Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Magnum?

Magnum?

Moderators: Curt!, Pa

Post Thu Jan 10, 2013 1:28 pm

Posts: 919
Location: RENO,NV. U.S.A.
I have several sets of 45" cases and several XR750 top ends,which for years I've contemplated on building a XR-Magnum. Does anyone have any input on this? BREWSKI

Post Fri Jan 11, 2013 2:45 pm

Posts: 17
Location: POLAND
I saw several Magnums, here in Poland. WLA was here popular so it had many modifications. There is one of polish Magnums, which have a lot of modifications improving engine performance, I think the builder of this bike knows all about modification 45 to Magnum:
http://www.youtube.com/watch?v=wvVTcS_zqRY
http://www.youtube.com/watch?v=J4rBNri9I-c

Post Fri Jan 11, 2013 5:23 pm

Posts: 111
sounds like a good idea. like a ( XRWLCH ) :D it may be relatively easy using the xr studs. i recommend using sporty flywheels, rods, oil pump, cams etc. What is the OD of the xr cylinder spigots?

Post Sat Jan 12, 2013 4:00 pm

Posts: 919
Location: RENO,NV. U.S.A.
I will let you know on the O.D.,when this happens the whole bottom end will be XL ala my KR/WLas in S&S bottom end. I have 6 sets of 12.5 Cosworth pistons for a XR which I intend to use

Post Sat Jan 12, 2013 4:36 pm

Posts: 159
I think 12.5 compression is going overboard? Or are you going to race it? A pig to start I'm sure, you'll end up over the handlebars!

Post Sun Jan 13, 2013 12:29 am
Pa Site Admin

Posts: 5668
Location: Ohio USA

I know several who have built 45 magnums and they say the bottom end will give early if not tragetly.

Post Mon Jan 14, 2013 4:31 pm

Posts: 783
Location: Victoria, Australia
Hi Brewski, you may find this information useful for your project. The engine will not grenade unless you treat it like one (Randy Smith). many have been built in the past (as you are probably aware using only the std 45 rods and flywheels. Mine is fitted with WR Rods, WR Crankpin , mild XL cams and pistons machined to lower the compression.

http://enigmas.customer.netspace.net.au/Magnum%20Part%202/Magnum%20Construction%20Part%202.htm

Post Mon Jan 14, 2013 7:10 pm

Posts: 20
Location: East Central Illinois
That link was interesting. Do you have Part 1 for us to look at?

Post Tue Jan 15, 2013 2:49 am

Posts: 693
Location: somerset, oh usa
There's stuff available today that wasn't in the 70's. Last i knew our host still made 45 flywheels with a modified XL crankpin allowing use of XL rods, bolt in. I believe that another common flywheel manufacturer also makes a product for the same application. If i wanted to stand on it occasionally, and why not, I'd consider modifying the left case for a ball bearing so that the stepped WR sprocket shaft can be used. Should make a solid bottom end for what you're planning. Going to an early XL pinion shaft and bearings may even be looked into. The cases likely then will become the weakest link.

Post Tue Jan 15, 2013 5:37 am

Posts: 783
Location: Victoria, Australia
No, I don't have part one as the method of presenting that info was just a trial. I do have a lot of build pix archived...if I can find them! There are 2 ball races on the drive side of this engine...my own mod.

[imghttp://enigmas.customer.netspace.net.au/Magnum%2018.08.06/MVC-005F.JPG][/img]

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It's kind of difficult to see on this image but there is a retaining plate fixed to the sprocket shaft side of the case locating a 'second' ball race bearing (2 on the drive side. (I'll search my archive for some more detailed pix of this)
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Post Tue Jan 15, 2013 9:29 am

Posts: 766
Location: CA USA
I've used the S & S special flywheels. The Wichita, KS guys told me that they use a recess pocket in their flywheels to make it possible to run stock CH rods and pin. Several years ago I successfully modified a set of early iron head CH rods to use with stock WR flywheels. I surface ground the thrust surfaces of the female rod to the same spec as the WR/WL rod. I then reduced the width of the early steel CH rod cages to match. I used a WR stepped crankpin and fit everything up with standard CH rod bearings. Worked just fine. Much cheaper than WR rods, plus I could use new parts with the WR flywheels. Should work the same for a Magnum bottom end. I'm told that a late EVO XL flywheel thrust washer should reduce the need for grinding the CH rod in this modification, but I've never tried it. From what I learned back in the day, Smith's failures were not due to sprocket shaft bearings, but rod and case failures. Not much you can do about the case weakness except use the late thicker WR cases. Going to a stronger CH rod should solve that potential problem. HD thought that the WL rod was too weak for the additional power and stress of both the WR and the K . WL rods are probably OK if you don't beat on it, but what fun would that be. One man's thoughts.

