Author Topic: Riding a Mark 4.  (Read 843 times)

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Offline Vitesse

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Riding a Mark 4.
« on: 17 May 2020 at 22:03 »
Well that's different!  First ride on it and I have a few questions (apart from what have I done?) that the experienced can hopefully easily answer:

1. How smooth should gear changes be?  I'm not expecting a hot knife through butter but it makes my Guzzi feel like a GSXR!
2. Should the front mudguard clatter against the fork legs.  I can't see how to stop it but it looks a strange design and takes the paint off.
3. What oil should be used for damping in the forks. Previous owner was blase about just undoing the top screws and throwing any old oil in! I can see the level  plugs.
4. Tyre pressures.  I've done a search here but the only thing for Mark bikes was one vague comment of 22psi for both.
5. Is the front brake only for decoration?!!!

Apart from all that, and sailing past junctions because a right hand side reversed gearshift fries my brain, it was quite fun.

Offline flea

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Re: Riding a Mark 4.
« Reply #1 on: 17 May 2020 at 22:18 »
LOL LOL .. following as have a few of the same burning questions

Offline isettaman

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Re: Riding a Mark 4.
« Reply #2 on: 17 May 2020 at 23:13 »
It sounds as if you need the Mark series maintenance guide by John Holmes
Try this link
https://www.douglasmotorcycles.net/aa-files/documents/2016/Mark-Series-Maintenance-Guide-2012.pdf

There is detailed steps on curing front mudguard rattle and fork oil sae.
Hope it helps
Dave

Offline EW-Ron

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Re: Riding a Mark 4.
« Reply #3 on: 18 May 2020 at 02:23 »
Tyre pressure may depend a bit on what tyres you have fitted.

Old type tyres had really stiff sidewalls, and advised fairly low pressures.
Modern type tyres have softer sidewalls, and require generally around 28-30 psi.
So something like 28 psi front and 30 psi back would not be uncommon.
A few lbs more if you have a passenger or intend high speeds (!)

It will probably handle like a drunken walrus if you use the pressures advised back then.
Especially if any of them are under 20 psi....

Brakes are a different subject entirely.
Sanding the shoes so they fit the drum is something that can be done - but watch out that old type shoes may contain asbestos.
Lightly blueing the linings and seeing where they contact the drum (if at all) can be revealing !

Offline Vitesse

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Re: Riding a Mark 4.
« Reply #4 on: 18 May 2020 at 09:17 »
Thanks both. I have already downloaded that manual but I'll be honest that I'm waiting to go to work to print sll 40 odd pages! Incidentally, it refers a lot to plates (pictures). Are they in a separate document?

I forgot to say which tyres.  Good OLD Avons. Ribbed front and Squaremaster rear.  Haven't seen those for years.  Replacements will have to be sorted sometime.  In the absence of any answer I went for 23/24 which seemed adequate.  I'll experiment.  Similarly the front brake will get some attention at some stage.

I'd also forgotten that I'd bought a copy of the 1960 Maintenance Manual which provides a good starting point.

Offline eddie

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Re: Riding a Mark 4.
« Reply #5 on: 18 May 2020 at 17:15 »
The 'plates' are pages from the spare parts book that accompanied the handbook.

  Eddie.

Offline Keith

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Re: Riding a Mark 4.
« Reply #6 on: 19 May 2020 at 22:42 »
Changing gears on a Mark  -  Ah yes, I remember the symptoms well when first riding my Mk3s    :shock:

Because of the direct drive to the clutch from the engine there is a different technique required with the Mark series with changing gear. The trick is to match the gearbox rpm to the engine rpm. With changing up you will need to let the revs drop away before snicking in. A slow careful engagement will give a smooth change. Likewise for changing down the reverse is needed and you will have to keep the revs up to engage smoothly. Once the technique is mastered it's a nice gearbox to use - just no racing changes though! 

