HL500

[Marc.com]

Yeah thats the one BSA Regal .... you still see a few in Japan and they were sold as BSA.

Anyway back to the HL, its not like the early YZs were the last word in handling with most of the weight being high in the frame.... I think as well set up HL would give one a run for its money which is probably why Yamaha pulled the plug.

[pancho]

 I would be interested to know just what engine the XT 500 you are saying was copied off.
 While I admit it is not the first ever single o.h.cam engine ever seen since Otto fell of his cycle but with its small number [as I see it] of design weeknesses, very impressive power and reliability even when stressed with mods to cams and compression it's an individual design.
 For instance I don't remember seeing a more weird oil system!, but it works.

[firko]

That motor was a copy of the English single MarC

I would be interested to know just what engine the XT 500 you are saying was copied off

Yeah me too Wal .....the TT500 Yamaha motor's nothing like anything British, even to this day. I guess being a 500 single puts it in the ballpark but when you consider how bulletproof and simple the big Yammy is the Poms would only wish to have built something like it. Funny thing though, as sweet a motor as the TT/XT is, it's no faster, maybe even a tad slower than an obsolete old BSA B50 in a drag race......Go figure

[Marc.com]

That motor was a copy of the English single MarC

There was talk of the ProTec race bike stroked to 600 that Rick Johnson raced had close to 60hp. I guess stratispheric compression and race gas a lot of things are possible. Definitely the Japanese race SR500s got some serious hp.

http://www.powroll.com/P_YAMAHA_TTXTSR500.htm

[Davey Crocket]

I probably worded that wrong Poncho (not like me ), the breif Yamaha gave its designers was basically to come up with a 500 single 4 stroke because they could see how popular it was and the versatility it could be used for, they could see the potential and I'm pretty sure the BSA engine was the one they based their design parammeters off..size, horsepower,low vibration etc and we all know the japs do it better. The bike could be used as a commuter bike, weekend warrior, tourer, bla bla bla....that engine has powered so many diferent styles of bikes and stayed in production way longer than they could have ever imagined....Dakar wins, 500GP win, countless local MX and Roadrace wins, its probably done more miles around the world bar the mighty Honda postie bike....and as far as "pretty" bikes go the TT500 C, D, E, F, G would be up there. Theres a site you can go on and it explains it all, very interesting read. google it up boys and enjoy the read.

[Marc.com]

the breif Yamaha gave its designers was basically to come up with a 500 single 4 stroke because they could see how popular it was and the versatility i

Yeah there is nothing really bad about the motor. But not sure the B44/50 motor was their inspiration, the BSA motor is quite a bit physically smaller and push rod. Maybe the G50 engine. Anyway Yamaha's engine designers got it right but they sure as shit didn't do it any favors over at the chassis department. 

The XT chassis you can forgive them for as bomb proof collection of water pipe, but to saddle the competition TT version with anything other than the HL frame was criminal. When Yamaha knew what chassis the motor needed to win at GP level why they never developed it is beyond me.

[huskibul]

    So other than the obvious electrics and a few brackets the tt was different to the xt ?

[VMX247]

the ProTec race bike stroked to 600 that Rick Johnson raced had close to 60hp.

The most expensive VMX Magazine on the market #4 is full of weapons of choice pg 41- and an article including the Husky TT500.
Just what the Doctor ordered 
cheers A

[cloggy]

  The only 4 stroke copy of a brit bike was the Kawasaki 650/BSA. BSA must have sold the design but the truth has never come to light. Why would anyone want to copy a B50? Once it made power it was hideously unreliable and did for the engine upgrades industry what the XTand XL did for the aftermarket frame industry

[Marc.com]

  The only 4 stroke copy of a brit bike was the Kawasaki 650/BSA. BSA must have sold the design but the truth has never come to light. Why would anyone want to copy a B50? Once it made power it was hideously unreliable and did for the engine upgrades industry what the XTand XL did for the aftermarket frame industry

Kawasaki bought the rights to produce the BSA A7 from BSA. Kawasaki was didn't have the same capability to produce a big multi cylinder bike in 60s that the others had I guess. As for the B50, BSA raced the B44 at GP successfully but seemed to do very little to improve the design and address its weaknesses, but it a compact engine and not crazy heavy. BSA knew its weakness but fixing the gearbox etc would have meant re jigging and out dated 4 speed push rod motor so I guess they couldn't justify it/  the after market solutions like 3 speed box were pretty shit really.

[Colin Jay]

 to saddle the competition TT version with anything other than the HL frame was criminal.

To my knowledge, the TT500 was never intended to be a competition bike. I have always belived that the TT500 was designed to be a "Play Bike" intended for use by those who wanted a reliable, easy to ride and maintain big bore 4 stroke dirt bike to play around on and do a bit of trail riding and low level club enduro riding on, but didn't need a bike that was road legal (i.e. an XT500).

I think that Yamaha got it pretty right if that was the design brief that they were working too.

CJ

[Marc.com]

 to saddle the competition TT version with anything other than the HL frame was criminal.

