Board index Flathead Power-Technical Questions, Answers, and Suggestions K-Models KR 2

KR 2

Post Sun Apr 15, 2012 8:57 am

Posts: 56
Location: Central Fl.
Regarding my previous post on the KR, maybe it would have been helpful to describe what the article by
Kevin Cameron was about.

Neil Keen and C.R. Axtell discovered a way to improve the airflow to the KR cylinder by 50 percent.
This led to a call to Dick O'Brien who got involved and this evidently led to the development of the
dome head KR.

It would be nice if there was a indepth book on the Kr from beginning to end on all technical tidbits,
including information from the various men who was involved with racing and building of the KR.

Post Sun Apr 15, 2012 10:32 am

Posts: 591
Location: Crewe, Great Britain

Tongue in cheek...

Is that why flat top piston KRTTs could do 149mph in 68 but the dome piston ones, otherwise similar, could only do 140mph in 69???

As usual, what happens on the dyno and reality are miles apart,... litterally!!!

Got my own theory on this, the best part of any std side valve is the shelf in the head, but it disappeared on the dome variant...

Yes, no decent books for sure on KRs, but you can always visit my site :wink: ...


Post Mon Apr 16, 2012 10:49 am

Posts: 56
Location: Central Fl.

Your post does not refer to article I brought to your attention. Pick up a copy of Cycle World and read it and
quite possibly you be a little more knowledgeable about the subject in question.

I probably have read just as much as you about the disaster at Daytona and I do know that O'brien and his
crew were pretty smart and very determined. They proved it after the rain delay.

Maybe the original domehead setup used did not work out, but that part of the setup which increased flow
as mentioned in the article, I believe,was used.

Think about it.

In my thread "Chance Encounter" I mentioned that the domehead engine from Bart Markels bike was sold
to a man named Diamond. Do you have any explanation as to why a domehead engine was in the bike
when Markel sold it to Fletchers HD.

Your opinion will certainly be appreciated.

Post Mon Apr 16, 2012 3:40 pm

Posts: 591
Location: Crewe, Great Britain

Hi Payton,

As I said, tongue in cheek!!!

I will cerainly not belittle the efforts/time spent/dyno experiments of Axtell, Branch and others in making my beloved side valve go a bit further. Bit too far away here in GB to find the article you mention.

But from what you said in the 1st post, I deducted, wrongly or rightly?, that the flat top piston wasn't suitable for the flow improvements discovered, hence the use of dome ones.

There aren't many guys alive today who still think in terms of side valve tuning.. I met a few old guys in my time, and did pop the question to them, flat top or dome... Most of their answsers can be summed up that it don't matter too much as long as the sacred shelf remains. That's why I noted above that getting rid of the shelf in the dome experiment wasn't probably a smart move.

The dome top still had its day, Dan Haaby still raced his during 1970 with some success if not outright wins... I can't neither deny that the dome came too late due to change in AMA rules, so did not have the time to get properly sorted. Given a few more years and given O'Brien and his crew's tenacity, no doubts we would have seen better results...

But, back to the delayed race in 69, what I read between the lines is that all the factory top guns reverted to the flat pistons/shelf heads during the god sent week's delay, that must surely say something.

As for who owned what in the good old days, I'm stuck in GB, a bit far away for decent research, so do wish some of you guys in the States that value the KR effort for what it really was, a damn good effort considering the odds stacked against it, to do your home work and make it public for all to enjoy and savour.

I particularly appreciated in the recent past the 54/69 GNC book by Gregory Pearson, what an smart single handed effort!!!

KR mad Patrick

Post Tue Apr 17, 2012 9:59 am

Posts: 56
Location: Central Fl.
Good old Patrick: What would this forum be if not for you? I pick up a copy of Cycle World each month
just to see what is in it. I mainly like Kevin Camerons column "TDC' because its usually about technical
issues related to racing bikes, past and present. The current issue deals with the KR.

Keen and Axtell had someones KR at the shop and decided to analyze the top end of the engine and try
to determine ways to improve air flow. They felt that the flow when it got past the intake valve and hit
the top of the chamber was the big problem, so they made some 1/4 inch gaskets, checked the flow and
discovered a flow improvement of almost 50 percent. After working with clay on the heads and the ports
to maximize the flow, O'brien was made aware of their findings, and after that O'Brien and Roy Bokelman
welded up some flat top pistons for domes and the finally came up with the domehead KR.

Keen and Axtell also stated that the use of mikuni carbs probably would have increased the HP by at
least 2. Harley had to use the tillotson carbs because of a contract with tillotson.

Sorry you could not get your hands on Cycle World. I felt sure it would be available in the UK.

The article will probable be on line sometime in the future.

Post Tue Apr 17, 2012 1:49 pm

Posts: 575
Location: devon,england
cheers for the heads up payton ,
cycle world can be obtained through " the magazine man" online . also there is a download service provided by someone ,however its pay as you go and i wouldnt like to chance my arm with the possiblilty of internet fraud.
regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Tue Apr 17, 2012 1:50 pm

Posts: 591
Location: Crewe, Great Britain

Hi Payton,

Hum, good old Roy... Found this shot some time ago on the web, couldn't put a name to it but did recognise the chin!!! Quick email to Jim Haubert to get the answer, I tend to get confused with all the guys with German ancestry/names working at H-D!!!

So here he is testing an XLR engine in the late 50s, sure looks like a Pohlman posed shot to me...


I live in the countryside, can't stand big towns... Give me the issue number, there's a guy selling all the mags in the world at the bike shows in GB, he'll probably have it...

PS, thanks Jib, that's the man!!!

Post Wed Apr 18, 2012 9:38 am

Posts: 56
Location: Central Fl.
The article is in the May 2012 issue of Cycle World. Magazine man not showing the May issue.

Post Wed Apr 18, 2012 12:11 pm

Posts: 591
Location: Crewe, Great Britain

To make a living, he probably buys his magasines from unsold stock direct at the distributors, will wait a bit before asking him. Thanks again for the lead!!!


Post Sat Apr 21, 2018 7:31 pm

Posts: 54
Location: felton,Ca.USA
Hi Folks
Thought I would jump in here on the dome piston issue. I have a dome motor build in the queue, I have discussed this at some length with Jim Belland who built the KR's for the Brelsford's and Mert Lawill among others. He said one of the most critical things required to make them work is getting the dome in the head concentric with the bore. This required dowelling the heads to the cylinder finding and marking bore center in the head an fixturing on center in a lathe and re-fly cutting to center the the dome radius to the bore. Mert's last dual carb dome KR used Mikuni's. They actually tried 3 different dome heights. .200, .400 and .600. Settled on the .400 for the #8 heads which I am using.
As a side note I am just about finished with the Andres short rod KR bike project and will be posting pictures shortly on that other thread.
Regards Mike

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