SPEED DEMON Yamaha TZ750 had TOO MUCH of EVERYTHING!
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- เผยแพร่เมื่อ 4 มิ.ย. 2024
- The legendary Yamaha TZ750 two-stroke racer was a bike three-time world champ Kenny Roberts said had "too much of everything." Technical Editor Kevin Cameron knows a lot of things about a lot of things, but he might know the most about Yamaha's world-conquering road racer. Kevin and Editor-in-Chief Mark Hoyer talk about the impact and evolution of this affordable production machine that leveled the playing field with factory racing machines.
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Im 65 years old and have listen to Kevin Cameron for over 45 years and hoping to listen for 45 more.Thank you Mr.Cameron.
I read cycle world cover to cover, during the 80s & 90s.
Yeah. I started reading Cycle when Mr Cameron was the "new guy".
This was awesome.
The Yamaha TZ750 was basically two 350s sharing an engine case and transmission.. they were supposed to make approximately 140 hp. We had to replace the pistons, about every 600 miles, you had to replace or rebuild the crankshaft every thousand miles..
whatever jetting, you set them at at sea level or in Mexico City, that was your jetting, and I hope you got it right. Because if you jetted near the edge in Mexico City, or in Denver, and you went to down in elevation to Daytona, without fattening the jetting, you probably seized. .. A fellow mechanic at a shop I worked at in those days, seized at Daytona, and broke both wrists and both ankles..
today’s MotoGP machines are cranking out more than double the horsepower, reaching top speeds here in 2024 of 227 miles an hour, not kilometers per hour..
The parts man at the Yamaha dealership I worked at still owes me $400 more than 50 years later, when I loaned him some money to buy his TZ 750 brand new.. I believe the price was around $7000.. my TZ 250D was under $4500 ..
I remember Giacomo Agostini coming to Daytona for the first time, riding a TZ 750 in the 200, winning the race, and almost collapsing from exhaustion as he got off the motorcycle in the pits after the race..
other racers winning the Daytona, 200 on the TZ 750 / Roberts, Baker, j sarrinan..
in those days, factories wanted to win the Daytona 200 because it was one of the most prestigious races in the entire world, --in those days..
I can’t describe the thrill. It was pulling into the pits at every race track and smelling blendsall.. Robert Duvall loved the smell of napalm in the morning, I loved the smell of blendsall in the morning…
when you ride any type of two-stroke in roadracing, you would be smart to ride with two fingers on the clutch lever. At the end of a long, Burn in top gear is the time they were most likely to seize, as you let off the throttle to start downshifting for a corner.. some say it’s because when you let off the throttle and The carburetors close their slides, you’re shutting off the air, you’re also shutting off the fuel and oil on a two stroke.. I can tell you from personal experience.. I woke up two days later in plaster in the hospital.. ending my racing career after eight years, six championships, two time national champion, all of my personal racing machines were always two strokes. I have ridden four strokes in two of the 4 24 hour races I competed in. Four riders per machine, I must say it was not a worry about a seizure on the four stroke motorcycles I was racing on those occasions…
there was nothing like the sound of unsilenced expansion chambers. on the TZ750s. The most painful ear piercing two-stroke was the Yamaha TA 125 twins without silencers. I’m not sure but I think they revved past 12 or 14,000 RPM, I’m not sure about that , I have no experience with the 125 twins, but I felt sorry for their clutches on the starts..
My TA125 had a 13,000 RPM redline. Never had a full seizure on my TZ750. One piston would seize but the other three would carry it through. Different story on the twins, sometimes your finger on the clutch wasn't quick enough. I would always do a plug chop on the first lap of practice for each day. Jetting came first before gearing changes.Tearing down top ends after breaking in new pistons and sanding high spots will help prevent the dreaded 2 stroke squeak. Air cooled singles, twins and Kawasaki's center cylinder on their triples lock up solid the most. Suzuki's air cooled 500 Titan had terrible seizing problems. Cal Rayborn's bike was converted to methanol but they seized on gas as well. However the worst type of seizure 2 or 4 stroke would be a gearbox lock up where pulling in the clutch won't do jack shit.
Jarno Saarinen drove 1973 in Daytona Yamaha TZ 351 against 750:s...and won.