Offline EW-Ron

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Re: Riding a Mark 4.
« Reply #7 on: 20 May 2020 at 06:22 »
I don't know about the Mk4, but older bm's and guzzis sound like they use the same technique, indeed
- you pause on the upshifts until the revs drop back a bit, and blip the throttle slightly
on the downshifts, so the revs match.

And if you've ever practiced doing clutchless shifts, you get good at it.
I broke a clutch cable somewhere very awkward, and it came in rather handy.
I think always carrying a spare cable may be a better plan though ...

Offline Vitesse

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Re: Riding a Mark 4.
« Reply #8 on: 20 May 2020 at 10:46 »
Thank you.  I should add that I'm no callow youth - much closer to 60 than 50 and do have a Guzzi Le Mans. I've owned several Guzzis and boxer Beemers so a steady gearchange is not alien to me. This just seemed particularly difficult. Early days though so I'm not that concerned.

One further question for the experts.  The oil 'filter' mesh. It looks like I need to strip the oil pump to get to this. Do you do this every oil change? Bizarrely the Maintenance guide doesn't mention it, nor even the details of an oil change. Perhaps they assume everyone knows how to do this and they can concentrate on the full engine strip! I can see the access plate on the sump but am loathe to just take that off if I end up unfastening a worm drive that can only be reconnected from inside!

Offline eddie

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Re: Riding a Mark 4.
« Reply #9 on: 20 May 2020 at 11:54 »
Looking at the oil pump 'access plate', you will see it is retained by 3 studs and nuts. When the 3 nuts are removed, the plate (which closes the pump body) will come away (with a thin paper gasket). You will then be able to see the pump shaft and 2 vanes with a light spring between them. Put the vanes and spring in a safe place before attempting further dismantling. You will now be able to see the flange on the pump body - there is a thin cork gasket under the flange. Carefully use a pair of pipe pliers to wriggle the pump on the studs until the gasket breaks free. You should then be able to withdraw the pump. (Don't try to lever the pump off the gasket as this can easily damage the flange). Withdrawing the pump is a simple remove and replace operation - there is nothing inside that can come adrift. When replacing the pump, fit the cork gasket between the pump body and crankcase, and the thin paper gasket between the body and cover plate (Don't be tempted to fit a thicker paper gasket as this governs the internal clearance in the pump). Put just a smear of grease on the new gaskets (jointing compound usually sets and makes future pump removal more difficult). With the pump removed, you will find it has a gauze screen around it to prevent the intake of particles large enough to cause blockages - these days it would hardly be considered to be a 'filter'! Being nearly 70 years old, these gauzes can be in a poor state of repair, but replacement of the mesh is a fairly straight forward soldering job.

  Hope this helps,
                            Regards,
                                          Eddie.

Offline franky

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Re: Riding a Mark 4.
« Reply #10 on: 26 May 2020 at 22:52 »
Just making a few comments regarding my Mark 4 which has done 1100 miles since the resto. My gearbox responds to a positive upshift and reving on the down change. The box has a good selection of false neutrals if you are vague or looking at something shiny whilst up or down shifting.
The new Penrite Enduro HD 25-70 mineral oil used in the last change has made a difference coincidentally to the behaviour the gearbox. When cold, it can still be cantankerous to shift particularly between first and second but when the engine is hotted up it is a different bike. This is a motorcycle only oil and on the web suitability specs Douglas is mentioned.
On the front I run a ribbed Avon speedmaster 3.25x19 with 32 psi and a Dunlop K70 3.50x19 running 34psi. These tyres and pressures have come from experimenting with mid twenties and ending up at the 32-34 combo. I run the bike as a solo and have a 95kg chassis. The bike points and steers well and only gets a little upset on rough patches which prevail near home in regional Australia. The fork oil I run is Castrol 15W and I add a dribble or about 20 grams of Molibond formula 2.5 oil supplement into each leg on maintenance day. This fork oil "mix" I have used on the front ends of my bikes since the early 70's and it seems to help seal preservation.

 

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