Vintage Expansion Chambers

[Walt Zahn]

Steve
Very interesting reading. I am just getting into this karting/2 cycle enigne hobby and am curious as to what things are and how they work on a detail level. When you say that some of the smaller expansion chambers "killed the engines" are you referring to some sound effect that causes predetonation and higher engine temperatures in 2 cycles ? The engine that has the expansion chamber I showed earlier came to us with a small hole burned down the side of the piston terminating at broken rings. It is a WB580 and the GEM header and gasket seem too small for the WB's ports. I am afraid if we put it all back the way it came to us, after I rebuild the engine, we could be facing this damage again (excess heat + expansion chamer?). What do you advise? I want to restore the Simplex for my son, but I don't want to have to find another piston 2 months later. Should we mess with the potential extra horsepower or just go for a simpler exhaust cover/pipe?
Walt

[Ronald Cubel]

Walt, Simplex with 580 about 1959-60 They did not run expansion chambers. The one you have on there was probibley added later and who knows what it was designed for I bet not a 580 west bend. If you what a 1966 Simplex /wb580 it will be hard to find and info on it being by then they all where in the back yard with a 8yr old running the heck out of it.

If you are wanting to really restore this Kart then do the research first. If not enjoy the chamber.

Ron Cubel

[Rob Voska]

WB is a loop scavenged engine. Mac's and all foreign engines are scavenged engines. Please don't ask me to describe it. Get a book adn read about it.

[louie figone]

Early West Bends (510,580,700 etc) are cross scavenged, 610/820 are loop scavenged. Put a can muffler (gem,palimi,reed etc) on it and have fun and it will be period correct.

Louie

[Rob Voska]

Thanks Louie My head knows what my fingers can't say......

[louie figone]

Rob, I already passed that age a long time ago, I knew what you meant, I do it all the time. Glad I could help.

Louie

[Jeff Campbell]

for those wanting to read some of the "vintage expert" knowledge, here are some classic Gordon Jennings articles written back in the early 70's...(these are acrobat files)

http://www.bridgestonemotorcycle.com/do ... eally6.pdf

oh my, look someone scanned the entire "Two Stroke Tuners handbook" (this sells for big bucks if you can find a copy)...its over 7MB in size, a biggie file:
http://www.bridgestonemotorcycle.com/do ... ndbook.pdf


...you can pick through these cool tuning articles that are in this folder...
http://www.bridgestonemotorcycle.com/documents/

theres a bunch of good research in there, things like the effect of crankcase volume on engines using expansion chambers, etc...

Jeff

[Jeff Campbell]

Steve
Very interesting reading. I am just getting into this karting/2 cycle enigne hobby and am curious as to what things are and how they work on a detail level. When you say that some of the smaller expansion chambers "killed the engines" are you referring to some sound effect that causes predetonation and higher engine temperatures in 2 cycles ? The engine that has the expansion chamber I showed earlier came to us with a small hole burned down the side of the piston terminating at broken rings. It is a WB580 and the GEM header and gasket seem too small for the WB's ports. I am afraid if we put it all back the way it came to us, after I rebuild the engine, we could be facing this damage again (excess heat + expansion chamer?). What do you advise? I want to restore the Simplex for my son, but I don't want to have to find another piston 2 months later. Should we mess with the potential extra horsepower or just go for a simpler exhaust cover/pipe?
Walt

Walt,
What I believe Steve meant by "killed" was that those early pipes were not optimized and made the engine run hot. Look at the drawings I posted at the beginning of this thread. The last drawing shown, is a more optimized pipe in a vintage style, note the diameter is 4.5" (vs typical 3.5" diameter) and the stinger is a 1" ID, while the typical vintage pipes had approximately 7/8" ID / 1" OD tubes for stingers. What Steve is saying, is that, a pipe with more volume and a larger stinger size can run better than the older style pipes. Yes, some can say, a vintage pipe is vintage, so we should run it exactly as it was, but then if a more optimized pipe with vintage design intent allows the motor to run cooler and last longer, then maybe it is a good idea.

Jeff

[Ronald Cubel]

Jeff, ?????? expansion chambers on 580's. Why not oil clutch it too??? Were are you coming from???? Ron

[Michael Burke]

This pipe thread has some interesting thoughts. I personally choose to run engines, pipes, mufflers, manifolds etc that are close to the year of the karts original build year. We all own our karts and are free to modify them as we see fit, but I thought the intent of vintage and especially REAR is to run them like they were when built or very close to that time. Unfortunately that usually means using components that were later found to be less than optimum. Pipes evolved to work better, but most of the better improvents came after the years that define a vintage kart. I don't remember seeing pipes on karts here in So Cal until 1967. That puts them out of the period correct category for many karts if the karts are being restored to represent a time close to their build year. Until the mid 70's I don't remember seeing pipes that had a larger volume. I realize the later pipes could be built to look more like an older pipe, but then we're getting into improving things to gain a performance advantage rather than to be authentic. Even the hot running pipes are pretty safe if the carbs are left relatively rich. Many of the current vintage kart crowd are aware of how to improve the old karts to a level not seen near the karts build year. Some do that and others choose to retain the performance ( or lack of) of the karts when they were being raced. I would hope that the majority will keep their karts closer to how they ran when new rather than to steadily improve them with better pipes, clutches and brakes as some are doing. If that trend continues, we'll soon have a lot of karts being used that don't represent a period appropiate kart. There are lots of later karts available that will give the handling and speed increases that some want. In the end these karts are ours to do with as we please and I acknowledge an owners right to modify them as much as they want even if it means running them in ways not seen in the old days. To me vintage means living with whatever problems that existed when the karts were first built. I hope that most of the vintage karters will also feel that way.

Michael