[nicholastanguma]

I mentioned this in passing. As for running out of money,I e-mailed Allan Hitchcock to ask about progress, and you guessed wrong, the pandemic and lock-downs over here have left them really short staffed, and keeping the day to day orders going out has taken top priority. If you look at another of their Instagram pictures there's a whole bench full of 4 valve heads looking tantalisingly close to being ready for shipping. I would hope that, with the UK in phased easing of lockdown, they can pick up where they left off with this fairly soon. While the HAVE managed to come a very long way with this project, I'm sure they'll want to see some money back on all that investment and start selling a few.

As for short-stroke configuration, they've also built one with a long-stroke crank for a 612.

Of course this is all for the CGT535 and is not relevant at all for an iron barrel engine. Or is it?   

That's great news, thanks for the update!   

Of course this is all for the CGT535 and is not relevant at all for an iron barrel engine. Or is it?

Of course it is.

[Bullet Whisperer]

Here is a twin port, two valve 500 Bullet model J from 1939, back when this would have been considered a 'Sports model'.
 B.W.

 https://youtu.be/xLTJGh8C5Uc

[Citrus]

My road registered clubman gets 31 hp AT THE BACK WHEEL (not BHP and is dyno tested) using a standard Bullet head with simple 34mm porting and sports cams. No need to do extra valves, pipes etc etc. It uses an electra bottom and barrel (giving better oil flow). Runs nice up to the standard electra ECU rev limiter of 6500 rpm. That power is about 50% more than the standard GT535

[Adrian II]

The dual exhaust single was quite a common thing on pre-WW2 bikes. Post-war, the last examples were probably the M120 650 Panthers, not noted as racing machines!

A.

[Seipgam]

That's a nice bike there Citrus, a shame that you see the need to sell it.

Geoff.

[viczena]

The dual exhaust single was quite a common thing on pre-WW2 bikes. Post-war, the last examples were probably the M120 650 Panthers, not noted as racing machines!

A.

And I always thought of it as a marketing gag. Looks líke a 2 cyl. , but with the price tag of a 1 cyl. bike.

[axman88]

The dual exhaust single was quite a common thing on pre-WW2 bikes. Post-war, the last examples were probably the M120 650 Panthers, not noted as racing machines!

A.

Wouldn't the Mahindra Jawas, in current production, be the last examples?

https://www.youtube.com/watch?v=qSKL5DbdcqM

I understand that these good looking machines are for sale in Europe now, but not yet in the USA.

[Adrian II]

I think that's because they are supposed to resemble (sort of) the old two-stroke Jawa 350s, which were twins. Purely a styling thing.

A.

[axman88]

I think that's because they are supposed to resemble (sort of) the old two-stroke Jawa 350s, which were twins. Purely a styling thing.

A.

Very likely true, I can't argue one way or another.  I was just pointing out that Mahindra's Jawa has a single cylinder and dual exhaust, and is much more recent than the M100 Panther.

But, Mahindra's Jawa DOES have dual exhaust valves. 

I don't know much about Triumph's Panther Model 100 but from the cutaway included in the article I link to below, this machine appears to have had a single exhaust valve.  Triumph's smaller Panther machines had single exhaust.  What do you think the motivation was to put dual exhaust on the 500cc Panther, if not styling?  The article also mentions that a single port head was available: "Cylinder heads are twin-port, but some bikes may have since been fitted with single-port (which requires a slight modification to the push rod tube fitting). The single-port was an option designed to facilitate sidecar attachment "   
https://sump-publishing.co.uk/panther.htm

[ace.cafe]

Back in those days, factories were still fiddling about with different ideas for both styling and running. The level of sophistication was not particularly high. They actually didn't know many things that seem elementary to us today. Maybe somebody in the engineering dept thaught it seemed "racy". Many bikes were still on hardtails and girders.

[axman88]

I don't know much about Triumph's Panther Model 100

Not Triumph, Phelon and Moore,   built the Panthers.  https://en.wikipedia.org/wiki/Phelon_%26_Moore

And not M100, the M120 was the machine cited.   

On the other hand, I suspect I can easily win any arguments brought against my being ignorant.

Anyways, thanks for bringing my attention to this machine, which I suspect is extremely rare in the USA.  As is my wont, I go from "never heard of it!" to "I MUST own one!" in about 10 minutes.

[AzCal Retred]

Re: 21 - 23:
Dual exhaust valves seem to be associated with separate exhaust pipes on Japanese machines that are built for HP production. I suspect they get more exhaust scavenging capacity and less wave  interference effects. The Jawa is the same idea, they are supposed to make near 30 HP out of 300cc.

[Nitrowing]

The only bike that springs to mind is Honda's CB250RS - it was one of my first bikes though, so I had little to compare it too. Felt powerful enough at the time