| Author | Message | ||
     Blake |
http://www.mikuni.com (for info on tuning a Mikuni flat slide high performance carburetor and for other good carburetor information. Venturi P/N 29179-88 Venturi Ring Fuel injection parts #156-8100-AS4 Beck Arney 02 #12014 Bosch 02 sensor C0130.L Clamp, Throttle Cable $2.90 CV-40 The tried and true performance enhancing modifications for the stock Kehein CV 40 carburator are as follows: 1)Change slow jet to size #45 (stock is #42) 2)Carefully remove brass plug covering idle mixture screw (drill it out carefully) and reset idle mixture screw to 2 1/2 turns from full-in or for best idle speed. If best (highest) idle is more than 3 turns out, switch to a 48 pilot jet and re-adjust screw for optimum idle. 3)Shim the needle a little higher (~0.01) 4)The best course is to then to run your bike on a dyno equiped with a wide band oxygen sensor (air/fuel ratio meter). Optimum safe high performance WOT A/F ratio is around 13.5. Anything over 15 is excessively lean and risks stressing/overheating your combustion chamber and holing a piston. | ||
| Halo |
Question on CV-40 tuning on a 2000 M2 Cyclone. I have looked through my manual and at my carb and can not figure out where the brass plug (to be drilled out) is located to reset the idle mixture screw. Some direction would be appreciated. | ||
| Jackbequick |
Scroll down and look at item 9 on this cutaway. The plug covers the bottom of tubular cavity the idle mixture adjustment screw is in, it is pushed in flush with the carb body. When you drill out that plug (it is a thin, cup shaped piece of metal) use a sharp 3/32" so drill, at high speed and light pressure. There is a gap between the plug and the head of the screw so stop as soon as you feel the drill break through. Use a sharp pointed #6 or so sheet metal screw and screw in into the hole 1/2-3/4 turn or so. Grab the screw with pliers and wiggle it side to side a little while pulling. The procedures described there can be printed out and followed, they worked perfect for me. It transformed my 2000 M2 into a perfectly idling, easily warmed up, smoother at low speed and better accelerating, absolute joy to ride. I skipped step #3 - I just did the #48 jet mod and mixture screw setting. The slide mods might be better left for bikes with improved heads and where you are working towards a higher state of tune. Some info in the KV recommends against drilling the hole out so I did not mess with the slide. When my bike is cold I start it on full enrichener and let it run for 15-30 seconds. Then I push the enrichener all the way in and open the throttle to bring it back up to a 1,500-2,000 RPM idle for another minute of warmup. It will probably pop or backfire if you do any throttle blipping before it is fully warmed up (2 or 3 minutes or more). A long warmup is good, this is one of the most important times in any engine's life. I take the time to look at and listen to things with my helmet off. I use the idle speed adjuster to set the idle up for warmup if I want to use my hands or not stay on the bike for warmup. Jack | ||
| Halo |
Thanks Jack, I was looking for a brass colored plug and on my carb it is the color of the rest of the carb body. Also, I was looking at the exploded view in my manual (they don't show it) but it is shown a few pages back in the "theory" section. Thanks again, Halo |
