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Old 02-09-2020, 09:57 PM   #1
Sporticus
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Default XL/XR hybrid mutt

Since I was bashing on the JJ in a recent thread, I thought I should contribute something. This is a project not typical of the JJ, but I hope you find it interesting. I've posted in an another forum already, so this may be a repeat for some of you.

I started with an '81 Sportster. It now has Ceriani/Yamaha forks, wheels, and brakes and an 18" rear wheel. I found a weird stash of parts and had to make it work. Those are XR750/XR1000 heads. The cylinders were homemade a long time ago by a now-deceased machinist I never met. He passed before finishing them (which I have done). They are standard XL or XR1000 dimensions. I'm running unobtanium JE 10.5:1 pistons (meant for an XR1000). The rocker boxes are special. They are completely homemade (not by me), use the XR stud patterns, and have ironhead internals. Genuine XR rocker boxes and internals are way beyond my pay grade. The crank has stock IH flywheels with Evo rods. I had to modify the cases for XR pattern studs.

Since these photos were taken, I'm picking up an aluminum featherbed style tank, a copy of an XR750 oil tank, and don't yet know what to do for a seat. I'm trying to keep people who think they know stuff confused.

The photos below are a VERY rough mockup, so please don't feel the need to tell me what's wrong with it. It's apart now for the 100th time while I assemble the engine, hopefully for the last time.





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Old 02-10-2020, 07:57 AM   #2
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Default Re: XL/XR hybrid mutt

Looks like a great flattrack style build. The XR750 style is probably my favorite H-D product. The jugs are round, with wide finning? The fin spacing seems to be much-wider than the OEM head. I'm wondering if that will negatively-impact cooling? The jugs have iron liners, or are they Nikasil-coated? The latter could help to lighten it up.

I ran-into some local guys with a lot of XR750 and XR1000 parts recently, also other vintage H-D OEM parts.

Do I see a Goose big-cubic inch touring bike back-there?
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Last edited by Elektron; 02-10-2020 at 04:03 PM.
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Old 02-10-2020, 06:14 PM   #3
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Default Re: XL/XR hybrid mutt

Thanks Elektron. Yes, that's a Guzzi V11 LeMans. It runs great and does everything I ask of it because I don't mess with it. I change the oil, get it new tires occasionally, and leave it alone. It has never let me down.

I wish I had posted a photo with the rearsets I put a lot of thinking into. Once I get the right bodywork on it, it will hopefully look a lot more vintage roadracer-ish. I don't know about the finning - XRs been that way since 1972. I don't know if the genuine XR cylinders have more finning than these. I never had one in my hand. I got these one-off cylinders as you can see in the photo below. They were rough bored and the relief for the pushrod covers wasn't right. I'm guessing these were destined for an XR1000. The XRs have essentially straight aluminum tube for pushrod covers and don't need as much space as an iron sportster cylinder has. You adjust the clearance through eccentric rocker shafts in the head. I need more space for pushrod covers because I'm using regular ironhead collapsing covers with adjustable tappets.

Nikasil is very cool stuff, as any Guzzi will agree. I'm not sure how to make it work here. The cylinder liner (see photo below) has an integral fire ring - the raised portion on the top. Its an iron liner from LA Sleeves intended for an XR1000 (they still make them). That mates with its female counterpart in the head. No gasket is used. I guess if you made your cylinder from scratch you could incorporate the fire ring into it and Nikasil the cylinder wall. That's all way beyond me.



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Old 02-10-2020, 09:07 PM   #4
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Default Re: XL/XR hybrid mutt

> please don't feel the need to tell me what's wrong with it.

I can't resist. *Nothing's* wrong with it. Bad-ass and beautiful.
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Old 02-10-2020, 10:05 PM   #5
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Default Re: XL/XR hybrid mutt

One of my friends has a couple of project Sportsters, a '70 and a '76, I believe they are. He has a Low Rider, an '80, 80 cu. inches, he bought new. We're getting ready to go to Daytona next month. I've been on him to do something w/them, at-least they aren't sitting outside rusting into nothingness. I've sent him pics of yours, and the thread link, trying to motivate him. He has an S&S stroker kit, without the jugs, it's currently got the re-located cylinder holes in an OEM pair. I've suggested that he just build the ^$##! engines stock, and to sell-off the S&S parts. At least build one of them, and get the bike going!
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Old 02-11-2020, 06:02 AM   #6
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Default Re: XL/XR hybrid mutt

A friend who has raced a Vincent Comet in AHRMA and built motors for others has used these vendors for Nicasil and says it is bulletproof. They should be able to help you.

https://www.millennium-tech.net/serviceInfo.php?id=7

https://www.advancedsleeve.com/power...rts/xr750.html
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Old 02-11-2020, 08:36 PM   #7
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Default Re: XL/XR hybrid mutt

Nikasil has worked very well for Guzzis, though I have heard stories of it peeling off in early bikes. I had a '75 850T and the cylinder walls looked beautiful on it, with no signs of peeling. The only way it work with an XR is if the stock liner wore, but not in place of it. I still needed the stock cast iron liner inside my bare cylinders. Elektron, I'm extremely honored that my mockup photos could inspire your friend. Ratso - thanks for the accolades, but that mockup has a long way to go. I'm picturing the final version with an aluminum Norton Manx style tank and seat. The pipes are going to need some work, and I need to build the transmission right (with the right Andrews gears) so I don't punch a hole in the cases I have put so much time into. I'm already planning on a Barnett Scorpion clutch assembly to not deal with the 1000 cc Sportster clutch shortcomings. My goal is to vintage road race this in the spring, but am building it so it can be made streetable without a ton of work should I realize it sucks on the track or I don't want to risk crashing it after so much work. Here is a similar photo to the earlier ones, but you can see the right homemade rear-set assembly. The stock oil tank is gone, and I'm waiting for a repro XR750 tank to take its place.

