sot, help: tuning a/f on a AF18

[patallen]

Hi, so i finaly made that project for my son, i builded him a scalled jeep using a AF18 motor. its not all done yet but i am close.
It all runs ok but i feel that it could need some better tuning.
It uses a custom exhaust with a longer pipe, and an open foam air filter, for space and technical reason so no need to yiel at me to use the oem air box or wastover.

How can i tell "scientificaly" the proper a/f mixture on thoses motors ? i am used to cars and have a wide band 02 meter that is semi portable but i think it wont work good on a 2 stroke motor (??).

Motor is freshly rebuilded, new cylinder, new piston, new coil, bearings,...

It realy runs great but would like advices.

Thanks.

[Wheelman-111]

Greetings:

Wow!! Now why couldn't my Dad build me stuff like that?

I don't know much about no Stoichiometric Science, but a good guide to use is a cylinder head temperature gauge. As a rule, you shoot for around 350 degrees and you're getting all it can give without blowing up.

You should also be aware that 2-strokes are exquisitely sensitive to pipe diameter and length. The setup with the remote muffler won't allow much pressure-wave charging unless there's a cone-shaped reflector before the long pipe under there. If you can get your hands - or at least a look - at a proven performance chamber, you'll have some idea how that needs to look. I'm not sure the long ride to the muffler and tailpipe will affect anything after the chamber section, as long as the pipe diameter imposes no significant restriction.

[Dio89Elite]

Very cool!

[patallen]

thanks for the reply.
i am well aware of the tune pipe designs and how they works, there is just not enough space up front to fit such pipe so i decided to leave it alone.

how does that temp stuff work, you run WOT and then check the temp ?
the thing is, if i want to do that i will need to go drive the thing in the street, i thought there would be another method...

isnt there a known way to assume it may needs a bit more fuel since i use a open foam filter ? but of course the pipe design doesnt help there...

is there jet kits available for theses motors ?

EDIT: what/where can i see/get one of theses head temp kit ?

thanks

[Bear45-70]

http://www.ebay.com/itm/200773829388?ss ... 1438.l2649

[patallen]

Hi, project goes very well. It all runs and i want to make it run better.

i want to improve part throtle response.

I bought the TTO 14mm meter.

I have a stock AF18E with #75 jet (factory), but longer exhaust pipe and open foam filter.

What temp should i look for that i would assume "normal" ?
I have some bigger jets (78, 80, 82, 85, 90)

The thing revs quite a lot imho and pulls very good.

Attached picture, my son paiting himself his new toy. He his MAD about this toy (which is not realy a toy for him but for me...lol...)

Thanks.