For those that advocate using 87 octane in these bikes

[UncleMike]

All Suzuki motorcycles were two strokes at the time, so how relevant is it?

And 87 octane WAS premium-grade at the time!

 

[hampshirehog]

All Suzuki motorcycles were two strokes at the time, so how relevant is it?

It isn't.

What Suzuki meant was don't use rubbish fuel - and you could get some real crap in the old communist eastern Europe, for instance, that was smuggled across in to the west every now and then. Suzuki weren't referring to the octane rating. The UK owner manuals at the time always just said leaded 2 Star (our lowest rating) - 87 octane - for the whole range.

 

[UncleMike]

Second, don't know what part of the country you lived in in the early 70's, 98 super high test was available in Ohio.

First off, I was born in '79. Second, just a joke - relax.

 

[UncleMike]

Wow, why does everybody just assume contradition is an argument, seeing as you were from Ca, and in the early 70's emissions starting coming into play, and Ca was always ahead of everyone else due to smog control, thought maybe Ca only had 87. I was stirring the pot for the die hard octane guys, and everybody has a tender spot for controversey as of late.

Wasn't assuming anything. Just highlighting the fact that I'm younger than most of you geezers for a bit of Sunday-morning ribbing.

 

[UncleMike]

I thought maybe you thought I was getting mad or something, far from it, see, the post worked, started some morning coffee spilling <---should have used more of these

Yeah, I've never warmed up to the emoticons and that's my own reluctance to fully abandon typographic culture. Maybe I'm a conservative after all?

(Sh*t, we don't want this turning P!)

I wasn't salty in the least, I promise. Reading it again, I can see how "relax" could seem aggressive. I just meant it as "I'm WAY too young to have a reliably-informed opinion on the matter at hand, so please disregard my conversational contributions as their intended folly, nothing more."

 

[Allie]

You stirred the pot, so don't cry when ums gets spattered... I still think it's an interesting question, how does fuel grade and/or octane rating (I didn't mention octane either, just asked a question) compare from two stroke to four stroke engines? Impossible to tell from original fuel specs, but I bet a lot of folks that have both bikes and run on modern fuels have insight.

 

[Allie]

I can see how "relax" could seem aggressive.

Well I AM RELAXED!!!!!!!!

 

[7981GS]

You stirred the pot, so don't cry when ums gets spattered... I still think it's an interesting question, how does fuel grade and/or octane rating (I didn't mention octane either, just asked a question) compare from two stroke to four stroke engines?
Impossible to tell from original fuel specs, but I bet a lot of folks that have both bikes and run on modern fuels have insight.

I have two 2-stroke motorcycles and a 2-stroke twin boat engine.
They all run on premium fuel mixed with synthetic oil/dino oil blend.
Two are piston port engines and one has reed valves.

Eric

 

[Billy Ricks]

Second, don't know what part of the country you lived in in the early 70's, 98 super high test was available in Ohio.

I used to be able to buy 100 octane at any station around here for about 32 cents through the mid '70s.

 

[Allie]

I have two 2-stroke motorcycles and a 2-stroke twin boat engine.
They all run on premium fuel mixed with synthetic oil/dino oil blend.
Two are piston port engines and one has reed valves.

Eric

Just curious, what are the compression ratios, and what are the factory fuel recommendations? Of what vintage are they?

 

[Billy Ricks]

Just curious, what are the compression ratios, and what are the factory fuel recommendations? Of what vintage are they?

IIRC the cr on my old 305 was down around 7.3:1 or so. They are firing every stroke so combustion temps were probably higher than on a 4 stroke and detonation was a bigger problem on two strokes.

 

[Allie]

IIRC the cr on my old 305 was down around 7.3:1 or so. They are firing every stroke so combustion temps were probably higher than on a 4 stroke and detonation was a bigger problem on two strokes.

That's the kind of info I'm interested in. I guess a four stroke cylinder has a lot more time to cool between explosions. I wonder how number of cylinders affects cylinder temps? I'm far from an engineer, but it would seem that multis might have an advantage in that even more time elapses between a cylinder's firing? Are there any engines where more than one cylinder fires at once? I'm picturing a Ferrari v-12 here.... each little cylinder waiting it's turn to fire... Surely there there's some overlap? Or would that take away some of the smoothness? Maybe it's one at a time but one cylinder fires while the previous is not quite finished yet? Anyone ever driven a two stroke Saab? And, and, where do little mechanics come from? What is our purpose in life?

 

[Billy Ricks]

The last of the two-stroke GP bikes were running big bang engines to tame the wheelspin coming out of corners. Cylinders firing close together instead of at even intervals. More cylinders would just raise redline so temps would go up. The GT750 went liquid cooling mostly to keep that center cylinder cool. Before Suzuki built the Titan it was thought a two cylinder 500cc two stroke couldn't be built because of the heat problems. Trying to get three big cylinders to stay cool meant liquid cooling.

 

[7981GS]

Just curious, what are the compression ratios, and what are the factory fuel recommendations? Of what vintage are they?

Impossible to find any useful info on my '75 YZ 400 MX as so few were made.
I got it literally in boxes and could not find any manuals for it when I put it back together.

It looks a lot like this only my seat needs recovering now and one of my son's lost the right side cover out in the desert somewhere.
I have been looking for years for a replacement. ray:

As for my (ugly) green '72 TS 250, I found this: http://www.bikez.com/motorcycles/suzuki_ts_250_1974.php

Eric

 

[Reaper0001]

na 93 less ethonal more power

 

[Billy Ricks]

The reason for the relatively low compression on two-strokes is everything has to happen in one revolution. Intake and exhaust are both happening at the same time at the bottom of the stroke. The fresh charge coming in pushes out spent gasses and part of the stroke is spent clearing the ports. Until the piston clears the port no compression is made.

 

[7981GS]

OS, the '75 YZ 400 MX was not only the fist mono-shock Yamaha MX bike (under the fuel tank), it was a one year only model.
Not easy to find parts for this dinosaur.

Eric

 

[koolaid_kid]

I remember that Yamaha as being a beast, but fun as long as you did not nail the throttle and stayed within the limits of the suspension.
Of all the TS models I preferred the 175, not as powerful but a bit lighter. Still would prefer the 250 over the 125 which was just too underpowered.

 

[7981GS]

I remember that Yamaha as being a beast, but fun as long as you did not nail the throttle and stayed within the limits of the suspension.
Of all the TS models I preferred the 175, not as powerful but a bit lighter. Still would prefer the 250 over the 125 which was just too underpowered.

It is actually much easier to ride in the tightest of rock-filled (boulders) turns on some of the most technical trails around here.
It is so low to the ground, easy to turn and has gobs of low-end torque.
Effortless compared to my big XR600R and XR650R Honda's and the Yamaha YZF400FK.

26 miles per 2.1 gallons of gas though.

I try to ride it at least once a year to remind me of what a beast it was when I was 16 YO when the dinosaurs still roamed the earth.

Eric

 

[Suzukasaurus]

Helium...

Less un-sprung weight.

Which is why if you're driving a tanker truck filled with helium cargo and you go across the scales overweight, you just have to add more.

Or maybe not....