We understand that tuning a motorcycle carburetor can be a daunting task for those not familiar with it and for others who struggle to tell when a setting is not too rich or too lean, but just right. Novices at tuning may want to seek help from someone with experience. However, we will do our best to try to help you understand how to get your carburetor properly dialed in. If you purchase one of our kits, we jet the carburetor and set the float height, as well as place the needle clip in the proper notch on the needle. The engine should start fairly easily and need minor adjustments if any. If we have not fitted an OKO onto a model like yours, we jet it with our best (hopefully educated) guess.
To start your bike when cold, pull the choke knob up until it clicks into place. If it does not click into place, pull a little harder, it will. Keep the throttle closed. Kick the kickstarter or push the start button. The engine should come to life with just a few kicks. As the engine begins to warm up, the rpms will start to drop. At this time, push the choke back down, but be prepared to "feather" it as needed to keep the engine running. You may need to screw in the idle screw some (angled upwards screw with spring) to raise the idle speed. Adjust this to get a fairly slow idle that won't die, and then turn the air screw (horizontal screw near the intake) in a quarter turn. If the idle speed decreases, turn the air screw back out, an eighth to quarter of a turn at a time until the idle speed stops increasing. Then turn it in until the speed begins to drop. Adjust the idle speed with the idle screw. If, when you first turn the air screw in, idle speed increases, continue turning it in until the idle speed begins to drop. Stop there. Blip the throttle slightly. The engine should accelerate smoothly and return to idle quickly. If it does not return to idle quickly, it is too lean and the airscrew should be turned in until the engine does return to idle quickly. If a two-stoke engine four strokes when given throttle (fires every other time), it is too rich and the air screw should be turned out until it accelerates smoothly. (On a four stroke, it will hickup or accelerate slowly). The best idle should be achieved with the air screw between one and two turns out from fully seated. If it is turned out less than one turn, switch the pilot jet (small jet with slotted head) to a larger size. If the best idle has the screw out more than two turns, switch the pilot jet to a smaller size.
Once the idle is dialed in you can move on to the needle position. The same symptoms occur for richness and leanness with the needle. Ride your bike at about one quarter throttle and hold that position, checking for leanness or richness. If lean, it will be slow to return to idle. On two-strokes it will "ring ding ding". If rich, two strokes will four-stroke and four-strokes may be loud and feel "heavy" and not run smoothly. Raising the needle by lowering the clip will richen the mixture. Conversely, lowering the needle by raising the clip will lean the mixture. Find the needle position in which the bike accelerates smoothly and returns to idle quickly. Because the needle controls the mixture from 1/4 to 3/4 throttle, check running at half and 3/4 throttle. If half or 3/4 throttle is not as 1/4 throttle, call me. It could mean you need a needle change, though this is rare with the kits we offer. Once the needle position is set, now you can check the main jet. Make sure you have enough riding room to hold full throttle for several seconds before releasing it. The engine should pull strongly and smoothly. When the throttle is released it should return to idle quickly. Slow return to idle indicates the main jet is too small, as does backfiring. If the jet is too large (too rich), two-strokes may four-stroke and four-strokes will miss. Also, when the throttle is released, if the engine "loads up" (idle drops, then returns to normal), that is an indication the main jet is too large. Find the main jet that allows the engine to accelerate smoothly with good power and returns to idle quickly when the throttle is released, without loading up the idle. If all of this seems a bit complicated, give Roger a call (shop phone) at 410-635-6722 or (cell phone) at 443-821-6154 and he'll try to talk you through it. Please note: If dialing in is done before the engine is completely warmed up, you will need to go back over each setting once it is warmed up since the engine will run richer when fully up to temp. One note concerning carburetor size: If the carburetor is too large, there will be a lean spot just off of idle when all else is dialed in. If there is a rich spot just off of idle that indicates the carburetor is too small. Again, if this happens, give us a call so we can make sure you have the correct size carburetor.
