Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Increasing Size.. 45 to 74 ?

Increasing Size.. 45 to 74 ?

Post Sat Feb 05, 2011 8:20 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

The email is legit. It is a notification that a new post that you have relplied to has come up. You can turn off that notification in your preference page. I don't have mine turned on. It seems more of a pain when i come here many times per day as it is. As to why the link won't work, Your security is probably set higher than average. Personally, I don't open any emailed links from my email inbox. Pa

Post Sat Feb 05, 2011 8:48 pm

Posts: 575
Location: devon,england
ok pa,thanks . has it changed then? sure it used to be info@ss...... cheers jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Sat Feb 05, 2011 9:16 pm
Pa Site Admin

Posts: 5843
Location: Ohio USA

Yes. It did change and will probably change once more. I learned about it the same way you and DD did. :( Hopefully I'll get a heads up this time around.

Post Sun Feb 06, 2011 1:59 am

Posts: 1654
I'm sorry to say that these days I route all emails from web forums ( fora? ) into a separate email account which I keep for the purpose, I actually use hotmail for immediate personal matters with the filter set to "exclusive" so that all unknown addresses go straight to the "junk" box and are destroyed unread.

I also list my own email address as a spam sender on my web-forum address because there is a category of junk which lists your own address as the sender.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon Feb 14, 2011 9:16 am

Posts: 202
Location: Middle England UK
I've read through this thread,skimming over the gun parts.I know a guy that still does contracts for the oil industry,standing by people such as 45Brit with a side arm and pump action,while operating in "sensetive" areas.
For me,if I never see another gun or it's efects,it will be too soon.
To the subject in hand.
The Matchless G3 had a Burman CP Type gearbox and clutch,the AMC box was fitted from 1954.
Power output would have been nowhere near 25BHP,a good roadgoing 500 of the time made around 23,a 350 made around 17 BHP.
A ZB350 Goldstar made 25 BHP @ 6000 RPM on an open pipe,a different animal alltogether.

As to the Tug-o-War from a tensioned chain,my money is on the 45.
The OHV requires more revs under drive with the clutch engaged to develope any usable power,it wouldn't make it.
When the flag dropped it would face a test far more severe than starting from any hill in a MCC trial.
Using the "towing with a M20" example (13 BHP) it doesn't hold water.
In the 60's we used to take off on week end trips,it wasn't camping,we took a couple of blankets and slept in bus shelters etc,and eat in cafes.
On returning home one Sunday night,a Norton twin sidecar outfit lunched it's engine,big time.
Also in our party were a couple of 45's.One of the riders called Tiny,he was anything but,tied a rope to his 45 and the outfit carrying Steve and his girlfriend.When he pulled away,it was that easy,Tiny looked round thinking the rope had broke.He towed the outfit the remaining 60 odd miles with no problems.
Thankfully,by the time we reached London,they'd found a compromise on cornering techniques. :mrgreen:

Post Mon Feb 14, 2011 10:37 am

Posts: 1654
If you are defining the tug-o-war as a tensioned chain on a metalled surface, then I would opt for the 45.

I used to know someone who went touring with an ex-AA M21 outfit, towing one of those tiny caravan things shaped like a teardrop. It did it all right, but you could probably have walked there in about the same time.

The AMC gearbox and clutch was and is, pretty much indestructible, being used an all sorts of bikes up to the Norton twins. In my experience it's far superior to the 45 unit. However the clutch will not stand prolonged slipping, being an oilbath unit unlike the dry H-D one; it will glaze and/or burn out. It doesn't have the sheer mass of the H-D unit.

One thing I would say about 45s, is that when I was first working on land-rigs ( late 1970s ) there were still quite a few of them knocking around the North African coast, having been left over from Operation Torch and the subsequent supply build-up for the Sicily and Italy invasions. They were great on the unsurfaced roads but off-road, hopeless; the weight and lack of ground clearance meant they would sink in, bottom out and then dig in the back wheel very quickly. This wasn't helped by the numerous protrusions at ankle height which coupled with the foot clutch made "legging" the bike both difficult and dangerous.

The BSAs were much better all round.
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon Feb 14, 2011 12:14 pm

Posts: 202
Location: Middle England UK
As per my last post,the Matchless in question,had a Burman box and clutch.The only interchangable part was the pressure plate.I used one on a '49 500 as that's all I had in the parts pile.Locked the pushrod adjuster up solid then ignored it,and adjusted at gearbox cover end,as per Burman.

