Uim 125 class...

[win-or-flip]

Im sure a lot of people became aware of this before I did, but the uim rule book states that you can run double the engine capacity for a 4 stroke in the 125 class. However, the apba rules allow for only 1.5 times the displacement for 4 strokes. I just see a problem with the gap between uim and apba with all of the World Championships that have been held in the US. I was wondering what you pro guys thought about this

Thanks,
Nick Hooten

[David Weaver]

hmmm

4 strokes belong on fishing and pleasure boats not at UIM world championships for engines running "open" on methanol. Just my opinion until I see a 4 stroke race in a competitive manner.

4 strokes also will run against one another on a large enough boat.

[propfxrO84]

I don't even want to think about the 4 strokes coming in to boat racing. They already ruined motocross (for me). Everyone said that the 2 strokes would never be pushed out in a dirt bike. Now they are gone. Hate the thoughts of no more smoke and no more of the ultimate smell.

[joejohn44]

I don't even want to think about the 4 strokes coming in to boat racing. They already ruined motocross (for me). Everyone said that the 2 strokes would never be pushed out in a dirt bike. Now they are gone. Hate the thoughts of no more smoke and no more of the ultimate smell.

Amen, Brian!!! gimme an old CR500 or KX500 ANYDAY!!! I actually miss my elsinore 250 from the late 70's!!!

[G Stillwill]

Yes and when someone goes out on a limb to produce a new racing two stroke for stock racing all you hear is whining its going to fast or its going to obslete the 27 yr old motors or this is wrong with it or that is wrong with it.

[Schiada]

Some words!

Can you say E.P.A. ???? what a bunch of B%^ S&*( !

[dwilderacer]

!

I'm with George' I will just go out and put my SIDEWINDER on my little ASR and wait for people to figure it out...

[Smitty]

4-strokes are fine and add variety; just make them use the same displacements and other limitations as the 2-strokes.

[bill van steenwyk]

For quite a number of years, the AMA (Bike racing sanctioning body) use a two to one fourmula for 2 vs 4 stroke. You could run 2 strokes against 4 strokes but the 4 stroke had a 2to1 displacement advantage i.e. 500CC 4 stroke competed against 250CC 2 stroke. This started when the 2 strokes gained performance by leaps and bounds after WWII with expansion chambers, loop charging, rotary valves, etc., etc., and were eating the 4 strokes alive on bike race tracks all across the country. I think the AMA even banned them for a while competing against the Harley's in flat track racing. Either an outright ban or handicapped them so much they just could not compete.

I can remember up to just a few years ago, even with the advances in 4 stroke technology, they could still not keep up with 2 strokes as the 2 strokes also had not stood still as far as porting, reed valve design, piped, programmable ignitions, etc.

As a previous poster pointed out, the biggest reason for 4 stokes today is the EPA here, and other agency's like them around the world. Nothing beats a modern 2 stroke for HP per cubic in in a package that is simple, and reasonably inexpensive to build and maintain.

If you look at the Bombardier products, they (2 strokes) can be made "clean" also, but all the small engine mfgr's have already converted so would be very expensive to go back the other way, and don't discount the tree huggers either. Withe modern design and electronic engine management techniques, 2 strokes can still be the best way to go if manufacturers had the will and money to do the research and build them.

[Steve77t]

you hit the nail on the head

For quite a number of years, the AMA (Bike racing sanctioning body) use a two to one fourmula for 2 vs 4 stroke. You could run 2 strokes against 4 strokes but the 4 stroke had a 2to1 displacement advantage i.e. 500CC 4 stroke competed against 250CC 2 stroke. This started when the 2 strokes gained performance by leaps and bounds after WWII with expansion chambers, loop charging, rotary valves, etc., etc., and were eating the 4 strokes alive on bike race tracks all across the country. I think the AMA even banned them for a while competing against the Harley's in flat track racing. Either an outright ban or handicapped them so much they just could not compete.

I can remember up to just a few years ago, even with the advances in 4 stroke technology, they could still not keep up with 2 strokes as the 2 strokes also had not stood still as far as porting, reed valve design, piped, programmable ignitions, etc.

As a previous poster pointed out, the biggest reason for 4 stokes today is the EPA here, and other agency's like them around the world. Nothing beats a modern 2 stroke for HP per cubic in in a package that is simple, and reasonably inexpensive to build and maintain.

