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  #11  
Old 12th January 2022
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Originally Posted by Steve9 View Post
People bring up valid points

I'm not any kind of engine builder, but it sounds like a fine undertaking with many things to overcome.

And your reasons are your own....I hope you do it and post along the way it will be interesting as hell!
Yeh child psychology works well on me
I'm pretty fond of doing things that no one else wants to do. Lol.
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  #12  
Old 12th January 2022
Tomcatt Tomcatt is offline
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Originally Posted by Tippy_Toes View Post
it would be an over-square 883 for sure.
I would have to destroke a larger bore, not a standard 883 bore.
I think the Buell 900 was the 1200's 3.5" bore with a 2.8"ish stroke. 900cc with room for big valves... I don't know what length rods they used.
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  #13  
Old 12th January 2022
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Originally Posted by Tomcatt View Post
I think the Buell 900 was the 1200's 3.5" bore with a 2.8"ish stroke. 900cc with room for big valves... I don't know what length rods they used.
3-1/2" bore, 3-1/8" stroke, 7.270 rod ... the combination of which delivers the same deck height as the 3-13/16 stroke motors, with the same 1.200 compression height. Heads and cams identical to the XB12, which came out a year later.

Factory rev limit was 7500rpm.

I dyno'ed bunches of them back in the day. Here's a pretty typical result from a stock one:

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  #14  
Old 12th January 2022
Tomcatt Tomcatt is offline
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Originally Posted by aswracing View Post
3-1/2" bore, 3-1/8" stroke, 7.270 rod ... the combination of which delivers the same deck height as the 3-13/16 stroke motors, with the same 1.200 compression height. Heads and cams identical to the XB12, which came out a year later.

Factory rev limit was 7500rpm.
Thx, I wasn't sure. 4,500 ft/min MPS would be just under 8,700 rpm. 63.6 cu in with the 1275 kit bore. Will the valve gear live at a 9,000 rpm rev limit? Could fit what Tippy_Toes wants...
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  #15  
Old 13th January 2022
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The valve train could be made to twist that high, but not in stock form.

The XBRR turns 9K, but it has Ti valves and about 270lbs of seat pressure, among other things.

The XB9 crank isn't a bolt-on for a 4-speed case at all. It's not even a bolt-in for the 1991-2003 generation, although we've developed the parts and services to do it. We recently did one for a Bonneville racer who wants to run the 1000cc class with a Sportster.

What's more, the crank is discontinued and unobtanium.

So he'd be looking at a custom crank, if he wants to do this in 4-speed cases. S&S could probably make one. Pretty sure it'd have to be a pressed pin, though. There's not enough room for crankpin nuts with that short of a stroke.
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  #16  
Old 13th January 2022
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Originally Posted by aswracing View Post
The XBRR turns 9K, but it has Ti valves and about 270lbs of seat pressure, among other things.

What's more, the crank is discontinued and unobtanium.

So he'd be looking at a custom crank, if he wants to do this in 4-speed cases. S&S could probably make one. Pretty sure it'd have to be a pressed pin, though. There's not enough room for crankpin nuts with that short of a stroke.
For some reason I was thinking he had an '04 - '06 bike... 1100 parts and a newer bike he wanted to use them on to downsize it... Lotsa reasons this isn't really feasible.
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  #17  
Old 13th January 2022
Maxeffort Maxeffort is offline
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Originally Posted by Tippy_Toes View Post
Valve train isn't my big worry about doing a high rpm build, there are plenty of non-harley valve train components that are up to the task. My biggest would be the stress on the cam bearings and the case.

Bottom end would consist of destroking the crank and having the assembly built as light as possible and balanced at an unusually high rpm (maybe around 7k rpm?) to keep it together in the operating range.
The crank wouldn't necessarily need to be as robust as a low rpm motor since torque numbers would be relatively low.
The first plan of 1100 is better.
Very high compression is overrated, especially if it requires a big dome in the chamber.
All the power is in the heads, get the best ports put in that you can. You only need enough compression to support decent duration cams and then match the intake and exhaust.
If you can get a modest dome and machined squish band in the heads, that is proven the best.
All of that will get what you want.
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  #18  
Old 13th January 2022
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Originally Posted by Maxeffort View Post
The first plan of 1100 is better.
Very high compression is overrated, especially if it requires a big dome in the chamber.
All the power is in the heads, get the best ports put in that you can. You only need enough compression to support decent duration cams and then match the intake and exhaust.
If you can get a modest dome and machined squish band in the heads, that is proven the best.
All of that will get what you want.
I could likely have the heads milled down for a compression bump and have the bowl reworked and squish band machined. That MAY be the best option depending on valve to piston clearance.

That's definitely the most feasible option and probably the path this motor will go down. I already have notoriously good heads, I just want to do something out of the box with an 1100. It's such a bastard motor that it would be really fun to take some wins with.

I like to throw out a WILD idea every once in a while and see where reality actually takes over. Clearly this is a K.I.S.S. moment where sticking to the road more traveled is better.
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  #19  
Old 13th January 2022
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I like to throw out a WILD idea every once in a while and see where reality actually takes over. Clearly this is a K.I.S.S. moment where sticking to the road more traveled is better. build a sort of "FU 1100"


I guess nitrous or turbo is out of the question on a decent engine build to handle the stress.
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