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Dirt Bike Discussions By Brand
Yamaha MX & Off-Road Dirt Bikes
yz85 oil out of silencer
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[QUOTE="_JOE_, post: 1428728, member: 77507"] It's harder to tune the 50s as you can't ride them yourself to feel for changes. You have to rely on sound, temps and smoke/spooge. Excessive smoke and /or oil out the exhaust (spooge) points toward rich jetting or lack of air flow. Ensure the air filter is clean and repack the silencer. Remove the carb and pull all the jets, floats and choke assembly out. Use aerosol carb cleaner to spray through all the jets and carb body passages then blow everything out with compressed air. Write down what main and pilot jet is in there and note the needle clip position. Check your stock jetting specs for comparison. Make sure the float valve is in good shape, both the "rubber" tip and it's seat in the carb body should show no wear. When you reassemble check that the float valve seats when the floats are parallel with bowl seating surface and the idle screw is turned in so that it just starts to lift the slide. Assuming your reeds, crank seals and top end are all in good shape you're ready to start jetting. Pilot circuit(air screw) first. Start at stock, usually 1.5 turns out from closed. Get it warmed up by RIDING THE BIKE for a little while. Once nice and hot hop off and turn the pilot screw in listening for the idle to break up. You may need to set the idle a little higher than normal. When the idle breaks up back it out a little, maybe an 1/8th turn. If it doesn't respond to air screw adjustment the pilot jet is likely too large. Go up a size and retest. Now you're ready for another quick test ride. Go out in 1/8th to 1/4 turn increments while riding at lower speeds and rpm and blipping the throttle to about a quarter turn. You should notice the difference in response as you go. When you're satisfied with the pilot circuit tuning move on to the main jet. I usually go pick up a couple different sizes in either direction. If you think it's rich go a size leaner (smaller number). Run it hard for a while on a fresh plug, 3/4 throttle up is main jet. Ideally you should have a plug viewer to look at the carbon ring at the base of the insulator, but you can usually tell if you're the ballpark by looking at the color down in there. Seat of the pants dyno will tell you if you're going the right way. It's easier to tell if you a large flat area to ride the bike. Once you're happy with the main it's needle time. Needle adjustments are usually the easiest to feel. One groove either way to start with and you should either feel it in the mid range, say 1/4 to 3/4 throttle or so. All this will take you an afternoon and about 20 or 30 bucks worth of supplies and jets, but once you're done you're bike will probably feel alot faster and run much cleaner and you'll have a feel for what incorrect jetting feels and sounds like. Once you tune a few bikes it'll all make sense and you'll be surprised how easy they are to get running well..... PS: Hows your 7 year old like the 50SR? [/QUOTE]
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Dirt Bike Discussions By Brand
Yamaha MX & Off-Road Dirt Bikes
yz85 oil out of silencer
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