Dick Mann Lean angle

lcrken

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Re; “Maybe we are talking about two different bikes?

frequently referred to as TZ700s, but they were officially cataloged by Yamaha as TZ750 right from the start.

They expanded it to 748 cc in 1974 by increasing the stroke.

All of them had reed valves.”

The TZ range in the 1970s more or less until they changed them, all had 54mm stroke at one time, the 700 were made from the 500 GP racer at the time but fitted with 38mm carbs -later reduced for the reed block 750s to make them more rider friendly. There was a lot of mix and match of parts barrels, I have had a 350LC with a 350 TZ barrels on, seen a TZ350 with TZ 750 barrels on, (for someone who wanted to race at clubman level in the 500 class.


https://en.wikipedia.org/wiki/Yamaha_TZ750

https://www.carolenash.com/insidebikes/reviews/yamaha/yamaha-tz750/

tz 350;

http://www.tz350.net/tz350page.htm
Yeah, I got the stroke and bore numbers mixed up. I went back and edited it to correct, but apparently not quick enough.

But I still think I'm correct about them, including the 700s, all having reed valves, at least when they left the factory. Every reference I've seen, including the Carole Nash one above, agrees on that.

As you said, lots of possibilities for barrel swaps between the 350s and 750s. I have a friend who races an RZ350 here in AHRMA vintage races, and he says you can now buy aftermarket cylinders and crankshafts to take them out to over 500 cc. That should make a real monster of a street bike.

Ken
 
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A friend of mine has an RZ350. It is not easy to get genuine bits for it. But he rode it in a race recently and did very well. I said to him that it is probably as quick as a TR3. Converting it into a 500 would probably make it go slower. Personally, I prefer to look at race bikes as fitting into certain capacity classes, so going bigger by over-boring doesn't actually do much. The RZ350 has most of the modern improvements which gave two-strokes more torque and made them more rideable - so faster. Making the motor bigger doesn't necessarily make the bike faster. Is a 1970's T140 Triumph quicker than a 1960's T120 Triumph ?
 
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I suspect the gearbox in the RZ350 is the same as in the RD400, which has TZ350 ratios. Apparently a lot of guys who race RD350s in the States, use the Banshee box - which is similar if not the same. They are of the wet clutch type. The right gear ratios is a good way to get a bike going quicker.
 
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Yeah, I got the stroke and bore numbers mixed up. I went back and edited it to correct, but apparently not quick enough.
But I still think I'm correct about them, including the 700s, all having reed valves, at least when they left the factory. Every reference I've seen, including the Carole Nash one above, agrees on that.
As you said, lots of possibilities for barrel swaps between the 350s and 750s. I have a friend who races an RZ350 here in AHRMA vintage races, and he says you can now buy aftermarket cylinders and crankshafts to take them out to over 500 cc. That should make a real monster of a street bike. Ken


Re; “But I still think I'm correct about them, including the 700s, all having reed valves, at least when they left the factory. Every reference I've seen, including the Carole Nash one above, agrees on that.”

Then I suggest you do some more in depth research as, I am beginning to get a bit bored with you as once again I will have to correct you –the original TZ700 NEVER HAD REED BLOCKS !!!!!!¬!!!!!!!!!!

As they were an upgrade from the TZ500 to enter in the 750 class and used slightly detuned (again NON REED BLOCK) TZ350 barrels- and this is where the confusion lies also - as Yamaha called them 750s which they were not until the reed block 750s arrived.

I have had and sold a Spondon TZ350 with one NON REED – PISTON PORTED 700 barrel fitted!!!!

Re; "you can now buy aftermarket cylinders and crankshafts to take them out to over 500 cc. "
They are called Banshee 325cc cylinders not quite 500 unless someone some where has found a way to openup the crankcases to fit larger barrels!
 

lcrken

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Re; “But I still think I'm correct about them, including the 700s, all having reed valves, at least when they left the factory. Every reference I've seen, including the Carole Nash one above, agrees on that.”