@@mauril811 Not really fair to compare 2 strokes to 4 strokes of that era. Kawasaki and Suzuki had 2 stroke 750 triples that had reliability issues. 1974 were the first 4 cylinder TZs and they were 700s making 90 HP, more than mortal man could handle! Ago won with 4 cracked flat sided down pipes. Don Emde was the first 2 stroke to win the Daytona 200 in 1972 and that was a Yamaha air cooled TR3 350 twin. I'm a big Jarno fan and he was an incredible rider influencing King Kenny Robert's riding style. What he did at Daytona was the beginning of the 2 stroke era. Yamaha's TZ750 is history after that, so much so that people forget the 350 class.
Wow, thank you for taking us on that fantastic real life ride. What an incredible thrill those oil burners must have been. Fast as hell. In great and not so great ways. Much Respect.
IMHO This podcast is the best thing Cycle World has done since the internet age took the magazine out of print. Thank you for making these!!
WOW!!!! I grew up reading Cycle World & Cycle magazines in the 70's... reading each issue about the F750 road racing... ( with my RD 350 in the garage) I read and STILL READ ANYTHING written by Mr. Cameron... he is a genius... THANK YOU Mr. Cameron!!!!
I love listening to Kevin. He has more knowledge about motorcycles than anyone I've experienced.
Never going to get bored sitting by the knee of Grandpa Kevin and listening to wisdom of the ages.
This video kindled many memories for me. In 1979 I discovered that a guy named Erik Buell had moved in at the end of my alley in Milwaukee. He and another guy, Fritz Huebner, who was an ex-Yamaha factory race team mechanic for Kenny Roberts, were working on prepping Erik’s TZ750 for an upcoming AMA race. I stopped and talked to find out who they were and a years long friendship began. I was building custom bicycles in my basement but I also road sport bikes. Erik got me out on the racetrack which really improved my riding tremendously and taught me the engineering principles that he later developed into his Buell motorcycles. Fritz happened to be the mechanic that did the chassis work on the TZ750 flattracker, so I heard lots of details about that strange experiment. I was hanging out with them as they developed and built Erik’s first motorcycle, the RW750 square four race bike in his garage workshop. It was an experience I haven’t forgotten.
I'd really love to hear an episode about Erik Buell. He gets mentioned in a lot of these podcasts and clearly you two have spoken with him in depth. Also I can't thank you enough for these podcasts. It's so refreshing to hear these motorcycles discussed with technical intimacy, instead of just regurgitating Wikipedia articles and press releases like most motorcycle media these days.
Raced against Eric and his Barton at Nelson Ledges back around 1981/82
@@macmorgan6685 Man to be a fly on the wall of that paddock!
Fun Fact the 1st bike Buell really engineered was his 500 4cylinder AMA 2 stroke race bike....Based on an ill fated UK engine design....Had tons of motor issues.
How about a series of podcasts that feature KC detailing his year by year career beginning with the first year he was involved in motorcycle racing?
.
In early 1973 I began working as a mechanic at a Kawasaki dealership. These were the heyday years of Team Kawasaki road racing and KC was heavily involved in both the triples and the Bighorn singles. I remember a magazine article where he was making a rod bearing cage from billet. I was blown away by his skill set.
I mrt Gary Nixon and Erv Kanemoto in the UK...their van was full of expansion chambers for three triples and different circuits...pre exhaust valves...you changed the whole exhaust.
I worked with Cros at the Kawasaki distributors when we werent long out of our teens, he was a bit of a cowboy but he eventually got a grip on his riding and ended up winning a world championship, I went and worked with the Yamaha distributors and spent a summer as team manager for the Yamaha works team with Hideo Kanaya riding, and had a few test laps on the OW72 and gosh it was a monster to ride, huge power but abysmal handling.
It was an amazing era when a privateer could buy a yamaha TZ and be competitive. We had the Marlboro series here in NZ which was full of 2 strokes. Very special times never to be repeated.
A very special time, never to be repeated…full stop.
Kenny was my neighbor when I was a kid. He bought land from my grandad in Hickman California and built his dirt tracks. That's where I learned to ride.