Post Mon Feb 14, 2011 12:33 pm

Posts: 336
Location: Kirksville Missouri United States
I have researched building a big inch 45 based flathead engine for a year or so.I've sought advice from Jim Leineweber,Paul Osborn,A tech I know at Axtell from our mutual interest in all k model based bikes and parts,Randy Torgenson<sp> owner of "King of Cubes",Pat Leahy,Panic,Larry Wahl,and several others.
Based on the information I plan to machine a big bore set of cylinders out of ductile iron.Randy Torgenson gave me the number to his supplier and the specific code for the 2 pieces of ductile round stock I bought,each measures 7" high X 12" O.D. I have access to the cnc and one of the guys that can run it better then I to cut them for me.
Paul Osborn suggested I run 3 1/4" bore Indian pistons and told me the Kiwi among others offer short pistons for strokers.Paul also told me that I could positively run cylinders without skirts if needed.The 3 1/4" bore with 4 5/8" stroke equals approx. 77 cu. in.
The tech at Axtell I do business with took into account all dimensions and suggested a 3 1/2" bore piston from a 1200 evo sporty ,told me if I went with the KH height cylinder and a 4 5/8" the unmodified pistons absolute bottom would lack ever exiting the bottom of the cylinder by .0025.He further stated that you'd have to move the cylinder studs but would have no reason to open the cases spigot bore diameter.This bore and stroke equals approx. 88 stock 3 13/16 stroke and 3 1/2" bore equals approx. 73 cu. in. and would be more cost effective then buying stroker wheels,etc.
Jim Leineweber said to run the biggest valves possible additionally that a thumb nails width between the valves edge and the cylinders bore was enough.He referenced the UL specifically when advises valve diameters.He suggested his #25499-67R (.395" lift,1967,J cam) as being about right for the engine build.
Panic both directly and indirectly suggested a multitude of ways to assure the valve stems lined up with lifters.He also offered a few options if the alignment was less then perfect how to compensate.
The larger piston bore would require the valves to be straight up and down instead of at 2 angles like the KHK cylinders I now have.As explained to me as the valves were moved at the head outward away from the piston the stem ends are to be kept the same relative to the lifter.The amount the valve head could be moved to result in the stem being straight would determine the valve size as the available area between the cylinder bores edge would be the limiting factor.
Lastly as this is getting lengthy I don't know how many are aware of who Pat Leahy is but he's ran a successful independent shop in Cali. for 41 years,was the co-builder with Randy Smith of the first magnum.He recently restored the magnum and other of Mr. Smiths bikes.He was a successful fuel sportster drag racer,big bore cylinder maker,known in a very huge circle to be one of the best aluminum welders currently on the planet,etc. He suggested a couple ways he's personally used to go big bore on ironhead drag bikes,etc. One method is to plug and weld an engine cases existing lifter block bores.Build up the surrounding area with weld,then mill flat.Lastly bore new openings further away from their current relation to the side of the case.This is quite a bit of work but usually provides the needed space to allow bigger cylinder bores and valves without interference.The cam lobes have to be turned off their gears then the lobes alone are spaced to the cam cover on the shafts then timed and tack welded in 3 spots to the shafts.The amount possible to move the cam lobes is largely determined by clearance issues.The second was to have a 1/2" wide spacer machined that bolted between the case halves.S&S offers a 1/2" longer pinion shaft.He said this was the way to get large cylinder deck surfaces for your cases back when.S&S,Delkron,and I'm guessing most now offer wider case halves to provide an easier method.
Anyway I've typed more then most want to read.I have the ductile iron and needed equipment available.I will be machining at least a set of these once my engine build is done for my solo.It's being assembled by Larry Wahl for me and should be a runner.For those interested in the specs and don't want to refer to posts I've made in the past .I have a set of 51 WL cases,4 5/8" stroke flywheel assembly,ironhead rods,enfield racing silicon bronze lifter blocks for roller lifters on angled lobe cams,K model pistons,KHK cams,cylinders,intake,a set of K model heads I'm,per Jim Leinewebers near insistence,converting to KR combustion chambers,restored M53 with original bomb site ventura,etc.I've also been blessed to have the assistance of a pro wrench,ex fuel bike record holder,head porter with the latest equipment and trained by Joe Mondello (a race car engine legend).He has designed and tested the design of a dual linkert intake that he's given me dimensions based on my set up for.I have a couple M51's I plan to ultimately run on this build.I'm taking the advice given to me by Tom Faber and getting all the new build issues worked out with the single M53 before adding the dual M51's.He shared following his advice would leave the dual carb setup as the only possible source of trouble if it was the only change to a well running engine.
l Lastly Larry Wahl a member of our board has been instrumental in taking the time to ask a multitude of questions over the last year or so.He has the answers to flatheads that can only result from decades of experience with them.I owe him a debt of gratitude for being patient and freely sharing so much flathead related information.I have build and owned bikes just over 30 years but my oldest,prior to this flathead, was my 1960 pan.
Well I hope this didn't put anyone to sleep..............

Post Mon Feb 14, 2011 10:08 pm

Posts: 976
Location: Markt Einersheim, Germany


Greg, long time no hear...Sounds like quite the engine project.

How's the trannie coming?


Post Tue Feb 15, 2011 4:25 am

Posts: 575
Location: devon,england
excellant post greg
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years

Post Tue Feb 15, 2011 9:01 am

Posts: 304
Location: Jonesville, Louisiana, USA
Great post, Greg. I thoroughly enjoyed reading it.

I look forward to hearing more about this flathead beast.

Post Wed Feb 16, 2011 12:28 pm

Posts: 87

Put us to sleep? This is what wakes us up! Enjoyed your post - you thinking big allows others to dream big. Had a couple comments.

You said -
3 1/4" bore Indian pistons and told me the Kiwi among others offer short pistons for strokers.

FYI, if you go the 3.25” route, Kiwi has several different pistons, the stock implement type with 4 fat rings, which you wouldn’t want, forged JE pistons, which I also think you would not want (Kiwi reports longevity issues with these in Chiefs) and a cast piston with a nice narrow ring pack that I think you would want (Kiwi reports excellent results with these). I believe these cast pistons are available in compression heights of 1.84”, 1.54”, and 1.48”.

You also said -
run the biggest valves possible additionally that a thumb nails width between the valves edge and the cylinders bore was enough.

Regarding the valve circumference to bore placement, if I were making your investment in the one-of-a-kind large CNC billet cylinders, I would not place the valves anywhere near “a thumbnail” from the bore. I’d want the highest probability of survival possible, and that would occur with at least some meat between the bore and the seat in order to minimize bore distortion. The IN, which runs cool, is not nearly as critical as the EX, but to move the EX in close to the bore is knowingly running with unacceptable bore distortion. If it was my investment, I’d want at least 0.125” on the IN and 0.250” on the EX. In my mind, dimensional stability of the bore at temperature is far more important than getting the largest valves possible into the cylinder.

I also like your cam selection, as this cam pretty much represents the finale of decades of KR refinement by the moco.

Keep us posted on your progress.


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