'Blueprinting' a Jetex Carb

[Doom Patrol]

Oi, I do on a 200 engine. It's a Spaco too and it goes fairish. It's quick and I'm told I've had 60 MPH out of it. That's plenty fast enough for me.

There's been a lot of fingers pointed at crap fuel as a cause of engine problems too. These days it seems to vary from garage to garage.

[dennis]

Fuel,correct me if i'm wrong,

1-unleaded burns hotter than the old 4 star, (googled it)
2-you need alot more heat to burn oil (2 stroke oil is oil) chuck some on a fire or poor some on the ground and chuck a match in it and see if it burns straight away.
3-you get less miles to the gallon on unleaded, older members might remember when it all changed,
4- our engines were designed to run on very low grade petrol,so what do we all do, we put in the highest grade possible.
5 modern fuel is full off s**t additives.
6-not that it makes a lot of difference the old fuel had lead in it, who knows,
oh, and one more,they change the fuel mix winter/summer, it's not only diesel they change for winter/summer.(googled it).
I reckon we're lucky they run at all with what ever carb we fit.

[dennis]

For got to copy this
http://auto.howstuffworks.com/fuel-effi ... -fuel1.htm

bet you didn't know this.

[nelson pk]

Fuel,correct me if i'm wrong,

1-unleaded burns hotter than the old 4 star, (googled it)

Very true but this is due to the octane rating of the fuel. Normal unleaded has an octane rating of 95. Super unleaded has an octane rating of 97-99 (depending on brand).
The higher the octane rating the cooler it will burn that is why if you use a high compression head you must use super.
I personally would advise to use super on any machine as i have been advised this myself by a very well respected tuner simply due to the octane rating and i for one have had no issues.

Granted fuel is not getting better but worse so it makes sense to use a higher octane rating and for a road bike put more safety margin in on jetting and timing to combat the fuel issue.

That is also why (in my opinion) a more adjustable carb (PHBL/PHBH) is better because you can adjust to suit your throttle position that you ride at much more accurately.
I certainly prefer a carb with a conical needle rather than just relying on an atomiser and main jet.

[dennis]

Just been reading on google, apparently the higher the compression,the higher octane is better,i stand corrected on that one, was still low octanes in the 1950s and early 60s
4 star was rated at about 95/100 mid 60s on.