C15 SS Rev limit

[MICKREEVES]

My C15 seems to have developed an RPM limit at 6500. I dont think it was like that before.
going full chat in third gear, it halts abruptly at 6K5. Why could that be?
I have tried it with original exhaust with absorption silencer. with high level trials pipe and mini silencer, open, and with two sizes restrictors.
Top speed is about 70 MPH at around 6k.
It has ignition from a shaft driven flywheel.
Accelerating towards top speed, reducing the throttle from full improves  the power. It will hold top speed at 7/8 throttle.
I think the engine should be able to reach 8,000, though I dont want to go that far.
Mick

[JulianS]

I think the BSA claimed the SS80 gave a maximum of 20bhp at 7250 rpm.

If the figure is accurate and I doubt it, you would need a really good engine to achieve it and from what I recall you have been running it very hard, so maybe it is already wearing out and power is declining.

I dont think it is going to rev to 8000 rpm on the road, what would be the point of running it past maximum power.

[DerekAnderson8]

My C15 seems to have developed an RPM limit at 6500. I dont think it was like that before.
going full chat in third gear, it halts abruptly at 6K5. Why could that be?
I have tried it with original exhaust with absorption silencer. with high level trials pipe and mini silencer, open, and with two sizes restrictors.
Top speed is about 70 MPH at around 6k.
It has ignition from a shaft driven flywheel.
Accelerating towards top speed, reducing the throttle from full improves  the power. It will hold top speed at 7/8 throttle.
I think the engine should be able to reach 8,000, though I dont want to go that far.
Mick

main jet too small?

[AdrianS]

I have never managed to get any of my BSAs over the years to perform as good as BSA advertise!
I agree with Julian, Have you got accurate measuring equipment for your figures? I also would question why you would want to thrash the balls of a tired old machine!

[MICKREEVES]

If you mean by 'THRASH', using the full performance. Yes I do.
If you mean by 'Tired', worn out. No it is not.
Have I accurate measures. Yes for RPM. No for speedo, but I have calculated speed from RPM and gear ratio.
I want to have an accurate speedo, so I could draw a new dial to correct the readings.
I think the max speed on my bike is just over 70 MPH. Does this sound right for a C15 SS? Anyone?
Mick

[MICKREEVES]

I find that I can ride my bike at maximum performance, most of the time, which is fun.
Had I a much faster machine, I could not do that in safety. Anyone agree with that??
Mick

[STAR TWIN]

I like to ride a modestly tuned bike reasonably hard but with due consideration to its age. My Velocette is an MSS, the lowest tuned 500. Good enough to ride to work I suppose, as one old codger put it. I rarely see more than 70 mph on it but am not afraid to use full throttle. It cruises at 60 mph or thereabouts. My 1951 A7 Star Twin gets plenty of hard use (400+ miles last weekend taking in the Beamish Trophy Trial) and cruises at 65 mph give or take. However, I rarely if ever exceed 4,200 rpm these days. These are grand old bikes and give a lot of fun but they ain't new. Reliability is paramount to me. They don't deserve a rod through the crankcase.     

[AdrianS]

If you require an accurate speedo to measure against yours, 3 options are a possibility:

Fit a bicycle speedo calibrated to your wheel size

Put a satnav on the bike - the speedo on the sat nav uses GPS so should be accurate

If your local community has a " Speed watch " team, they have a radar device used to measure accurately the speed of a vehicle.

[DON GRAY]

Whilst I admire your determination Mick in achieving good performance from your old Beezer, maybe, as others have said, its a few years old by now & probably past it's best - performance wise. If you like going fast, how about getting something more suitable that's gonna satisfy your need for speed & take it on a track away from the public in case it goes BANG in a big way!  Good luck!

[Tony1951]

Back in the day (1971) I had two C15s, one a five year old C15 with lowish mileage and one that was te years old. Neither would  go faster on the flat than about 72 mph to 75 mph when I weighed ten stone.  The speeds quoted are the indicated speeds on the speedo.

I can't imagine why one would flog one hard these days when they are quite valuable and more importantly not that common. If I had one of them now, I'd be treating it with care and respect. Even when they were newish bikes they were renowned for blowing up when abused.

[B44R Victor]

I had a B44R in 1972 that was 5 years old (1967) and did exactly what it said on the tin.  85 mph was no problem when it had warmed up and conditions were good.  This of course was achieved whilst burning leaded petrol.  I remember using 2-star most of the time. 

I now have a B44R that's 51 years old (1967) and wouldn't dream of asking it to achieve 85 mph, especially on lead-free!

When I was 14 years old on Sports Day, I got a first in the 100 yards, a first in the the 220 yards, a second in the 440 yards, a third in the 880 yards and a 4th in the mile. 

Thank goodness no-one expects me to win the 100 yards these days!

[MICKREEVES]

My main jet was 180. I fitted a 190 some time ago .

My Velo MSS only managed 60 mph.

I have a bicycle speedo, but it fails at about 60 mph.

I need to fit a 12 volt socket for my satnav.

I have worked out that 2500 rpm is 30 mph, 5000 is 60 mph and 6000 is 72.
Mick

[berniej]

Mick,

If your satnav uses a USB cable you can get a switched socket with cable and bracket from eBay for not a lot. The one I got also has a rubber cap to keep it dry when not in use.

I've fitted one to the frame downtube under the front of the tank running the wires back under the tank to the battery.

Being switched I can leave it off when not is use so there's no battery drain.

Although advertised as for 12V it works fine with 6V too so useful on both my Bantam and M21 which have original electrics.

FWIW I use an old smartphone with the TomTom app installed and attached using adhesive velcro strip.

Cheers,
Bernie

[Richard Mills]

My main jet was 180. I fitted a 190 some time ago .

My Velo MSS only managed 60 mph.

I have a bicycle speedo, but it fails at about 60 mph.

I need to fit a 12 volt socket for my satnav.

I have worked out that 2500 rpm is 30 mph, 5000 is 60 mph and 6000 is 72.
Mick

My 1961 Velo MSS will happily cruise at about 60mph on not more than 1/3 throttle. Top speed is supposed to be about 80mph, but I haven't pushed it that far.
Reading some of your posts, I can't help feeling that you would like a Morini 350; light (similar to a C15), fast (but revvy), and frugal. I am enjoying mine even though I mainly ride British singles; the contrast makes it such fun to ride.