Mégacycle 560 nr performance

illf8ed said:

I hear you, but it doesn’t make sense as when new there wasn’t any need for aftermarket crankcase breathers. My new ‘72 combat in 1973 had no problem blowing past 100mph. What has changed with regard to crankcase pressure as the engines got older?

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Making sense might not be in my wheelhouse.

Nobody really knows what the cumulative changes are on the OP's bike. It's possible the breather plumbing was modified so that it is now ineffective. IMO if nothing was changed, this thread asking for help would not exist, and the bike would be running great using your experience as an example. At least this example, not so much the next one where you were fighting this problem for years. I resolved this issue in about a week before the interweb existed. Got a tip from an old road racer at a motorcycle show and swap meet at the San Jose fairgrounds, and made something up that worked on my engine.

I don't need to be right about anything. I'm just trying to help, and stay in my own lane whenever possible.

What clearances are you running on the valves?

mark parker said:

No I haven't tried porting a Norton, lots of people do it well, and the information is very interesting. Norton owners seem to appreciate how much it effects an engine. It seems a bit lost on many BSA owners as they sort of fail to see what it does. And are thinking cams and compression and stuff and do not realize what cfm does especially if the port is efficient not huge.

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Oi!!! I hope you're not inferring BSA owners are a bit thick....
'Cos the Guv'nor's just bought one, so beware!

I have a Megacycle 5600 cam in my stock 850
My engine builder contacted Megacycle and was told to set both the intake and exhaust to .009
this is so very close to the stock .006 intake and .008 exhaust anyway
I like this cam a lot, in fact I feel it is strong than the stock cam

I don't think Doug Hele ever got around to BSA, that might be why they are stodgy old bikes ( my 63SR sure is)
Doug certainly left a mark on Norton.
If you have ever ridden a 600cc 99 and 650ss back to back, you really start to appreciate Doug Hele.
He turned a 30 HP tractor into a little rocketship. That was mostly in the head redesign, ie the downdraught heads, although the SS cam is excellent as well.

Glen

On the 560 NR it should be set at .013 I'm not sure what effect running it tighter than that would have? I run mine at .013 and the bike runs great. Even up to 11,000 ft. It's a 72 Combat with free flowing exhaust 2 into 1

worntorn said:

I don't think Doug Hele ever got around to BSA, that might be why they are stodgy old bikes ( my 63SR sure is)
Doug certainly left a mark on Norton.
If you have ever ridden a 600cc 99 and 650ss back to back, you really start to appreciate Doug Hele.
He turned a 30 HP tractor into a little rocketship. That was mostly in the head redesign, ie the downdraught heads, although the SS cam is excellent as well.

Glen

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He worked for Triumph and was very committed to the threes. I doubt he had any interest in BSAs at all. There was competition between the factories even if both were owned by BSA.

In 1970 dyno testing at Umberslades they were testing on the threes using different configurations of 3 into 1 pipes, and carbs. They put a big A65 on the same graph, with an A10 crank, they were only revving to 7,000 because the crank's a bit fragile at those power levels, (why they did the A70 crank). They were trying to make the 3 match the twins 79hp, with it revving to 9000 or so, but the torque of the twin was much better and I guess vibration was a problem but it had a little more hp than the works Norton 750s in 71-72 tested at 76 at the engine and 67 at the wheel.

The head on the three has inlet ports crowded by the head studs, and with all the subsequent development 84hp was about their limit. The A65 doesn't have crowded ports so breathing wise it isn't handicapped in it's potential. The A70 configuration worked but I expect the 80X74 configuration would have been easier, better and vibrated less and pulled high rpm. Though vibration's just gets pushed around with balance factors and at least needs 90degree cranks to get it as smooth as a three.

But the three was Triumph and BSA so the factory road raced them with Doug. If they had not used the 3 he would have used a 750 Bonneville derivative. There is a bit of folk law that the Triumph twin was superior to the A65s for solo racing but I think that's more to do with what factories were doing. The A65-A70s were cleaning up in US flat track when the factory shut, so after that there was little point, and though riders might run them it wouldn't pay like riding for a factory and development and that motivation would cease. The twins also dominated side cars and that needs hp and torque.

If it was factory run in road racing it would have been interesting. Norton ran a twin very successfully.

