The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: orabanda on 21.02. 2010 12:26
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Well, On Friday we got Mario's '55 GF on Ray Moore's dyno.
It had done 1,500 miles since I restored (recreated) it.
(http://i302.photobucket.com/albums/nn82/orabanda/P1020104.jpg)
It had nipped up on the LH pot at only 150 miles, so we wanted a few miles up, before the dyno run.
The LH pipe also showed more discoloration than the right, which had very little.
The dyno run showed that the midrange was lean, and the top end rich.
The air / fuel ratio was very good on the RH pot, but leaner across the range on the LH pot; Josh, I should have used the anti bias spacer!
The needle was already second notch from the top, so we lifted it to the top. Main jet was a 240; we went down to 220.
Timing was 33 degrees BTDC LH, 34 degrees RH.
This was the result:
(http://i302.photobucket.com/albums/nn82/orabanda/P1020107.jpg)
The carb adjustments were great; we maintained pretty much a constant air / fuel ratio of 12.5 : 1 across the engine speed. The LH pot remained leaner than the RH, but acceptable.
I had slotted the mag mounting holes, and was able to change the timing over a range of 18 degrees.
We tried several settings, from 34 degrees, to 28 degrees, but the best results came from 30 BTDC. This gave the maximum torque figure (152 ft lb), but more importantly the fattest torque curve over the widest rpm range (900 rpm), and at the lowest rpm.
This mirrors the results for my '54 GF and '51 plunger (all three bikes have 356 cams, but Mario's has a monobloc).
Timing was checked with a light, read off a SRM disc on the primary drive. There was only 1/2 degree variance between pots, which is really good.
At idle, the reading was 2 degrees BTDC.
This is the third A10 I have had on the dyno (4 to go, including the alloy head Rockets).
This was the final runs.
(http://i302.photobucket.com/albums/nn82/orabanda/MarioCudiniGolenFlash1955run2.jpg)
This is the results from my '54 GF; the only difference between the bikes is carb (the '54 has a type 6).
(http://i302.photobucket.com/albums/nn82/orabanda/54A10resizegraph.jpg)
The ugly bloke on the left is master mechanic Ray Moore, the much uglier one on the right is Mario (the Italian Stallion).
(http://i302.photobucket.com/albums/nn82/orabanda/P1020110.jpg)
By golly, the bike sounded beautiful under load at 5,500 rpm; what a bark!
So, what was the end result?
Mario's verdict; "fantastic". It has more power across the rev range, and is smoother.
We took it for a run to Menzies today; 280 km. We couldn't get grin off Mario's face (couldn't keep up with him either; I am still running in the rigid at 50 mph, and he is streaking off in front at 70 mph).
(http://i302.photobucket.com/albums/nn82/orabanda/P1020111.jpg)
Here we are at the Menzies roadhouse, for breakfast.
Tony is on the left; he rode the Road Rocket. He is in charge of one of our police stations, and normally rides a Kawasaki VN1500 everywhere (Philip Island, etc; he will be at the Albany Ulyssis rally), but likes to ride the BSA(s) at every opportunity (he keeps repeating phrases like "small", "nimble", "good power" "no brakes").
Tony lent me an air mattress cushion; they work; the trip was comfortable - will be buying one!
Richard
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nice!
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Great work! I guess I will have to look around a bit to find a dyno here.
What CR is the bike running? Am looking forward to the Rocket power figures!
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7.25: 1 in the '54 and '55 (and the plunger '51.
(http://i302.photobucket.com/albums/nn82/orabanda/P1010169_resize.jpg)
(http://i302.photobucket.com/albums/nn82/orabanda/P1010166_resize.jpg)
This is the graph for the plunger bike
(http://i302.photobucket.com/albums/nn82/orabanda/RichardArgus.jpg)
The Road Rocket and RGS replica engines feel much quicker (both have big valve heads, and the RGS has 357 cam and bigger carb), so I am particularly interested to see how they compare and WHAT THE OPTIMUM timing is!
I will do both bikes within the next 4 weeks (and the rigid). However, I am using the chromed air cleaner on both rockets (and the SR special currently building), and am awaiting K&N air cleaner elements which are a direct replacement for the original paper ones.
My experience of K&N elements on dirt bikes, is they are an excellent high efficiency element which will improve air flow. Therefore, once they arrive, the bikes are ready to run!
Richard
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I agree, I also swapped the paper filters to K&N filter elements. Had to use a larger main jet afterwards. They are excellent and considering the fact that they can be cleaned and reused, they definitely are worth the money. I'm also using one in my everyday car (a Diesel), which has far better throttle response at low revs (before the turbo kicks in).
The timing setting on the Rocket will definitely be very interesting, I'm curious already...
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After my experiences so far, I suspect the best advance for the higher compression engines will be 33 - 34 degrees.
Richard
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Bkes look fantastic - any chance of a clip on utube so we can hear it go?
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This is the graph for the plunger bike
http://i302.photobucket.com/albums/nn82/orabanda/RichardArgus.jpg
Is that bike giving maximum power at 2600 rpm?
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I suppose it is either zoomed and the slope looks a bit weird and/or there rpm scale isn't correct?
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Stu,
Bring out the gimp: http://www.youtube.com/watch?v=6--KI2_k344
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Superb - sounds great, hearing the machine keeps me going on mine, can't wait to hear mine chuffing away on the drive.
Thks Stu.
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Richard,
forgot to ask last time: Do the curves show the power/torque measured on the rear wheel or are these the (calculated) crankshaft values?
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MG,
This is at the rear wheel.
Ray says the crankshaft (factory) figure is about 30% more.
He uses third gear for the run(s).
Richard
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I see, thanks.
Looks like the factory figures had not been too unrealistic.
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Time to revisit this thread, (thanks to Manosound AKA Richard L)!
As I have detailed in a separate subsequent post, I found the lost potential (neddies) of the 51 plunger, by basically improving the air cleaner (adapted a K&N element into the original BSA air cleaner assembly), installing an induction bias adaptor, and jetting and using different spark plugs in each pot, to minimise the induction bias.
This is the subsequent result:
Found it's MOJO!
Richard
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Part introduction to me and my bike, a 59 A10RR. Had it for far too many years, rebuilt and repainted it some 20 years ago. It is due another overhaul but just keeps on going. Fitted a new 28mm Mlkuni and decided to put it on a dyne to check out the mixture and see how the bike performed. The pistons are about 7.25:1 and the rest of the bike is "standard".
Impressed with the web site and the information on it. Well done to all concerned.
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Some nice tasty bikes there fella, welcome to the forum.
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Superb machines but where on earth did that torque figure come from ?
My 2003 FJR1300 has 143bhp with 99 ft lbs of torque at about 8500 rpm.
Same year Suzuki Hyabusa 101 ft lbs.
152 ft lbs sounds quite a lot for an A10.
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A10Rocket,
You were more alert than me!
From the dyno run data sheet, the 152 is lbs (pounds) Tractive Effort.
By my calcs, 21.2 ft lb of torque is produced @ 5,455 rpm and 22 HP.
Oh well, back to reality!
Richard