Board index Flathead Power-Technical Questions, Answers, and Suggestions 45 Flatties Custom frame

Custom frame

Moderators: Curt!, Pa

Post Mon Jan 24, 2011 3:01 am

Posts: 42
Location: seattle, washington
regarding the custom frame being manufactured that utilize the big twin 4 speed transmission, i am looking for real data from someone who has actually purchased, visually inspected one or even rode a built bike ??

What are the good points and what are the bad points of this chassis ??

I have interest in these frames to build a unusual street bike, any helpful data would be good.

has this topic been discussed before ??

Post Mon Jan 24, 2011 7:43 pm

Posts: 2684
Location: Los Angeles, CA

Post Sun Jan 30, 2011 11:17 pm

Posts: 42
Location: seattle, washington
thanks for the link, that is the frame i am wanting information about, has anyone purchased and built one?? does anyone know of someone who has built one of these willing to share real information ???

Post Mon Jan 31, 2011 12:51 am
Pa Site Admin

Posts: 5668
Location: Ohio USA

That frame was discussed fairly extensively in another topic. I don't recall the topic though.

Post Mon Feb 07, 2011 9:24 pm

Posts: 42
Location: seattle, washington
thanks for the reply, i thought there was a post on this frame, i certainly cant find it or i would just read it, can anyone help me find some real data on this frame ??? thanks for your help.

Post Mon Feb 07, 2011 10:16 pm

Posts: 2684
Location: Los Angeles, CA
handshifter wrote:
thanks for the reply, i thought there was a post on this frame, i certainly cant find it or i would just read it, can anyone help me find some real data on this frame ??? thanks for your help.



Call Paughco in Carson City, NV and ask for Ron.

Post Tue Feb 08, 2011 12:49 am

Posts: 1633
the main criticisms offered of this frame have tended to be that (1) it lacks various mounts, notably footboard and/or footpeg mounts (2) is dimensionally incorrect for various stock parts that people may wish to use (3) is plain unsightly, which is a purely personal matter

(1) can be seen from the various pictures

(2) I can't comment on

(3) is up to you, really, but it doesn't work for me
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Tue Feb 08, 2011 11:09 am

Posts: 199
Location: Cedar Springs Mi USA

45 brit, to add one more issue to your list.........the engine is mounted 1 1/2" off center to make up for the alignment problem between tranny and engine. Not the best balanced solution, and in my opinion, poorly engineered.

Post Tue Feb 08, 2011 6:29 pm

Posts: 139
Location: USA
I must admit I too have pondered with the idea of using this same frame especially after seeing the Bonneville bike that Paul Friebus of American Cycle Fabrication built and the bike built by Steve Garn at Brew Bikes LLc. However I wonder if a big twin transmission from maybe a 1954 panhead would be narrower than a later model and be part of the solution to the 1 1/2'' offset previously mentioned or would an old Norton transmission really be the best choice.Offhand it seems like the big twin transmission would be excessively heavy for such a small bike ,parts availability for the big twin transmission is what really appealed to me.Any real world solutions?Thanks for looking. :D :D

Post Wed Feb 09, 2011 5:22 am

Posts: 1633
The Big Twin is just a larger machine all round. The Norton or BSA transmission is a much better option for the 45, being smaller, lighter, much cheaper and quite able to handle anything a 45 will ever produce.

Either box is narrower than a Harley unit so the box needs to be offset to make the chains line up, Victory book and numerous webthreads cover this. You will need a special engine sprocket
Shoot, a man could have a good weekend in Dallas with all that stuff...

Post Mon Feb 21, 2011 5:17 pm

Posts: 42
Location: seattle, washington
thanks for all the info, i have looked at a couple useful photos of this frame, and can really see the 1 1/2 offset written about, its easy to see by the location of the generator strap hole on the cases, its location compared to a stock frame is very far off set.
I guess my last question would be, could this negatively affect handling of the bike by having the engine set off to the side ?? i wonder if the added width and weight of the big twin trans would counterweight the engine off set ??.

Are there any other builders of custom 45 frames, or are we just stuck with stock frames to work with ??

Post Tue Feb 22, 2011 1:49 am

Posts: 1633
I can't believe that having the engine offset in this fashion is beneficial to the handling, let's say.

I've seen various pics about of bikes which seem to be Big Twin frames with 45 engines slotted in, pretty much by redrilling the engine mounting bolt holes and fitting spacers under the mounts, and various people have posted that the BT frame is about the same weight as a 45 unit. Given the huge forgings contained in the frame, and that various parts such as forks and wheels are much the same weight, I could believe this.

Personally, I'd feel that visually the 45 engine looks too small for the frame, but that's in the eye of the beholder. But it seems an easier, cheaper route if you fancy the end product.
Shoot, a man could have a good weekend in Dallas with all that stuff...


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