ESE's works engine tuner

[Hemi Makutu]

The TZ twin for instance did the jackshaft to reverse the crankrotation only to increase piston life over a 100KM or so.

1, TZ twins never - "did the jackshaft" at all, but won many G.P. races well in excess of 100 Km in length.

2, TZ fours "did the jackshaft" - to utilize a pair of twin cranks geared together inline, with centre PTO.

3, TZ fours won the Daytona 200 mile ( ~320 Km) race 9 times in a row.

[Frits Overmars]

TZ inline 4s used their 1-1 jackshaft for ignition on one end, & clutch pinion on the other...

Yes they did but that was to minimise the width, they did a two up two down config likely more to lower costs. The jackshaft costs HP, not and issue in 750 but not ideal for a 125.

As it happens, you've got a bit to learn yet, eh fella.. see the 1960's 4 cyl 2T G.P. 125s.. & as such see the 2-stroke thread current on the F1 Technical Forum, wherein the value of a even-fire multi 2T engine is discussed.

Forgive me for asking Hemi, but weren't you the one starting a discussion about inline 4s? None of those 1960s rotary inlet fours were inline.
And since you mention it, judging by their comments, nobody on the F1 Technical Forum appears to have any hands-on experience with the Yamaha inline fours.
None of those engines had a 1 to 1 crankshaft / jackshaft ratio because of their hunting-tooth layout, so no way could this jackshaft have been used as a balance shaft, nor carry the ignition on one end as you claim.
The jackshaft itself propelled another shaft that carried the ignition. And this ignition shaft rotated with crankshaft rpm. Feel free to enlighten the F1 Technical people:
38 teeth on the crankshafts, 39 teeth on the jackshaft, one more 39 teeth gear on the jackshaft, 38 teeth on the ignition shaft.

TZ twins never - "did the jackshaft" at all

Don't tell me you've never seen a 1981 TZ250H, a 1982 TZ250J, a 1983 TZ250K or a 1984 TZ250L...

[Frits Overmars]

got a Ø20*Ø35*7 teflon lipped seal and wrapped it with a paper strip, slid it over a crank and weighted it up so it was enough to overcome static friction and slowly rotate around the shaft with a 90 gm weight. (see pic). Working backwards, this level of friction equates @ 14k rpm, to equal 0 .0226 kW. Stuff all really.

I must admit this is less than I expected, because we've experienced that the very first parts to heat up in a running engine are the places where the seals run.
So I did some backwards working too. Here's what I did:
circumferential force at radius 0,035/2 = 0,09 * 9,81 = 0,883 N
Preservation of torque gives:
circumferential force at radius 0,020/2 = 35/20 * 0,883 = 1,545 N
Circumferential velocity at radius 0,020/2 = 2*pi * 0,02/2 * 14000/60 = 14,66 m/s
friction power = force * velocity = 1,545 * 14,66 = 22,6 W = 0,0226 kW.
So I shouldn't have bothered. Next time I'll just believe whatever you say, Ken .

Of course most engines have more than one seal, and the direct power loss caused by the seals is converted to heat which causes additional indirect power losses in a two-stroke. And the fact remains that labyrinth-type seals are practically frictionless and bulletproof.

[wobbly]

The only TZ to have piston issues was the 250G, as it had a ludicrous inlet port width and shape - along with a short skirt to suit the lifted port.
As Frits rightly points out, all the engines directly after that had the crank spin backwards with a jackshaft, thus enabling a big
inlet setup with no piston issues.
Obviously the race division got a right kicking in the arse over the G affair, and fixed it for good.
I guess Yamahas accountants had more sway than the engineers doing the 500 and 750 inline 4 cylinder layout,but as it turned out
the big bang 180* firing and reverse spinning crank was never considered a technically backward step, and they certainly weren't noted as being
prone to vibrations enough to annoy riders or crack frames.

[wobbly]

The 50cc pipe shown is an early version ( based on Aprilia style cones ) done for a customer that wanted peak power at only 13,000,and that translates to a tuned length
in the 760 ballpark.
Later more powerful versions of that pipe were even fatter,and had a single rear cone , but the length remained similar to suit the powerband requested.

[rodg]

Two curves from my RS125 on the ESE dyno. The one with the dip is V Force reed block. The other curve is stock reeds. V Force reeds and block in good condition. As they say, stock is best!

[Muciek]

Any other mods in engine?

[wobbly]

RS125 with VF3 makes no better ( less ) power as the petal frequency is wrong, but if you can find a VF2 then thats worth an extra
between 1 and 2 Hp everywhere.

[Hemi Makutu]

Forgive me for asking Hemi, but weren't you the one starting a discussion about inline 4s? None of those 1960s fours were inline.
And since you mention it, judging by their comments, nobody on the F1 Technical Forum appears to have any hands-on experience with the Yamaha inline fours.
None of those engines had a 1 to 1 crankshaft / jackshaft ratio because of their hunting-tooth layout, so no way could this jackshaft have been used as a balance shaft, let alone carry the ignition on one end as you claim.
The jackshaft itself propelled another shaft that carried the ignition. And this ignition shaft rotated with crankshaft rpm. Feel free to impress the F1 Technical people:
38 teeth on the crankshafts, 39 teeth on the jackshaft, one more 39 teeth gear on the jackshaft, 38 teeth on the ignition shaft.

