Gyro Exhaust Mod ---Will this work?

[motormike]

Looking for some opinions about my logic regarding modification of the exhaust on my '85 Gyro s............the go-kart guys running Yamaha 100's use a CAN-type muffler in spec-class karts........how about a home-brew can to 1/2 the size of a 100cc can=works on 50cc...I"ve looked at the data on this subject, thanx to Bear45/70 for posting that link.....I'm not the mathmetician I once was, so any thoughts, suggestions about the feasibility of this theory.??........... ,.......................... ...... subliminal

[Pierce ramsay]

Yes and no to my understanding the exhaust will need a expanchion chamber because theses small engines like atleast some back pressure, adding thins muffler to the end of a stock pipe or aftermarket performance pipe will most likely work and possible well as long as it isn't restricting exhaust flow........ All I'm saying is don't straight pipe and put it on the end and dont run without expansion chaber.... Otherwise best of luck!

[motormike]

This "can" is the only exhaust component .......no pipe, no expansion chamber......the can IS the pipe, as used on Yamaha 100 karts................................................................ Look at the size of this stock muffler....it's huge....and is heavy.....you can see that the pipe wraps forward under the trans, then has a flange just in front of the left rear wheel....that's where the muffler bolts on and where I would like to start the modification..........

[motormike]

Spent some time trying to find out what the internals of the can look like......no success......I've seen these cans being run at kart races and they are no bigger than a 12 oz. coffee can......anybody have input?.....

[bakaracer]

there has to be a certain tune length for the pipe to work with the cylinder and the power that your looking for. if you notice your pipe, it starts off small then gets larger. the first section is the header pipe. that has to be a certain size diameter wise and length. it then tapers a certain angle and diameter. the kt100 kart engine exhaust is the same way.that piece you posted is the baffle section for the kt100 chamber pipes. you need to find out first what diameter is the exhaust port on your cylinder, then whats the exhaust port duration(how long it stays open). then find a pipe or make one that will work with those numbers. read the graham bell 2 stroke tuning book or the gordon jennings one. you can find someone that has it online in pdf form for you to read. that will help you if your planing on building your own exhaust on where to start and what to do.

[Pierce ramsay]

I agree with bakaracer if you can find the dimensions out and fine one to fit it might work otherwise I'd say you would get more sound than power you can try it if the exhaust intakes are the same size and take a short test, anything under 10min shouldn't hut your bore. If u have lost power or doesn't sound good stop and replace with stock pipe

[motormike]

that piece you posted is the baffle section for the kt100 chamber pipes.

Thanx for the response bakaracer, and Pierce........a conversation with Steve at Comet Karts has confirmed that the "can" is INDEED the complete exhaust pipe and not a baffle section for a pipe......he described the inner components of the can and my next call will be the manufacturer, RLV.....they may already make some exhaust for 50cc, I hope................. ............I've got the port timing numbers, but not the port dimension.....exhaust is OPEN @ 73.5 degrees BBDC and CLOSED @ 73.5 ABDC......which I think is telling me that duration is 147 degrees.................

[bakaracer]

yeah with a duration that low, you looking for a pipe that makes power at around 6k. I doubt the rlv makes a pipe that makes power that low. most of the 2 stroke kart engines makes its power above 11k and rev up to 17k. I'm sure they can make one, you just need to give the port diameter, length from the piston to the edge of the flange and the port duration. then you need to tell them where you need the power the most.you might have to raise the cylinder to up the durations and deck the cylinder.that will give you more power and higher rpm's.

[motormike]

Good point about rpm/hp.... ...had a conversation with the tech at RLV, name Rod.... He said that the volume of the can had little to do with the cc size of the engine,.....more critical in this formula was the number and size of the holes, both the inside "baffle" and the outer can.....he also said that the W.K.A. [world karting assn.] rulebook will have detailed description of specs for these cans, maybe a schematic.......couldn't find a pdf anywhere, but local kart/machine shop probably has it on paper................................................. ....... ...
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I've come to a decision... .....I will purchase from Comet Karts an RLV Yamaha Super Can,[cost=$82] then mod the flange for fit to the gyro headpipe,......that will take some thinking once I get the can.....finally, "tune" the can for optimal operation, if that's possible......I've got a couple of "aces" here to help with all the mods and tuning.......old skool racers Charlie Southgate and Ray Dey.......even if the thing fails miserably, I will have in my posession an example from which to copy, re-design, whatever it takes..........I am, if nothing else, determined to do something that has not yet been done

[bakaracer]

keep mind to that a kart engine flows way more than your gyro engine which will make a difference also.if you can get a chamber that was ment for a 60cc engine, that will put you really close to what your looking for. using a 100cc chamber is going to make tuning very hard and loose lots of torque and power.

[bakaracer]

here is a free download for 2 stroke exhaust design. http://www.iwt.com.au/mota.htm

[motormike]

They offer an 80cc can.....nothing smaller.....read quite a bit from Gordon Jennings.....I'll take a look at the link, thanx........... ..........I really think that buying a can to start with will end up being a good move......

[motormike]

here is a free download for 2 stroke exhaust design. http://www.iwt.com.au/mota.htm

I read some on the home page, but free download for expansion chamber design was a no-go..........

[bakaracer]

They offer an 80cc can.....nothing smaller.....read quite a bit from Gordon Jennings.....I'll take a look at the link, thanx........... ..........I really think that buying a can to start with will end up being a good move......

you can find some cheap chamber pipes on ebay for pocket bikes and the 49cc scooters(razor scooter style).

[motormike]

I dont like the idea of a chamber pipe sticking out the back like a stinger......you know how it is,.....you race......seems like an accident waiting to happen.....the whole can idea was to keep it all compact.......I figure if it works for 100cc, it will work for 50cc..............