Mk 5 'S'

[NeilR]

Here's a few pics of the finished Mk5 special.

Cheers,

Neil

[Hampshirebiker]

Beautiful job & love the plumbing Neil.

[oily bloke]

Is that some kind of forced induction? or are my eyes deceiving me?

[coles1933]

Yes it does look really great, how does it perform? Who"s  charger is that? and why haven't we seen them
 before. What more can you tell us we are all very interested.  John Coles

[richson]

Hi, I put some detail up a few months back here: https://www.douglasmotorcycles.net/index.php?topic=5780.0

It's not fully sorted yet so I don't know how it performs. I can get it going on the paddock starter and it idles ok which is easy to set. But, I need to spend some time experimenting with timing and mixture at various engine speeds and blower pressure before I run it properly. The Amal 920 I've used has lots of scope, but I don't want to ruin the motor so, gently bently. Thanks John, for the cams, followers & oil pump! The blower is a smog pump from a US Nissan truck. I thought it handy because it has twin outlets but one exhaust runs quite a lot hotter than the other so maybe a balance pipe on the inlets is needed. Not that I'm an expert, but I didn't think different lengths of inlet pipe would make a difference but maybe it does, or there is a variation in pressure between the two by design..
If I can get the motor running ok, I'm pretty sure it will handle nicely with it's new back end even thought the wheelbase is about 6" longer than usual.

Cheers,

Neil

[coles1933]

Hi Again. I am certain the longer wheel base will help you, I can well remember as a lad the problem of "Bunny
Hopping" when pushing my Mk 3 sports hard into bends and curves. You might find balancing the inlet pipe lengths
will also help, looking at the pictures you may find as you develop it that larger pipes between the blower and the cylinder heads with nicer curves will help you. I think if you keep with it you will have a super bike with what you are doing. Those cams with the higher lift also work better if you advance them up one tooth all round, but check
your clearances well before running it.  Regards John Coles.

[NeilR]

Not had a lot of time to work on this, but had the bike running reasonably well static. Did a few laps of the paddock ok, then took it up the lane (not a highway). Got about 1/4 mile in 3rd, then horrible crunching, grating, vibrating, so clutch in engine off & push back to garage.  Turns over fine and rolls along ok in neutral but when in gear it sounds pretty bad especially with clutch out. Checked oil levels and found no dipstick on gearbox filler. Dead sure it used to be there. So, that's lying about in the 'box somewhere and has probably done some damage, so it's going to have to sulk at the back of the garage until I get over the annoyance of it.

Cheers,

Neil

[eddie]

Neil,
        Gearbox dipsticks dropping off is quite a common problem. They are only soft soldered into the filler cap. If you want the convenience of being able to check the oil level, make a new dipstick that is a good fit in the cap and long enough to almost touch the bottom of the gearbox case - then if it works loose, it wont be able to fall out. With any luck, your old dipstick will still be in the rear section of the gearbox - mixed up with the kickstart gears. You should be able to get at it by removing the final drive and recovering the bits.
  Good luck with the repairs,
    Regards,
                 Eddie.

[NeilR]

No more dipsticks for me Eddie, and I'm snapping the one off the comp's filler cap too. I don't think it's going to be an easy repair. Since it rolls along in neutral ok the final drive must be ok? I can take that and the gear change housing out and see what I can see, but I just bet that the dipstick got into the gears. That's pretty much a total strip-down since I can't get the 'box off the engine without taking the whole back end off first. Groan . . . I think it's a job for a snowy day!

Cheers,

Neil

[eddie]

Neil,
       With the box out of gear, just the final drive shaft and gears, the mainshaft and the gears for 2nd and 3rd rotate when the bike is pushed along. With a gear selected and the clutch lifted, all the gears and shafts rotate (including the kickstart drive gears), so it would appear that the problem lies somewhere in the kickstart mechanism (as it rolls smoothly when out of gear).

  Eddie.

[richson]

It took me a few years to get back to this for one or other reasons, but I got around to looking at the bike. With the final drive off I couldn't find enough bits of the dipstick to make a whole one, so took the gearbox out to see what I could see. With the kickstart gears out I found some extra bits sprinkled around in various places. A thorough good washing out yielded what I hoped was the rest. Nothing seemed to have been damaged, so put everything back together and refilled oil etc. The crunching/grinding noises are gone, hurray! But, now I seem to have two new problems. One, the drive does not seem to be engaging fully. Its as if the shock absorber on sprocket is slipping (but it isn't) or the chain slipping over the sprocket (but it's not). Doesn't do it on very gentle acceleration. Perhaps the drive bevel pinions are not fully home? I did make sure the sprocket nut was tight! There are three brass shim/gaskets fitted to the cover which I did refit, but maybe something else has changed. Secondly, the point at which the kickstart engages seems to have moved, so that I can only get a little leverage on it before it reaches the bottom of its arc - makes difficult starting. Could these two things be related? Any suggestions? I really hope I don't have to take the 'box off again!

Cheers. Neil