Post Tue Jan 15, 2013 1:59 pm

Posts: 693
Location: somerset, oh usa
Where i found the evo thrust washers beneficial was repairing a WR flywheel with a washer spun as they are larger on the OD. They also have a .030 step in the thrust face that helps with fitting XL cages into WR rods. It doesn't help with fitting the XL rods but allows for only removing .060 instead of .125 from the cage stack. Your results may vary.

Post Tue Jan 15, 2013 2:45 pm
Pa Site Admin

Posts: 5668
Location: Ohio USA

Man Vince !!! That engine is beautiful !!

Post Tue Jan 15, 2013 3:32 pm

Posts: 139
Location: USA
Hey Beachdog ,in your post you referred to the 45 crankcase being weak.Exactly where and how would you suggest a way to strengthen it. It looked to me like there is plenty of material on around the motor sprocket shaft, but I think the weakest part of the case is on the left side above the tappet blocks ( the case is really thin here ,maybe about 1/4" thick,there is a sad story behind this knowledge). I have been kicking around the idea of using an INS bearing similar to the new Harleys opening up the motor sprocket shaft opening and using a Sportster flywheel assembly with rods,pinon shaft and motor sprocket shaft . Vince ,that Magnum is jut OUTSTADING. What kind of clearance did you you machine your case to utilize the double bearing set up ? Thanks for your time. :D :D

Post Tue Jan 15, 2013 5:55 pm

Posts: 783
Location: Victoria, Australia
Thanks Paul :) , I am pleased with the way it turned out. It was built quite a number of years ago now before S&S hosted this forum. There was quite a lot of info posted into the original forum (as I built the engine) but I don't know if an archive still exists? As I said, I have countless pictures of its construction archived someone at home... in a box!

I believe George G. (in Germany at the time and still posting to this forum I've noticed, copied many files). Like all things 'individual' there were false paths and changes along the construction route as I found better or easier solutions.

Celticdodge, it's been many years since I completed the magnum so I can't recall 'off the top of my head' but I'll endeavour to find the files. From recollection the drive side of the case was machined to take a ball race bearing (it fitted snuggly on the sprocket shaft). A second bearing went up against this and protruded slightly out of the case. I machined a retaining plate (with a bearing recess) that located the outer bearing. This was held in place by countersunk hex head bolts around its periphery to the sprocket shaft case boss. This left approx 1/2" of the sprocket shaft protruding to take the drive.

I tried to keep the reciprocating weights on the crankshaft down for obvious reasons. ~ Vince

Post Tue Jan 15, 2013 9:46 pm

Posts: 975
Location: Markt Einersheim, Germany

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Last edited by George Greer on Sat Feb 09, 2013 1:17 am, edited 1 time in total.

Post Wed Jan 16, 2013 5:57 am

Posts: 139
Location: USA
YO Brewski,life is too short , Man if you got the parts do it do it for all of us. I have been wanting to do this also.Go ahead and stroke it while your at it and add nitrous. Ever think about some Buell parts,were any of the Buells water cooled ? Oh yea I was looking at a remote gear and chain driven oil pump from a Victory capable of about 80 psi that might be able to be adapted. You see where I am going with all this. Anyway good luck,I believe you can do it and it would set a fire on this forum just like the old days. Just do it and share it all step by step. Thanks guys for all your input, this is still my favorite forum. :D :D :D

Post Wed Jan 16, 2013 7:57 am

Posts: 783
Location: Victoria, Australia
Hi George...Won't they let you go home? Well, as consolation I suppose your German must be outstanding by now. :)

I found some of the build pix and info that I'd archived. It may prove useful to someone considering this project.
There's a lot of welding on the cases required and this needs to be done carefully and in a considered manner not only for the final aesthetics of the engine,
but also for structural integrity. Most of the additional welded material I hand filed off...then had the surfaces milled true. Randy Smith used studs running from the case to the heads. Lots more machining. I simply used base studs.

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Last edited by enigmas on Wed Jan 16, 2013 4:36 pm, edited 1 time in total.

Post Wed Jan 16, 2013 10:21 am

Posts: 766
Location: CA USA
CD, Harley found that the 45 cases were prone to cracking in race apps. They improved them by increasing the thickness of the cases around the mainshaft bores for the later WRs. Enigma, your sprocket shaft upgrade is first rate. Just curious, why did you develop your own mod instead of machining your case for the WR sprocket shaft bearings?

Post Wed Jan 16, 2013 4:34 pm

Posts: 783
Location: Victoria, Australia
Beachdog, it just seemed easier to me at the time. The bearings are readily available here (in Oz) and the case race needed to be machined. ~ Vince

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