Stock carb mod

Egor

New Member
Jan 30, 2008
714
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Hurricane Utah
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.
 

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misteright1_99

New Member
Mar 21, 2008
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Treasure Coast, Florida
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.
 

Egor

New Member
Jan 30, 2008
714
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Hurricane Utah
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

Member
May 25, 2008
304
1
18
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

New Member
Jan 30, 2008
714
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Hurricane Utah
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
 

Biker Mike

New Member
Mar 21, 2008
143
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Cropwell Alabama
A quick intake timing mod. I use this in a pinch, works well. A pic is worth a thousand words. Have fun, Dave
This really caught my eye. Could you give a little more detail about this. How much do you grind off the piston skirt? Does this increase the air/fuel flow to the cylinder? It looks like a great mod. Thanks for any elaboration you can provide. :confused:
 

Motoschwinn

Member
Jun 27, 2008
434
1
18
Independence MO
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.
A step by step photo group would be nice...
 

Egor

New Member
Jan 30, 2008
714
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0
Hurricane Utah
OK I will get a set of pics up to enplane in Photos. I know it is worth the effort. The mod is to fetch air that contains fuel in it, as the carb for these simple engines is missing a slow speed circuit. Have fun Dave
 

jasonh

New Member
Jun 23, 2008
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Longmont, CO
I thought about doing that the other day when I had the carb off. Didn't do it as I don't have the proper dremel bits.
 
well :)
all I can say is that I could get my pinky much further into either side of the carb when I was done but I dident really measure it
I used some of the tools I use for porting heads on cars with
the pic is terrible
I did use the solder & drill method on the fuel jets & got the thing dialed in really well at lower speeds but I used to be able to get it to clean out much higher in the RPMs & thats where my speed came in
so Im hopeing for that too
have a great weekend
JAK
 

Biker Mike

New Member
Mar 21, 2008
143
0
0
Cropwell Alabama
A quick intake timing mod. I use this in a pinch, works well. A pic is worth a thousand words. Have fun, Dave
Hey dave, does the shaved piston skirt go on the intake side or both. If you shave it to much will it cause the engine not to start. I just re assembled mine and it will not hit a lick :-||. It has good fire and is getting fuel. It just will not hit. Any suggestions would be appreciated. Thanks, Mike.
 

Motoschwinn

Member
Jun 27, 2008
434
1
18
Independence MO
Hey dave, does the shaved piston skirt go on the intake side or both. If you shave it to much will it cause the engine not to start. I just re assembled mine and it will not hit a lick :-||. It has good fire and is getting fuel. It just will not hit. Any suggestions would be appreciated. Thanks, Mike.
I think I'm going to invest in a extra carb before I do any mods on my only one.