Graham Crosby ,legendary character,watched him doing continuous donuts down the main straight on a Kawasaki 1300 with a female passenger after the race
Love the TZ750 but one thing that bugged me was setting the ignition timing. Of course you could get cylinders 1 and 2 right on however 3 and 4 would be off due to slight play in the cranks. I used to think you should split the difference but dyno results proved this wrong. Set 1 and 2 to spec, at least 2 cylinders are firing at the correct time. YZ125 reeds with raised cylinder exhaust ports, matched and polished transfers, (the TZ had 4 and factory 0w31 had 6 transfers) Lectron carbs and Swarbrick pipes really increased power. I ran Yamalube R at 25 to 1 and cranks would last me a season. New rings every race and if I could afford it, new pistons every other race. Only problem was the lower crankcase cracking from the 2 cranks flexing. Back then we used epoxy to fix the crack. There is a company making new cases for the big TZ and I wonder if they are reinforced in this area.
So glad you brought up the dyno results on the 750. I’m convinced that the 90hp figure that Yamaha gave for the first 694cc TZ750A was a conservative net figure with typical out of the crate “chicken jetting”. An early out of the crate test in the UK got 97hp at the wheel for the A model which would indicate approximately 112-114 at the crank. The following full 747cc B model was at around 120 gross. The factory bikes that Kenny and the developed later privateers like Dale Singelton won on were likely pumping in the 140-145 plus range.
Steve Baker, the Legend, took this beast to the top!
I sat and visited with Steve Baker one afternoon in the mid 80’s. He told me so many great stories….
Just found this channel....head up my arse I guess! Could listen to Kevin forever as he dips into his seemingly bottomless well of knowledge & experience......love it.
These lectures are fantastic. I enjoy them as much as reading your books and articles. Thank you Mr. Cameron. Keep them coming
This was a great interview and I learned much of the history I didn't know. Thanks to Mark, Cycle World and Kevin for this video. I became a fan of motorcycle racing during the last days of the TZ750, shortly before the RS500s came out. I saw the last of the 1000cc Superbikes and the introduction of the 750cc class. But what I didn't know is that my friend Dale Herbrandson (that Kevin mentions here in connection with reed valve intakes) was such a pioneer in those days. Dale never talked about that. I knew him from his drone engine business but we connected through a totally different hobby, related to military vehicles.
Kevin is a great storyteller. I met him once, about 24 years ago, when Cycle World and Dave Despain's show (MotoWorld?) were doing an event with the Honda Superbike team for the introduction of the RC51. This was at Willow Springs in 2000, and I was contributing some hardware for one of the riders. Kevin was quite the gentleman and I appreciated his write up of the event in his column.
Love the piston headphones!!!
RZ guy here..... thanks guys
Absolutely awesome listening to Kevin remenis about the beast. I'm an engineering nerd and could listen to this content all day long. The KR flat track TZ reserection video is killer! Thanks for sharing such amazing history!! I'm a huge fan of the 2 stroke era.
These talks with Kevin are terrific. I have been reading his tech articles dinve the late 1970s and eanted to become an ME because of him.
I'm an EE instead, so I don't have to make motorcycle parts, but love working on bikes asva hobby.
In 1986, I bought a well-used TZ250 (B model I think it was, circa 1978) for $800AUD, raced it once (stalled and last to leave the grid, but overtook so many riders on faster bikes) and sold it for $1,200AUD to a guy who claimed to be a "collector" ... wow, I made 50% profilt in a few months, 'grabe the money & run' job :) ... but what the bike is worth today could be bit more. Any regrets? No. Any memories? Definitely.
this is the most interesting tech documentary i have ever heard.
15:04 Early Yamaha monoshock units were vacuum assisted rebound multipliers if you hit them hard enough.
Compression damping relied on gas pressure in the reservoir to keep the oil from cavitating, once it did there's no compression damping at all , just, pushing the oil into the reservoir instead of through the piston valving, as it pulled a vacuum/void in the oil column.
That collapsing vacuum, plus gas pressure and spring pressure, all combined into the rebound stroke, punched back hard until the void collapsed and the rebound valving could even start to cope with something it really couldn't handle.
My friend made his TZ750 into a street bike..........but I was too scared to ride it when he offered !!!
