Somewhere to start

[Mike's Shee]

Need a little help on jetting the banshee. It's an 87 that is bored .100 over, has 28mm Makuni (sp) carbs, some kind of a port job ( was told that there was extra holes drilled into the sleeves ), T-5s and no air box. I don't know where to start. Thanks for the help, Mike

[spoin39]

What does it run like? What jetting does it have now?

[Mike's Shee]

What does it run like? What jetting does it have now?

342995[/snapback]

 

It will only idle with the choke on. As soon as you give it any gas it falls on its face. I'm not sure on the jetting. From what my buddy told me he didn't do anything to it. Bought a set of new carbs off ebay and put them on.

[spoin39]

Sorry man, but need more info. What carbs are on it? (size and make). And what jets do they have in there now?

[Mike's Shee]

28 mm Makunis. I'm not sure what jets are in it. The bike is about half the world a way.

[Ducman]

Are they stock carbs bored to 28mm or aftermarket. An easy way to tell is aftermarket carbs will both have their own choke. If aftermarket, are they mikuni flat slides or round slides? You should be about a #30 pilot and for the mains somewhere in the 300 minimum to 380 maximum range. Pilots and main numbers for aftermarket mikunis will be similar to stock carbs. There are different styles of pilot jets and needle jets but most use the same main jets as stock carbs. The way the carb came stock, the needle may not be anywhere near the correct needle jet orafice. If its a flatslide TM carb, you may need to change the needle jet orafice but you should be able to get it to at least run (between 1/4 and 3/4) by lowering or raising the needle the carbs have now. The extra holes in the cylinder are probably added exhaust ports, usually refered to as a "tripple exhuast port job" or exhaust boost ports. Usually used in more of a top end power emphasis port job.

 

I would start by making sure the carbs are in sync, then adjust airscrews in (since you said it would only idle with choke on) to richen up the idle maybe 0.5 to 1.5 turns out. (idle gets leaner as you turn airscrews out). Make sure both carbs have airscres adjusted evenly. Get the bike to start and idle good. (What the poing of going any further if you can't at least get the bike to start and stay running) Also make sure the main size is at least a 300, preferably about a 340. When you say its falling on its face when you give it throttle, I'm not sure if you are way to lean or too rich, but if its when you crack the throttle its probably the needle setting, and/or a combo of needle and pilot. If you get it to start and idle good W/o choke it may get better when you crack the throttle too. If you get it running good enough to ride, but your a little off on the needle, but it will run good WOT then you can get your mains somewhat dialed in. In the process of dialing in the mains you should get an idea if you are rich or lean on the needle.

 

From experience dialing in my TM 34mm Mikunis (Flatslide), they came new with way too rich of a needle and pilot but I don't know what your 28mm's would come with. If they are flatslides, the needle jet orafice that worked good for me was a P-8, they came with a Q-2 (P-8 is 2 sizes smaller orafice,each size orafice is about equal to 3 clip positions or so) When I got the carbs and dropped my needle all the way down it was still way too rich with the Q-2, now it is good on the middle clip with the P-8.

 

You might also call or e-mail Sudco.com, they sell mikuni carbs and pre-jet them so they are reddy to run on a particular aplication. You need to determine the model of Mikuni carbs you have first.

 

From sudco website:

Sudco can "Special Set" any Mikuni Carburetor for your particular application. Below is the information you will need to provide our Carburetor Techs so they can provide you with the correct carburetor and jetting, when you are purchasing a carburetor.

 

1. Carburetor Size (mm)

2. Type of carburetor (Clamp-on, Spigot Mount, Flange Mount, Flat-slide, etc.)

3. Application (Model, Year, Displacement)

4. Modifications to motorcycle (Explain)

5. Type of motorcycle use (Street, Road Race, Drag, Motocross, Enduro, etc.)

6. Type of fuel used

7. Climate Conditions (Altitude, etc.)