Can FCRs be mounted on straight manifolds on a Commando engine?

MichaelB said:

Kenny Flowed some Mk 2 manifolds for the FCR's.
And removed the cross plate, gusseted the sides.
I believe he was first to use the FCR's.

The Kenny Dreer VR880 undressed

I have been planning on doing some kind of blog on this bike for Jerry. As you'll see, it's somewhat apart now so I don't have any clean pix of the whole bike. It may be awhile till I get it back to photo stage, so here is what it looks like under the skins. Just so everyone knows these...

www.accessnorton.com

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I did mean Kenny Dreer. I'm not sure where the Greer name I used came from. Typo or spell check

I only mentioned Dreer because he did it at basically the same angle that a Norton engine would or could be set at in a Seeley frame, and used straight manifolds if GP's images are correct. The install in a Seeley frame would not be like it was done in an 880 Commando. Should be much easier. I knew about GP's build. Thanks anyway.

Here is some irrelevant info about Mk2 manifolds and FCRs: I modified Commando Mk2 manifolds to use with the Sudco 35mm FCR Norton 750/850 kit on the straight up motor in my P11. I doubt I was the first to do it considering it was not difficult to figure out. My creations flow fine for my use. Getting the filters on scratches my frame paint though. I had to go that extra 1/16" and paid the price.

Testing flow a slight curve in a manifold doesn't do much to reduce flow, they were also longer which has an effect as well, short flow slightly better on a bench. I ordered some inexpensive 36mm PWK carbs to try on my BSA. To see if I can get it to punch harder. Has anyone used them? They are 2stroke and I expect to have to mess with them a bit to jet them. Smaller PWK work once you get the jetting, needle etc.

I don't know about down draft as in it being better for a carb to aim down, I think that is in reference to the port aiming down at the back of the valve squarely, that flows better. If it aimed up the same I doubt it would make a difference if that's where the valve and combustion chamber were. Nortons are good because they get the charge better onto the back of the valve. Those carbs look the business at that steep angle.

I asked the man himself, Steve, he tried it before and saw no real difference. That’s saved me a load of fruitless pissing about !

mark parker said:

Testing flow a slight curve in a manifold doesn't do much to reduce flow, they were also longer which has an effect as well, short flow slightly better on a bench. I ordered some inexpensive 36mm PWK carbs to try on my BSA. To see if I can get it to punch harder. Has anyone used them? They are 2stroke and I expect to have to mess with them a bit to jet them. Smaller PWK work once you get the jetting, needle etc.

I don't know about down draft as in it being better for a carb to aim down, I think that is in reference to the port aiming down at the back of the valve squarely, that flows better. If it aimed up the same I doubt it would make a difference if that's where the valve and combustion chamber were. Nortons are good because they get the charge better onto the back of the valve. Those carbs look the business at that steep angle.

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Mark I would consider trying a torque wing from thunder products and a intelajet for more of a punch feeling. The intelajet is a mid throttle to high end gain, and the torque wing is a bit more subtle, but will help to half throttle. I have moved away from the PWK back to Mikuni VMs after finding the UFO and these others I mentioned here. I run the Keihin CR from Jim Schmidt on the Norton due to fitment issues with dual VM Mikunis. However, I run a torque wing and I am working on fitting a intelajet as well.

PWK are hard to jet, I just use Mikuni needles. What I'll do is measure flow through a few combinations of manifolds like the 36mm carbs on 34mm runners and 36mm runners and head and use the smallest. With the 34mm carbs on the big valve heads they knock back flow a bit if the 36s give 10cfm more that maybe good. The main idea though is to reduce 38mm runners to 36mm without losing any CFM just increasing speed. I made and fitted plates in the 38TMs if they made a difference it isn't enough to be noticeable. Swapping 38TMs to 34PWKs on a 734 is very significant. But with that it flows no less than the 38mm. The head on the 883 though is more modified with lifted guides and had more flow than the other 38mm head. The difference wasn't that both heads 38 and 34mm didn't give the 734 power it's just the smaller ports kicked in early and really hard and revving it to be in decent power was not necessary. The power difference and throttle response was very noticeable. So the 883 feels lazy in comparison till it revs, it should be possible to make it respond and be alive like the 734. If you were racing with it the 38s would need to stay at high rpm. And on the road you would need to change back. VMs are good carbs.

These things cost $88au the pair. They are physically pretty big like a TM. So, these will get flow tested on a big valve 34mm port head it's not much 1mm all around difference. I'll just see the total flow difference with both carbs. I think with 38mm Lectrons the 38mm ports had around 197cfm. The TMs would be less. Goodness knows what I will need to do to get these PWKs jetted right on a 4stroke. These are pretty close to smooth bore the slide isn't very wide.

may be it is not what you need , but it could be interesting to have a look