Then I suggest you do some more in depth research as, I am beginning to get a bit bored with you as once again I will have to correct you –the original TZ700 NEVER HAD REED BLOCKS !!!!!!¬!!!!!!!!!!

As they were an upgrade from the TZ500 to enter in the 750 class and used slightly detuned (again NON REED BLOCK) TZ350 barrels- and this is where the confusion lies also - as Yamaha called them 750s which they were not until the reed block 750s arrived.

I have had and sold a Spondon TZ350 with one NON REED – PISTON PORTED 700 barrel fitted!!!!

Re; "you can now buy aftermarket cylinders and crankshafts to take them out to over 500 cc. "
They are called Banshee 325cc cylinders not quite 500 unless someone some where has found a way to openup the crankcases to fit larger barrels!

OK, you are letting this get too personal. I'm not attacking you, just trying to get the facts correct. You have so far posted no references to support your claim that the TZ700 never had reed blocks. I have listed several that claim they did. I am posting additional references below, as well as some pictures of TZ700s clearly showing the reed valve cylinders. Believe them or don't, whatever you choose.

Yamaha's TZ750:
Where Legends Began ...

Kel Carruthers recalls the early days of the TZ700
by evan williams

“Although it initially displaced 700cc, the machine was called the TZ750 because it had been designed for the Formula 750 class in Europe.”

“The spec sheet tells the tale: the TZ700/750 was an in-line four two-stroke, with reed valve induction and a fragile dry clutch.”


Carole Nash
Content Writer
Published: 11th August 2008

“It is a common mistake that the 750 four is just two 350 engines coupled together, nothing could be further than the truth as it is actually based on the 1973 factory 500 four GP machine and shares no common components at all with the smaller roadster based twin.”

“So later in 1972 Yamaha built their first F750 prototype, which was actually a 700cc, four cylinder machine.”

“Barrels were similar to the reed valve induction, TZ350 racer, featuring identical bore and stroke measurements,”


The mighty TZ 750
at
http://www.tz350.net/bigbrothers.htm#tz750

“Yamaha unleashed it's first production 4 cylinder 750 two stroke racer monster on the public in March 1974, in the shape of the awesome TZ750A. Priced at around $Aus3,500 this bike had in fact been under development as early as 1971. This ground-breaking model weighed in at 157kg dry and produced 90bhp @ 10,500rpm from it's watercooled 694cc engine. Formidable figures in the early seventies by any standard. Interestingly, Yamaha claimed the bike had the potential to produce almost 140bhp with TZ350 cylinders fitted.

Technically, though very similar to the TZ350 motor-wise, it differed in a few crucial areas, these being:

1. The head's squish band was reduced from the 350's 2.0mm to 1mm and it's combustion chamber was made a little deeper so as to keep the compression ratio to 7.3:1.

2. The exhaust port was lowered 1.5mm and four petal reed valves added to help control the influx of fuel mixture from the 34mm Mikuni carbs and to help "tame" the power delivery of this awesome machine , along with an additional fifth transfer port, "inlet" port if you like.

3. The 64mm dia. pistons had inlet holes cast into their rear, though a few of the early examples did not have this.

4. The four cylinder firing order was 1 and 4 (simultaneously) then 2 and 3.

The picture below clearly shows the TZ700 with the same reed valve cylinders as the late TZ750 above it.

TZ700 vs TZ750 Image.JPG


This is a closer detail picture of the reed valve cylinders in Wolfgang Fuchs original TZ700.

Wofgang Fuchs 1974 TZ700 Reed Valve.jpg


If you hunt enough on-line, you can find a lot more pictures of TZ700 engines, all showing reed valve intakes.

Ken
 
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Oh dearie, dearie me. Once again you have fell into the trap on mixing the TZ750s with the TZ700s by looking at photos and claiming that they are TZ700s with reed blocks when in fact they are not.

As for claiming the TZ700 has reed blocks I have 3 questions for you, did you see the barrels stamped 348cc?

Did you ask the owners if the 700 is actually a 700?

Did you ask the owners if the 700 has had a pair of 750 barrels fitted?

