The bottom line is--if you want a bigger engine, go get one and leave the 45 alone. After a lot of time, money and work, all you will end up with is a loud expensive noise as overstressed parts explode. The 45 is a great machine and there is nothing wrong with mild hop up, but modifying cases, magnum topends and tranny swaps are futile.
Hey..51F-3, I may be a 56 year old graybeard punk, but I do know my Harleys......the reason one would install a big twin transmision in a 45" is BECAUSE the primary and drive chains are on the same side. During very hard driving the trans would tend to turn in the frame of a 45, this would loosen the chains......get the picture? CT.
i had a 42 wla years ago.you may want to get a bigger motor sprocket[i think the wlrd racing 45s had a bigger spocket]check the heads for the compression.it should be stamped on the side of the alumimun heads.you may want to up that.i used to know a place that delt with hop up stuff for the flatheat harleys but that was 30 years ago. check on the net.
I've never done it myself, but here's what I've read. -The model you were looking for is a BSA M20, although any pre-unit brit bike tranny will work great. -You will need to figure a way to build a primary drive, I'd go with a brit bike open belt. -You will also need to machine the outer diameter of the Harley motor sprocket and the inner diameter of the brit motor sprocket. Fit the brit outer to the Harley inner. I think people weld them together usualy. Check this out http://victorylibrary.com/BTRAN.htm They shoud have all the info you're looking for.It doesn't look like rocket science (SProcket science ) to me, so you could do it without ordering the booklet. Hope this helps
... I've never been called practical... And ya, maybe modifing the cases would be impractical... but the weight of the whole package when setup as a 45 is what attracts me. Anyone have a diagram of where they crack?
Flat Ernie, the od does need to be shaved and I'd seen a set that was pork chopped so she'll rev higher/quicker and decelerate when you get of the gas in a turn. my dad always was into flat head hillclimbers and was once talking with an old timer, the man said he built a trap door in the bottom of the cases(WL 45's), weld two channels and put a piece of sheet metal(22 ga I think)and used a mag advance unit(the lever kind w/ cable)to pull on the sheet metal. Here's how it woked, at the bottom of the hill you'd rev the piss outta your motor and right when you would let go of the clutch you push the lever and it would dump all of the oil out the bottom of the motor and it would rev about another 5-800 rpm, remember no shifting so the more you rev the quicker/faster you go. -Jesse
That sounds, well, insane. But racers are known to do whatever they can for that extra little bit...seems like a total loss oil system with a gaping hole in the bottom of the cases would prodcue the most HP then, eh? My only concern with the big twin flywheels cut down that much would be balancing. Which I'm sure they didn't bother with back in the day, but on a daily driver...still, an interesting concept.
Nothing you can do will make a 45 fast or dependable. Wait a minute. I take that back. You could always get a big twin motor, tranny, frame and...Never mind No matter what you do some guy with a 350 cc bike will blow you off. So you'll be slow and look stupid. There are things you can do to get a little speed out of it (heads, carb lightened fly wheels etc.)and drilling and wiring everything is a big to-do. It would be a waste of time and a pain in the ass to install a big twin tranny in that frame. BTW I have a nice tight turtle top tranny I can let you have for $900. Get a copy of Questions and Answers "A Mechanical Manual for the Beginner and the Experienced Motorcyclist" The copy I have is 1984 and from: Antique Cycle Supply, Inc. Cedar Springs, Mich. 49319 (616) 636-8200 Theres lots of specs and info on old American Motorcycles and a nice section on Speed essentials for flatties and other motorcycles. If you want something thats old and you can make go fast get a knuckle, Pan or Shovel.
******Nothing you can do will make a 45 fast or dependable.****** Only the unknowing would make such an absurd statement. The 45 is THE most dependable Harley ever built!!!!!!!!!!!!!!!!!
Maybe he meant fast AND dependable. That would be tough. But just dependable???...no doubt about it!!!...I think WWII proved that. I know I would like a little more power, without spoiling the looks of the bike. I think with some of the ideas and links this can be possible. My days of tire shredding strokers is over, but I would like to be able to ride with some degree of safety and comfort at 50 mph...and a little bit of extra power when needed to get out of a dangerous situation. This has been an interesting thread.