I went to a bike night at a pub in Bellingham, WA. There is a guy up there that has a street legal TZ750 dirt tracker. He rode it to the pub. That bike is awesome!
How come you guys mentioned the TZ750 and never mentioned Steve Baker?
One last thing, I know it's a podcast, for us that watch in on youtube how come you guys didn't have a TZ700 or a TZ750 for the background?
Keep these shows going, I like Kevin and his style!
Raced a 700 once, hard work animal to ride quick.
Hi Mark and Kevin, great discussion on the TZ700/750. Having started racing with the RD350 there was always thought of using a 350TZ top end to go faster. I also had a 400 that I used for modified class. Kevin you mentioned wanting a TZ750 top end for your 350- I have on my RD400 a Fahron watercooled top end. You might remind Kevin that I gave him a TD-1 back around 1978 while on his way home from Daytona.
Mac Morgan, Yorklyn Delaware
Kevin needs to show us that TD1. I wonder if that’s the same one he’s been restoring?
I used to race a Nico Bakker TZ750 (ex Jack Middelburg) in the eighties. Great memories. Unfortunately the bike got stolen and now some guy is showing of in classic demo races in the Netherlands with a stolen bike.
A lot more people should take their time to listen to Cameron talking, and with Hoyer as a host and interviewer, the show become even better. Thank you!
Back in the 70's I raced a TA125 that Kevin ported for Steve R when Steve switched to Honda. Compared to the engine I was running it was a rocket ship.
I was lucky enough to ride a 409 model, updated to 1X2. The first thing that really grabbed my attention was that it felt like it pulled the same in top gear as it did in second gear on the straight. I was going faster. The second thing I noticed was the Lectrons were very sensitive to the first touch of the throttle and as a 250/350 rider, struggled with that. I was going slower. Wish I had the opportunity to spend more time on it. Unforgettable experience on an an amazing machine. PS. Mark, ask Paul about his seat in his Dad's Thames van.
Interesting you mention Graham Crosbie , another backyard kiwi racer also got a T/T under his belt
Great video guys, Now throw in the modification of case volume vs. intake length, and a cross over pipe, and boost bottles, and soon they become "mythical contraption designed to torment the soul of man". However, I love them, raced them, own 4 triples, an RZ350 race bike, dirt bikes, and Husqvarna 480 chain saw!
Excellent presentation gentlemen. I have pitted TZeds🇳🇿 for over 45 years and a TZ700 on unsilenced pipes is my sound of choice. 😊
My second new bike was a Gray 1974 Yamaha YZ-80-A I had the Yamaha Brochure for that year that had the Yamaha TZ line on it too. I will have to try and see if I can find it at my parents house.
Thanks gents, that is the best TH-cam vid I have watched in a very long time.
Thank you for a great video, I'm 66now two years ago I sold all my bikes and they were all 100cc two stroke dirt bikes, cheers mate 👍
As a stupid youth i was at Pukekohe when the TZ700 had it's first appearance at the track (John Boote). Coming over Rothmans heading for the start/finish line the bike visually twisted under acceleration. Love it...... More than two strokes and you're a wanker.
Another great podcast. Thank You.
I always learn a lot from Kevin. Totally enjoyed this - Thank you!!!
Let's get some history on the H2R. I never heard stories about how one originally would purchase or acquire those bikes and what was included if any factory support parts and tools. Plus would be interesting to hear some old school racing stories.
H2R is a recent bike. The 70s bike was the 74hp H2. The racing bike was the 100hp KR 750.
I have several 2 strokes including liquid cooled bikes as well, but I love my rd350 and rd400's as far as simplicity and once ported, piped and carbed correctly, they double in power!
The TZ750 would have made one heckuva healthy street bike had it been made street legal. Great video.
When does Kenny Roberts get mentioned? I worshipped that dude. Not literally but as a teenager wishing to follow in his huge footsteps.
Oops, at 7:45 ~
I love this pod cast. He is my favorite
This was excellent, so informative
Please keep the 2 stroke content coming. Especially the RD stuff because these are street bikes that our generation grew up with. Like to hear what Kevin's thought on tuning. I have seen porting on a RD350 top end that was told were tuned by Erv Kanemoto. Upon measuring the ex port height compared to other know RD tuners, found that for the street the consensus is 27mm height (rd350) So I ported all my 350's that way and like the power and rpm delivery. Hope you guys can do a segment on rd or 2 stroke tuning.
