[what do you prefer]two stroke vs four stroke

[Hoolander2]

I would urge you, Rianna, and everybody to go to a road race sometime.  Preferably in Europe or Asia! Ha!  Anywhere close is good though.  He's in the true racing position there --  notice he's not leaning on the handlebars like you see so many crotch rocket riders doing.  I think Mr. Roberts was one road racer who didn't like wearing the big racing boots.  Notice his footwear in the picture.  He was the best there ever was and probably ever will be.  Of course there were and are plenty of other great riders too.

OW-31 was the engine designation.  The road race bike was called a TZ-750

In the 1970's and early 80's, if you showed up at the track with anything but a 2 stroke, you could count on last place. Once the OW-31 came out, you could forget winning on anything else.  Harley's lobbying and such eventually got the rules changed in their favor and the two strokes were history.  Watching a road race in the USA after that was never the same. 

[Rianna]

I would thoroughly enjoy going to one. I doubt I will ever make it to Europe or Asia. I see what you mean about not leaning on the handlebars. His posture is set properly to take care of business. I'm sure it takes practice and skill to perform like he did. And he sure had some beautiful bikes!

It's a shame that when politicians get involved things get ruined like this. I didn't know the story about how HD was behind it until now. I can understand now the anger it stirred up. Thank you, Hoolander for sharing the pics!!

Oh, and I like them boots!

[Hoolander2]

Yep.  I'm sorry I can't credit the photos.  I just snatched em off the web.  I should probably take em down shortly once the regulars have had a chance to view. 

[axy]

Weed eaters, motorized hedge trimmers = 2 stroke.  Model airplanes too.  Those have something called a "glow plug" instead of spark plug.  It's on all the time -- no need for timing at all.    Small ones will fit easily in your pocket.  Fuel tank the size of an aspirin bottle.

I think you got something wrong.

Glow plugs are not in engines instead of spark plugs and do not work "all the time".

Glow plugs are used in diesel engines to pre-heat the area of the engine where diesel is injected when the engine is cold in order to avoid thermal diffusion. They are typically turned off after a few seconds in newer and 10-15 seconds in very old diesel engines.

They are not used in gasoline engines and especially not in very small displacement engines.

[axy]

In the 1970's and early 80's, if you showed up at the track with anything but a 2 stroke, you could count on last place. Once the OW-31 came out, you could forget winning on anything else.  Harley's lobbying and such eventually got the rules changed in their favor and the two strokes were history.  Watching a road race in the USA after that was never the same.  

I think that this bike had around 90 hp, very low by the current standards.
Times have greatly changed.

There are two world famous race tracks near my town, both 10 kms from the very center. World moto GP was driven on them too - from WWII to 70s on the first and throughout 70s and 80s on the second.

This is Preluk:



This is Grobnik:

http://www.grobnik.hr/History.en.html

I spent the time between 1993 and 2000 going almost daily towards Preluk and driving during the night, learning to understeer, oversteer, take corners along the proper line etc... but with my car, not bike.

[Rianna]

My, My! You have EVERYTHING within 10kms of your house, axy! So they still race with 2t engines in your country then. axy?

[axy]

My, My! You have EVERYTHING within 10kms of your house, axy! So they still race with 2t engines in your country then. axy?

I am not that much into moto championships.
However, I know that currently, in the world moto championship there are the following classes:

1. MotoGP, max. 800 cc, 2 stroke is not allowed
2. Moto2, all race with 600 cc 4 stroke Honda engines
3. Moto 125, 80-125 cc, 2 stroke is allowed (in fact, I think ALL are 2 stroke)

[Hoolander2]

These small 2 stroke model airplane engines I speak of do indeed run on glow plugs only.  You connect a battery to it while cranking.  Once the engine starts, disconnect the battery and the glow plug continues to glow due to being a hot spot in the combustion chamber. The model is then launched and flys with no engine electronics whatsoever. The engine runs till out of gas.   I used to fly them when I was a boy.

[Hoolander2]

Compare:
 
the              1974 TZ700                  and the             2000 R7 Superbike 
Wheelbase     56.28"                                                56" 
Weight          345 lbs                                               356 lbs 
Front Tire      3.25 x 18                                            3.5 x 17
Rear Tire       3.5 x 18                                              6 x 17
Horsepower   145                                                    173


from: Superbike Planet.com

Also: http://www.motorcycleshopper.com/articles/tz-750.htm

[axy]

Compare:
 
the              1974 TZ700                  and the             2000 R7 Superbike 
Wheelbase     56.28"                                                56" 
Weight          345 lbs                                               356 lbs 
Front Tire      3.25 x 18                                            3.5 x 17
Rear Tire       3.5 x 18                                              6 x 17
Horsepower   145                                                    173


from: Superbike Planet.com

Also: http://www.motorcycleshopper.com/articles/tz-750.htm

To compare 2 stroke and 4 stroke engines, you should at least double the displacement of 4 stroke engine.

[axy]

These small 2 stroke model airplane engines I speak of do indeed run on glow plugs only.  You connect a battery to it while cranking.  Once the engine starts, disconnect the battery and the glow plug continues to glow due to being a hot spot in the combustion chamber. The model is then launched and flys with no engine electronics whatsoever. The engine runs till out of gas.   I used to fly them when I was a boy.

I've checked and you are right, these plugs for RC models are called glow plugs, even though this term is not exactly correct.
However, "real" glow plugs are used in diesel engines as I have explained.

[Hoolander2]

Well, this has been an interesting diversion of a discussion.    I would like to say that I do like the feeling of a dependable 4 stroke under me in my daily riding.  But I wouldn't mind a big FUN 2 stroke to play on. 

I got a few details about the big Yamaha wrong.  OW-31 was the FACTORY works racers.  TZ-750 was the production model available for sale to independant racers. To a layperson like me they appear much the same but surely were not.  Both were dominant over just about everything else for about 9 years, though.

Also, I oversimplify by accusing only Harley Davidson of affecting rules changes. Other factors were probably involved.  One being that all the bikes (even non-Yamaha) were getting just too fast for the tracks.  Same as NASCARs of the same era which were getting above 220 mph on the big tracks.  NASCAR knew they would have to do something or there would start to be massive deadly crashes in the future so they put in severe limits on engines.  Perhaps the cycle racing sanctioning bodies thought the same about the future of unrestricted 2 strokes.  Maybe I'll research all this in detail someday.   

[Rianna]

Well I have thoroughly enjoyed this whole thread, including the diversions, and have learned a few things too. I do think I would enjoy the 2 stroke and maybe I will have the chance to find out someday.

Yes, there probably were many factors involved, but it's still a shame. If nothing else on the track could touch them for 9 years you know they had something good going on. It would have been nice if there was a better or different solution put in place.