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Old 04-25-2012, 09:58 PM   #1 (permalink)
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Any other 2-stroke lovers??

Raced outboard hydros many decades ago, have always liked 2-strokes for their simplicity while recognizing their drawbacks (although is it really a drawback to be able to pull in front of some snotty tree-hugger in his Prius and bury him in the deadly blue cloud??!!).

I currently have a '76 Yamaha RD400C 2-stroke streetbike, one of the early good-handling quick middleweights of the kind that led to the coinage of the term, "crotch-rocket". But I can't justify having two bikes around, with all of the other junk, so I might be selling it to get something lighter in weight that I can load in the back of my work truck for chasing parts when the truck is on the job. It will be another 2-stroke, a '75-'76 Yamaha RD125 twin. I'll fabricate my own pipes for it, and do some mods to improve handling and make it look cooler.

So far I haven't related this to fuel efficiency, which is not generally one of the shining attributes of 2-strokes. Since this is a little bike with a little engine, the mpg numbers will be good compared to most cars, of course, and there are a couple of small tricks I'll do to improve them. But I expect that among this gathering of brainy gear-heads we do have some dedicated "'strokers" here. If so, has any of you heard of a company called Envirotech? They have engineered some sort of retrofit fuel injection system that they claim to have sold widely in the 4th World to owners of smoking 2-stroke scooters and tricycle-cabs and such. Have any of you managed to acquire one (the company won't sell them here), or know anything about this?

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Old 04-25-2012, 10:26 PM   #2 (permalink)
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Yup - I love 2-strokes. First street bike was a RD400 back in '79. Also owned a RZ350 for a while.

My RD was almost identical (same paint, same cut-down seat, expansion chambers, but mine had Clubman bars) to this one I found on the web -

.

I had numerous 2-stroke dirt bikes as well.

Right now my oldest son is trying to talk me into a CR125 instead of the XR100 he's riding now.

One of my riding buddies had a Suzuki GT550/3 cyl with chambers that sounded amazing. I used to follow him just to listen to it. I loved the smell too...


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Old 04-25-2012, 10:53 PM   #3 (permalink)
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I still have my old 75 RD350 and 83 RZ350, they were purchased new by me. They sat from 1984 (when I retired from roadracing) until last fall when I drug them out of my shed and disassembled them. My RZ is running at present and my RD still needs a few weeks of work.

My wife has two smokers as well. She has a Honda elite 50 with an 87cc stroker and a Yamaha Zuma 50 with a 70 big bore. Once in a while she will get a comment that her bike is smoking....

She is also planning on riding the RD.


Ah the good old days.
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Last edited by Varn; 04-25-2012 at 11:08 PM.. Reason: typo
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Old 04-25-2012, 11:05 PM   #4 (permalink)
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2 Stroke Lover!

I love that band.
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Old 04-26-2012, 01:19 AM   #5 (permalink)
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+1 on the 2-strokes! There is nothing like a 2-stroke when it hits the pipe. Not that I own one anymore....
I did fix an RD350 for my neighbour. What a blast! Basically, way too much power for the chassis.

A stock RD will only get around 40-45 mpg.

The number one upgrade for these engines is digital ignition. The later RD400s had CDI which basically eliminated spark plug fouling issues. With a stock RD, you basically have to take a handful of spark plugs along at all times. There was a company that made a timing advance setup for these as well, which basically doubled fuel mileage around town. I would seriously look into that, because I believe there was no timing advance on these motors. I think it even had a TPS for timing inputs.

Good luck!
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Old 04-26-2012, 01:05 PM   #6 (permalink)
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Mechman I would like to comment. Actually you want an ignition retard as the engine comes on the pipe. Sort of the vacuum advance mechanism that was common in automobiles of the time. Light load advance... heavy load, start retarding. My RD is going to stay with the points. It has made it 37 years with them.

As far as having too much power for the chassis, remember the TZ350, about twice the power and in a chassis that was 50% lighter and still manageable. When compared to models 6-8 years newer (The RDLC and then RZ) it is bouncy, twitchy but without that comparison it was state of the art.

When I rode my RD on the road. It got 40 mpg but I could get 50 on the road. About 12-15 mpg at the track.

I do believe that time has passed the 2 stroke engine. At least as I know them. Using the crankcase to scavenge the engine, carrying oil and unburned fuel with it is just not politically correct. If you want one better find it and rebuild it. Almost all the parts are still available. My RD is going to stay the same as when I raced it. Stock pipes, rear sets.

My bikes are now antique or historic vehicles and will probably be ridden less than 1000 miles a year. I haven't ridden the RD since back then but rode my RZ a couple of weeks ago. It hits the pipe at about 6500 and lasts to 9500. The variable exhaust port really fattens the power band. It still is very old school when compared to what more modern performance two strokes can do. But it is pretty light weight and with the short wheelbase it makes it fun. Seems like every time that I have gotten it out is was just after a rain and the clay on top of the gravel makes it just want to slew.

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Originally Posted by mechman600 View Post
+1 on the 2-strokes! There is nothing like a 2-stroke when it hits the pipe. Not that I own one anymore....
I did fix an RD350 for my neighbour. What a blast! Basically, way too much power for the chassis.

A stock RD will only get around 40-45 mpg.

The number one upgrade for these engines is digital ignition. The later RD400s had CDI which basically eliminated spark plug fouling issues. With a stock RD, you basically have to take a handful of spark plugs along at all times. There was a company that made a timing advance setup for these as well, which basically doubled fuel mileage around town. I would seriously look into that, because I believe there was no timing advance on these motors. I think it even had a TPS for timing inputs.

