Angle of the dangle

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I have a sigle Mikuni on my MK III. I have to run the carb at an angle to clear the back bone of the frame. I assume they all do this. Is this a problem? Is there a fix?
 
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What size carb is it ? A 34mm fits without issue, a 36mm is alittle taller and the cable exit is alittle tight. A 38 or bigger is probbaly too tall.

Ken G.
 
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The throat measures at 34mm, but there is no way to install it without angling it to the right. I have recently had issues with the bike crapping out at anything much over 4,000, and the left cylinder is fuel fowling the plug. I found a small notch in the needle and it appears slightly worn in the needle jet. I am going to re-jet it to P2-159 / 6DH3 / Main 240 / and Pilot at 40. I am just not sure if installing the carb at an angle to the right could be a problem also.
 

ML

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Angling the carb over to the right is not good. The left cylinder is fouling due to fuel bias. BSA A10 650's had a similar problem due to a minor imperfection in the manifold casting and they had to fit a very slightly wedge shaped manifold / carb gasket to overcome the bias.

There is something possibly not correct with the manifold fitted to your Mk3. The carb has to sit upright and central to work properly. The manifold may well be not the right one for a Mk3 in relation to the junction of the frame tubes. It may be possible to get the manifold face machine milled slightly to bring it to a more suitable mounting angle for the carb.

Mick
 
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I may have figured it out. I was speaking with Bill Bibbiani of the local Norton Club (So Cal.) We talked about the "Sonny Angle" manifold that was on the bike when I got it. He said he was familiar with that brand, and that most of the ones they made were for the Atlas. If memory serves me correctly, the cylinders on the Atlas are upright, where the Commando cylinders are canted forward. That could be my problem with mounting the carb. Now I start looking for an inexpensive two into one manifold for the Mikuni VM 34 to mount on a MK III. That could solve several problems at once.

Thanks to all for your suggestions. I'll let you know what happens. (The suspense is killing me :shock: )
 
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Well that's good info to know. I just bought a brand new VM34 2 into 1 carb kit from Rocky Point. I'm gonna be installing it on my Commando bobber when I get the frame back. I don't think I will have an issue as the Amal's were far enough from the back tube there wasn't a clearance issue. But I will have to wait and see.
 
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Can you turn the manifold over to change the angle or is it all machined square, the notch in the needle may be standard as my 6dh3 also has one, your running problems are more than likeiy ignition related. the cable still runs very close to the top tube,mine has a 90* steel bend in the top.
 
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splatt said:
Can you turn the manifold over to change the angle or is it all machined square, the notch in the needle may be standard as my 6dh3 also has one, your running problems are more than likeiy ignition related. the cable still runs very close to the top tube,mine has a 90* steel bend in the top.


I don't think turning the manifold over would work. I think that would just make the top of the carb higher and more in the way of the back bone of the frame.

I ordered a new needle and needle jet, along with the other jets and etc. When it gets here, I'll examine it for grooves or notches. I also ordered a new manifold. We'll see if there are any clearance problems with it.

My mechanic/mentor said the notch in this needle should not be there, it looks like a worn spot. He also said the needle jet looks like it is worn a bit at the top. He also gave me a shim to put between the plate that goes on the top of the slide and needle. This keeps the needle from wobbling around and wearing a notch in itself and the needle jet.

Again, when my new parts get here next week, I'll let you know.
 
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My carb parts arrived this week. I took a close look at the needle. I found the new one to be asbolutely smooth, with no grooves, notches, or wear marks anywhere. I also found the new intake manifold is shorter than the Sonny Angel manifold I had on there before.

I had foot surgery a couple weeks ago and it has slowed me down considerably, but It looks like the new manifold will allow me to mount the carb straight up and down rather than at an angle to the right as before. I am excited to get everything back together and see how she runs after these modifications. Damn this cast!!! :x
 
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Good luck at getting yourself back together, it sounds like you are on the right track now.
 
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I hobbled out to the garage today and started putting the Commando back in order. The new manifold fits perfect, allowing the carburetor to sit straight up and down under the back bone of the frame. When I reassembled the carb, I turned the air/fuel mixture screw all the way in, and then back two full turns. I added fuel and pushed the starter button. I'm not sure it turned all the way over before springing to life. So far with no further adjustments, it is idling better than ever and responds instantly to a twist of the throttle.

Now I have to wait to put it on the street and see how it really runs. Damn this cast on my foot!!! :x
 
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