I suspect the answer to each question is No.

In realise that Carol Nash knows a lot about motorcycles but was not aware she dealt with racing motorcycles. But you sir are taking what’s on her and others website pages as gospel, which it is not. They may have originally a TZ700 and insured as a tz700 but. . . . . .with the reed blocks they are 375/TZ750 barrels!!


I brought a TZ350 in the eighties and tried to upgrade the engine by buying, borrowing or stealing a 350 barrel with a pair of reed blocks fitted, I asked Roger Keen, Dennis Trollope Racing, Padgett’s and others where I could get them, they ALL came back with the same reply-Yamaha don’t do TZ350s with reed blocks but they did do 375s barrels from their TZ750s!!!! In fact right up till 1981 when the FIM stopped the 350 GP races, Yamaha where now up to the TZ350 H model by then, and as on the Yamaha spares websites ALL show the 350 barrels as piston ported - NOT a reed block among them. They did not exist then at all and this was the 1980s!!!!!

So, here’s my challenge to you –find a TZ 350 barrel that is clearly stamped 348cc and has reed blocks fitted as made by, as you claim, Yamaha and show me the pictures as proof . . . .


I suspect that I am going to have a very long wait, waiting for someone to find proof of something that simply didn’t exist in the 1970s
 

lcrken

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Well, first of all, most of the reputable sources I've managed to find all point out that the TZ700 did not just use a pair of TZ350 barrels, but that they designed similar barrels, but with the provision for reed valves added, so I'm not sure what difference it would make if I could fine TZ350 barrels with reed blocks, and stamped 348.

As for pictures of TZ700s, I've found several from owners that claim them to be original, unmodified TZ700s, and all show the reed valve cylinders. I'm pretty sure that no matter how many such pictures I find, you will claim they are not TZ700s.

But that's enough. I give up. This is my last post on the subject. I don't want to see this turn into one of those endless threads that are more about ego than facts. No offense intended.

Ken
 
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I could believe that Yamaha might have made a TZ700 using two TZ350 barrels, but who would try to ride it ? If it ever existed, it never came to Australia - and we were usually the first to get anything different from Japan. My friend Bob Rosenthal corrected me when I mentioned about him being sponsored to ride the TZ750 by Milledge Bros. He said it was TZ700. I also asked him if it was true that he had tried the bike with two TZ350 barrels fitted. He said it did not happen.
When Ken Blake was riding Jack Walters' TZ350 and TZ750, he only brought the TZ750 to Winton once. The TZ350 was quite enough for anyone. A double TZ350 would be horrendous. It would tie itself up in knots and you with it.
 
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There is a guy here who has the ex-Jack Findlay TZ700. He had it at Winton, entered in the Period 5 Historic class with the four cylinder superbikes. To my mind, that is a waste of something which is very nice. Back in the 70s, we had races which were full of H2R Kawasakis, TR750 Suzukis and TZ700/TZ750 Yamahas. There was rarely ever a four cylinder superbike amongst them. It is the same with the TZ350/TZ250 these days - they run against four cylinder superbikes. I was never keen on two strokes, but some of those races in days gone by, were like watching ballet.
 
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You guys still don't seem to believe that my Seeley 850 oversteers. And that the extreme Dick Mann angle of lean occurs when the bike understeers as so many bikes do. Has anyone bothered to measure the yoke offset on a normal Commando, which I believe has the same rake as my Seeley - 27 degrees ?
 

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I owned a late model TZ750D for a while that was licensed for the road. It was a full-on race bike with a license plate stuck on, and absolutely no street equipment. I bought it from the guy who restored it. He said he had a friend in the local (San Jose?) DMV who managed to get it registered for him. The only concession he made to street riding was to put treaded tires on in place of slicks. I later sold it to an owner of a bike shop in Britain, who was here in the US buying bikes to ship back. He said he wanted to put it in his showroom window. Unfortunately, I've lost his name, so I don't know what happened to it later.

