May be the way the manifold is machined but the flanges look like they are about to fall off the ends when in place on the heads, as if the manifold is too short. ???

It'll be tomorrow before I can get to my stuff. I'll post some photos and measurements.

With the manifold only held between the heads, at the ports, there should basically be very little space, almost need to rotate a bit just to get into position and then very little room to move it fore and aft.

 

G'day t150.
"With the manifold only held between the heads, at the ports, there should basically be very little space, almost need to rotate a bit just to get into position and then very little room to move it fore and aft."
Yes that is right. With it held against the front head there is about 1mm gap to the rear head.
Nearly ready to dig out the old manifold and compliance fittings.
Thanks heaps for your help M8.
Cheers

 

Late to the party...do you have the old O-rings so you can compare with the new O-rings? Something is not right like that intake or maybe it's the O-rings that are to large? Are the O-rings OEM?

Your in good hands with t150vej's guidance, but a second set of flanges and problem remains (if I am understanding things correctly) has me thinking of other causes to your problem.

Not sure what to tell you at this point. Sorry, wish I was more help.

 

G'day Yankee Dog.
Unfortunately the original rubbers went in the bin and am sure there were no "bulges" with them. The new rubbers that came with the new OEM flanges were in a plain bag so would say not OEM. They are the same size as the James Gaskets (pack of 10) that gave the same problem. I use new ones every try! They measure ID 45mm, OD 48 ish, 3.5mm thick.
I can't see any damage to the manifold, the tubes (that mate to the head) are still round, the support bracket is OK.
The only thing I can think of now is the rubbers are for BT 90up, mine is a 88 but the manifold conversion is for 84-99.
G M F'd.
Cheers

 

I studied expanded copies of the last photos and if I knew nothing of this job or parts used, my first thought would be they were not tightened correctly in alternating order. But I'm willing to wager your brand new ones are warped and probably not from any mistake you made.

Unless you can get genuine OEM flanges from an actual Harley dealer, and if you have the original "Y" by all means go that way. I've wished dozens of times (at times) I still had mine cause if I did that;s what I'd be running!

 

G'day T150.
Every time (quite a few times now) I have tightened them correctly one flat (1/6th turn) at a time.
Just for an experiment tonight I mounted the manifold and reused the crack front flange and left it just over finger tight. The rear I tightened one flat at a time. Before it got to 1mm from seated I heard the click. Yep cracked that one too!! The flanges were OEM in HD packets and flat, the rubbers were James.
I have a new front on it's way but now need a rear as well.
I think I'll order new compliance fittings and mount the old manifold keeping the CV40 to that manifold.
The whole conversion exercise was to get away from the "prone to leak" fittings and butterfly carb.
Thanks for your help. I owe you a weeks bed & breakfast if you ever venture down this way.
Think I'll ride one of the BSA's to work tomorrow, I need the stress relief !!
Cheers

 

I had my hands on the answer 2 days ago but forgot to measure it. Remembering you said it was 48mm didn't light the bulb till I measured a spare I have.

The spigots OD should be about 45.5mm (+/-) .2mm. That totally explains everything.

If you go back with the compliance fittings the replacement boots, even aftermarket, are much better quality than factory originals. I'd been thru that year ago with mine. Be sure to lube each gear drive on the hose clamps and leave them loose until the compliance fitting, carb and air cleaner back plate are bolted down, then tighten the clamps. You'll be leak free for years.

Mikuni makes the same one you have manifold as does genuine S&S. I'm sure they'll have correct dimensions.

 

G'day T150.
That explains a lot. If I put the rubbers in the flange without the manifold it works out to be only 1.5mm crush on the rubbers! I wondered why every video I watched it was easy to slide the rubbers onto the manifold where I had to stretch mine on.
So now I'm wondering if the rubbers supplied with my kit were thinner. It was running quite well for two years till I bought new rubbers. I've read (not sure where) that S&S rubbers are different, as in smaller.
I'll do a bit of digging tomorrow.
Cheers

 

I'm back.




Did a bit more measuring tonight.Head inlet port 42mm, Manifold ID 45mm OD 48mm, O ring ID 45mm OD 53mm so there's mismatch there. Manifold carb side ID 48mm, carb ID 40.5mm. So inlet gas has a bit of work to get to the valve!
Did a bit of an experiment and turned up a bit of nylon to 45mm. Put the flange and O ring on and bolted to the head. At finger tight there was about 1.5mm of crush and bolted up nicely.
Tomorrow I'll ring EasyR and ask what they sold me 2 years ago. Could it have been a copy of the S&S manifold/flanges/O rings.
Missing another ride this weekend 500 miles to a mates 73rd.
Cheers

 

G'day Fellas.
My suspicions were right. The conversion kit is a copy of the S&S by V-Twin. It uses S&S rubbers that are a little larger in the ID and about 2mm shorter. I only had 1 good flange left so I trial fitted the manifold with that and a cracked one with the S&S rubbers. You Beauty that's better. So I've wasted about 3 months and 1/2 a weeks pay (and your time & thoughts) by not knowing about the S&S rubbers.
Waiting for new flanges, more rubbers and exhaust gaskets & flanges should be here next week.
Cheers.