Topic: Mixing 750 forks and wheels

[Tim2005]

Hi all, just a little project I am considering. If I were to use a pair of late 750 forks & brakes (750F2, Comstar type with 2-hole caliper mounts) with an earlier 750 fitment front wheel (a Lester actually, but with the original measurements as per the wire spoke wheels) what discs could I use?

I think the earlier discs are too large diameter and probably the wrong offset, and the later ones are 5 hole but the early hub has 6.

i imagine I'll have some issues with spindle, speedo drive etc too, but the discs seem the biggest difference.

Thanks in advance

[newday777]

Here's an old thread on using GL1000 front end (same forks as F2), gl1000 wheel and RC51 rotors(6 bolt), and 6 pot calipers.
I haven't done it myself but am considering going that way on a build.

http://forums.sohc4.net/index.php?topic=95709.0

[scottly]

Hi Tim. The 550 rotors are the same 276mm diameter as the late F, and will bolt right onto your Lester, stock spoke, or Morris wheel, but should be thinned a bit. The calipers need to be shimmed inwards a bit, as the rotors are narrower than the F rotors. Use the early axle and speedo drive; any issues there are addressed the same as with the old calipers. Also, the later 2 piston calipers, which are much better, come in different sizes, like 30mm and 32mm. I'm currently using a single 32mm caliper with a 320mm Ducati rotor on the Morris wheel on my Seeley, and it works quite well.
http://forums.sohc4.net/index.php/topic,89771.100.html

[Shtonecb500]

yep, 550.

[Bankerdanny]

Hi all, just a little project I am considering. If I were to use a pair of late 750 forks & brakes (750F2, Comstar type with 2-hole caliper mounts) with an earlier 750 fitment front wheel (a Lester actually, but with the original measurements as per the wire spoke wheels) what discs could I use?

I think the earlier discs are too large diameter and probably the wrong offset, and the later ones are 5 hole but the early hub has 6.

i imagine I'll have some issues with spindle, speedo drive etc too, but the discs seem the biggest difference.

Thanks in advance

I put an F2 front end and wire wheel replacement Lesters on my F1. You use 550 rotors and will need to shim the calipers to make them work right. I had the rotors thinned and drilled by Godferry's Garage. He also countersunk the hunbs where the nuts that hold them to the hub go, which eliminates the interferance issue you can have on the right side rotor.

You can re-use your existing speedo drive, you just need to cut off the lip on the hub end. No need to modify the rotor hub like I initially did on mine (picture 3) pressure from the fork holds it in place just fine. I have a few thousand miles on mine.

**edit** the biggest PITA is the brake light switch. The single disk F and K bikes have it built into the block attached to the bottom of the triple tree. F2/3 bikes have the switch built into the master cylinder and a double ended distribution block on the triple. You should change out the master anyway for best results. But if you opt to retain the single rotor master, get a longer banjo bolt for the lower block so you can run both brake hoses to one side.

[Tim2005]

Thanks all, this is brilliant information. I'll get on the lookout for the parts to do this. Danny I'm ok with the brake light switch, luckily, as my master cylinder as one. Scottly, this is actually for my white Seeley, which I'm thinking of getting out of storage & using a bit. The forks in it currently are GPZ ones with blanking plates over the antidive fittings, a huge single disc on the left leg & a 4 pot Tokico caliper on a very awkward looking mounting plate. The set-up actually works alright but it looks really wrong.  Originally it had early type 750 forks (which I still have got though the stanchions are rotten) with the early type caliper fitment (I still have 1 of them), I could return to that but 2 of those calipers + discs weigh loads, and historically I found that 1 of those calipers isn't enough brakes, also getting hold of a second early type caliper etc wouldn't be easy either. Hence I think I'll gather the parts for this conversion which should then be fairly straightforward, give or take re-modifying the Seeley mudguard bracket.