Hatch, the 45 will run 80 mph or more in stock form. The WWII Harleys had a metal tab on the gas tank saying 'Do not go over 85". Its a great machine for around town and backroads. If you want to ride with big twins, they will out accelerate you. You will not want to run on the Interstate Hiways. The 45 will do it but its running wide open. I have a 1946 that I have been riding 28 years. I have other 45s too. Simple modifications I mentioned above are great, but chopping up the frame for a big twin transmission is STUPID. Magnum top ends overstress the lower end and transmission and frame and require chopping up the frame. The 45 is what it is. If you want to go faster, get a bigger Harley and dont ruin 45s!!!
I don't plan on doing anything radical on the bike. I will freshen up the top end...new pistons, rings and valves and maybe put the hotter intake cams in it. Thats it for me. Maybe change the final gearing to a 31 tooth countershaft sprocket. I don't think the bike will ever be on the interstate as long as I own it.
I take exception to the dependable portion - the fast portion is all relative. But isn't that what hot rodding is all about though? Taking something old and massaging it to do its best? I imagine by your criteria, there's probably nothing I can do to my Flathead Ford to make it fast & reliable either. And by modern computer controlled standards, maybe you're right, but that's not why I fool around with them. Anything can be built bigger, better, faster. The latin phrase, "How fast do you want to go?" is translated directly into "How much money do you want to spend?" - Case in point: You want to make the 45 bottom end bullet proof? Carve one out of billet instead of using 60 year old castings. Then slap on that Sportster top end and see what happens. I drove a 48 WL daily for about a year and a half and it always cranked on the second kick and never left me anywhere. Even when I finally killed it with a melted piston (high speed lean-out), it still ran on one cylinder and got me home! So what you're saying is is that I should ditch my Flathead Ford & put a Y-block in, right? But why stop there? A heavily breathed on Knuck, Pan, or Shovel is no match for a mildly warmed over Evo or TC88. You wanna drive a 53 Vette, a 67 Vette or an 03 Vette? Bottom Line: Old things (especially mechanical) have gobs of character. If they're a little bit slower and maybe even slightly less reliable, isn't it worth it? If not, go hop in your Honda and bling down the road comfortably, reliably, economically, and quicker than me! Courses for Horses! NOTE: No Honda drivers were injured during the formation of this post.
Yep" I have to argee with Manyolcars I to have been throwing a leg over 45s for about twenty years as well, dont take much to make them ridable, gearing is the answer for sure my latest got a 33t front sprocket stock rear I relieved the top end and slightly pumped up the compression this ol heap will run 65 all day, Dont forget these things was made over sixty years ago, I carnt remember the last time a 350 for the same period got around me whislt riding Gruntis
Gruntis...did you shave the heads to raise the compression, or find some different pistons? The replacements I have found are 6 to 1 compression ratio. Is that what you used? Also, could you give a little more detail on relieving this motor? Man...I can't wait till spring!!!!
Hey HATCH keep in mind the maximimum compression you can reasonably put on a 45 is 7.5 or something like that according to (I think??) Tom Sifton. I know its low for a flathead but it becomes inefficient after that its what i've read. A with running a big twin tranny isn't there a axle or sproket problem?? I heard something like that from a couple people. Well anyway I'm going english P.S This might be my first 45 but not my first Harley I built my 58 165 by myself when i was 11 and when i was 5 i was the youngest member of the antique motorcycle club -but now i've been corrupted by Hot Rods. Thanks for the help
I imagine the flathead harley is similar to the flathead ford in that there is a limit you can go on compression before you get diminishing returns. Seems like on the ford it was somewhere around 7 or 8:1 even with aftermarket heads. Someone with more knowledge about the harley will have to chime in on what their limit is. The flathead combustion chamber can only handle so much. Those old bikes are awesome, I love examples from every era stopping around the shovelhead era. Wish my old ironhead was as reliable as the old flatheads! Can someone explain the differences in the WL designations? Someone the other day asked about good chopper/bobber sites and I hate to say it but the HAMB is probably one of the best, way more/better info here than The Horse website... I am afraid that is why people keep asking bike questions here...