Thanks Frits, mea culpa, I was being a bit naughty.. to provoke a knowledgeable response.

I knew someone would show the pix ( knowing the TZ 4 ignition was driven from a gearing corrected aux shaft),
and that without the qualifier 'contemporary' to match the early TZ twins with the 4's the later jackshaft ones would be noted.

I was a bit mean I suppose, to show Husa that his 'backlash' reason for non gear driven ignition didn't apply.
But I figured his "100Km" piston life idea - was too funny to let slide.

But nevermind the fun, did you see the research links?

Here is Kevin Cameron on 'wrenching' (rebuilding) the TZ 750.

http://www.cycleworld.com/2016/01/18...meron-insights

[Hemi Makutu]

I guess Yamahas accountants had more sway than the engineers doing the 500 and 750 inline 4 cylinder layout,but as it turned out
the big bang 180* firing and reverse spinning crank was never considered a technically backward step, and they certainly weren't noted as being
prone to vibrations enough to annoy riders or crack frames.

Yamaha did have big troubles with their 4T 750 twin 'omniphase balancer' TX at that time too, although
the TZ racing engineers likely would've laughed at all the chain stretching/oil frothing horrors..

[Hemi Makutu]

May be of some interest to those dealing with injectors.

http://www.diva-portal.se/smash/get/...FULLTEXT01.pdf

[rodg]

Any other mods in engine?

Just a VHM head. 250km Old piston. We found another 1 HP by retarding ignition 1 degree after this

[rodg]

RS125 with VF3 makes no better ( less ) power as the petal frequency is wrong, but if you can find a VF2 then thats worth an extra
between 1 and 2 Hp everywhere.

Thanks Wobbly. One of the pieces of knowledge that would have been useful prior to that acquisition

[Frits Overmars]

Thanks Frits, mea culpa, I was being a bit naughty.. to provoke a knowledgeable response. I knew someone would show the pix ( knowing the TZ 4 ignition was driven from a gearing corrected aux shaft), and that without the qualifier 'contemporary' to match the early TZ twins with the 4's the later jackshaft ones would be noted.
I was a bit mean I suppose, to show Husa that his 'backlash' reason for non gear driven ignition didn't apply. But I figured his "100Km" piston life idea - was too funny to let slide. But nevermind the fun, did you see the research links? Here is Kevin Cameron on 'wrenching' (rebuilding) the TZ 750. http://www.cycleworld.com/2016/01/18...meron-insights

I knew the article about the opposed-piston HCCI two-stroke but it was not the most informative paper I ever read.
I also saw the link to the Snowmobiler magazine that you posted in the Oddbike-section but it didn't work for me. Luckily I had already received the same information from Rotax.
You're right about putting the Rotax 850 cc E-Tec engine in a motorcycle chassis. Somebody at Rotax may have had a similar idea, because about a year ago Rotax presented their 600 cc E-Tec engine, combined with a six-speed gearbox instead of the usual CVT. But when I made further inquiries, it appeared that the engine did not really exist; it was just a teaser, published in order to fathom the interest in such a unit.


Regarding Kevin Cameron's TZ750-article: yes, I knew it. I love reading whatever Kevin writes. Did you know that once upon a time we were colleagues?
Kevin impersonated a technical editor at Cycle World and I was doing the same at the dutch Moto73 magazine.

A counter balance shaft might be okay for a generator side of things i had that idea myself, but i think it would be not so great for timing as it would have a fair bit backlash built in. thus the timing could be a little eratic. The Aprilias had a pickup sensor built into the crank wheel...
The TZ twin for instance did the jackshaft to reverse the crank rotation only to increase piston life over a 100KM or so...
The jackshaft costs HP, not and issue in 750 but not ideal for a 125.

Husa was of course exaggerating about the piston mileage in the Yamaha TZ250G but apart from that I must agree with him on all accounts.
The TZ250G was remarkable. Power-wise its cylinder block was a big step forward, with better transfer ducts, smaller exhaust duct volumes and the huge inlet ports that were detrimental to piston life.
The following year Yahama reversed the direction of crankshaft rotation by means of the jackshaft, but we'd already found a much simpler solution: we reversed the cylinderblock on the 'G': piston problem solved.

[Hemi Makutu]

Thanks Frits, I appreciate the considered reply,

I had meant actual research as per posts # 23745, #23746 & # 23771.
It goes to show the difference between Kaaden-type racer-engineers & academic thesis writers..

Although KC does write so nicely, I also find, he's always worth reading.
I do note his view that the 180' rocking couple was responsible for TZ 4 crankcases fatigue failure,
( not that Yamaha likely ever expected them to do so many Km)...

Here's a fresh KC blog, giving his 'big bang' appraisal.

http://www.cycleworld.com/why-single...od-in-the-dirt


Sorry, that link won't , for some reason, but tjbw has kindly put it up on post #23783, if you want to view it.