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Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776802 06/18/19 11:51 pm
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Hmmm, that bike raises a few questions...... Why gear a 750 a65 for 140mph at a circuit with a 350yd straight?
They closed the long straight at snet in about '71. The 'club' circuit was quite small and gearing for much over 105mph
would be a waste of time.
What class did he race in? He would have been up against tridents and kuhn commando's etc. Unless he was racing
in production class or similar.
Why only 13 starts in a season? Most meetings have/had at least 4 or 5 races per class over a race weekend.
The only 'billet' cranks that i am aware of for a65's were 85 or 90mm stroke so the bike would have been at least 850cc
with the 750 top end fitted.
Sounds like a 'selected race' bike. Trophy hunter eh?
That was around the time that the SRM outfit was cleaning up, that was 80 x 91 around 900cc, they started loosing out when
the Nourishes, big triples and imp's started appearing on the classic scene.

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Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776829 06/19/19 9:28 am
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Hi Nick, I will quote from the article , its all the info I have.

"Motorcycling mythology says you cant make a solo race winner out of a BSA unit twin. if you still believe that you havent seen Tony Price on his phenomenally succesful A65 based special.

over the past couple of seasons the Norton Featherbed machine,,,,, has proved as fast as anything else in british Classic racing,
In 1986 Price notched up a run of 11 wins from 13 starts- the other two were 2nds.
At the time of writing he holds classic lap records at Cadwell park, Mallory Park, Oulton park and Snetterton.
During 1987 he has proved that he can mix with the best in Classic Bike/ Norman Hyde thunderbike racing, and in 1988 hopes to post the Unit Beesa message in the revived Battle of the twins.


...He was passengering chair racer Derek Wood on 750 Beesa outfits in the 70s. Ended that partnership in 1973 after winning the ACU championships, The outfit was sold and TP kept the motors....

Constant developement has produced several engine mods since then, but the only mechanical failures Tony has suffered in 3 seasons have been a broken rocker arm, a piston seizure due to running with road tolerances and a broken crankshaft in 1984 "That was my fault for using a second hand crank" he says.

( doesnt actually say if its billet crank or not , my bad)

"Tony carries out his own crankshaft conversions to eliminate the timing side bush achilles heel, using a needle roller and end feed oiling similar to the well known Devimead conversion"

"The std A65 clutch has been driven by the same triplex chain for four seasons. The chain runs without a slipper tensioner, kept wet by automatic transmission fluid...
..."Ignition timing is very critical" he explains " If you move it a degree either way it knocks off about 200 rpm" The 11:1 CR promotes pinking on any other petrol than Esso, but no Avgas is used"

"The magic of this motor is according to Tony , all in the cylinder head, he is understandably reticent about the port work , he admits his head developement work took him through 5 castings."

When the article was written it mentions he planned to use a longstroke jumbo motor in the coming seasons, thats all I know.
Scanned images here.
http://www.britbike.com/forums/ubbthreads.php/topics/776830#Post776830


Last edited by gavin eisler; 06/19/19 10:04 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776884 06/19/19 10:50 pm
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I stand corrected Gavin. I remember Derek Wood's outfit. Didn't correlate Tony Price to that.

From notes i've read though, it was questionable that the bike was 750cc, most thought more like 900.

Bit of a weapon though, sure showed a few what the old beezers can do.

Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776969 06/21/19 12:07 am
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It turns out that Blod who lives a few miles NorWest of me in Benderloch does work for Tony Price, I think he still races old outfits, will ask Blod about this. handy man to know.
The article mentions stock 75 stroke and 79 mm pistons, ive peered long and hard at the pics and the barrels seem to be the same height as my old Devi set. The one thing it doesnt mention is engine breathing , I dont see any extra pipework. The exhaust tweaks are very good, no primary chain tensioner allows the Pipe to tuck in neatly.

Attached Files Scanned Document-2.jpg

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776979 06/21/19 8:51 am
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Very interesting Gavin, thanks for sharing.

I googled Tony Price A65 and found a forum where its mentioned that he was the passenger in Derek Woods outfit. There's also a couple of photos of the pair on their Triumph engined mount.