As mentioned, I'd have to guess the limit on CR is based on the transfer area of the head - similar to Flathead Ford. Interesting side note, one of the Flathead Ford books (can't remember which one) has a diagram of a WR? cylinder that's been step relieved as a comparison to the chapter on Flathead Ford relieving. HD probably did this so they could mill the head more trying to find the best return-on-investment for flow vs CR. WL - Solo 45 WLA/WLC/WLD - Military (D = AL heads, C = Canadian) WLD/DD/DR - Factory hi-po/racing versions WR - Factory Racer There are several others, along with the G (servicar) designations. I cheated and copied these outta my 45 Restoration catalog, but I think this info is on their website too.
Since the last post on here, I've been doing a lot of research for my project & here's a little of what I found - mostly from Victory Library's 45 Performance Book - well worth getting their big book if you're serious about mucking around with these little engines. Truet & Osborn make the repro stroker wheels that bolt-in & use all stock components. S&S still make stroker wheels for the 45 in lots of strokes, but you have to use Sportster rods - which isn't a big deal, just something else to buy/acquire. Currently, no one is producing stroker pistons, so you either have to run stroker plates or have custom pistons made - JE will do them for about $120 ea(!!) The WR cams are being reproduced, but there is a timing issue with them & they are such a mild grind, you're probably better off with reground cams or adapting K or early XL cams. Lots of good info & some really smart folks (including many folks who support the aftermarket stuff) on this board: Flathead Power Forum Enjoy!
A little OT but I have been thinking about getting a flathead to ride around town. This would be my first street bike,I have ridden dirt bikes for 20 years. Would a 45 be a bad choice for a first bike or should I think about something newer thats not a rigid. bzneil
I once experienced a same brand/different model parts swap with a WLA that may have some potential for you.In 1959 a friend bought a cheap(50.00)WLA and when we made it run found it had one ventilated piston.I had just pulled a set of .010 pistons from my 54 KH so we fitted them to the 45 and then we found the pistons from a 55 incher had a different pin height so the pistons barely touched the head.We added some head gaskets to get running clearance and put her on the road.It was the fastest 45 we ever fooled with(all basically stock).Possibly you could use the KH higher piston height to advantage-trimming the piston crown or relieving the head for squish area and compression improvement.The slightly higher ring position in the cyl was not a problem in our engine.I seem to remember the KH was relieved considerably and HD had lowered the ring positions accordingly.I have a HD publication "specifications & instructions -competition racer model KR-KRTT" that well shows the cylinder relief shape and dimensions in usable detail.Also remember the K's used an aluminum head with NO gasket.I have also seen this done on a Indian sport scout to raise compression for competition.Have fun.
Using the K-model pistons in the WL is a common trick - reading through Victory Library's tuning papers, there's a lot of talk about this. Check out the flatheadpower forum. I think I even saw Panic posting on here recently (he's the author/compiler of the Victory Library)
Use a carb off of a 74. My Sport Scout uses a Chief carb. It runs a lot better than before. An HD 45 just isn't a fast bike. But it should keep up with traffic OK. I agree with the others, play with the sprockets a bit. That's what I do. 30 years ago the shovel, pan, and knuck guys didn't like to ride with me too often, they said it was too hard on their bikes. The HD won't run with an SS, but it should be suitable, a bobber is even better. You aren't running a 16" on the back are ya? Those things kill the acceleration. Try some porting, the usual flatty stuff. How fast do you want to cruise? I don't see a lot of point in changing the trans. unless you just want to do it for fun. Enjoy it for what it is, a neat old bike, I think that's what you're already doing!
I have some old info and part #s to swap the bushings to roller bearings and I think some other internal stuff.PM me if you want the info.I have it somewhere,I haven't looked at it in 15 years.
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