Kenny Roberts dirt tracking a TZ750 changed everything. He learned to never try that again. 🤠
Great to hear this,
I live in the UK, and really miss Team Obsolete bringing the bikes over,
With Dave Roper and others,
Have a word with Bob I ,
Thanks for everything
Excellent, I have Top Dead Centre one and 'Too' and wish I had this knowledge imparted to me when I was racing TZ350s back in the day!
Let's have some more please!
"There's no such thing as too much horsepower.
There's just not enough traction"
Carroll Shelby
Thx for the tech tips. Excellent research and experience, guys, I loved it. Big 2 strokes 💙 and the smell of the synthesise race oil. Bring back 2 stroke race bikes.
I saw the (I believe) debut of the TZ700 (pre 750) in Wellington, New Zealand. Probably late 1973. It kind of wobbled around the corners (it was a street track - basically a large square industrial block that ran over railway lines. Classic New Zealand street circuit) but it squirted of down the straight squirming it's tyres with the rider barely hanging on it and it made me laugh. It was so ridiculous. It was the opposite of watching the batter of the two parallel twin Kawasaki 250 strokes fighting into and out of the corners. I think it was Greg Hansford and Kork Ballington.
Waauu.. I love your podcast. I really like listening how racing engine are mase.
Greetings from Slovenia
Always loved reading Kevin Cameron, a true genius in engine tech!
Love these talks. My only complaint is that there are too few of them. Love all the Loudon refrences as I am a 20+yr Loudon vet. I would recommend doing more shows on specific bikes. History, specs etc. I will open voting for the EX500 and VTR1000.
Fascinating 👍🏻
Thanks🙏🏻
You could maybe buy a used thrashed TZ750 for $3500? But when I wanted to buy one in 1979, they were $13,500! Now this included the factory spares kit, but that wasn’t an extra ten grand. $13,500 in 1979 was probably the equivalent of $50k today. They were NOT a cheap way to go roadracing.
They did not require 2 semitrailers and 3 fulltime mechanics. Top level racing was accessible. Now the bottom of the pyramid has been removed leaving empty stands.
@PeacefulRallyCar-pw3cs and let's not forget in those days riders often competed in multiple categories on the same day. People seem to forget this and call today's riders like Rossi and Marquez the G.O.A.T.
There's only 1 G.O.A.T - GIACOMO AGOSTINI, 15 times World Champion!
@@robg6485 ... I agree . ago was a fantastic racer in his early days, battling against mike hailwood and many other GP gods, ... BUT ! ... for way too many years he was "touring" arount the circuits, displaying the total dominance of the MV agusta against antiquated british single cylinder nortons and machless machines ! ... NOT until he changed to Yamaha bikes did he once again show the brilliance that he had displayed in earlier years. !!! ... So many of his world championships were just "GIFTED TO HIM " !!!
Excellent rant. 🙏🙏
They said it before I got a chance to comment. The Bikes had more power than the Tires could handle.
Indubitably, Buell would be brilliant
I worked at a Kawasaki dealership during the 70s and rode the 500 and the 750 as a demo when I was 18yrs old !
Just subbed gr8 video ,and ive been looking at the rd twin as an off road base and discovered those crafty indians are now making this yammy abroad under other name
Hi Cycle World, awesome watching the video mate. What's the fellas name you've got speaking in this episode?
Epic game changing bike. Its a legend where i come from
Kevin, Kevin. Kevin! Nicest, smartest guy ever. I was but a punk ass filthy hippie walking into Arlington Motorsports and meeting Kevin and his business partner (Carlo??). You might of thought I was Agostini with the level of attention they gave me. Much respect
Kenny came to Oulton Park in the UK he high sided it at 90 mph and late flipped it at 120 mph.
Any prospect of a chat about Dr Robert Freeth (RIP) and his aerofoiled TZ750 VIKO special? NZ bike in Trevor Taylor's extensive mainly Yamaha collection. Also has Ginger Malloy's Harley 350 2stroke.
