FZR/XR650R Build Thread....... It's Alive!

[tgold]

My buddy grenaded the motor on his FZR400 at a trackday and he liked the ZX6R that he borrowed fron me enough that he bought it.... I wanted another lightweight racebike, so he gave me the FZR to put a motor in. If I was just going to have a lightweight with some decent horsepower I would have put an RZ350 into the FZR chassis, but I eventually want to develop a new 4-stroke cylinder head design so that means a single cylinder four stroke to use for testing. Enter ebay and the XR650R motor I found for $900 shipped:



The FZR Chassis waiting to be stripped:



Lots of junk that is never going back on the bike:



Engine looking for a home:



The main problem.... The rear mount for the XR650 is designed to be on the same axis as the swingarm pivot:

[ragedigital]

We need Y-G around here more often to correct my comments, but it doesn't look like an issue to me - just some measuring and modifying of the existing swing arm. Notch it out where the new engine's rear swingarm pivot attaches and stick her in there.

Course, I'm assuming that you have a machinist friend or access to a machine shop to do it properly.

Keep us in the loop as to the project. Looks very interesting!

darrin

[tgold]

So here's the solution:
Machine a cutout in the swingarm:


The hole in the XR650 case is smaller than the diameter of the swingarm pivot shaft so I had to get a smaller hollow pivot shaft and matching needle bearings, machine spacers for the bearings and press them into the swingarm, and then machine down the pivot bolt diameter slightly to fit inside the new pivot shaft, and then make a small collar to take up the space in the frame hole... easy!





Machined pivot bolt and collar:



Sliding the swingarm forward to install the pivot shaft:



All in place:





I decided not to modify the stock frame rails, so here's the bending jig I rigged up to help fab some of the new engine mounts:



Upper engine mount plate and downtubes:




Fabbing brackets:





Installing rivnuts:



More braces installed:



XR motor close to its final position:



Anybody need a subframe in decent shape? ..... I'm building a separate upper shock mount out of aluminum and a one piece seat/tailsection out of carbon fiber. I hope to have the total weight of the carbon tail between 3 and 4 pounds
The swingarm will get some reinforcements with aluminum and carbon fiber as well.

[nicrod]

that bad ass dude! I wanna see your subframe design.
also why that engine?

[Bike_junkie]

Awesome. I want to do something similar but use an xr600 to have the kickstart and aircooled. My guess is that an xr engine has many upgrade options, its lighter than the 4cylinder, it has plenty of torque, and will run forever if maintained.

*edit* And from the pictures it looks like the sprocket will be close to lining up.

[tgold]

that bad ass dude! I wanna see your subframe design.
also why that engine?

Thanks nicrod,

The subframe should work on an FZR400, but it would require relocation of all the electrical components.

I chose a big single as a test mule for a cylinder head design I've been working on. The XR650R won out because I don't think the currrent batch of big singles would be as durable and it's 30 lb lighter than the FZR motor. (I'm shooting for something south of 270lb total bike weight)
I also looked at the 700 Raptor motor, but it's nearly as heavy as the FZR400 mill.

[tgold]

Awesome. I want to do something similar but use an xr600 to have the kickstart and aircooled. My guess is that an xr engine has many upgrade options, its lighter than the 4cylinder, it has plenty of torque, and will run forever if maintained.

*edit* And from the pictures it looks like the sprocket will be close to lining up.

I like the XR600 engine, and the aircooling would definitely simplify things, but I'm thinking I'll need the watercooling for the very compact cylinder head design I'll be testing.

Speaking of the sprocket lining up, thats one of the main issues that makes it difficult to use a kick starter due to the offset of the engine to the left along with the relatively wide frame of the FZR. The other issue is the position of the rearset blocking the stroke of the kickstart lever itself.

I've roadraced a big Honda single before (an Ascot punched out to 591cc) and they have loads of grunt. Easy to ride..... Just rev it till your balls tingle and shift!

[Bike_junkie]

I fully understand the reasoning behind going for liquid cooled. For me it would be a project for simplicity, air cooled, maybe a cam, and custom exhaust on a pretty stock motor. Light, fun reliable. Plus I have dealt with the kicker issue on other bikes, To get it to clear the frame I would make an extension for the kicker shaft and support it using either a heim joint or a bearing mounted to the frame.

[tgold]

I fully understand the reasoning behind going for liquid cooled. For me it would be a project for simplicity, air cooled, maybe a cam, and custom exhaust on a pretty stock motor. Light, fun reliable. Plus I have dealt with the kicker issue on other bikes, To get it to clear the frame I would make an extension for the kicker shaft and support it using either a heim joint or a bearing mounted to the frame.

I thought about an extension for the kickstart shaft, but I'm not sure I want to use a folding footpeg that it would require..... Maybe I'll rethink it, although it'll be quite the beast to kick over once I punch it out to 680cc and drop in a high compression piston.

[Bike_junkie]

Yeah, that might make it pretty hard to kick over even on a good day. Either way I love this build. I will have a spare 400 frame after I build my hybrid and this gives me ideas of what to expect to make a "supermono" style bike.

[JustinLonghorn]

I am on board for this, sir. I can dig it.

[sweekster]

Sweekster approved, this is.

[Bike_junkie]

Just thinking out loud here, but suppose you were to make a "gearbox" for lack of better term that allowed the kick arm to swing forward instead of back. Then when not in use it could tuck inside the frame, and could have extra reduction to make kicking easier.

[pefrey]

Easy to ride..... Just rev it till your balls tingle and shift!

LMAO.

[pefrey]

Oh, and nice build. You are inspiring me and I don't need that, too many unfinished projects already.