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KR crank options?

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mike100m

Posts: 51

Joined: Fri Jul 23, 2004 12:01 am

Location: felton,Ca.USA

Post Sun Jan 27, 2008 7:31 pm

Re: KR crank options?

We've wandered off of Slindo's original question a little and I would like to post my experience with the dirttrack bike Chris and I and Jim ( XLR), prior to his un-timely death, run. The engine is a set of trapdoor K cases with KR cams, cylinders and heads. We use a sportster crank and rods with the double timken and needle bearing, and torringtons on both ends of the cams. We gear this motor for 6800 rpm and it occasionally sees as high as 7200. We are on our 3rd season with this set up and it has been dead reliable, knock on wood. I use a 1/4 speed pump and a .060 restrictor in the cam cover oil passage to the crank. I use 15-40 Delo 400. Also tightened up the scraper clearance with the crank. The most oil I will get out of the sump after a race is 1 1/2 ounces. I sealed off the primary from the crankcase and plugged the stock breather and put a breather hole and baffle at the rear top of the cam cover and run it thru a one way check valve. Adding this system dried up the few spots of oil seepage on the motor which makes me believe its running with a slight negative pressure in the crankcase.
I believe a lot of the oil consumtion quoted for these motors was because of the 50-60 weight oils used back then and one piece oil ring design that was common. When I drain this motor I get back 98+ percent of the oil I put in it. It shows minimal sign of burning oil in the combustion chamber and no smoke when on the track.
Mike
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45Brit

Posts: 1412

Joined: Tue Nov 27, 2007 2:29 am

Post Mon Jan 28, 2008 3:33 am

Re: KR crank options?

that's my experience of older British motors - modern lubricants and oil control rings have disposed of what was once a fairly common issue

so... I have to ask ... does a Sportster crank fit into a WL motor?
Shoot, a man could have a good weekend in Dallas with all that stuff...
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panic

Post Mon Jan 28, 2008 9:38 am

Re: KR crank options?

No.
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thefrenchowl

User avatar

Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Mon Jan 28, 2008 12:09 pm

Re: KR crank options?

I think it'll fit if one machines the right crankcase to get rid of cam supports that stick in... same on 52/53K...

Patrick
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panic

Post Mon Jan 28, 2008 1:02 pm

Re: KR crank options?

It's the distance between the thrust surfaces of the main bearing races - about .100" too narrow.
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Payton

Posts: 56

Joined: Fri Aug 31, 2007 8:31 am

Location: Central Fl.

Post Mon Jan 28, 2008 2:10 pm

Re: KR crank options?

Patrick wrote:

What you have are most probably KH/KHR cylinders that have been shortened for use on a K/KR... I've seen it done a few times, I even have a KH pair like that!!!
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What I have is a 55R KR cylinder. The only thing that has been shortened is the flange. It was chucked in a lathe and the
flange was thinned to about 1/2 the thickness of a KH flange, which in my opinion is a lot.

I was told by the man who gave the cylinder to me that it came from people who had great running KR's.
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thefrenchowl

User avatar

Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Mon Jan 28, 2008 2:17 pm

Re: KR crank options?

Maybe an extreme pop up engine?

Patrick
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Payton

Posts: 56

Joined: Fri Aug 31, 2007 8:31 am

Location: Central Fl.

Post Mon Jan 28, 2008 2:30 pm

Re: KR crank options?

Mike wrote:


I believe a lot of the oil consumption quoted for these motors was because of the 50-60 weight oils used back then and one piece oil ring design that was common.
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Harley used the less efficient oil rings and the heavy oil to make the engines live with the 1 1/2 thou. piston clearance
the engines were built with.

You had some good information in your post Mike.
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Payton

Posts: 56

Joined: Fri Aug 31, 2007 8:31 am

Location: Central Fl.

Post Wed Jan 30, 2008 10:08 am

Re: KR crank options?

Patrick wrote:

What you have are most probably KH/KHR cylinders that have been shortened for use on a K/KR... I've seen it done a few times, I even have a KH pair like that!!!

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How were those cylinder shortened Patrick?



Jack
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thefrenchowl

User avatar

Posts: 584

Joined: Fri Mar 10, 2006 3:18 pm

Location: Crewe, Great Britain

Post Wed Jan 30, 2008 12:14 pm

Re: KR crank options?

On a lathe I suppose... I put one back to KH lenght by brasing four steel spacers on each corner and filling the rest with Defcon, did not seep...

Patrick
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