Super Rocket Carb

[worntorn]

I finally got the fuel taps sorted and drained all of the gas oil mix from the sump, primary and oil tank. With fresh oil in the engine and ATF in the primary things went much better. The clutch has stopped slipping, I thank the type F ATF for that.
The bike starts and runs beautifully and has good pull down low but puffs out at higher revs. I could not get much more than 80 MPH out of it. It might have managed 85 if one was patient.
I don't ever expect to get the kind of top speed results that period magazine tests claim to have seen . Cycle claimed 116 MPH for the late Super Rocket with mufflers removed and a smallish rider on board. I believe they saw 110 MPH with  mufflers in place.

Surely the bike should do the ton?
The stock 1  5/32" Monoblock has been replaced with a 28 mm Concentric. 1 5/32" is close to 30 mm so the 28 mm is undersized.
Could a 2 mm undersized carb cause a 20- 30 MPH speed loss?

Glenli

[KiwiGF]

In my opinion it should do the ton even with the concentric on it, my A10 easily does 85 and would probably get to 100 if I dared.....and it only has a 1 1/16 carb and 356 cam and flat top Pistons....

I assume the ignition and jetting is ok? And gearing is standard? Albeit the correct jetting for the concentric might not be "in the book" so you might have to experiment or get advice from others with that carb.

I would not be surprised if the concentric was very close to the mono bloc in bore size but others would know for sure.

[muskrat]

G'day Glen.
She'll never keep up with your Vinnie but should do the ton for short bursts (one or two miles). Are the plugs the same colour ( no induction bias and identical timing)? Do a few plug chops. Try a higher octane fuel with a few ° advanced timing. The 28 should feed her enough with the right jetting.
Cheers

[worntorn]

Will do some  investigating this evening.
 I'm also wondering if the mufflers are holding it back. They seem very restrictive and super quiet.
My Oz Vin would not rev out when it arrived here. Max speed was about like this Super Rocket. A friend noticed how quiet it was (and sluggish) compared to his near identical bike. I drilled the muffler out with a long 1" diameter drill and it suddenly was capable of 115 MPH indicated and would go by his Rapide.

I'm thinking the Super Rocket should be a tad slower than the Norton 650ss , but fairly close overall?
Both are 650cc, similar weight,both are 9 to one CR but the SS has the advantage of twin carbs and the Doug Hele downdraught head.

Glen

[chaterlea25]

Hi Glen,
Your a brave man  thrashing your new aquisition like that 
Do you know what jetting is in the concentric? this is where I would look first
Have you checked the ignition timing?
What gearing is the bike set up with? A lot of BSA's exported and even home market models were fitted with very short gearing, and will run out of steam at higher speeds

Cheers
John

[worntorn]

Gee I didn't think 80 or so for a short blast  would be thrashing it?
I guess I must remember it's age and mine
 Trouble is I went out on the silver nutterbastard Vincent 1360 thing the night before. It only has 500 miles on the engine so the rev limiter is set for 5000 rpm. 5000 rpm on that one is 122 MPH and it hits the rev limiter in fifth in about 9  seconds from a standstill.
So it was a bit unfair to the old Super Rocket, which is actually a very comfortable ride and has a great running motor.
.....but it would be nice to squeeze a bit more out of it.
SoI will investigate the things suggested, thanks.

Glen

[worntorn]

I went for a fifty mile ride last night and tried to assess things a bit. The engine starts easily, idles well but has a little stumble just off idle. This is at perhaps 1200 rpm (tach not working) after which it runs cleanly and pulls well to probably about 3000 rpm. Above that rpm it feels starved for fuel and bogs. If the rpm is coaxed up a bit, it shuts off completely ( like the kill button is depressed) for a couple of seconds. Returning the throttle to idle position allows the engine to restart and then it cruises away merrily again for as long as you want  as long as the revs are kept down.

Will pop the Carb apart tonight and have a look.
I refilled the tank after fifty miles at fifty MPH and used 6.3 litres. Somethings not right there!
On the positive, the bike is completely oil tight to the point that I checked everything again just to make sure that there really is oil in all of the appropriate places.
It also shifts well and the clutch works perfectly. The front brake is not so great, but I did pick up a 2 leader  Lightning front wheel on the weekend.

Glen

[Topdad]

No something amiss in the fuel stakes , I did about 50 miles last night on what was still in the tank, cap off and rocked bike , not very scientific but saw a splash of juice and thought that'll be ok didn't even get to reserve  ,that was 2 up by the way at about 55-60 mph, Bob.

[muskrat]

G'day Glen.
Might sound silly but the mainjet might have fallen out. I've had that happen with similar results.
Check the fuel height in the bowl. In a concentric it's to be 0.17" to 0.24" below the carb/ bowl joint. Can be hard to get much higher than 0.24" with a concentric on a slight downdraft.
Cheers

[Rocket Racer]

• She'll never keep up with your Vinnie but should do the ton for short bursts (one or two miles).
  

The 28 should feed her enough with the right jetting.

I agree with Musky, the odd bit of ton up shouldnt be a problem unless its geared way too tall.
I'm assuming no tacho and its running out of puff, not screaming its heart out.
Something certainly amiss unless it's a cooking 500 in disguise.
[/list]

[worntorn]

I suspect it is standard gearing but have not had the primary cover off yet. No time to get at the bike tonight, the diesel truck Turbo decided to have issues, so that took precedence over the A10 (or is it an A7?)  Don't think do it does say DAR 10 and HHC on the engine case, so I think we are OK there.
Glen

[Rocket Racer]

HHC: High lift cam, High Compression 

[muskrat]

Just to be sure count the fins on the barrels. 7 = A7, 8 = A10.
Cheers

[worntorn]

Yep, 8 fins present.
The mag is a k2f but there is no provision for manual control, it is the auto advance model. Did the 1963 SR come with this type, or has the mag been changed?

Glen

[muskrat]

G'day Glen.
OK it has A10 barrels but has it an A10 crank . But then if it has an A7 crank I doubt it would get to 85mph (a problem another member had)
All the sports models (alloy head models) were manual adv/retard.
Cheers