70cc Athena /17.5mm Delorto jetting help

[ex-racer#2]

Just installed a 70cc alum air cooled Athena cylinder on my Yamaha BW (verticle). I have a 17.5 DelOrto. What is the jetting people are using on similar setups?

If you are using a different sized carb mention the carb and the jetting for that so I can make some estimations.

I am running oil injection and a modified stock airbox with mallossi red sponge filter. This is a street not race set-up.

Thanks in advance.

 

[MONZAV8]

Jetting is going to vary for every bike, even when they have a very similar setup. I would recommend testing it first with the jet the carb came with to set a baseline. Most likely it will be lean, so then you can start adjusting upwards.

 

[ex-racer#2]

Jetting is going to vary for every bike, even when they have a very similar setup. I would recommend testing it first with the jet the carb came with to set a baseline. Most likely it will be lean, so then you can start adjusting upwards.

Thanks for stating the obvious. If you read my post (did you?) you would have realized I was looking for input so I could devise a rough baseline to work from. If everyone with similar setups says you need a 120 main and I am running a 100 it might be too late to realize I am lean. If they run that 120 with an open carb that is different than running with an airbox. But to say these things is also stating the obvious.

Just for sake of arguement with Captain Obvious the carb came with a 72 main. Lean even with the stock 50cc Yamaha bore. Possibly fine for a stock bore with stock airbox and stock pipe.

Contrary to your methodology the proper way to jet is to go rich and then come down. Your methodology of test and if it doesn't sieze, read the plug and keep going until you sieze or get it right could be a little expensive. If I can get rough estimates of what other people use I can get an idea of how high I need to jet before I come down.

I am sure someone is using a 70cc setup and some sort of carb so any input is appreciated.
Thanks in advance.

 

[narx]

Just installed a 70cc alum air cooled Athena cylinder on my Yamaha BW (verticle). I have a 17.5 DelOrto. What is the jetting people are using on similar setups?

If you are using a different sized carb mention the carb and the jetting for that so I can make some estimations.

I am running oil injection and a modified stock airbox with mallossi red sponge filter. This is a street not race set-up.

Thanks in advance.

Depends how you modified the airbox, I'd say you should be fine with 70-80 mainjet, 90 should be ok to start with.

I was running modified stock airbox (total airbox inlet diameter was 26mm) and due plus/giannelli shot setup with 21mm carb with 76 mainjet. I am sure it wasn't lean because i did more than 10 000 km with it.
It was horizontal minarelli engine.

 

[ex-racer#2]

Depends how you modified the airbox, I'd say you should be fine with 70-80 mainjet, 90 should be ok to start with.

I was running modified stock airbox (total airbox inlet diameter was 26mm) and due plus/giannelli shot setup with 21mm carb with 76 mainjet. I am sure it wasn't lean because i did more than 10 000 km with it.
It was horizontal minarelli engine.

Thanks for the help. I did my second heat cycle last night and after it cooled I started jetting it from 100 on down. I am at 95 or 93 right now with the needle in the mid clip position. Raising the needle 1 clip was too rich so I went back to mid for now.

My needle is raised one clip from my 50cc setup and I ran 80 main with that motor so I guess I will be close to 80-85 based on your setup and the early indicators I am getting. My inlet diameter is probobly close to yours as well. It seems to flow lots and keeps noise respectable. I really want to keep the smaller carb as it gives wicked throttle response and picks up well off of corners and in traffic.

 

[Eoin70]

i mean for example i run the stage 6 oval exh port cylinder with 17,5mm and Yasuni r and i use an 84 main jet with Std airbox ,its similar to your setup

 

[ex-racer#2]

i mean for example i run the stage 6 oval exh port cylinder with 17,5mm and Yasuni r and i use an 84 main jet with Std airbox ,its similar to your setup

Excellent! I am glad I am not flying blind on this. Here in Canada there is not the same numbers of scoots as Europe so getting info for comparison can be tough. It is pretty much find the parts and then you are on your own. Local tuners are pretty much non existant. Parts availability is getting slightly better but there is really only one source unless you order online from out of country.