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Old 07-15-2019, 07:23 PM
gms955i gms955i is offline
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Engines

Hello, everyone! I haven't been here in a long time. My 2nd bike was an 81 Venturer. That was in 2005. I've had several other makes/models since, but am down to only one. An '85 Rebel 250. It runs well and gets me around on pennies, literally.

I can't ride this thing very far, though. It buzzes my hands to sleep after a while, and I loose feeling in my rear end. Not to mention it's torture to my old 250cc engine. So I've decided to get an XS Eleven.....









.....engine.

I want to start with an engine, build it good and stout, and then buy a beat-up Special to put it in. All of the bikes in my youth have been worn out beaters, including the Rebel I ride everyday. I'd like to have a bike with a fresh engine and carbs. The other stuff I can work out later.

I am within 200 miles of several salvage yards so no doubt I can find a complete engine or two to get me started. Would like to build something stronger than stock but not crazy. Maybe just a modest overbore, different cams and some port-matching/polishing. I really intend on using it primarily for highway travel, but I want to be able to shame as many H-D's as I can, y'all understand.

I was wondering what are some common mods for the XS1100? What is the best reference material to use? Who (in USA) would you entrust your machine shop needs to? Thank y'all so very much for your time and input!
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Old 07-15-2019, 10:14 PM
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DiverRay DiverRay is offline
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Weisco big bore kits, number one.
I need to look up the shop in CA that re-grinds the cams, but they are mostly fro race and not that good on the street. Best thing is get a set of '78 cams and use those, as they were the "hotest" of any year.
Head flow is just finding someone who knows what he is doing. Look at some of your local racers and see who they use.
Valves and springs are next, but you don't need to go overboard on them.
You could mix a '78 cam with the '80 big valve head and overbore pistons.
After that, it's just moving the air in and out via pods and a freer flowing exhaust.
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Old 07-16-2019, 09:04 AM
gms955i gms955i is offline
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Thank you DiverRay! Is Megacycle who you are thinking of? Is the '80 model the only year for the 'big valve' head? How much can the stock connecting rods handle and still last a while? I did find the 10.25:1 wiesco pistons on eBay.
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Old 07-16-2019, 10:13 AM
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jetmechmarty jetmechmarty is offline
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There is a YouTube channel called Andy's Motorcycle Obsessions. He did an entire series on his XS1100 "Basket Case". He did all that stuff you want to know, including flat slide carburetors. Go digging in there and you'll find some good stuff. I believe he did ship his cylinder head to California for machine work. He's in Tasmania.
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Old 07-16-2019, 10:24 AM
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DiverRay DiverRay is offline
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The '80 and up are "big valve" heads. The only thing is the chamber is larger, so compression is down a bit. I think the Wiesco drops to about 9.75:1. You will want the early TCI and advance mechanism as well. the '78 had the most advance of any year.
Stock rods are shot peened from the factory, and should be good for about 130 crank HP. I'll be trying to run a bit more, but it's going to be at least a year before I can get my '78 together again. I did spend about $800 on the crank and rods I'm using, but that was 10 years ago. they've been box since, but it IS balanced to 13K RPM from a company out of Fontana, CA.
With the exhaust you will need some backpressure to have it run properly. Yamaha stock exhaust is best for street, as the design give you a great low end without killing all of the high RPM power. Four into one, if a good pipe, also works well but you do loose a bit below 2,500RPM. If you can find a Kirker, that is probably the best. Whatever you find, it will have to be designed for the XS1100, as nothing else will fit or work correctly without a lot of re-work.
I do have a set of 1196 pistons, but they are packed for a move and I won't be able to get to them for about 3 months...
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Old 07-16-2019, 10:28 AM
alaskey2 alaskey2 is offline
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Quote:
Originally Posted by jetmechmarty View Post
There is a YouTube channel called Andy's Motorcycle Obsessions. He did an entire series on his XS1100 "Basket Case". He did all that stuff you want to know, including flat slide carburetors. Go digging in there and you'll find some good stuff. I believe he did ship his cylinder head to California for machine work. He's in Tasmania.
That's a great video collection.
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Old 07-16-2019, 12:43 PM
gms955i gms955i is offline
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I've found an XS Eleven standard in a salvage yard near me. $250 for entire bike, but I really don't have room for the whole thing... He didn't catch the year off of it when he went to look. I guess I could have it for a place for the motor to live when it's done, but I really like the style of the Special models.

So the 80-up has big valves and a bigger combustion chamber? Perhaps the earlier models might achieve similar performance? The cam I was looking at says VTP clearance might be an issue, so milling an 80-up head to raise compression might be out of the question. Will look into degreed cam sprockets just in case...

Those flat slide carbs are about $1000! Would the stock Mikunis and maybe airbox mod(?) feed a modified engine? Or are they too anemic? I remember the carbs on my Venturer were YUGE!

Thanks again DiverRay! I appreciate your input! It's helping me build the engine in my mind before I buy anything. I reckon I would be happy with whatever I wind up with but like I said, I don't wanna be shown up by any smug Harleys.
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Old 07-16-2019, 02:30 PM
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The first stock HD faster than the XS1100 was the V-Rod! With a little work, you can outrun most Harley's in a "normal" race. I like to race one way, put both bikes in high gear at 30MPH, then roll the throttle without down shifting. Almost NO bike can catch the XS in that race.
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Old 07-16-2019, 06:06 PM
gms955i gms955i is offline
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I never lost to a 'vette or mustang, or any car for that matter, I don't recall ever racing it against other bikes... I played cat and mouse several times with my little brother, mostly on a cb750, a cb900 and a gs500. Once he got a Valkyrie that stuff became no fun for me. Now he has a Gixxer 600 with a 750 motor in it. I'm left in the dust. I need this to work out.
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Old 07-16-2019, 06:31 PM
gms955i gms955i is offline
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Not a lot of oem stuff still available for these engines is there
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Old 07-16-2019, 08:19 PM
gms955i gms955i is offline
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Are the XJ1100 engines the same as XS? He has a couple of Maxim 1100's. Cool bike except for that stepped seat. My very first bike was a black xj550j.
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Old 07-16-2019, 10:29 PM
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Yes, they are almost the same. I believe they have the "YICS" system, a balance tube between all 4 carbs. They DO have the bigger valves, though. It should be easy to block the ports between the carbs, and just go from there. All the XS parts will bolt to the engine EXCEPT the alternator, as the XJ has brushes that the rest of the line don't.
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Old 07-17-2019, 04:24 AM
gms955i gms955i is offline
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And the the XJ engines will bolt into XS frames? I want to pick the engine in the best condition. If it is an XJ engine that's fine with me. Maybe I can get an earlier head to go on top of it.

I know that lowered compression is good for emissions, but bad for performance. I wonder if that's why they added bigger valves, to compensate. But another benefit to lowered compression is less wear on the engine itself. Trying to decide which way I want to go. The Venturer was plenty stout... Decisions...
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Old 07-17-2019, 10:19 AM
gms955i gms955i is offline
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I've been busy on with Google search today, found many of my questions answered. I just must decide if I want pre-80 or post 79 compression first. The bottom ends are all the same. I don't want yics but I can plug that and have more parts availability.
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Old 07-17-2019, 10:23 AM
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jetmechmarty jetmechmarty is offline
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There is nothing anemic about the stock carburetors. If you run them, the airbox works perfectly left unmodified. If you want to run pods, the flat slide carbies will work better. The stock carbs will work with pods, but you'll gain nothing, except more noise, which is fine, if that's what you want.
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