Author Topic: 80 / 90 plus front hub dismantle. Repair alloy cooling ring.  (Read 460 times)

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Offline John Caffrey

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Hi all !     Am rebuilding a plus front wheel and would appreciate advice on :

(a) Trying to separate the bearing housing from the brake drum.  Nuts + bolts removed and marked for replacing but the bearing housing won`t budge, don't want to damage valuable wheel ! Any tips appreciated.

(b) Another plus wheel has a crack in the finned alloy cooling ring. Anyone welded one up, would Devcon be up to it ?

(c) Are Plus gearbox / bell housing  interchangeable with Dragonfly housings ? My "fly" has the horrible single carb set up and I`d like to fit twin carbs. 

(d) Will Plus cylinders & heads fit a "fly" engine ? I believe "fly" crank, casings and importantly oil pump are better ?

Thanks in advance J.C.

Offline Neville Heath

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Why do you need to separate them? You can do every thing needed including drum skim (better done in the wheel anyway).
The alloy fins are renown for cracking due to expansion of the drum. A loose one jangling about in the front wheel might give you a fright. I have used BA screws to bolt my broken one to the drum.
Neville

Offline John Caffrey

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Thanks for prompt reply !  I was hoping to separate them to clean off old paint and paint remover prior to re enamelling Black.   I think I`ll leave it on as it is really tight !      I`ve now removed the cracked ring off the other wheel and will argon weld then use the lathe to  bring back to std shape and i.d.    I imagine heating will enable ring to be refitted, possibly with bearing fit ?  Thanks for your help.

Offline isettaman

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Hi John
One of my cooling rings was cracked so, as it's not structural, I used "Epoxy Super Metal 4 Aluminium" product code 7704. It comes as a two part paste which can be filed etc after hardening. My repair survived blasting and painting - can't tell where it was done now!
BTW - black enameling on a plus front wheel??
Dave

Offline roger h

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Gold on the 90+, and the lovely dark maroon? on an 80+. Nothing looks nicer!!. Good luck.

Offline John Caffrey

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Thank you all for your suggestions.

Re the cracked alloy muff;      I`m considering your suggestion re Epoxy repair, but I`m not entirely convinced that it isn`t a structural item - I   fitted large "Bacon Slicer" muffs to my Manx and it was an improvement - less fade.

The reason its being painted BLACK is because its going on a BLACK & silver Dragonfly !!

The other 90+ wheel will be the appropriate colour on a proper 90+ RACER. Renewed my ACU / FIM licence through the Club !

 I even studied putting Two 90+ hubs back to back but making patterns and casting a "back to front" brake plate would take ages and all that brake on a Douglas would be overkill anyway.

Not being computer literate I`ve probably omitted / lost the other question I asked ;

(a) Is there any reason I can`t fit a Mk gearbox onto a Dragonfly ( for twin carbs. ) ?

(b) As the Dragonfly has a better, stronger, bottom end and better OIL system than the 90+ can the Plus heads and barrels be fitted without too much work ?

Thanks in anticipation. J.C.


Offline eddie

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John,
         As a reply to your other questions:

  (a) Physically, no! But fitting a Mark gearbox makes topping up and checking the oil level somewhat awkward as the filler plug will be under the toolbox. Why not just remove the intake tubes and fit carbs direct on the heads and retain the original gearbox?

  (b) I don't believe the Dragonfly has a better, stronger bottom end than a Mark - let alone a Plus. The modified oiling system used on the Dragonfly may give better oiling to the bigends when in good condition, but any subsequent wear biases the oiling toward the front big end, and starves the rear. Eddy Withers had the same problems with the works 'Plus' racers - engines often only lasted for one race! Also Plus/Dragonfly crankshaft centre webs are drilled right across, creating a weakness that often results in the web cracking and loosening the crankpins. There are also other lubrication problems with the Dragonfly caused by the timing gears sitting too deeply in the oil retained in the timing chest - the usual result being that continued use of high revs causes the excess oil to be trapped in the timing gears, thus straining the teeth until they eventually break off (usually from the camshaft idler gear). There is an easy cure - just drill 2 drain holes in the back of the timing chest to reduce the oil level so that the cam gears only just dip their teeth into the oil.
   Plus barrels will not fit on the Dragonfly, but the heads can be - if they are modified for through bolt fixing (as on the Dragonfly). This also means the rocker blocks need modifying to clear the nuts on the lower pair of head/barrel studs. To get any worthwhile benefit from the heads, Plus cams will also be needed.

  Regards,
                  Eddie.

Offline John Caffrey

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Thanks for that Eddy.  I need to spend some time studying these engines over the winter, nice to find such helpful members !   Are 90 plus cams available, or does the club know someone who can re profile std ones ?

Offline eddie

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John,
         The Club spares scheme used to stock 'Plus' number 3 cams.

Eddie.

Offline Neville Heath

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John
You may be interested in the attached photos of the double front brake I made for my bike. I used a standard drum and machined the radius off the other side of the hub  flange. If you look carefully you can see the BA screws I used to fix the damaged fins to the drums. There is a spacer threaded on the screws between the drums and fins. Racer George Eastern made a double brake for his bike but machined a twin drum from the solid.
Neville 

Offline tck

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Re: 80 / 90 plus front hub dismantle. Repair alloy cooling ring.
« Reply #10 on: 25 Jul 2019 at 14:57 »
Cant wait to see the drum picture!

 

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