There's also an amazing picture of an A65 converted to DOHC and on the dyno, lord knows how much power this engine made.

See This Link for details.

Last edited by gunner; 06/21/19 4:54 pm.

1968 A65 Firebird
1967 B44 Shooting Star
1972 Norton Commando
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gunner] #776983 06/21/19 10:58 am
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Originally Posted by gunner


There's also an amazing picture of an A65 converted to DOHC and on the dyno, lord knows how much this engine made.

See This Link for details.


I beleive the factory looked at OHC but because the price to "tool up" wasn't worth the cost in the gains they would have made in performance they never did. A westlake style head would have had a much better influence on the power.


beerchug
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #776997 06/21/19 3:23 pm
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The DOHC head appears to be 4 valve. You can see four holes on the exhaust side. The problem with getting power would be the bottom end. Without a centre main bearing the crank would probably break too often.
One problem with putting it in an existing cycle frame is the height. It appears much taller than stock. Not a problem for a sidecar rig.
The intakes on the sidecars are curious. They have the bellmouths pointing directly into the drivers crotch. There does not appear to be much room there are I think it would restrict the air flow quite a bit.

Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: DMadigan] #776998 06/21/19 3:31 pm
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Originally Posted by DMadigan
They have the bellmouths pointing directly into the drivers crotch. There does not appear to be much room there are I think it would restrict the air flow quite a bit.


Its how you stop the engine getting too hot and pre-igniting the fuel and racing away...... just drop a B*****ks worth of racers leathers in each bell mouth and stop the engine dead wink


beerchug
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #777019 06/21/19 11:56 pm
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It was always a laugh talking about the 'ballroom' on an kneeler outfit.
When i was a novice and you had to wear an orange jacket, that used to get sucked into
the amals i used at that time, had to bind tape around my waist before starting.
The weber and a65 wasn't so bad as the motor sat lower and the bellmouths i used
later were the short rolled edge type. Once tailored and sorted the clearance was ok.
https://i.imgur.com/LEQRzc1.jpg
As for the power breaking cranks, Weslake had big success with engines in outfits,
they used an EN40B billet unit, i knew of a couple that broke but it was rare. The
need for a centre bearing is more important for high revs i think, most of the Weslakes
were bloodlined at 6800-7200. Their big advantage was torque.
A DOHC a65 arrangement was used occasionally by a Belgium pair but i don't think it was
as much of a gain as all that. You had to go some to get up with a 970 triple or a 900 Weslake.
OR a 1000cc 4 cyl imp motor. Handling, brakes and testicles were much more important.
(That's why i was such crap!)
The 'giveaway' on the stroked motors was a plate fitted under the barrel with the old devi jumbo
kits. It wasn't all that thick as normally different rods and pistons were fitted.
I think the secret was in the headwork with his setup, having tried several approaches and
ruined several heads myself, i resorted to what i had which worked for me and stayed together.
Mark has done some great stuff with his one and i would think that mr prices motors are similar.
We tried various things but never used a flowbench, our testing was lap times, not scientific
enough anymore.

Last edited by NickL; 06/22/19 12:34 am.
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #777407 06/27/19 2:24 pm
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Thanks for the links and insights Gents.

Spoke to Blod, its a different Tony , dead end.
I recall chatting to one of the Gs at SRM about TPs motor , they had one of his old power units at the time , it was up for sale, I didnt ask how much, that was only a few years ago.

Buried in the article are some other details . In summary.
End fed crank, different balance factor , smooth at higher RPMs
Boyer ignition, constant loss battery.
Race cam, power coming in above 4k through to 8K.
32 mm Mk 1 Concs with port extensions and velocity stacks.
4 speed box, CR 1st and 2nd, stock 3rd and 4th ( my favourite too for 4 speeds)
B44 pistons. Comp ratio 11:1,
Std primary drive , no chain tensioner ? ATF lubrication for primary.
No mention of rods or valve sizes or valve springs or gearbox outriggers or breathers.
Front brake Norvil 11 " disc with lockheed caliper ( cracked regularly)


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783357 09/03/19 12:44 pm
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Weather is turning, had a couple of decent runs down to the Firth of Clyde and back, SPR at the mo.
"Your real-world MPG average is 54.57, covering 140 miles using 2.57 gallons of fuel.",
keeping motor over 4 most of the time in response to "Myth of the high revving A65 " thread. Just for science sake, changing down twice for most overtakes.


