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[Jakub]

One more observation. I have dual exhaust, like 1958 Super Meteor, not 2 in 1 like Constellation should have.
Perhaps that drains some power away?

[Jools G]

Knocking more than 25mph off the top speed would require a seriously duff exhaust system, restrictive in the extreme!

A 1-into-1 system won't have any detrimental effect on performance at all, and was indeed a factory option (I run the same setup myself as I prefer the more symmetrical look).

I think a back-to-basics approach will reveal where the problem lies; a logical work-through of valve timing/valve lift, ignition timing, compression check, carburettor settings, etc should at least eliminate the most likely culprits.

[Wheaters]

Not forgetting to check that the brakes aren’t binding!

[Bulli]

Hi Jakub,
just try a 19T Sprocket, this should eliminate the big jump in the gearbox from 3. to 4. easily. The 21T sprocket is only fitted to be able to travel continously with lower revs. Using the 19T sprocket yours already checked 6.000 revs in 3. gear will be at 73 mp/h.... and the bike will easy go into the correct revs for going forward in the 4. gear to end up with 6.000 revs at a maximum speed of 100 mp/h.... But remember: Don't try that longer than you can held your breath.....
@Wheaters: the brakes are completly overrated driving a constellation.....

[Vince2]

Going back to your original blog, what size carb are you running? Vince

[Jakub]

It has taken a while but managed to change 21T sprocket to 20T.
Getting moving from stationary is easier, obviously. The engine revs on top gear were pleasant to the ears at 50MPH now it’s 46-48 MPH. Understandable. But the top speed improved marginally. From 70 to 76. I am talking GPS app registering top speed but the original chronometric speedo is extremely accurate. Indicated speed is practically the same. Same as before I am getting more or less similar results on third with engine really screaming.

Gear ratio is 29/56/20/46.

Now the funny bit. Last Saturday I was riding with female passenger of 65 kg. Since we were on the expressway and there wasn’t much traffic I opened up and surprise, surprise we were comfortably riding at 70MPH indicated.

And one more observation, nothing to do with speed but more with bike design.
I was riding same road, same passenger on Sunday but with my modern BMW R1200R.
Wouldn’t dare to go 70MPH with passenger, somehow I did not feel comfortable. It’s like old bike was design for two people and on the modern passenger seat is only accessory.

[Vince2]

Hi, I'll ask again, which way do you move the advance/retard lever? Vince

[Jakub]

Sorry Vince, sort of obvious question, when retarded it is about 0mm or 0 inch for that matter.
When fully advanced it is about 14-16 mm. For measurement I am using electronic gizmo wit LED which tells exactly when points are open nad an rod with some markings.
Also when on the move I am trying move the lever little bit either way to find the sweet spot - somehow it sound like an instruction for bedroom activities .

Obviously retarded for start up, most advanced for high RPM.

[Vince2]

Hi, magnetos come with pull lever to advance and also push lever to advance depending on the set up. If the cable goes into the back of the mag you close the lever to advance. If cable goes into front then you open lever to advance. Running retarded will certainly knock you top speed down. Vince

[Vince2]

Hi, rereading your previous entry 19mm is way too much advance. Fully advance is 3/8 inch or 9.5 mm. Vince