From:Gorm Wæhrens
Subject:RE: RE: RE: RE: RE: exhaust for K 1920 Date:Wed Dec 17 16:01:16 2008
Response to:2239
Lennart Bäckman, Sweden send me this picture of his Henderson early 1920. The illustration I put on the site here is like his bike.
My cylinders have the oval flanche, and the exhaust too.
My manifold is like Lennarts.
Thank you for all the comments and informations.

Some years ago Bent Granberg from Norway sent me some pictures of the round exhaust port variety that you describe. I couldn't find them when I did the earlier posting on cylinders but I've since had time to search a little deeper. Attached is the best of the bunch.
My exhaust pipe has the thickened end you refer to.
I have seen an early inlet manifold with a priming cup but mine is plain - very similar to the Deluxe manifold except for the stud spacings and port sizes for cylinders/carb which are as we have described for the Model K. Interesting because my gas tank cap has the priming syringe but nowhere to use it! All interesting stuff eh? Steve

I have been working on a 1920 Model K for a number of years. My opinion is that the 1920 K is different from the 1921 K in both the intake and exhaust manifolds. The cylinder ports are also different. The early K exhaust is a threaded port. I believe it was originally intended to take the long down pipes with ring nuts, like earlier F head Detroit Hendersons. I have seen NOS nuts. I borrowed one and had some made then I also realised that there is only about 7/8 inches (2 cm) between the frame and the crankcase so I set about looking for a correct exhaust manifold. That is when I found out there were a few attempts by Schwin to get it right.

The earliest has flanges that were machined and screwed onto each exhaust port. The flanges had 1/4 inch fine thread studs that took nuts which I believe were 3/8 hex outside as there is almost no room to use a wrench. The early cast exhaust also has a different angle at the exit to the tail pipe. I don't know why. They probably kept burning a leg or something. The early K also used 1 inch ports both IN and EX whereas the later ports are 1 1/8. I have tried a few times to cast replacement EX manifolds but the patterns were not quite correct and did not allow for a nut to be used. No clearance as I have mentioned. I eventually talked to Dick Winger and purchased an old manifold he had so I stopped working on the problem.

Another problem is no one in my area wants to cast the thing for me. I tried all the local foundrys over a three year period with no success. I do have two that are slightly wrong but that foundry won't do it again. I am not sure how many would agree with me but I think the Model K was a very late release, like after the new year started. Remember that Schwin and Henderson had had a parting of the ways and Bill Henderson started the ACE, reportedly sometime in 1919. Schwin on the other hand had a totally new design done for the Henderson and also moved the company completely to Chicago from Detroit and also had to re-tool for new production.

This brings me to original drawings. The intake manifold was drawn in February 11, 1920, revised July 6,1920, and finally to what people recognize on a Deluxe April 4, 1921.

The early intakes also had a smaller carburator mounting flange that accepted a 3 1/2 carb as opposed to the 4 that came later. There is a notation in the print of July 6, 1920 That says a 7/8 inch carb outlet has a 2 1/4 inch centres for the flange mount to the intake manifold and 2 3/8 inch centres for the 1 inch carb outlet (3 1/2 vs 4). So I would guess that both sizes of carb were available after that drawing was done.

The exhaust print was done February 11,1920, revised March 22,1920. I think there was another upgrade as I have seen cast exhaust manifolds on K's with the exit to the tail pipe reenforced with a thicker wall on the last inch. I believe they were very brittle and would break easily. That problem would be exagerated by the heat, like when a woodstove eventually breaks from use.

Based on this there was a list of Hendersons started years ago. The model Ks had the serial numbers listed. I have some information that states 1920 Ks start at engine K1200 and up, 1921 carries on from K1900 and up. I have seen K24XX I believe somewhere. They are pretty scarce.

I could go on but this is getting pretty long.

Hello Steve
Thank you for your prompt answer. My infos is from photocopies and this illustration fraom Thomas Bunds "AMERICANX". It might only be a drawing, a prototype. My 1920 has the manifold with oval flanges.
Thanks again

Hello Gorm
The 20/21 Henderson exhausts didn't have the long downpipes - they didn't come in until the width of the frame was increased and the motor fitted on forgings rather than fitted with bolts doing through the frame tube iteself. Model K's were fitted with a cast iron manifold which tucked in under the carburettor. Early 1920 machines had circular flanges onto the cylinders but quickly changed to oval flanges similar to those on the later DeLuxe. But note that the stud spacing on the K's was less that the DeLuxe so manifolds/cylinders are not interchangeable inless you swap the whole lot (including inlet manifold and carb!) Hope the picture helps

Looking for drawings, pictures for exhaust profile for Henderson 1920. The sales brochures 4 tubes going down must have a very close passage betwin frame and engine. Looking forward to have profile for those - trying to make repros.
Thank you.