More of the same.
"Your real-world MPG average is 54.91, covering 146 miles using 2.66 gallons of fuel.".
Same , keeping it stoked over 4K.

Defect list for Winter.
Steering stops , weld up.
Replace leaking "points" idler pinion oil seal
maybe new front pipes.
New oil pressure switch, old one has totally failed, never lights up.
The horn has stopped working, last time was a bad connection, need to get the tank off for a look.

The bike continues to run well, starts easy, not bothered by rain, brakes work V well.

Very low maintenance this year, change fluids and ride. chain adjustments/swaps have settled to + 1,000 miles.
luvvin it. mileage now over 13K since fitting new barrels, 6K with new 5 speed box.

Last edited by gavin eisler; 09/06/19 12:49 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783381 09/03/19 11:59 pm
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I had a go at the 4000rpm thing over last weekend, with 21-47 gearing i'm over the speed limit 90% of the time.
The town limit is 60kph here mostly, 50kph in some places. With 21-47 gearing you'll be wearing out gearboxes
or getting nicked every 20 mins for speeding or making too much noise!
My motor is happy to plod at 3000 or less, around town, i don't expect to just open the throttle and pull away from
much less than that.
I think that 4k thing is crap.

Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783599 09/06/19 12:50 pm
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"I think that 4k thing is crap."
Fair point Nick, I have edited ," all the time" to "most of the time"
I choose my times and places, its not over 4K in town. My gearbox is fresh . Its over 4K when conditions allow.
Ive edited out the " all the time bit" , that was not true, my hyperbole.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783667 09/07/19 6:44 am
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I wasn't having a pop at you Gavin, i was just reflecting on that recent post where a65 revs were talked about.
I'm damn sure people don't ride around at 4000+ rpm all the time, i like to give the old crate some stick but if
it was tuned so it would only run like a race bike, i would have to sell it, it would be too much like hard work
riding it. I can clunk along in traffic when i have to at 30mph in 3rd or top, no pinking and snatching etc. The
bike's not doing anywhere near 4k. I do admit though, traffic sucks these days, i spend 90+% of my riding time
around country areas, much more fun.

Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783672 09/07/19 11:20 am
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One other thing for the Winter to do list.
Set up the spare 71 L head with stock valve sizes to work with the OKO, PWK , knock off 32 mm flat slide carbs.
I have slowly been accumulating bits for this.
The spare head is stock , just needs a thread repair to the rocker cover joint, D ports, new guides and a check for flat.
it still has an unmodified combustion chamber so i should get a slight squish effect, the current head had the CC opened up to match the big bores before I knew any better.
I have plastic t140 air box lids opened out to take the larger carb inlet rubbers.
However I am reluctant to disturb the current set up just for the sake of it. So this may be shelved for the foreseeable future.
next job fit new rubber, I have a new pair of Avons waiting for me at the LBS , better get on with wearing the old set out.
other back burner jobs.
Make oil pump OPRV test rig, John has loaned me a sawn off case for this.
Fit case vacuum gauge to old tach drive flange.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783681 09/07/19 2:43 pm
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Hi Gavin, if you retard the cam a few degrees and even it up more the inlet opens later and gives better valve to piston clearance, the inlet also shuts later and gives good performance. Which means when doing your new head you do not need to recess the valves. MAP have very nice nitrided valves slightly O/size 42mm and 37mm approx.


mark
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783723 09/07/19 9:01 pm
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Thanks for the tip Mark, I have a cam pinion with 3 key ways it , IIRC they move it 5 degrees either way, its on stock timing at the mo. retarding the cam timing, Does that move the surge up the rev range? i have never messed with the BSA timing before.
What does " even it up more " mean?
I dont plan on fitting the big valves this time , I have a good set of inlet valves on the shelf that are stock 71 size.
It turned into quite a palaver fitting big valves to the last head , if you dont cut the seats , how do you get the correct valve spring distance,? my main prob was valve spring binding , even if I had retarded the timing I would still have needed shorter springs or longer valves, it also caused a lot of pushrod grief. i got the big valves from SRM , I wonder if the MAP ones are longer?