To my knowledge, the TT500 was never intended to be a competition bike. I have always belived that the TT500 was designed to be a "Play Bike"

Not sure Yamaha sat down an decided to build a 'play bike', but that is certainly how it ended up. That Yamaha supported the HL500 development to some degree means they had visions of doing something more with the TT500. Also the HL had won a GP so the potential was there, I would imagine it is more likely that Yamaha chose to go no further with the TT500 because it could take YZ and IT sales away.

If they had produced a 3 valve Yamaha HL500 as production bike I would say they would have sold bushells of them.

[Graeme M]

Funny thing though, as sweet a motor as the TT/XT is, it's no faster, maybe even a tad slower than an obsolete old BSA B50 in a drag race......Go figure

Hmmm... now I know nuthin about Brit singles so I may be way off track here, but I am not sure we are comparing apples with apples. I recall a similar statement in a Two Wheels test of the SR500 in that they referred to the superior output of some old dunger velo 500.

The Brit singles were unemcumbered by anything remotely resembling muffling or intake restrictions. I'd be interested in knowing the HP figures of a standard cooking model Brit 500 and a TT500 with similar spec inlet/exhaust arrangements. In any case, serious power from a Brit bike requires some degree of fettling. How does a TT500 compare once it's been tuned for decent top end? Put another way, a stock TT500 is indeed a playbike and shouldn't be compared to a tuned race bike. How different are they once they are in similar states of tune?

As for being designed as a playbike, I have always understood that was the case. At the time, serious MX was for 2-strokes and that was generally the Japanese company line. I doubt that they expected a major sales success for a thumper MXer, whereas a playbike for the American market would have been far more successful. There used to be an advert for the TT500 that featured a cutaway of the engine etc and had a lot of sales pitch copy - I can't recall but I don't think it suggested that you'd end up winning any MX races on it. I also think VMX magazine had an extensive feature on the TT500 some time back which clarified Yamaha's design intent.

[Marc.com]

I recall a similar statement in a Two Wheels test of the SR500 in that they referred to the superior output of some old dunger velo 500.

The early SR500s not a crazy powerful motor at approx 30hp in stock form but reliable. I think part of the reason is that early on the motors had oil temperature issues in their development and Yamaha left them in a pretty soft tune with 8.3:1 compression and gifted them with heavier flywheels.

A dunger Velocette Venom will put out about 35 hp so both bikes are about the same power and then it comes down to weight. Tuned TT500 should be able to muster a lot more hp then most 500 Brit bikes.... note I said should given it is overhead cam and a much more modern engine. But then again Manx 500 engines can 55+ hp in their modern form and were not too far behind that in the old days.

[firko]

Hmmm... now I know nuthin about Brit singles so I may be way off track here, but I am not sure we are comparing apples with apples. I recall a similar statement in a Two Wheels test of the SR500 in that they referred to the superior output of some old dunger velo 500.

Why not compare apples with apples. The B50 BSA came in a number of similar guises to the Yamaha 500.
The B50SS is the equivalent of the SR Yamaha, the B50T equates to the XT trail version and the B50MX compares directly to the TT500. There's only four years difference in their release dates, the XT/TT taking over the market niche left when BSA closed down. Most B50'MX's never saw a motocross track, they were mostly purchased as play racers, just like the TT500 was.

One of the biggest misconceptions one can make is to pile all Brit bikes into the same 'Pommy shit' category, usually by those who've never ridden a Brit bike let alone owned one. While the BSA B50 isn't the cutting edge pre '75 racer it's still a very competitive bike and when compared to others from its 1971 release year it compares quite well. 

The Brit singles were unemcumbered by anything remotely resembling muffling or intake restrictions. I'd be interested in knowing the HP figures of a standard cooking model Brit 500 and a TT500 with similar spec inlet/exhaust arrangements

I'm not suure what you mean by inlet and exhaust restrictions Graeme. While I'm no authority on XT Yamahas I don't recall them having too much restriction on either end with the exception of the humungeous muffler they stuck on there. The B50T also came with a rather restrictive muffler that weighed a ton and the final 1973/4 B50MX was fitted with a giant chrome muffler to get through newly introduced US noise regulations.

. In any case, serious power from a Brit bike requires some degree of fettling.

I think the same can be said for the Yamaha too Graeme. Both engine's are vastly under engineered and can be turned into fire breathing monsters with the right bits. At the same time, in stock trim both bikes will still do a stellar job for whatever you want them to do. I'm not a blind crazy BSA fan, in fact I have no inclination to own one yet I've owned an XT500 (and TT600) and have respect for the engineering that went into them. The big lumps are strong and pretty bulletproof but having ridden Jonesy's different B50 variants over the years can truthfully say that the old Brit single is probably equally as bulletproof. Jonesy's had his B50MX for 30 years and it's never had the head off. Until recently it was used pretty regularly and I've often ridden it and find it a lot of fun. I reckon the bias against British machinery more often than not comes from those who've read about them rather than having ridden them.
I cop it about my Jag too until I give 'em a drive....then their attitude invariably changes. It's the same with old BSA's. Every year at Classic Dirt Jonesy offers one of his bikes to anyone who wants a ride. I've seen his B50 change many a stubborn opinion in the past as has his B44 Metisse converted a new lot of fans in recent years.