If you look at the Bombardier products, they (2 strokes) can be made "clean" also, but all the small engine mfgr's have already converted so would be very expensive to go back the other way, and don't discount the tree huggers either. Withe modern design and electronic engine management techniques, 2 strokes can still be the best way to go if manufacturers had the will and money to do the research and build them.

Yup Bill, you are correct on that, 2 cycle ban has been going on since the late 80's and it is world wide, Bearing manufactures for 2 strokes like FAG and Ina have stopped making the common bearing for connecting rods as manufactures went to other motor designs for Bunny Hugger standards. What we all must realize is this is coming and there is little we can do about this. The Stock guy's will soon be racing the Yamato 4 stroke as their current motor ha been out of production for some time now. I have drawn and base motor for capsule boats using a 4 stroke and i think it will be more than competitive. You will see soon I think a 125 4 stroke from one of the race motor builders we have today as they too know what is ahead for 2 strokes. Steve

[PRO-MOTIONRACING]

125 cc RC149
Power output is 38 bhp at 20,500 rpm
http://www.vf750fd.com/Joep_Kortekaas/1966.html#RC149

[Steve77t]

125 cc RC149
Power output is 38 bhp at 20,500 rpm
http://www.vf750fd.com/Joep_Kortekaas/1966.html#RC149

Ys but rules only permit 1 cylinder not multiples, Steve

[bill van steenwyk]

125 cc RC149
Power output is 38 bhp at 20,500 rpm
http://www.vf750fd.com/Joep_Kortekaas/1966.html#RC149

Current single cylinder 125CC engines from VRP/GRM probably exceed this by 20HP or so, though the 4 stroke technology you reference is 30+ years old.

If I had my druthers, I would rather continue to race the modern 2 stroke design, simple, lower cost, more HP at lower peak RPM, and all the other pluses for it versus the 4 stroke, than have to put up with small valves the size of a dime or smaller,in multiples, hairspring type valve springs and all the associated valve train that goes with it, and the cubic dollars to keep up with parts replacement and repair. The only thing I see as a saviour for two strokes in boat racing is the EPA exemption like the Bass brothers got for the Tohotsu in Stock.

If you think racing is expensive now, just wait till you have to have a 18-20 thousand RPM 4 stroke to keep up and be competitive. And as Steve pointed out, these engineering exercises by Honda in the previous post were multi-cylinder factory engines not available to just anyone. I seem to remember a 6 cyl 250?? What a parts and money nightmare that must have been.

[Smitty]

Two-strokes ran into a problem in grand prix bike racing when they made so much power . . . smooth, turbine-like power . . . that the back tire wouldn't stay hooked-up to the track. Tuners were forced to go to a special crankshaft that made for an odd "droner" firing order, where instead of (a four cylinder) engine going "bang . . bang . . bang . . bang," the new firing order was something like "ba-ba-ba-bang . . . . . . . . . . ba-ba-ba-bang," etc.. This had an effect on traction that was like anti-lock brakes in reverse; the power strokes would break the tire loose, and the long dead spot in the sequence would let the tire hook up again. Four-strokes, by firing every other revolution, tended to have a traction advantage already, and Ducati and especially Harley 4-strokes had a huge traction advantage with their "Ba-Bang . . . . . . . . . . Ba-Bang . . . . . . . . . " power output.

(I don't know so much, I just read about all this over the years)

None of the above applies to boats. A taildragger outboard keeps the prop hooked up all the time, and can use any power you can put to the propshaft, without any dopey firing orders. A smooth, 2-stroke power delivery is also less likely to break shafts, gears, shearpins, and blades.

[VRP engines]

Interesting discussion.
The new 125 engine from VRP and GRM have abouth 47 HP.
This is possible also with a 4 stroke engine 250 cc .
The problem is than the 2 stroke have the possibilite have a good torque at low RPM only with a simple telescopic pipes, with a 4 stroke is not possible.
But the first problem is : who pay 10.000 dollars for a 250 sigle cylinder engine?
Other problem is at displacement control than disasseble engine for control and after riassenble cost abouth 3 hour of time and 100 dollars for the special gasket one time use.
Best Regards

Carlo Verona
VRP ENGINEERING