That would be Roger Freeth and Ginger Molloy eh, good times
Real good work fellows thoroughly enjoyable insight to a beast.A fellow i knew and dealt with some years back before his untimely departure , alex campbell was a motor cycle racer and outfit racer and local yamaha dealer, probly had a fair bit to do with yamaha developing the tz 700 /750 . He in fact had joined to 350 twins together and used a norton gearbox in and outfit , fast, generally unreliable . But did spark enough interest to bring the yamaha gurus from japan out here .A mate of mine still has the engine and the frame and has thoughts of restoring as he used to work with alex and had the pleasure of running in the engine on our local roads with instructions to stay under 90mph 😅 . Im not sure how to add a link on here but a quick google search of alex campbell motorcycle racer makes an interesting read.
Walking encyclopedia. Hie recollections and observations are of substantial interest to me as I rehab a '75 RD350.
Surprised kevin didn't pass comment on the tyre dunlop developed for the big tz , ... the DUNLOP DAYTONA 200 !
Mark, are your headphones made by Grado Labs by any chance? Thanks for the video, been a fan of Camerons for a long time. I used to dragrace a yamha SSR 440 snowmobile in my youth, and then moved on to dragrace a Kawasaki H2 built by Fast by Gast. Both machines were wild rides. The twostroke is ultimate race engine in my book.
They are custom Grado Labs phones with pistons as the vented chambers, yes! Seemed the best option for our podcast and they sound great.
@@markhoyer1736 Very Nice!
6.5.24. ⚠️”Wickedly Quick”™️
Some of them 500 Yamaha's had read on top 2 case induction on bottom 2
Several years ago I bought a subscription to CW archives. Is this service still available? I certainly would like to have access to it again!
Thanks fellas!
I was reading your Performance Manual again Kevin just yesterday (I had to endure several lengthy bus trips) If you have access to an FZR750, could you show and tell us how the heads design / bad design led to needing ridiculous levels of spark lead? (for a modern DOHC inline 4 bike engine) .. Wouldn't you know it, just as he mentioned the Agostini TZ, I was reading Colin Mckellar's Yamaha Race Bike book and was looking at a B&W snap of that exact bike (the OW31 I believe)
Blair wrote a great book as well.
Oh yes , who knows what evil lies in the harts of two-strokes? The sparkplug man doses. And he has a NGK tee shirt on. Thank you gentlemen 4 a nother great podcast. If i close my eyes, l can still smell the klots 2 stroke oil coming from my RD 350.......48 years ago.
I'm putting a flat slide carbonater on my single at the moment, gotta love ya carbons.😅
WOW! $3500 for a TZ750 that you could basically race against the factories. Is there even anything close that that in todays world for motorcycles or cars? I would imagine a clean example of one today would bring a pretty penny. My 1st two bikes were RD250 and a race prepped RD350 and today I own a '76 RD400. I was just getting into H.S when King Kenny won those 3 crowns.
All this [very interesting] chat about the big TZ , ... but no images for the uninitiated ???
Kenny Roberts after he rode the OW31 said the bikes where too fast. He asked for a max carb choke size of 28 mm. Kenny said with 34 mm carbs and ported barrels the bike would hit 190 mph. Others said NO. Steve Baker flrw on it. Kenny said dont sell them to club riders they will kill themselves....doom merchant.
If i recall correctly , ... it was the AMA who introduced the carb size restrictors due to lots of pressure from Harley Davidson because their "tractor engines " were totally outclassed , ... NOT kenny Roberts !!!
Hmm🤔 So what you actually saying is that mr.fox ideas predates Mr. Kent
Öhlin's!?
P.s. Mr. Technical editor, you really are a world of knowledge👍🏻 highly interesting😊 Also ,thank you ,for your contribution for making motorcycle's of today better . You and KingKenny seem to have been the "influencers" of the day👍🏻(influencers in the r e a l meaning of the word that is !!) Greetings from the country of Ōhlins. 🇸🇪
Intresting shoul heard this when i was 16 yoa.
Are your earphones air-cooled?
What were the torque ratings for these bikes?
