ESE's works engine tuner

[Buckets4Me]

Some rotary valve covers from vintage go-karts. The valves are 95 or 108mm and some have 34mm carbs.

I think the port area is no bigger than the carb.

Gives some idea of the port shape the fast rotary valve karts were using back in the day.

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[speedpro]

Gives a good idea of the port shape fast AC50s used as well

[TZ350]

Suzuki GP100/125 Covers and Rotary Valves.

Std. Suzuki GP100 Inlet Opens 135 BTDC Closes 45 ATDC
Ex Opens 94 ATDC Transfers Open 123, 125, 126 ATDC.

Std. Suzuki GP125 Inlet Opens 145 BTDC Closes 55 ATDC
Ex Opens 91 ATDC Transfers Open 122, 122.5, 123 ATDC.

The round Suzuki port is the same size as the carb.

I did try to make the port more square’ish like the cart’s do and the books say too, but I found I wound up with a port much larger than the carb and it did not work well for me.

If I could run a bigger carb (Bigger than 24mm) then I could square the port up and match the port area to the carb.

For now I just clean and match the port without changing its shape.

The early Suzuki racers had round ports but there are later Suzukis with the square ports like TS90's and RG500's and my Kawasaki F81M racer also has the square port shape. They all seem to have the port area the same as the carb.

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[F5 Dave]

Well you could make a 100 & use any size carb, but if stuck with a 24 then no point making something pass through a venture & then open it up again only to have it pass through another restriction & a round tube flows best all things being equal.

However as with dirty nasty 4 strokes the entry to the valves is not simple, however they stuck a dirty great wedge poppet in the way so it serves them right. But what I am saying is look at how best to curve the gas after the valve so it flows over the crank. Perhaps it is best to transition the carb side from round to square at the top on the valve side, but only 2/3 height, ie: fill the bottom. So would that match the other side better is the question?

[TZ350]

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As its a 125 air cooled 2-stroke we are restricted to a 24mm carb.

F5 I like your idea of squaring up the top portion of the inlet port and raising the floor so the area of the port remains the same and the incoming charge has an easier time flowing over the crank and into the crankcase.

We have been putting a 45 degree chamfer on the inlet side crank wheel to help the incoming charge flow up and over the crank on its way into the crankcase.

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[Buckets4Me]

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Part 1

The Art of Squishing Things Till They Give (Power), Part 1

An excerp. By Dale Alexander. Its worth a read.

"My own experience with road racing was just beginning to develop. I was soon to observe that the RD would run pretty strong in 6th gear out of one corner, only to be reduced to 5th gear and finally 4th gear by the end of the race. The engine was consistently losing power as the race progressed. Something was overheating, BUT WHAT? Suzuki had Ram-Air heads on their 380 and 550 triples, after-market water-cooled heads were available but even the factory water pumpers were having a like problem so what was the point?

To make matters really confusing, all manner of porting ideas were being tried, but everyone was going pretty much the same speed or slower. So it would seem the whatever the problem was, it was related to heat, the development of power and the amount of time that the power was being used."

........................So, What IS Going On ?

The rest can be read here:- http://www.aircooled-rd.com/default....ge=squish1.htm
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[Buckets4Me]

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Part2

The Art of Squishing Things Till They Give (Power), Part 2

By Dale Alexander. More good reading.

Now the head is centered. Use a 1/8" "gun drill" which is simply a very long drill bit and drill down between the fins through the head and into the barrel. Don't go more than about 5-7mm, you just need enough to hold a dowel pin.

The rest is here:- http://www.aircooled-rd.com/default....ge=squish2.htm

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[Buckets4Me]

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Part3

The Art of Squishing Things Till They Give (Power), Part 3

By Dale Alexander

"Well, we've got a motor now that runs better than most others out there and all that we have done is close up the squish clearances to a proper value and eliminate a bothersome head gasket leak. Is there anything else that can be done? Yes, there is an even easier method of sealing the head."

And also the part "A Better Way To Cook " talks about ceramic coating the piston.

It all can be read here:- http://www.aircooled-rd.com/default....ge=squish3.htm

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[Buckets4Me]

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Rotary valve 50cc Suzuki triple racer with the round inlet port shape.

I think the GP100/125 was based on the racers from this era., Late 60's.

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[TZ350]

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By Dale Alexander "A Better Way To Cook " talks about ceramic coating the piston.

It can be read here:- http://www.aircooled-rd.com/default....ge=squish3.htm

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Thanks Buckets4Me they are great pictures, its been great to see how the inlet port has been arranged by factory racers and carts. The artical by Dale Alexander and especialy the bit on ceramic coating the piston crown, thats very interesting, gets me thinking again!

We are also looking at the exhaust port tract and the heat uptake in this area and have a few ideas.

There is a niggling thought in the back of my mind, that if copper is so good why has'nt the factory racers used it before?

Are we going somewhere new or is it a dead end that the factory has explored and pulled out of? Could it be possible that they got in their own rut and over looked it? it;s a bit sus.

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[Chambers]

Where can I get a 14 speed gearbox for my bucket
The thermal issue is the secret where the power is (or not) and it will be interesting if the copper helps. Have you got a dyna?

[Yow Ling]

Where can I get a 14 speed gearbox for my bucket
The thermal issue is the secret where the power is (or not) and it will be interesting if the copper helps. Have you got a dyna?

roadranger will have one for you , might only be a 12 speed though

[Buddha#81:Me]

roadranger will have one for you , might only be a 12 speed though

Two speed diff would take care of that.

[Buckets4Me]

As cooling for the air cooled 125's is the power limiting issue.

An excerpt, from an aero modler artical that talks about ducted cooling and aero engine cooling.

"It goes like this. Blowing cold air at high speed over an engine is a lousy way to cool it. Never mind that that is standard practise, it is still lousy. The heat transfer is poor, and the drag is very high.The correct way to cool is to blow low speed, high pressure air over the fins."

That chamber formed by the upper cowling is called a plenum chamber: it has a wonderful property. Being of large volume, the air that rushes in through the intake holes is permitted to expand to fill the volume of the plenum chamber. Now the magic part is that when air expands in the fashion, its speed falls and its pressure increases! Wonderful, just what we wanted, low speed air at high pressure.

how this is done can be read here:- http://www.supercoolprops.com/articl...ed_cooling.php


More on cooling airplane engines:- http://www.supercoolprops.com/articles/gwhite.php

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[TZ350]

Thanks Buckets4Me for all your very interesting input.

We have a problem with the copper combustion chamber.

Heat from combustion reaches the combustion chamber surface in two ways, radiation and conduction. The boundry layer reduces conduction and heat take up from radiation can be minimised by having a polished surface with a low emissivity value.

Well we have discovered one of the problems with using polished copper in the combustion chamber. That is, it discolours when heated and goes a very dark brown/black where as polished aluminium retains its polish and reflective properties after normal heating.

Looking at the emissivity charts we can see that coloured copper has a high emissivity and will take up radiated heat in much larger quantities than polished aluminium.

Now we have a problem, there is not much point in having a copper combustion chamber that sheds heat twice as fast as aluminium if it takes up heat five times faster.

We think this could be a real problem and we are looking at gold plating the copper combustion chamber to try and retain its reflective properties.
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