M45A vs M74B Carburetors

[chgofire5sqd]

I have a 1950 FL and my bike has a M74B carb on it. I would like to put it back to its original M45A carburetor. My ? is will I lose any power or performance by going to a M45A. I ride this bike on the highway offen and it has no problem doing 70mph with the M74B, so I don't want to lose the speed for originality If I can help it.
Also for some reason, my rear fender hinge (the top part) was riveted on the outside of the fender not underneath the fender wall. I have only seen this one other time on a 1950 pan on the internet. I'm sure this has to be a big mistake on someone's part when this bike was repainted 25 years ago. Any thoughts on this ? I'm in the process of having the bike repainted. If this is not some rare way Harley mounted this fender hinge, I need to have it changed and rerivited. Who or were can I get this done ? Thanks Dave

[Sidehacker]

Can you show a picture the rivet is supposed to pass thru the outside of the fender thru the hinge and is hammered down underneath.the heads of two rivets should be visible on the top of the stationary part of the fender one on each side of the fender and the gate of the fender ( the part that hinges up is called the gate ) should have two rivet that pass thru it to hold the hinge in place and the rivets line up two on each side of the seam where the two fender pieces meet. I've seen painters and body men cover the rivets or feather them in or countersink and fill but the heads on a stock bike should have the rivets showing . Unless I'm misunderstanding you in which case I get back to my original statement, can you show a picture

[chgofire5sqd]

Here is a pic of what im talking about. Look right below the luggage rack, you see how they mounted the top part of the hinge and rivets 228.jpg219.jpg

[Sidehacker]

Do you mean the rivets are peened on the outside of fender .

[chgofire5sqd]

you have to look close. I know all you should see is the hinge part not the top body. This mounting part of the hinge should be placed under the fender. Here they put it on top and painted it. Don't know why, but I just want to make sure some fenders were put this way before I go and have it changed.

[Sidehacker]

Nice bike , I've never seen that I forty plus years of doing this. Let me look in some text books get back shortly. That looks wrong but it looks like it works. Is there any way to take a close up picture. I'm sure other readers will want to see it also FNA

[chgofire5sqd]

No, i'm talking about how the hinge/gate is placed on top of the fender not the rivets. You see the bottom part of the fender is clean. All you see is the 2 rivets. Now look higher you see the hinge part then you see how they put the upper part of the bracket on top of the fender then they riveted it down and painted it. Sorry I don't have a closer pic.

[chgofire5sqd]

I'll try to get a better pic. It opens with no problems and I did see it on another bike(picture online). But only once.

[Sidehacker]

Hinge

I've got a lot of one off Harley experimental pics but none like that, is that a stock fender or aftermarket . Either way I would put it back correctly . There are a couple of wise old men on this site who have seen more than I, But restoring bikes is all I've done my whole life and that look like a bad body and fender man did that however one thing I do know about Harley is never say " they did them all that way" or "they absolutely didn't do that" every time a blanket statement like that is made they are usually proven wrong. Unless I find something absolute i won't comment on this anymore except to say its wrong but I will watch this post to see what kind of response you get . FNA PS Thanks for showing that.

[chgofire5sqd]

dave pics 1284.jpgdave pics 1224.jpgdave pics 1033.jpg Ok I found a better pic and the 2 other pictures are from a 1949 FL from the Harley museum in Milwaukee Wi.

[T. Cotten]

I have a 1950 FL and my bike has a M74B carb on it. I would like to put it back to its original M45A carburetor. My ? is will I lose any power or performance by going to a M45A. I ride this bike on the highway offen and it has no problem doing 70mph with the M74B, so I don't want to lose the speed for originality If I can help it.

Dave!

The M-45A lists as a replacement carb, according to Palmer's.

The differences between the two models are minimal, with the M-45 & A having a unique raised HS needle seat. The A introduced the large fixed jet as well, although the HS needle retained its wide angle.
It also retreated from the restricted venturi vent experiment of the M35TP to the same as the M74 series, but left the unused boss above it.

The performance advantage of either assembly would come down to the thoroughness of its individual refurbishing.

....Cotten

[chgofire5sqd]

It's looks to be a OEM fender (how could I tell for sure)but The guy I purchased the bike from said it was repainted 25 years ago. I'm the 3rd owner of the bike. Just don't know why someone would of mounted it that way. He did not know either when I pointed it out to him. Thanks for the help

[chgofire5sqd]

Thank u for the input, I see in my "Harley Panhead Service Manual 1948-1957 Rigid" You are correct, it was replaced from Harley when you did the conversion. Here is the Quote, If you wish to have carburetors converted under this conversion program, send them to Harley Davidson Motor Co. Applying to the M45 carburetor, the carburetor returned to you will be M-45A(HD#27143-50). Any of these numbers on carburetors returned to you indicate 1950 type carburetor. I just was not sure on the performance of the 2. But being there is none I will go with the carburetor that was made for my bike and sell the M-74B(later1951-1952). Thanks