Good luck!
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Old 04-26-2012, 02:08 PM   #7 (permalink)
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i heard about a company retrofitting those 2t paddicabs in India witha propane kit. You would need an oil injection engine though.

I am newly in posession of a Puch mk-II moped. It was my mother-in-laws fathers, but she is letting me boot about on it for the summer.

I love the smell of 2-stroke in the morning.
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Old 04-26-2012, 03:32 PM   #8 (permalink)
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Old 04-26-2012, 05:38 PM   #9 (permalink)
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Excellant! I didn't suppose this site was populated entirely by bark-eaters and CARB bureaucrats, but I'm glad to find you contrarian types!

It certainly is possible to manufacture more fuel-efficient and "clean" 2-strokes with port fuel injection, pressure oiling, computerized ignition getting feedback from various sensors, closer manufacturing tolerances, ceramic-top pistons, and so on.

It isn't likely to happen very often, however, because the Green crowd has cowed the manufacturers and brainwashed politicians by castigating all 2-stroke engines as "filthy" in testimony before Congress and elsewhere. Why this crowd is consulted for this sort of "technical expertise" is a mystery. By and large the Greens were liberal arts majors, have had their noses in books most of their lives, and have never had grease under their nails. They imagine that products on store shelves came to be there by some form of immaculate conception, and have no clue as to what engineers and blue collar skilled tradesmen actually do, and they share this ignorance with our educational, political, and legal establishments. So when they denounce 2-strokes as "filthy," the powers-that-be readily accept it, having no frame of reference by which to judge such "technical" assertions.

Yet even conventional crankcase-oiled 2-strokes like my RD are a whole lot cleaner than the old 2-strokes that made the reputation that stuck. Up to the late '50s, 2-strokes generally used about 16:1 pre-mix ratios, using oil we might now refer to as "bunker C". And since most owners of 2-stroke equipment were as clueless then as now, they would pick up their chainsaw, still half-full of stinky four-month-old fuel, and try to fire it up without vigorously shaking the saw to re-mix the oil that had all settled out of the gas. When the engine finally started, the oil still had only partially re-mixed from all of the shaking of the extended starting proceedure, and the oil-rich mixture would pour out clouds of smoke. Later on, of course, the engine would go oil-lean and maybe stick, which added the the 2-strokes undeserved reputation for reliability. To this day, hardly any homeowner knows the few easy tricks to keeping his weedeater and backpack blower and chainsaw and similar equipment happy, so the "unreliable 2-stroke" nonsense continues. Even guys who should know better . . . decades ago I'd go for a weekend of dirt riding, and when I got out of my tent Sunday morning, I'd go over to my bike and tip it back and forth a bunch of times, with other guys scratching their heads. Of course, that oil was SUPPOSED to stay mixed, but why take a chance?

Anyway, since the old days we have gotten oil that works at 50:1, 80:1, and even thinner, and some of it really does stay mixed pretty well. Result: a lot less smoke. Since the mid-'60s, outboard motors no longer drain excess gas/oil out of the bottom of the crankcase while trolling, but send it back to the carburetor (this change meant that the new motors wouldnt troll as smooth as the old ones, but that was a price worth paying). Unfortunately, the politicians, brainwashed by the Greens, are banning 2-stroke outboards from lakes all over the country. Funny, Kiekhaefer, maker of Mercury outboards since the Forties, had their own private "Lake X" in Florida where they tested engines. In the late Sixties, after they had run hundreds of thousands of gallons of (the old style) pre-mix through hundreds of engines (mostly lacking the crankcase re-cycle circuit) on that small lake, somebody thought to get a lab to test for oil pollution. Next to none was detected; the fractions were light enough to have evaporated. Banning 2-strokes to "save" lakes is like most of what the Green-influenced politicians come up with: High image, low content.

(This wasn't intended as a political editorial except as related to 2-strokes. But lest someone mmisunderstand, please accept a one-paragraph digression because I don't want you to think I scorn all environmentalists. Some are very sharp, have far more tech expertise than I do, and insist on practical results over feel-good band-aid fixes, and they are gradually moving their movement, kicking and screaming, toward a more productive and cooperative attitude. The knee-jerk Green-bashers and deniers on the other side need to be re-programmed in a similar way. And government at all levels needs to wise up (making bio-fuel from corn instead of the many alternatives is a particular example of poorly executing a basically good idea). End digression and beg pardon.)

I'm interested in hearing more about the variable timing system retrofit. My RD400 has what could be called the "First generation" ignition upgrade: a pair of K-Mart coils, and the points-cam reground mostly by hand for more dwell, oh and the plugs gapped to .032-.035". This was a popular fix in the mid-'70s, and gave a real improvement in ignition and plug life, though not as good as the later electronic ignitions, I understand.
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Old 04-26-2012, 07:18 PM   #10 (permalink)
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Well I had lots of two strokes GT380's one with chambers, and even a GT750 water buffalo and they never got even near the Mileage of my GS1000, i think I got over 50 mpg at 70 MPH and interestingly enough though the oil costs more because a four stroke , or most of them have no seperate gearbox, so if you ride hard you better change the oil a lot, like 2000 miles or less, and a two stroke running golden spectro uses only about a pint per 3 or 4 hundred miles if you lean them out , which you can do with the Spectro so your oil costs are actually higher with a four stroke , or very close, My GT 380 stock went from 100 top end to almost 110 with the spectro after a few hundred miles , Yamahas were tuned to go fast never very happy running slow like a Suzi.

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