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Random Quote: If the motors knock'n, turn the radio UP!
I have been going over my first 2 stroke engine for the past weeks and an pretty comfortable with how most of it works. 1999 Yamaha 150 saltwater. I understand the oil injection system, the oil transfer system, and the gearcase lube in the lower unit...
One dumb question... How does the powerhead crankcase get lube? From the mix oil that does not burn? That is pretty cool but seems a bit amazing that is works. Am I missing something? For the life of me, I do not see any other method.
Many, many years ago the quickest stock street machine in the quarter mile was a three cylinder two stroke Kawasaki motorcycle. The displacement of the engine was 0.5 liters (or 500cc as it was referred to back then). Kawasaki also had a similar machine displacing 0.75 liters but it wasn't quite as quick in the quarter mile as the smaller displacement machine.
The crankcase gets lubed from the "bottom up" What I mean is that the fuel/air/oil mixture gets applied to the "bottom" of the crankcase (think about where the oil pan is on a four stroke) and gets sucked up into the cylinders for ignition. Some engines also have oil directly injected into the crankcase via an oil pump and lines running outside of the crankcase to specific points around it. My HPDI has this second external system. The reed valves at the bottom of the crankcase prevent the fuel/air/oil mixture from being partially ejected backwards out of the motor once it is sucked inside it.
I had a '74 suzuki T-500 2 stroke and that mother would fly out of the hole. I learned a lot about 2 srokes working on that bike. Alas, it succumbed to red line fever while I was passing a buick. Those were the days! chip.
I had the Kawisaki 750 2 stroke triple (I think it was called the "H2". Throttle reponse was awesome - nothing quite like it for passing on a 2 lane road. I've had faster bikes (FJ1200), but nothing that felt nearly so quick. I have a hard time believing the 500 (H1) was faster in the quarter - maybe my memory is going. Handling was another matter - frame had a hidden hinge in it somewhere...
Yep, I had an H1, right about the hinged frame. Didn't seem all that quick to me either. My favorite of the time was an RD 350, sweet little bike. I just have no desire to get on a street bike anymore, now if I could have a WR426 I would definitely fit in with the geezer dirt rider crowd!
Those Yamaha RD350 would scare the crap out of Honda 750s and most Harley. They were incredible off the line.
Another dumb 2 stroke outboard question. How common is the use of roller bearing on the "big end" of the connecting rod and crank journals ? The 1960's vintage 7.5 hp Sears/Scott I rebuilt back in the 80's had them.
The only two strokes I am real familiar with is lawnmowers. The Lawnboy engines (OMC) had needle bearings throughout. My brother-in-law came over a few months ago with a LawnBoy mower in perfect shape, he said he didn't need it any more and wanted me to have it. I was so proud of that old thing. Then wifey decides to do me a favor and mow the grass for me one day. Oh well, she got about half the front yard done on that straight gas.
Ahh, the Yamaha RD 350. I owned a 250,350 and 400.
Between the three I allways had a bike to ride. The 350 was my first street bike. Damn fast. Used to eat Yamaha 650 Specials ona regular basis.
A buddy of mine (rode a 1950 panhead) and I used to ride together all the time. I allways got ragged on when we would go to the local biker bar. Mostly Harley's. Got to know the bikers well. Good bunch. I regained respect when I lined up with what was supposed to be one of the fastest Harley's at the Bar (Paradise Alley, Jackson,MS.). Fortunatley for me the race was very short. About 1/8 mile prior to hitting a redlight. Need less to say I absolutely embarrassed the hell out of the Harley "dudes".
Great, great times.
Sorry.....took a wrong turn down memory lane there for a sec. 2-strokes get lube from oil mixed in gas. Carb>reed valve>intake >crankcase>transfer ports>combustion chamber>compression>ignition>exhaust.
As stated earlier, the reed valves ensure a "one-way" direction of air/fuel flow.
No valves, camshaft, timing chain/gear.
Food for thought also. A 2-stroke can backwards. Think about it. I have done it.
DZNAM,
I don't know which was faster- the 500 or the 750, but the 750 suzi was watercooled hence it may have been slower. Don't know about the Kaw.
I wonder if there's any interest among bike makers in producing hpdi motorcycles?
Speaking of hpdi, how do they get lube in the crankcase? The fuel is injected directly into the cylinder right? chip.
quote:Originally posted by inkahoots:........
Then wifey decides to do me a favor and mow the grass for me one day. Oh well, she got about half the front yard done on that straight gas.
I can do better than that - my friend tells his wife that the car's radiator is leaking but to fill it and she can use the car. She filled it right to the top and drove off.........yep - the oil got filled to the top with water. Got about two miles out of it before the trip and engine ended.
Funny how much all us fishermen have in common.
58 AllState Moped $5. Never should have sold it.
Yamaha mini enduro
Hodaka 100
Hodaka Super Rat
Suzi TS185
Yami 250 Enduro
Suzi GT 380
Suzi IT 400
Yami RD 400
Kawasaki 500 (Thought they were Mach III's) tank slapping center cylinder burning SOB with no brakes. 0-60 4 seconds. Front forks weigh 4 oz under full acceleration at 100 Mph.
Suzi GT 750 Water Buffalo
Finally graduated to 4 strokes:
Kawasaki 900
Suzi GS 750 (3 of them) 1 with Stage 2 Yoshi kit
Honda 750 V overheating POS
2 crushed vertabrae, screw in the knee, hole in the leg (all from the dirt bikes)
Moved to FL where it's way to hot, no good roads, mountains or hills, way to many senior citizens so I took up fishing.
I think you are right Fish_on it was a Mach. III. Memories from that era are not all that clear! I also had a Hodaka Super Rat, ugliest dirt bike ever made! Didn't it have a big brother 125 called the Wombat? We really side tracked your thread jocko, I keep thinking we should have an off topic area to freely talk non-boating amongst ourselves. The off topic site states "you may not post new topics here." Any way still a great forum.
Inkahoots, you are correct it was a combat wombat if I recall. I realize I also left out a few more bikes. Yep those days are still a little vague to me as well. Never worried about breaking bones or anything else.
sorry to get off the thread topic as well. It's amazing how the engines have evolved and how much power the 2 stroke outboard generate.
I still love to see the 2 stroke bikes running at Daytona. Ah, the smell of synthetic 2 stroke in the morning. Smells like Victory!
Dumb, dumb 2 stroke question... 
