Performance for MK series?

[David H]

Hi Every one
A silly question but what would the top speed of the various Mk series be.
I have a Mk1 which after much frustration and arguing with the Victorian registration authority over frame repairs (you just pop down to the shop and buy a new frame if the old one breaks according to them) is finally on the road. Anyway my old girl cruises at 45 MPH and if you push it will get to 55 given a long enough road and a good wind. I thought this was about right. The guy's at the M/C club are trying to convice me that it should go faster.
I would love to hear what other members Mk1's do?
 

[Dawn]

Hi,

Am not exactly sure what a Mk 1 will do speed wise but I've followed one both at the Annual Rally @ Stowe & on the Dragon Rally.  Compared to the other models they are not as quick (but just a nice as the other models).  I think the one I followed at the Dragon Rally did around 50 - 55mph.

I have a Mark 3 Sports & I know that when this machine was in production it was tuned by Freddie Dixon so it enabled it to be the fastest 350 of its day (1948-49).  I have has 75mph out of it when the machine is warmed up nicely & the conditions are perfect for it (ie no headwind).

I think your mates may be referring to the later Marks (Mark 5 seems to be the most common of the Mark Series) which again featured the tuned engine. 

When I say tuned I know it had different profiles of cams but not sure what else.  Maybe Eddie can help here.  I know that the barrells & heads are a slightly different shape (I learnt the hard way that Mk 1 gaskets do not fit Mk3 Sports & later models) & they take a different grade/type of sparkplug. 

Hope this helps a bit.

Happy riding - Dawn.

[Doug]

David,

A few years ago I could get my Mark 3 Sports up to an indicated (chronometric) 70mph on a dead flat with no wind, but the last five mile per hour were slow coming and you need a lot of road and patience to get there. 65mph was normally the itermittant maximum, with about 50-55 a continuous maximum on the highway. It is happiest running 50.

-Doug

[eddie]

David,
          I have found that the post war Douglases are happiest when allowed to rev. Treat top gear like an overdrive for more pleasant cruising once you have got up to speed. My Dragonfly will regularly nudge 70mph on the flat, and my step daughter's Mk5 is about 3-4 mph faster than that. I bought my Dragonfly in 1972 and was thoroughly disappointed with it's performance, thinking  - like you - that 50mph was about it's limit, until advised by a long standing Douglas owner that I should rev it harder. Not convinced, I let him prove the point - which he did!!! Since then, it has been revved unmercifully and seems to thrive on it. The highest speeds I have ever managed on level ground are: 58 in second, 73 in third and 82 in top (indicated) - but you have to be cruel and test the throttle cable to the limit. Of course, riding like this becomes tiring (for the rider), so I usually settle for a cruising speed of 58 - 60mph - anything slower, and you have to play tunes on the gearbox. Incidentally, I have lowered the gearing on my Dragonfly by one tooth on the gearbox - to allow it to rev (more like a Mk3 Sports).
                                Regards,
                                        Eddie.

[Dawn]

Dawn again,

Sorry I forgot to mention that I have a plus gearbox sprocket that Dad fitted which may effect things.  Also when the cables were made, Dave (other half) made my throttle cable to fit exact with no play (took him most of the day to do) which means that you are not breaking your wrist to get all the power out of the bike. 

[David H]

Hi Dawn and Doug

Thanks for that information I think if the Mk3's are happy about the 50 MPH mark then My Mk1 at 45 is about right. I think that mine is a little over geared in top as it is fitted with a 19 tooth G/B and 60 Tooth rear sprocket I might get a 64 rear and see if that makes much of a difference.
I have an AMAL twist grip that I think is original? It gives full throttle in third of a turn. so no need to wring it out to get full throttle. I did have a lot of trouble to get both carby's to open in sync' fixed it by gluing the tow cables into the splitter box with silicon and electrical tape. Not elegant but effective.

Cheers
David

[David H]

HI Eddie

From what you are saying then my MK1 is definitely overgeared I don't have a taco on her but guessing maybe 2500rpm at 40 in top. defiantly not reving freely and it pulls quite slowly from there.  The rear sprocket has been converted to bolt on so no problems with changing it. I will pop down to Australian sprockets tomorrow lunch time and get a new one. I think we might have a new project for the old girl.

Thanks
David

[aggettd]

I have a 1947 Mk 1 with no modifications, completely stock. It cruises quite comfortably at 50 mph, but feels strained at 55. I've had her topped out at 60, but by that point the clutch was starting to slip a bit too. Interestingly, when my friend's Royal Enfield broke down one evening the Douglas carried both of us home, more than 40 miles, and again was comfortable at 50mph. I don't like to flog old equipment, but have gotten used to revving the Douglas and she seems to come alive at the higher revs. Most of the guys in my club have thumpers (Velocette, Matchless, RE) and wince whan they hear me ride, but the Douglas is one of the most reliable bikes in the group.

[David H]

Hi

Put the 64 tooth rear sprocket on I now have a 19 tooth g/box and 64 rear sprocket, and it has improved things She will now hold 50Mph without struggling very happy

Cheers
David

[Dawn]

Hope you are all sorted with the speed of your Douglas but............

I had a thought that maybe, just maybe, ever thought that your mates' speedo's could be out??  I had mine checked against Dave's car and mine is 5mph out so when the bike is doing 70mph (so you think) its actually doing 65mph.  Your mates could be the other way around i.e .stating for example 60mph when the machines doing 65mph.