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783734 09/07/19 11:24 pm
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I've not noticed any shift in where the surge comes in by retarding the timing. I noticed a shift once when I put offset rocker buttons in the big motor but it was running out of breath with the head I had then. Some of the springs supplied as A65 springs coil bind at the correct fitted length. SRM sell what they call 'race springs' they are what I use, they are not expensive, I set them up shorter than the stock fitted length to get the pressure I want, they do not coil bind even with increased lift. I've never used the SRM valves. The MAP valves are smaller o/size and probably made to address heads that have seats recessed a bit to restore valve height in the chamber, as well as to give better flow. Nitrided valves are good for running tight valve clearance especially in k-linered guides.

You should build a flow bench, what I built is very simple and cheap. Just need three old vacuum cleaners and pollypipe.


mark
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783739 09/07/19 11:58 pm
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The reason the srm valves are slightly shorter is that when recessed into the head they will clear pistons at full lift.
It's all about compromise. PM also make o'size valves which are very good. (they don't need cut back seats.)
Retarding the standard cam a few degrees by making a stepped key was standard practice racing, it does move the range up
but only a little. Balancing the cam across the two cylinders is more difficult with a single cam motor, easier with triumphs.

Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783740 09/07/19 11:58 pm
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"You should build a flow bench, what I built is very simple and cheap. Just need three old vacuum cleaners and pollypipe."

I like the idea of that, will get straight on to it after equiping the whole family with bows an arras, and making them them lethal at 20 paces, the bairns already pretty good the missus could be a pupil smiter,
geting, ready for Brexit. ( which looks more unlikely every day)
i will salvage some hoovers from the coup next time I am round

Last edited by gavin eisler; 09/07/19 11:59 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783758 09/08/19 8:17 am
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The stock cam timing is:
inlet exhaust

51-68 78-37

retarded 5 degree;

46-73 73-42

Figures some where near that are what to aim for, its unlikely to measure the same both cyls and unlikely to be exact. Sinking the valves loses compression and flow.

I found a drawing I did of the XR750 port the numbers inside the drawings are XR750 outside numbers are my progress measuring the BSA I could not get the width at the guide so the port in the BSA is a little smaller but both use 44.5mm valve and 38mm carb. A smaller scaled down version is what you want to suit your carb and valve size. The transition from round to oval can be in the head. When you widen it around the valve the flow jumps, it's quite remarkable. If you want to scale it down divide what valve you are using, say 42mm by 44.5=.943 and multiply the XR numbers by that. Ha, I'm just doing that and it's requiring a 35.8mm carb frown for a 42mm valve and a 35mm carb for 41mm valve. so these ports would be fairly big. If scaling the port works in practice the Harley port flows over 200 if we call it 200 then scaled down to 42mm valve and 35.8mm carb it should flow around 188! So the wall I've been hitting with the 30-32and 34mm ports I've been messing with, with std valve and 42mm valve are being restricted by carb size not valve size. The smaller port and carb size no doubt will work and have better midrange perhaps, but with a 42mm valve the best I've had so far was just over 160 with 34mm carbs, so more should be available with 36mm carbs but the ports getting bigger and the motor more revvy.



[Linked Image from i.postimg.cc]


mark
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783772 09/08/19 2:12 pm
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Thanks again Mark, great info, reminds me of a Cobras head, i think there is a Norton head tuner who describes it that way.
Jim Schmidt, here, https://www.youtube.com/watch?v=fpLpqJrZhXI

i could open up the current big valve head for the 32s and leave the spare as nearly stock, the current head already has a spigot mount, which would make mounting easy, but its a steel spigot, opening it up a mm or so will be a chore.

"Your real-world MPG average is 57.18, covering 165.5 miles using 2.89 gallons of fuel."