I run a unique new carb on my 200SX KTM dirt bike. It delivers much more mixture at a lower signal. Especially wonderful for smaller bores, as it offers power quite low in the RPM range. There's no waiting for the start of the classic powerband in the upper mid-range. The peak HP is also increased and broader into an extended top end over-rev. The SuperTorque Super X (38/40mm bore) carb is like adding a big-bore kit along with a mid to top end port job. The jet sizes increase by 5-10 steps. I found it best to use a slower turn throttle, as to regain a safe and usable power delivery. At the recent 2 stroke 1/4 mile drag nationals a Honda CR 500cc single placed 2nd in the 750cc class. I'm having a great result against bigger bore bikes at track and trail. No joke, it redefines 2 stroke potential.
Dr. Gordon Blair.
Supposedly he consulted with Kawasaki on the S3/KH400 engine.
Apparently they didn’t listen to him ……
Not too much for King Kenny!
My friend had a new RZ350, the signed Kenny Roberts Edition. Not the yellow and black one, but this one was white. So one Saturday Doug rode up my driveway on it and said "Sleepy. you need to ride this thing." Well, being 6'4" it felt small to me, but it felt good. He had the factory racing pipes on it too. So I took it for a spin around this 5 mile loop I live on with many curves and straights. I tooled along at the most around 5,000 rpm, noticing that the redline was 14,000. It felt like a normal two stroke, kinda okay, until I went into a sharp dropping 90 degree turn and downshifted a couple of gears. When I let out on the clutch, I gave it a bunch of throttle to catch up, that`s when it went to 5,500 rpm and I cranked it up. WOW! I came out of the corner sideways to the edge of the pavement with the front wheel in the air. For the rest of the ride, I kept it over 5,500 and hit 14,000 several times, that thing was a freaking miniature rocket! I was simply amazed at the power band when it was on the pipe. Doug and I talked a long time about that. I hope he still has that bike.
Thanks for doing this, I really enjoyed it, love old stories about older things. I really wish the day I met and told Kevin how he changed my life he would not have been such an asshole.....
Timing is everything in Motorsport, isn’t it.
What is the difference between a TZ700 and an OW31?
Cylinders. OW31 had their exhaust ports 2mm lower then the standard version. It didn't matter much for the top power but the powerband started about 1200 revs earlier. I did this on my Bakker TZ750 by shaving the material from the cylinder bottom (lowering the transfer ports in the process) . Because the piston crowns now came over the top of the cylinders, I also had to work the cylinder heads.
The OW31, was a FACTORY race bike ... NOT available for sale, ... It had magnesium crankcases and 6 port transfers , and i think 36mm carbs ... 34mm was the OE size for the production race bikes. also many more magnerium parts instead of aluminium.
Yamaha reversed the rotation because they were seizing there engines on the hot exhaust side. Pushing the piston up on the intake side solved the problem.
It was reversed because there was one gear axle more so they could build the ignition behind cylinder one. Otherwise the engine would have become to wide.
@@dutchsailor6620 is this the same reason they reversed the TZ 250’s?
@@conspiracytherapist2473 At least the 54mm stroke engines (250/350) never were reversed and had the ignition and water pump at the end of the crankshaft. It wouldn't make sense because those engines were relatively small and ground clearance was not an issue.
Later types I don't know since I stopped racing at the end of the eighties.
@@dutchsailor6620 my J Model was reversed. TZ’s had a reputation for seizing as the exhaust port got bigger and bigger. Simply reversing the engine solved this problem.
@@conspiracytherapist2473 I used to race with 2x TZ250F cylinderblocks in the 500 class and never had any problems, but heard from 250 drivers the horror stories of piston rings being snapped in the exhaust port. offcourse my bike had the "reverse rotating" crankshafts.
I bought a TZ750 many years ago. It was by far the worst Touring bike ever. Fuel consumption was terrible and hardly anywhere to add a Top Box and Panniers. Mind you, the acceleration was excellent.
I want to drink with Kevin.
For real,,I would let him do all the Talkin...!
I always assumed the TZ750 used 180 degree crankshafts with two cylinders firing together to give better torque characteristics and make it less peaky, but also wondered if they ever experimented with a 90 degree crankshaft to see what would result.