to tell from a photo, but the right pipe in the pic looks like it might catch asphalt, especially if there's a dip in the corner.

There's no reason you couldn't build a decent 2-1 exhaust joining in front, as long as you get the collector right. Michael Morse (of 650 Central) designed a 2-1 that delivers usable power and makes him happy, and it takes a lot to make Michael happy when it comes to performance. He can't get it built in a small run for a decent price, but he might be willing to share some ideas with you; give him a call.

[solo2racr]

I figure that since the FZ600 came from the factory with a 4-1 exhaust, then clearance shouldn't be any problem, whether I go with a 2-1 or a 2-2 with similar routing as the 4-1. It will end up with what the engine likes.

[solo2racr]

Sorry to dredge this back up. This project is still on my list of bikes to build. I did find a pic online that shows this swap. Personally, I think it looks great.

[grizld1]

If you do the project, you might want to tilt the motor more forward than that pic shows--top end about 15* off vertical would be good. There's plenty of room for that position if you ditch the side rails, which don't contribute much if anything to the rigidity of the frame. That position gets the very heavy head a bit lower, eliminating a bit of the characteristic top-heaviness of the XS650. Don't worry about lubrication issues--the XS650 motor was mounted with 15* forward incline in the prototype Ascot TT, and things worked just fine. Yamaha never took the Ascot to production, but the late Tony Hall bought the design and produced the frames.

[solo2racr]

I understand what you are saying about tilting the engine forward. My first thought was about the oiling but in the next sentence you addressed that. The other thing I was wondering about was, with the engine tilted forward on or close to the crankshaft axis, that will also raise the C/S sprocket and in turn, may do strange things with the relationship between the C/S sprocket, the rear wheel sprocket and the swingarm pivot. The chain pull would be higher (in reference to the swingarm pivot) and have more leverage on the rear suspension than if it were lower and will make the rear end squat more under acceleration. Possibly enough to be a detrimental effect.

[grizld1]

Depends on how you mount the motor. In the pic of the yellow bike, it looks like the crank center would be sitting pretty high above the line of the axle centers. Rotating the motor around the output shaft axis might get things where you'd want them.

[solo2racr]

Well, I finally pulled the trigger on this and picked up a pair of '81 year model engines for $200.00. Granted, both are locked up in the top end but that really isn't a problem. I figured on stripping whatever I got down and checking it all out anyway. Worst case, parting each out would get me back the $200.00 so I figured it was a no lose deal.

I also stripped the fuel tank of what the previous owner called "paint" and cut out a section that would be covered by the seat so I could see just how bad it is inside. It wasn't good. Had to braze up 4 holes and poured in some Evapo-Rust to clean out the inside. It worked rather well. The inside is good enough to use now. Just not sure if I want to use a tank sealer in it. I sand blasted around the lower seams all around where the 4 holes were and I don't see any other holes. I figured sandblasting would expose any weak areas. It's just if there are any really thin spots that may decide to leak later on are what worry me.

[solo2racr]

I pulled the head off on one of the engines and have been soaking the tops of the pistons and the bores with "Evapo-Rust". Day and a half later, I got the pistons broke loose and sitting at BDC. Now to place some wood under the cylinder and finish tapping the pistons down and out of the bores. I hope the second engine, which is also froze, comes apart this easy, relatively speaking.

Looking closer at the head, I discovered why the engine was originally parked. Bent intake valve on the right cylinder.