The valves are adjusted at 0.013`` clearance.
The camshaft timing was checked last summer at the same time we have put a new Pazon system.
The owner will bring back the bike soon.
You give me good advices, if the pipes, breather are ok, I will try 5 degrees of advance.
Thanks!

Through the years I ported a fair share of Brit Bike Heads so for what I would say, I'd reckon that the aftermarket exhaust e.g. megatone's are not Bad at all but one desperately needs to remove the vertical screen as it impedes free flow as well as disturbs scavenging waves, thus the gas dynamics will get disturbed and the volume of flow will get choked to the point (depending on rpm and used cam etc) to the point that one will have too much backpressure.

Regarding the lacking involvement in Bsa i assume, based on what little i know bout the english motorcycle industry, it had also to do with the non to jovial relationship between NVT and Bert Hopwood.

In my opinion the bsa heads are next in line to the commando heads, maybe not as good/modern as the commando heads, but in my book light years ahead of the usual triumph stuff (i remember literal kinks in the triple and daytona ports, while 750's showed anacronostic deep combustion chamber shapes and angles inbetween valves.)
Even in the A10 pre unit twins I found pretty nice port shapes due to Imho pretty modern shallow combustion chamber shapes, although on the pre unit's as well as on the A-series bikes obstructed by a neglected SSR that in some cases goes as far that part of the intake seat ring is visible from above.
How Bsa with there supposedly avant-garde foundry could neglect such detail remains a mistery to me.
On the single carb pre unit's, considerable flow can be found in re-working/-shaping the pushrod tunnel inner port walls vertically with a watching eye on wall thickness, as well as building the SSR up with JB-weld and reshaping the final parts in classic D-shape.

Kind regards

Christian

The head on the three has inlet ports crowded by the head studs, and with all the subsequent development 84hp was about their limit.

I was watching a prototype OHC Trident at an auction 2 years ago, and another interested chap said that they discovered the porting was the limiting factor, and they were stuck with that at the time.

@jan nelder

Based on my experience one can within limits work around that problem with semi exotic flow cross section shapes..
In the meantime one also runs into prob's with the oil passages.
In the end I think that also the deep combustion chamber impedes with more aggressive profiles or bigger valves as the valves might collide during overlap.
I'm sorry to sound so deluded by the triumph heads but as mentioned I find the starting base vastly superior on Norton and Bsa.


Kind regards

Christian

PS: on the other hand p&m's richard peckett must have found some ways to extract more power out of the triples, it seems.

jan nelder said:

The head on the three has inlet ports crowded by the head studs, and with all the subsequent development 84hp was about their limit.

I was watching a prototype OHC Trident at an auction 2 years ago, and another interested chap said that they discovered the porting was the limiting factor, and they were stuck with that at the time.

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Yep, OHC doesn't make much difference except the pushrods are boringly reliable. BSA CEOs thought they needed OHC. They even designed and drew them up and cast them for the A65 and after all that someone probably said it's more expensive, taller and will add zero hp, and have another chain and tensioner to stuff up. And they abandoned it. And to think they couldn't bother putting a sensible long lasting bearing on the timing side, that was already drawn up, they changed the casting quite often anyway, and they were chasing hp. Testing a 750 with almost 80hp in 1970?

I doubt management understood at all, the value of an engine being regarded as bullet proof. Honda claimed 67hp, tested at around 62hp, no doubt they got 67hp out of something, the threes claimed 58hp and some tested around 65-67 converting rwhp.

The 650 I'm interested to experiment with and see if it could hit 67hp just by flowing the ports. That would be around 59rwhp. BSA tested one at 66hp but I expect it was high compression, tuned pipes running to 7500. They probably also balanced it for high rpm.

This is my big road bike on the dyno, it actually has a Norton crank bolted at 90degrees on a new flywheel. It was lean on the sensor in the exhaust and we had no jets, so we didn't ever move the ignition which was a guess, it seemed alright though.

These mufflers are restrictive.

Jim kindly put up pictures and measurements of the XR750 oval ports on this forum, Harley copied the originals from a BSA 350Gold star, so I copied the XR ovals into a BSA A65 head. The operator said don't worry about these figures it's way lean and the best we saw was 85rwhp, about 97hp at the engine and about 73lbft in the midrange. The rubber mounted 883 doesn't vibrate much, well the engine does, but not the rider.