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #783825 09/09/19 2:15 am
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It was Jim who posted the dimensions and photos of molds of the XR750 ports on a Norton site. I think the BSA head is more suitable for the modification than the Norton. The XR head is based on the 350 GS head, so the BSA combustion chamber and valve angles are probably similar. Still cannot quite get it though. Definitely could by altering the head patterns a little. But a slightly smaller version is probably better anyway. The 883 graph doesn't start falling off even near 8,000rpm, the motor may sound fine up there but its very unnecessary with such strong midrange riding on the road. I might try doing another head and see what I can get with a 36mm port and 42mm valve, see if I can get 170cfm. I thought I'd need a bigger valve to get there but proportionally I don't. It would have been good to know this stuff back in the 1970s. With 170cfm on a 750 done for racing with good pipes and 11-1 comp it could make around 87hp around 8,500 a street orientated motor could be around 81hp. And most people would think that was totally impossible, especially in the '70s. The few people who have ridden the 883 usually go, 'Your speedo's reading fast' and I go, 'Yea, I know, but the GPS says it's reading 1mph slow at 60mph.'


mark
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #784991 09/21/19 8:18 pm
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After a decent long run
"Your real-world MPG average is 60.47, covering 155 miles using 2.56 gallons of fuel."

In and out to town
"Your real-world MPG average is 51.93, covering 163 miles using 3.14 gallons of fuel."

Got a pair of huge inlet valves from PES , meant for a B44, 44.5 mm OD and about 2 mm longer than stock.
They might work with some piston relieving, only just clear the head joint.
Now have all the jets ordered for the flat slides.

New tyres on the shelf, old ones are getting squirmy on road bands and the rear is getting thin in the middle.

On the last run the bike went onto reserve at about 155 miles just north of Duror, just made it the next filling station at Ballachullish, as I rolled up to the pump it died at 163 . The last few miles skirted the coast, there was a few pints left in the front of the tank.
Whew , something to bear in mind, the theoretical 200 mile range from the 4 gallon tank relies on lifting the front end to get fuel from the low spot back to the higher taps,. later on it ate the rear number plate, the lower left corner fractured off, other than that a rare day out .
The only low spot to the Ardnamurchan tour was getting behind a Billy Bowser effluent tanker on the hottest day for a month, it was despatched quickly.

I have been playing with the front brake, wow, it is almost up to the cagiva twin brembo set up, tons of feel, and more than you need really, if the surface is good and the rubber is hot, ridiculous short stops are possible.
Earlier today , leaving the chipper parking spot, there were some young loons with fast bikes , leathers and that ,parked beside me close by, as I got the tank bag ready the conversation went,
me " ill just get this pile of old shite out of yer way"
Jimmy no.1 . " its no a bad lookin pile o shite"
me," Ihve had it fer a while,"
Kick
vroom.
Jimmy no.2 " Woww ! starts first kick"
me, "Its a BSA , ayways starts first kick"
I give it a handful and squirt away into the path of a U turning tourist, thank friction for disc brakes, no prang.
The tourist looked suitably apologetic and I went on my way.
Just after that I had to get past twa harleys on the Bialach an Righ, that wis fun.


Motor is running great, starts 1st kick with numerous onlookers, gets the fish suppers back hot.
Handling is still look and go with a bit more arm input to wrestle the discs down. I might go to one, two is overkill , the bike is not as agile as it was in very tight going.

At the bottom of Neptunes Staircase, Corpach, with the Vic 32 , one of the Vital Sparks, still running.


Attached Files IMG_1230.JPGIMG_1231.JPG
Last edited by gavin eisler; 09/21/19 8:43 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: alloy barrels + 5 speeds A65 750 OIF 1971 [Re: gavin eisler] #785182 09/23/19 11:32 am
Joined: May 2013
Posts: 5,881
Allan Gill Offline
BritBike Forum member
Offline
BritBike Forum member
Joined: May 2013
Posts: 5,881
Great Photos Gavin, Your experience with the front end is very interesting to me and Im keen to hear how you get on with it. I was going to look at twin disc for mine but may just stick with the single. As mentioned some time ago Norman Hyde to 10" and 12" floating discs for these, so maybe the 12" would be a meet performance somewhere in the middle.


beerchug
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