ET: Engine (Twin) Questions regarding FT163 Magneto Cowl - Twin

[Texas John]

My 1948 Rapide did not come with the FT163 Magneto Cowl, so I ponied up and bought one. No way it would fit as the distance from the lower mount to the bolt hole did not come close to the tab (about 1/2 inch short) on the engine to lock it in place. Returned it and bought another from VOC Spares - same problem (but closer to fitting - about 1/4 inch short).
The one from my 1954 Black Shadow fits but it is very tight. It smashes very hard against the lower spark plug wire where it leaves the magneto pickup (shorter pickups would help here).
Distances - Old CTC (Center-to-center from bottom mounting hole to fixing bolt hole), LD (Longest distance from bottom of holes which gets it closer to the tab at the base of the cylinder).
Old BS one CTC 8.5/16", LD 8.3/8"
New one CTC 8.1/16, LD 8.1/8
Not able to move the holes very easily...
May make a longer tab, but it seems I should not have to.
If you have one sitting about, would you share measurements, please?
Am I missing something?
Thanks.

 

[chankly bore]

Hello there, John. You probably know this, but the acorn nuts shown on drawing M039 must be fitted. The front lead, 26 1/2" long has a short acorn nut, LUCAS part no. 455791 and the rear lead, 28 1/2" long has longer acorn nut, LUCAS part no. 410600. The Parts List wrongly gives LUCAS part no. 408120 as the short one, and lists 2 off, but this is a very long nut usually fitted to distributor caps. This may not solve your problem, but will, at least eliminate one cause of trouble. Why don't suppliers try parts on a bike before production? Now you've retired you have lots of time to sort this stuff out, eh?

 

[Peter Holmes]

I find it almost incomprehensible that the Spares Company are selling FT163 mag cowls that are dimensionally 1/2 inch out on the fixing hole centres, that is if I am understanding your problem correctly, surely this inaccuracy would have been noticed years ago, you surely cannot be the first person to have purchased one from the club, unless the Spares Company have sourced a new supplier recently.

 

[bmetcalf]

I have a Phil Primmer GRP cowl and his instructions were to drill my own holes in the lower lugs because of variations. The variations might be a contributor to the mis-match. Are your front engine plates standard? If not, that could also contribute.

 

[Simon Dinsdale]

I have just measured 3 mag cowels. One is a spare and that is 8-1/4" between mounting centers but it has been welded in the past due to the lower lug breaking off at one time so cannot be considered to be the original dimension, but it does fit a bike.

The 2nd one fitted to my C Rapide is a factory original and it measures 8-1/8" and fits fine.

The 3rd is fitted to my B Rapide and I know this is the original for the bike as the bike is a 1947 machine and has the engine number stamped inside the mag cowel, something the factory did on the first few hundred bikes. This cowel measured 8-1/8" between centers and below is a photo of it fitted.

From the dimensions I have measured it looks like the problem may be with your bike. Maybe your front engine plates are wrong?

 

[vibrac]

I find it almost incomprehensible that the Spares Company are selling FT163 mag cowls that are dimensionally 1/2 inch out on the fixing hole centres, that is if I am understanding your problem correctly, surely this inaccuracy would have been noticed years ago, you surely cannot be the first person to have purchased one from the club, unless the Spares Company have sourced a new supplier recently.

Read it again Peter.
He implied the 1/2 " out one was not from the Vincent Spares Company, unfortunately while he was happy to mention the Spares Company as source for his second attempt (which may be dimentionally correct) he did not say who were the 1/2" out company he originally got the first one from (USA?)

 

[bmetcalf]

Bob Chantland of Minnesota made some cowls in the early '80's. I didn't have one, but others did and I don't remember any complaints about fitting. They were a bit thicker than standard, as I recall.

 

[Michael Vane-Hunt]

I have two cowls both are 8.25 inches center to center between mounting holes. Original in picture. I have made a slightly longer tab at the top to give enough room to cram in all the electronic ignition gubbins

 

[Marcus Bowden]

Micheal my handsome, what's with the brass ball rammed between the prop stand and the engine plate, just curious.
bananaman.

 

[Michael Vane-Hunt]

Marcus, my old sausage. That is an auxiliary gear shift.