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Old 02-12-2020, 02:28 AM   #8
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Default Re: XL/XR hybrid mutt

It'll be a pig to race this beauty of an engine with this std post 82 frame... They were only designed to go straight, and even that they did not do well... Too long and too heavy...

Plus, does a special café racer has to have Norton Manx tank and seat on it??? The replica KRTT/XRTT tanks and seats are still available for not much more money!!!

But 5 stars for the motor!!!

Patrick
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Old 02-12-2020, 08:09 AM   #9
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Default Re: XL/XR hybrid mutt

Thanks Patrick. It's an '81 frame - does that make any difference? I'm really hoping the 14" shocks and much shorter forks make it handle a bit less like a freight train. I got in touch with Keenan Tatro of Tatro Machine and he suggested taking an inch out of the front down tubes, which I haven't ruled out yet. Rocker box to frame clearance is very, very limited already, though. I rode it once when it was a bone stock 1981 Sportster. It went nice in a straight line, but that's about it. I thought long and hard - in fact, far too long and hard about the bodywork. I just want to build something I haven't seen before, hence not using XRTT or KRTT bodywork. Plus, I didn't want it to look like something it's not. I'm not really sure what it is, or how to explain what it is to strangers in 100 words or less. I could talk here for quite a while about exactly what you have to do to "bolt" an XR top on onto a Sportster, and this isn't a 100% XR top end.


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Originally Posted by thefrenchowl View Post
It'll be a pig to race this beauty of an engine with this std post 82 frame... They were only designed to go straight, and even that they did not do well... Too long and too heavy...

Plus, does a special café racer has to have Norton Manx tank and seat on it??? The replica KRTT/XRTT tanks and seats are still available for not much more money!!!

But 5 stars for the motor!!!

Patrick

Last edited by Sporticus; 02-12-2020 at 08:15 AM.
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Old 02-12-2020, 12:52 PM   #10
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Default Re: XL/XR hybrid mutt

1981, you're right, I did not notice at 1st the front steering casting!!!

But any Sportster frames XLH post 67 and XLCH post 1970 are too long and getting heavier year by year...

On the KRTT/XRTT look, me thinks the Norton Café look has been way more over done in the past!!!

But that's just me, probably been living far too long in GB to have any sympathy left with that scheme!!!

You say you're using iron head internals... You could do worse than try to fit early EVO Sportster crank and rods, that will save you one inch in cylinder height, not negligible on such a tall alloy head set up... (XR 1000 rods could be said to be Evo prototype rods and were 1" shorter than their iron head sisters...)

Patrick
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Old 02-12-2020, 08:19 PM   #11
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Default Re: XL/XR hybrid mutt

I should have mentioned the crank. I'm using ironhead flywheels and Evo rods, which as you mention are the same length as XR1000 rods. Same crankpin diameter, just 6.926" center to center as compared to the ironhead 7.4375". Otherwise my pistons and heads would become close friends real fast. My friend who does this for a living is assembling the flywheels and rods and truing and balancing them. I'm waiting for that to be done before I can finally assemble the bottom end. Never tell someone you're in no rush. The cams are Red Shift 505 - Red Shift puts new lobes on your old shafts and gears. They were happy to orient my XL lobes in XR fashion. I didn't realize just how much material I would have to remove from the right case for those cams to fit. An old timer at Red Shift said that 1977 and up ironheads can't accommodate much larger than the stock Q cams. He sent me photos of cases they had clearanced (on a mill, of course). This lowered my anxiety amount removing that much material from my own case (done much uglier with a die grinder).

Quote:
Originally Posted by thefrenchowl View Post
1981, you're right, I did not notice at 1st the front steering casting!!!

But any Sportster frames XLH post 67 and XLCH post 1970 are too long and getting heavier year by year...

On the KRTT/XRTT look, me thinks the Norton Café look has been way more over done in the past!!!

But that's just me, probably been living far too long in GB to have any sympathy left with that scheme!!!

You say you're using iron head internals... You could do worse than try to fit early EVO Sportster crank and rods, that will save you one inch in cylinder height, not negligible on such a tall alloy head set up... (XR 1000 rods could be said to be Evo prototype rods and were 1" shorter than their iron head sisters...)

Patrick
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Old 02-13-2020, 07:42 PM   #12
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Default Re: XL/XR hybrid mutt

Patrick's post got me thinking, and then I saw these photos on the interwebs. These photos show an 1980-81 XL frame next to a factory XR750 frame (frame with cast neck is XL). The frames look remarkably similar (including that weird-ass rear section), though the XL is about 15 lbs. fatter. The steering angle difference is also significant: 26.5 degrees for the XR versus 30 degrees for the XL. I'm throwing out a guess here - I'm guessing flat track bikes have more generous rake than road racers. It's a good thing I'm not fast, even on a fast bike. I will look cool, though.








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