The XB4R build begins...

[buellxb9rs]

Huh, weird. 515 + 515 = 1030 so how does a 1030 kit equal a 1050? Also, an xb12 has the same bore as an xb9 but there is an obvious difference in the engine displacement. I'm just trying to understand how it's possible for different cc kits to be the same. Also the blast kit is made for the blast head which is different than the xb head which is what I'm using. The xb9 piston is done shaped, higher compression than the blast but the blast has the same bore and stroke as the xb9 but uses a flat piston which is where is loses compression but keeps the cc and also it is exactly half the cc displacement of the xb9

 

[loose1]

The stroke is longer on the 12 than the 9 and blast. You have to use bore and stroke to figure out your displacement.

 

[buellxb9rs]

Yes, I understand that exactly. That's why a 12 has more power using the same cylinder and heads as an xb9. Because it uses a longer stroke and a flat piston to keep compression high. I'm not confused by that, I'm confused about how a blast 515cc is the same as half an xb9 1050cc which is 525cc

 

[jetlee]

Its in the naming. An XB9 is closer to 1000cc than it is 900cc (984cc, but you know that); they're just rounding the cc's (incorrectly, I might add).

I know XB's have a different head design than the Blast, I'm using an XB9 top-end in my Blast.

I was merely pointing out that between the two kits, the displacement of each cylinder is the same.

Stock bore is 3.5" (88.9mm)
515/1050 kit is 3.5625 (90.49mm)
Stroke is 3.125" (79.37 mm)

Displacement (doing the math (pi*(bore/2)^2*stroke)/1000)
Stock Blast 492.663cc
Stock XB9 985.326cc
515 Blast 510.443cc
1050 XB9 1020.886cc

There's the real displacements of the engines.

Going for half of a 1050 kit would be the way to go, IF you already have an XB front head; and IF the shop is willing to sell half a kit.

FWIW - The shape of the piston/head have no bearing on the displacement of the engine/cylinder, only on compression ratio. Displacement is determined solely on bore and stroke, as in the above examples and calculations.

Because it uses a longer stroke and a flat piston to keep compression high

It uses a dished piston to keep compression DOWN, not high. If the 12 used the same piston as the 9, it would have an ~12:1 compression ratio. Buell gave it a dished piston to counteract the longer stroke to keep the compression ratio at a more reasonable and reliable 10:1.


Going by Harley's retarded rounding rules, the Blast should be a 400, not a 500...or the XB9 should be an XB10.

 

[expatriate00]

Ok this is some real engineering, I'm all over this like white on rice. More balls than most! Go for it. I realize were not talking uncharted territory here but this would make a hellified Bonneville bike! If this is lighter than a stock Blast this will be a crap ton of fun to ride.
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[jetlee]

It's essentially an engine swap on an XB9, most of the mounts already line up. A little fab is needed, but it's certainly not some amazing feat of mechanical engineering. The most difficult part will be getting the ECU to work properly without the rear cylinder, which is electrical. If you want Blast engineering, that's elsewhere.

Not talkin' down on the swap, if I had the parts I'd do it in a heartbeat. Also a huge fan of the color choice, the only XB-R colors that should've ever been offered, imo.

Do you have an XB-R front end, or using the Blast?

 

[buellxb9rs]

Xbr front, doing a tail swap to an s though. So far problems are the trans shaft have different teeth than the xb pulley, and there is no idler pulley mounts, no kickstand mounts, primary cover isn't exactly a direct fit. But that's just what I have so far. FedEx just called me, squidbuellies parts just arrived at my house

 

[jetlee]

What are you doing with the XBR tail?

 

[buellxb9rs]

I'm swapping with a guy, but his only transportation is his bike so I have to wait till he can do the swap. Supposed to be around beginning of August I guess

 

[buellxb9rs]

For an update, still waiting on a few engine parts and just realized that I didn't order the gaskets for the cylinder and such. I tried a test fit for the frame and front end which healped me find out that I need new steering head bearings and a new front axle because it's bent. The rear shock isn't attached so the rear looks low because of that. I have the fittings needed to make my own oil lines to work with the '07 swing arm. Also attached new fittings for the oil cooler.

 

[wolfo68]

lookin sweet, I may look into something like this instead of rebuilding my 9.

 

[buellxb9rs]

Unless you have a way of getting parts really really cheap, it's really cheaper to buy another bike. But later plans for this bike (way on down the road) is a turbo that would fit perfect where the other cylinder would be and a big bore 600cc kit. and I've been looking into building a water cooling setup for it.

 

[wolfo68]

I have a working blast and an xb9 that is down because of transmission issues. seems like it'd be something I could get done on a nice saturday as long as fitting the swing arm doesn't take too long.

 

[buellxb9rs]

Swing arm bolts right up. For the oil lines you will either need to buy the fittings to attach them or make some like I am doing. You will also need To swap the xb top end and cams to the blast. I would put a big bore on that bad boy too.

 

[wolfo68]

Good to know, I'd probably try out the swap before going to a big bore though.

 

[buellxb9rs]

I'm curious to see how far this bike will go before the fuel light comes on. The blast was getting 76mpg and my 9 would get almost 70 on the same ride as the blast. Now that "blast" will have a much larger gas tank.

 

[Daali]

jeebus, 76mpg! I get 55 on a good day. That must have been one fine tuned blast or lean as heck =)

 

[buellxb9rs]

I don't think the people we bought it from had it jetted for the exhaust, but I'm not sure. I know that when I pulled the heads off the exhaust valve was white, and I mean white.

But I also had another blast with a Vance and Hines and was jetted and I got 70mpg in the city

 

[jetlee]

You dont have to change the head to fit the engine into the XB frame. If you can't find the XB head, only slight modification of the front isolator mount is required.

Cams have no effect on the transplant between the two frames.

 

[buellxb9rs]

I personally wouldn't want to modify ANY engine to frame mounts. Each weld creates another possible weak link. IMO as far as just putting the engine into the frame, no I guess cams arent necessary, but why would you want to go from an xb9 to a straight up blast motor anyways?