Stock carb mod

Egor · #1 (**permalink**) 06-17-2008, 12:24 AM

This is an easy carb mod I use for all my engines that I still have the stock carb on. Start by removing the carb and take the slide out. Next take the float bowl off and get the float out of the way, I remove the main jet holder also. put a .040 drill in a Dermal or a small drill motor and, on the engine side of the under side of the carb, directing as far as you can in the direction of the air flow, hold the drill at a 45 degree angle with the drill in the direction of air flow, drill the .040 hole. Next insert the slide and look to see where the hole lines up with the edge of the slide, if you are good it is in the middle, no worry if not. Make a small slot in the slide over the hole, so that most of the air the engine will run on will come out of the float bowl. I think you will enjoy the results, my bike will idle down and run up with no faltering at all. I will post some pic's to explain. Good luck and have fun, Dave

PS: You will not have to mess with the slide needle as much, I keep it in the stock position.

Egor · #2 (**permalink**) 06-17-2008, 01:49 AM

A quick intake timing mod. I use this in a pinch, works well. A pic is worth a thousand words. Have fun, Dave

ran49 · #3 (**permalink**) 06-17-2008, 10:08 AM

Dave:Excuse my ignorance but what is the theory behind the hole in the carb.Ron

misteright1_99 · #4 (**permalink**) 06-17-2008, 10:25 AM

It allows a small amount of fuel vapors to pass directly into the intake improving idle. It works great I did a couple of months ago..

Pablo · #5 (**permalink**) 06-17-2008, 10:34 AM

So fuel vapor pulled up through the hole.

Does the plug seem more rich??

What happens at WOT?

misteright1_99 · #6 (**permalink**) 06-17-2008, 10:51 AM

Pablo I believe since you are only pulling vapor, and being at the top of the carb, above the fuel level it doesnt enrichen mixture that much except when at idle when the fuel flow thru the jet is lowest, therefore improves idle. This improvement takes the place of the idle circuit that most quality carbs have.

Pablo · #7 (**permalink**) 06-17-2008, 12:13 PM

Good point on the idle circuit. Mine idles pretty good right now.....what I want is a more dialable fuel/air mixture

Egor · #8 (**permalink**) 06-18-2008, 12:21 AM

Pablo - One of the things you will find is that with this mod you can spend time on the correct mixture for mid which is the needle and the top which is the high speed jet. I suspect if your bike Idles well your mid range is suffering. Ive seen your bike and with the performance you are looking for you should see if you can find a Mikuni, 18mm works good. Have fun, Dave

PS: The cut in the slide on the filter side affects the mix just off the idle, more cut leans it out.

Clotho · #9 (**permalink**) 09-04-2008, 02:18 AM

Quote:

Originally Posted by Egor

A quick intake timing mod. I use this in a pinch, works well. A pic is worth a thousand words. Have fun, Dave

I have noticed that the intake is never fully uncovered on my engine. With this modification should it now uncover it completely? Does it increase rpm? Torque? Both?

Egor · #10 (**permalink**) 09-05-2008, 03:08 AM

Clotho - It could increase the rpm but most of what I see is that it increases the Torque the most and that is HP. Remember the manufacturer is trying to keep the engine at the two hp limit and this is one of the ways to do it. You can trim the skirt if you are not comfortable with carving on the port. If you are OK with carving I go 1/4" down and wider, don't worry about the rest of the intake tract the engine will not be able to take advantage of any matching, that's high rpm stuff and this engine is not capable of it. Have fun, Dave