best fork yoke offset 750

what would be the very best fork yoke offset for a late 750 27 degree frame ? at the moment i have yamaha yokes with a 40mm offset the bike handles extremely well but as my fastback tank melted i have had to fit my spare roadster tank which has forced me to reduce the steering lock to avoid the stanchions hitting the tank,the bike now has a large turning circle has become difficult to turn from my alley way into my shed etc,the wheels are std 19" the rear shocks 330mm centres i was thinking of re making the yokes with a 60mm offset ?? the bike is for street use only i believe the original yokes were 2 5/8" or thereabouts could someone confirm this ? cheers baz

My 1968 750 has the original 2.25" (57mm) offset yokes & a 90/90/19" front tyre. With its 27* rake this gives a trail of 3.970" . It is quick steering but very nervous at speed. With a 100/90/19" tyre these yokes would give a trail of 4.2". With the 40mm yokes & a 100/90/19" tyre you have approx. 4.960" of trail. It should be stable but slower steering at lower speeds.
Martyn.

yes i am very wary to go altering it too much as the way it handles now is the best it ever has ,the only thing i get is a slight weave pulling away if i am riding with a passenger but when solo riding it is rock solid at all speeds up to 110mph and this is with a handlebar mounted screen so i may have to put up with the restricted steering lock or get a steel fastback tank from india and hope they have copied the fiberglas one exactly where it fits at the headstock so i can regain some steering lock!! cheers baz

If you get too much trail the bike might stand up and turn the wrong way under brakes, throwing you off balance, If you brake into a corner and feel the bike rising you will know this is happening and be ready to catch it before it crashes you. If it happens the best thing to do is find a bit of room, apply a bit of power and ride gently out of it.

acotrel said:

If you get too much trail the bike might stand up and turn the wrong way under brakes, throwing you off balance, If you brake into a corner and feel the bike rising you will know this is happening and be ready to catch it before it crashes you. If it happens the best thing to do is find a bit of room, apply a bit of power and ride gently out of it.

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finding a bit of space on the roads where i live would be near on impossible so i cant even think about crashing,the bike handles very well as it is so i shall leave it alone for now cheers baz

I think you are wise. Playing with steering geometry is not cheap, and if you've alrady found a good set-up, better to stick with it. Your post offers valuable information to others. THis is the reason that in the past I've posted the set-up of mr Seeley 850. You can go dangerously wrong with steering geometry. I found this out by having a very nasty experience. I survived it but 'arse beats class'.

Don't F with it. Change the tank

Don't mess around with fork offset unless you know what you are doing.
I stuck a set of Commando triple trees on a Featherbed frame & the trail was reduced so much that it threw me off whilst racing, any little bump would send it into a violent tank slapper.
When I laid the 2 different triple trees over each other you could see a substantial difference.

I always use an hydraulic steering damper.

not sure if this is the most recent thread where we were discussing different yokes on 750/850 frames.
Anyway I was out this morning giving my bike a good thrashing up in the twisties. 850 MK3 frame with my alloy Featherbed yokes, 13-1/4" rear shocks
19" Avon Roadriders. I never had the bike to high speeds (flat out) to see the result but I was giving the bike a good work out in the twisties and I can confirm its a good combination (for me anyway), probably better than I expected. handled like it was on rails, reminded me of a featherbed, pushing it very hard on smooth tarmac corners as well as concrete roads that arent real smooth, I couldnt get it to do anything that caused me to be concerned.
My front brake kit gave me confidence and allowed me to ride harder than using the standard brake, thats not a plug as any brake that will stop you quicker allows you to get from A to B quicker (corners).
Dunstall 810,my billet steel rods balanced 65%, Keihin CR33's, Megacycle 560-00. Comnoz head work,Alton, RGM dry belt. good power to 4500rpm and then hang on.
Fastest and probably the best handling Norton I've ever ridden.