the screws on the carb are for idle speed , and air mixture, the air mixture it underneath,but it really only affects mixture at idle speed.
you may need to try raising the slide needle, or go up a size in the main jet, do one at a time and keep notes about the changes and results
It should be the small plug up near the steering head with the dip stick, you need a small funnel, use only motorcycle oil, car oil can cause clutch slip.They hold about 1.1 litres . you then need to start it for a couple of minutes then check with the dip stick
Actually your exhaust, at the head, will glow red when the bike warms up - this is normal. Melting the plastic air filter case, however, is not.
The bike is obviously running way too lean if you were riding it during the 30 minutes you mentioned in your question. If it was sitting for 30 minutes, without air circulating around the engine, your exhaust would become extremely hot possibly melting the Air Filter Case. Check to make sure you air filter is clean and your carb(s) is/are set correctly. You should have an Idle Speed adjustment knob also - check your user manual to see if there is an idle speed RPM setting and set yours to it.
Another issue that might cause your problem is the use of improper oil in the crankcase. Again, check your user manual for the correct oil type that should be used. Some oils have additives that are not good for motorcycles and can ruin wet clutches and other engine parts.
Hope this gives you enough information to go on.
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Standard starting procedure for YZ400/426/450 is as follows: Push the engine around using the kick starter until you hit the compression stroke. The kick starter will get impossibly hard to push at this point. Now pull in the decomp lever and push the kick starter down a fraction, and I mean a FRACTION. This is where most people go wrong, they push it down too far with the decomp lever pulled in. Now give it a full kick without throttle and it should start.
The above should work fine for a motor that's already warm and was NOT stalled. If the motor stalls it will usually need the hot start button opened as well to let extra air in and bleed out the fuel that usually gets stuck in the motor when it stalls.
For cold starts, you will need to put the choke on, and if it's really cold you might need to prime the engine with a twist of throttle to get the accelerator pump to shoot some fuel in before you start.
As a general rule, NEVER twist the throttle while kicking when you are actually attempting to start the bike, it won't help at all. Also, having your idle screw adjusted correctly makes all of this a lot more easier. Standard setting is usually 1.5 turns out but it should be set to give the smoothest idle you can get using the minimum number of turns out from all the way in. If you have to wind your screw right out to get a good idle you need a bigger pilot jet. Conversely if you have to wind it most of the way in (less than 1 turn) you need a smaller pilot jet. I'm not sure about the 450 but my YZ426 came standard with a 42 pilot jet and changing to a 45 made it idle and start MUCH better. Incidentally the WR model uses a 48.
that is a good thing, that means you have oil presser!!!! you don't want the motor running when you check the oil, and make sure dipstick is screwed down before you run the bike
Depends on the type of carb, but you must remove needle and there is a sir-clip with slots on the top of the needle. it can be poped off and moved up and down on needle. may have 5 different spots on it. Factory setting will be the center slot. This will enrich the mix or lean it out.
Needle adjustment
Make sure everything is connected and there is a good fuse in place. To test the coil you'll want a Ohms meter and a Volt meter as well as the service manual! