Buell XBRR Engine Build Pictures

[aswracing]

I've started putting my XBRR motor back together. There is a lot of really different, 1-off stuff in this motor and I thought y'all might find some of it interesting ...


The itty-bitty flywheel assembly is one of the most interesting pieces. It's a 3.125 inch stroke (like an XB9) and uses similar 7.270" rods. The rods are unique though because it uses a 1.5" crankpin. The big crankpin is a very good thing for stiffness. I didn't disassemble the crank, but I did check the true and straighten it just a tad, as well as change the sprocket shaft and pinion bearings.

Besides being really light to allow the motor to spin up quick, a small crank like this makes more power by reducing windage. More space around the crank, with the same amount of oil flying around, means less drag.


The right side case half has a couple of interesting features. First, they did the whole windage area differently, and better. It doesn't have an integrated crank scraper like the S&S cases but with that tiny crank it doesn't really need it.

Notice it has two reed valves between the crankcase and cam box. A regular XB has only one. The idea of the reed valves is to help the head drains. The pistons go down, the air is evacuated. The pistons go up, it creates a vacuum, which helps pull oil out of the heads. The heads use external drains. The reed valves help with the drains but they actually hurt the scavenging, as the vacuum is also seen at the inlet to the scavenge side of the pump. The way S&S does it, with the scavenge inlet on the other side of the reed valve, is better.

Also notice the two little screws holding the pinion race in place. That's unique to the XBRR.

Both case halves are magnesium.


Here's the primary side. The sprocket shaft is different than any HD shaft I've seen. It uses a bolt to hold on the very strange looking rotor and sprocket that I'll show later. It's 1.25" in diameter, which is a full quarter inch bigger than standard XL or XB. It uses a pair of Timken tapered bearings like the pre-rubber mounts, except of course they're the larger diameter. It's actually Evo Big Twin size. I haven't figured out what it uses for a sprocket shaft seal, I figure I'll take the old one down to a bearing supply store and have them match it up. It's not XL or XB or Evo BT though.

The transmission cavity is standard XB stuff (dual rail shift forks), but it does use a trap door.

Lots more case half bolts than a standard XL or XB.


The cams are unique too. Notice how the #3 and #4 (on the left, an XB motor counts front to rear) have a longer shaft out one side. That's because the oil pump is integrated into the cover and runs off those shafts, one for the scavenge and one for the pressure. Also notice that the gears are inboard of the lobes. In other words, the gear is closest to the case. Makes the #2 cam really look strange because the lobe is sitting in between the two gears.

I rigged up the degree wheel and dial indicator and took all the numbers on the cams. I'm not going to reveal them, but I was very surprised at how mild they are.


The most interesting thing about the cam box is that there are no cam bushings or bearings in the case! The cams literally ride directly in the magnesium.


Since the oil pump runs off the rear 2 cams, there's no oil pump drive gear. Notice though how there's 3 dogs coming off what would otherwise be the gear. The pinion gear has 3 slots as well. Guess they didn't want any shearing issues.

I'll post more pictures as I put this thing together.

[new2HDfrank]

Originally Posted by aswracing

I've started putting my XBRR motor back together. There is a lot of really different, 1-off stuff in this motor and I thought y'all might find some of it interesting ...

Yes we do!

Engine build threads are great fun.

Please keep it coming!!

Frank

[aswracing]

Under the cam box. The fitting to the left is where the rear head drain enters the crankcase.


Cam alignment is a bit difficult to see because you have to look deeper, as compared to an XL or standard XB. But each dot is right on a tooth or between two teeth so it's impossible to misinterpret. It's just hard to see.

The cams are marked 1FX, 2FX, 3FX, 4FX. They are no "E" cams or .536's or 575's or any other already existing grind, they're specific for this motor.


The cover also doesn't have any bushings. Also, there was no gasket where the cover meets the case.


The cover is now installed. This is the oil pump built into the cover. On the left is the scavenge section and on the right is the pressure section. Between here and the little cover that goes over this, there's a paper gasket.


And here it is all buttoned up.


Interestingly, the cases have a facility for the conventional style oil pump, but it's not fully machined.

The tubes to the left are the scavenge out and feed lines.


Here's the state of the bike now. I like to bolt the swingarm up to the engine once I've got the cases together. Actually, on an XL motored Buell, you can leave the right case half attached to the swingarm block and just pull the left half off. But the swingarm mounts to these things differently and you have to disconnect the swingarm to split the cases.

[Loner]

I always wondered what one of these engines look liked inside,
Is the tranmission different than a regular Buell-XL

[ol38y]

Lemme git sum popcorn... Very interesting. Is Eric able to make any parts for your bike yet Aaron? Or is he going to?

[aswracing]

Originally Posted by Loner

I always wondered what one of these engines look liked inside,
Is the tranmission different than a regular Buell-XL

Yes and no ...



It's a regular XB transmission near as I can tell, except it has a trap door. What distinguishes the XB transmission is the dual shifter rails. But other than the rails and shift forks and the shift drum, an XB transmission shares a lot of parts with the XL transmission.

The trap door, though, was dropped for the XB when it came out in '03. As you probably know, HD dropped the trap door transmission from the Sportster in '04. But this bike has a trap door as you can see.

[aswracing]

So today I put the primary back together.


If you've ever put together a Buell XB engine, you know what this is all about. You remove the neutral switch and put this special tool in there instead. It's to hold the detent arm up out of the way while you install the transmission (or assemble the cases on a regular XB). Fortunately, Dan has one of those little tools, and also fortunately, I have a key to his shop, and he's out of town


Here's where the tool sticks through and holds the detent arm up out of the way.


Once the detent arm is up out of the way, the tranny slides right in. Then you remove the special tool an put the neutral switch back in.

I've already installed a new sprocket shaft seal by the time I took this photo. Turns out it's a standard XB part after all (PN 12068) and the local dealer had one in stock and is open Sundays.


The clutch basket is a unique piece too. Notice how it has a built-in cush drive. Also it as a needle bearing where the other bikes use a roller bearing, and the hub is not pressed into the bearing, it just falls in. No snap ring like the XL/XB clutch either.

No spring plate in the clutch pack. I didn't bother to disassemble the pack. I'm not that concerned about it, for what I plan to do with the bike. I really only need the clutch to get going.

Some of these things supposedly had slipper clutches in them. I don't think this is a slipper clutch, although I may not recognize one if I saw it.


Here's the primary drive installed. The chain is conventional but the alternator rotor is a unique piece - small diameter and turned inside-out from a regular XL or XB. Also note the crank trigger teeth. The whole sprocket/rotor assembly will only go on the sprocket shaft in one rotational position, by virtue of the spline sizes.


Here's the stator. Tiny little thing, don't imagine I'll be using heated gloves or vest on this bike. It lives in the primary cover. Also note the crank position sensor.


All buttoned up, chain adjusted, filled with oil. Note the wires for the crank position sensor and stator.

Next weekend I'll do the top end.

Then just put the frame/front wheel assembly back on, hook everything up, and tune it. Plus a bunch of safety wiring and stuff.

The plan is to have my wife ride this bike at Bub's, in MPS-PG 1350cc. If it goes well we'll also yank the fairing and run it in M-PG 1350cc. She already has that record, but it's a bit soft, it was mushy when she set it.

They say these things twist over 8000rpm and put about 150hp to the back wheel in the process. We'll see.

[Loner]

On the tranny can you get different ratios, when it came out I heard that Buell had
"close ratio" for tight tracks and more spaced out ratios available for more open tracks.

[Kel]

Great work mate!

[aswracing]

Originally Posted by Loner

On the tranny can you get different ratios, when it came out I heard that Buell had
"close ratio" for tight tracks and more spaced out ratios available for more open tracks.

Really? I didn't know that.

I noticed that in the picture of the detent arm, you can see a part number on the gear next to it, and it's a -05 part number.

Truth be told, I don't know anything about the tranny, other than it looks like an XB tranny but with a trap door. I just assumed it has all the same gears as an XB tranny (which is all the same as the XL) but you may be right, maybe some or all of the gears are different.

It's just amazing to me how much special tooling they had to do to make these bikes. Special castings, too. All for a production run of 56 units. It must've cost them a fortune to make those 56 bikes.