As Stephen says they are easy to tune but they have no idle circuit . I have one on a raptor and the carb makes power but it's ridabilty is not so good . On a minibike just part throttle is not good , trying to cruise at half throttle she kinda surges and is breaking up . If you let it idle to much it will load the engine with fuel .
Now if it's a racing bike and gonna be wide open when run then go for it , they really make power .
Now if it's a racing bike and gonna be wide open when run then go for it , they really make power .
I run one on a 5HP briggs that has some minor mods. It has a stock lift race cam and a billet rod and ARC adjustable flywheel all else stock. I made my own manifold and it has a slight rise from carb to engine. I had a lot of the idle issues and fuel dribble issues others have had until I mounted it with the stack down. Contrary to what some have said they do have a idle circuit but set up for racing they keep the stack upright for pull off a corner but it causes eratic Idling, and fuel dumping causing oil dilution. On mine it would idle eratically racing then slowing and when riding stalling. It also dumped fuel into the aircleaner when shut off as the stack has fuel in it and when engine is shut it comes out idle holes and dribbles out carb staining the cotton air filter and turning it green. I cut my manifold and turned carb with stack facing down and presto my troubles were over super idle, no fuel dumping and oil contamination, and it runs just fine like a stock engine. Then I started looking at chainsaws and old kart engines like west bend and Clintons that used them and they had stack down. Now when I shut it off gas stays in the stack. This is a picture of it with carb sideways but it did not fix fuel dumping issue or idle issues until I put stack on the bottom.
Found my pictures.
This is a very low tech and cheap solution to the " I want a bigger easier to tune carb problem "
A couple of years back I decided to try and drill my own carbs and rework the venturi.
This is what I ended up building.
It's actualy a Tecumseh series 5 carb body.
You do not have to go to this much trouble however.
Take one off a large snow blower ( this one is a off a 358cc unit ) and it will bolt to an aftermarket Tillotson intake manifold for clones.
The old style Tillotson air filter adaptor will also fit on it ( you must do a little tweaking to match the carb throat to the air filter for best flow.
It is not in the same class as a Tillotson racing carb, it will not have the fast snap of the throttle response or let you run as large a venturi.
It also will not slobber fuel.
BUT!!!!!
It will tune out to a mildly modified engine.
It can idle clean.
I will provide excellent low end performance and give you more head room at the top.
The primer makes it easy to start too ( no choke required ).
And its cheap to free with the option of going to the Tillotsons later.
Looking at Ole4s picture.
I am reminded of something EC birt told me once when he saw an unusual mount like that.
He said something to the effect the carb might go dry in the metering chamber under certain conditions unless its mounted upsidedown as God intended.
He was right and it took me a long time to understand how this worked and why.
This is a very low tech and cheap solution to the " I want a bigger easier to tune carb problem "
A couple of years back I decided to try and drill my own carbs and rework the venturi.
This is what I ended up building.
It's actualy a Tecumseh series 5 carb body.
You do not have to go to this much trouble however.
Take one off a large snow blower ( this one is a off a 358cc unit ) and it will bolt to an aftermarket Tillotson intake manifold for clones.
The old style Tillotson air filter adaptor will also fit on it ( you must do a little tweaking to match the carb throat to the air filter for best flow.
It is not in the same class as a Tillotson racing carb, it will not have the fast snap of the throttle response or let you run as large a venturi.
It also will not slobber fuel.
BUT!!!!!
It will tune out to a mildly modified engine.
It can idle clean.
I will provide excellent low end performance and give you more head room at the top.
The primer makes it easy to start too ( no choke required ).
And its cheap to free with the option of going to the Tillotsons later.
Looking at Ole4s picture.
I am reminded of something EC birt told me once when he saw an unusual mount like that.
He said something to the effect the carb might go dry in the metering chamber under certain conditions unless its mounted upsidedown as God intended.
He was right and it took me a long time to understand how this worked and why.