But the 650 I really want to test but not blow up, going toward 7500 makes the grips hard to hang onto, tight is the worst, lightly with a couple of fingers to turn it on, isn't all that great either. Plus it's expensive and the clutch is coping now, but boarder line.

That beast is making almost as much as my 1200 Buell, & by the looks of it weighs a similar amount. Remarkable! How have you rubber mounted the motor?

Matchless said:

That beast is making almost as much as my 1200 Buell, & by the looks of it weighs a similar amount. Remarkable! How have you rubber mounted the motor?

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It is mounted in rubbers front and back and has a couple of stay rods preventing it twisting. One is on a lug welded to the chaincase and running back to the frame in line with the chain, this stops the chain pulling the engine back toward the wheel. It took a while to get this mounting strong enough to not shear single big bolts, so I ended up with a strong bracket on the frame.

I tried different rubbers till I obtained a good compromise. If too firm they had no effect till high rpm which was interesting as it vibrated pretty badly then suddenly went perfectly vibration free as the engine buzzed the rubbers enough. But top gear speed occurred at far too high a speed. But it made you smile and was very nice. It's funny, the motor vibrates and feels like it's about to blow up and then it went dead calm with just exhaust noise like the motor was now loving it. It's interesting how that totally changes your perception but nothing going on in the motor.

Softer rubbers gave smoothness earlier, and the compromise meant high speed didn't seem quite as good possibly but all through the range was nice. The mufflers and collector are ridged mounted and under the engine are two flex joints in the pipes, like modern FWD cars have, these work great. I now have two mufflers coming through at 51mm rather than 38mm. That can be felt in the midrange as can the larger mains. Hard to tell top end but it doesn't want to let up. Beau operating the dyno wanted to run another 1000rpm and see when the power curve went over but I wanted to ride it home. It's noticeably lighter than a stock BSA which I'm experimenting with at the moment. It doesn't look it particularly but pushing it around makes it obvious.

mark parker said:

But the three was Triumph and BSA so the factory road raced them with Doug. If they had not used the 3 he would have used a 750 Bonneville derivative. There is a bit of folk law that the Triumph twin was superior to the A65s for solo racing but I think that's more to do with what factories were doing. The A65-A70s were cleaning up in US flat track when the factory shut, so after that there was little point, and though riders might run them it wouldn't pay like riding for a factory and development and that motivation would cease. The twins also dominated side cars and that needs hp and torque.

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The BSA twin that Chris Chris Vincent successfully raced was, despite what it stated in the race program was actually a 800 cc twin. Alongside his "home made" rear suspension setup he seemed to have had the British championship wrapped up.
He didn't have anything in the 500cc world sidecar championship when he visited the IOM TT

Bernhard said:

The BSA twin that Chris Chris Vincent successfully raced was, despite what it stated in the race program was actually a 800 cc twin. Alongside his "home made" rear suspension setup he seemed to have had the British championship wrapped up.
He didn't have anything in the 500cc world sidecar championship when he visited the IOM TT

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I think he ran a few sizes, through the years. I've seen one of the early A65 where Chris was saying they got 60hp fairly easily from the 654cc, and by 1970 Umberslade had tested a 650 at 66hp on their dyno.

With an A10crank and std over sizes they go over 750, to 770 or so. A big bore kit can get 835cc or so, but I'm not sure he used one.

An A70 crank is 85mm not 84, the A70 was popular because the sludge trap is different to make it stronger. My friends run a 745cc A65 in the Queensland championships with an A10 crank. They don't really need displacement the head can be made very efficient. I actually would like to see him run a 650 and rev over 6,800. He dominated the series last year and broke the previous lap record by 4.4 seconds, on the 745 beating hot 1200cc rigs and everything else. So I guess he'll stick to that.

The head is similar to the Thunderbolt head on my Firebird. In P3 they can not use the later twin carb head on an A65 so I experimented on the one Thunderbolt head I had to work out how to get them working. Till he messaged me to say 'thanks heaps' and I got the Firebird going, I really didn't know they would work so well.

This is the std 650 Firebird with Thunderbolt head and twin 34mm PWK Chinese carbs. It's very nice to ride.