Square four mk1 frame

[simon.holyfield]

I remember the article on friction dampers David, but do you have any more details on the cartridge emulator you fitted?

[john.mitchell]

Our much missed Vice President Bob Brassington did many miles in his MarkII SQ4. As has been mentioned before, he fitted dampers (Honda?) to improve the handling. On a trip abroad to France, he swapped with my Girder forked 1939 4G for a day. Mine was fitted with sidecar rear springs which had improved it a lot and I always felt made it a good handling bike. There was no doubt that the the 1939 handled infinitely better than Bob's MarkII even with the latter's fitted rear dampers. I had owned a Mark II for 6 months and I felt that handled far worse than Bob's damped one which is why I quickly sold it. Bob and I reckoned that perhaps the plunger suspension worked much better with girders because they had been designed to go together.

[Simon.Gardiner]

....but do you have any more details on the cartridge emulator you fitted?

I suspect there's a detailed description from David here:
viewtopic.php?f=21&t=61&p=1952

(I was going to fit some Dow dampers to the VH but maybe I ought to invest in a pair of those XS emulators as well !!)

SG

(Edit: Jan 2022 - forum thread link amended to the new forum URL)

[simon.holyfield]

Thanks Simon!

[nadab_sardar]

Interesting thread. One thing worth checking on a plunger Sq4 is the rear wheel alignment and the condition of the plunger boxes. Worn bushes or a slightly out-of-line rear wheel can make the back end feel a lot sloppier than it needs to, and it's easy to blame the frame or tyres for it.

Fletch, since you've got a complete frame with the plungers, it would be worth checking the bores for wear and lining everything up with a string or straight edge before you start building on it.

I'd also second David's point about damping. Friction dampers on the rear are a cheap way to calm things down, and you can always take them off if you don't like the result. Most of the "strange feel" people describe seems to come down to the suspension rather than anything mysterious going on in the frame.

It's also worth making sure the rear wheel is true and balanced, and that the tyres are in good condition. An out-of-balance wheel can add to that vague feeling on an old bike.