Anyhow, the point of this post is that I rode it briefly around the local streets, and can attest that it was quite rideable. If I could have fitted a starter, I would have wired it for lights and kept it. On the other hand, selling it let me buy a nice new heavy duty Miller TIG welder, as well as paying for half of a new Chinese milling machine. I've got a lot more use out of them than I would have from the TZ.

Ken
A bloke local to me in the UK had a road legal tz750 in the early 80s the noise from it was deafening
He pulled up next to me once in a pub car park and unclipped a Y shaped peice of rod and slotted it into the swing arm pivot as a side stand
It really didn't look stable so I moved my bike away from it
He had "the absolute bollocks" painted on the tank
Brilliant bike
 

baz

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You guys still don't seem to believe that my Seeley 850 oversteers. And that the extreme Dick Mann angle of lean occurs when the bike understeers as so many bikes do. Has anyone bothered to measure the yoke offset on a normal Commando, which I believe has the same rake as my Seeley - 27 degrees ?
Yep the offset has been measured many times
 
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Do you still use the standard fork yokes ? The last time I checked the price of a pair of billet yokes was about $700.
 
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Well, first of all, most of the reputable sources I've managed to find all point out that the TZ700 did not just use a pair of TZ350 barrels, but that they designed similar barrels, but with the provision for reed valves added, so I'm not sure what difference it would make if I could fine TZ350 barrels with reed blocks, and stamped 348. As for pictures of TZ700s, I've found several from owners that claim them to be original, unmodified TZ700s, and all show the reed valve cylinders. I'm pretty sure that no matter how many such pictures I find, you will claim they are not TZ700s.
But that's enough. I give up. This is my last post on the subject. I don't want to see this turn into one of those endless threads that are more about ego than facts. No offense intended. Ken


Re;” but with the provision for reed valves added, so I'm not sure what difference it would make if I could fine TZ350 barrels with reed blocks, and stamped 348.”

Oh dear! What a disappointment for all the TZ700 and about 1,500 TZ 350 owners in the world who would like to get reed block racing barrels while keeping them at 350cc for their bikes!

And as for the rest of your post you have misquoted me, I did not claim those bikes to be TZ700s –you did. They well have been a TZ700 when they came out of the factory (or so I thought, see below) but the owners found them too peaky as I stated in my earlier post.

As you didn’t look for proof as all I was asking you to provide, I went on the internet again and lo and behold, guess what turned up? (Look at the last pic- it's clearly marked 347cc)

https://www.ebay.com/itm/Yamaha-TZ7...633678&hash=item2f2f5567cb:g:458AAOSwyhVci-T8

In my defence the last time I saw a TZ700 was at a clubman’s meeting at Brands Hatch in 1988/9 and there was a TZ700 with piston ports, and the race program stated it was a 700, in a racing sidecar chassis- not a reed block in sight.
 
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Because you have seen a TZ700 with piston port barrels, does not mean it came out of the factory like that. About 15 years ago I had an Egli TZ700 frame and the opportunity to buy a TZ750 bottom end. So I collected two sets of TZ250 barrels and pistons to build a 500. However It turned out that the TZ750 bottom end had been used in a sidecar and had chucked a rod and slotted the cases.
 
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Have a look at the way John Kocinski's Cagiva handled at Eastern Creek in 1994 :

 
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My fave TZ. I was not fortunate enough to have aended the '75 race, but I was there for the '09 redux.
 
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It is very easy to build a motorcycle which would scare you shitless. The trick is to build one which is all-round faster.
 
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According to Jay Springsteen, who rode an example years after the ban, the TZ tracker had about a 40 bhp advantage on the Harleys of the day. And according to all accounts, had absolutely zero flywheel, which is why the only way Roberts could have won the '75 Indy Mile in the fashion he did was to screw the throttle to the stop and hang on. Anything that could put fear in Roberts' heart would kill mere mortals from the fright.

In flat track, superior horses don't always translate into a faster machine if you can't use the power without wheelspin. The Indian FTR 750s have an exterior-mounted quick-change flywheel to tailor the power effects to the particular track.
 
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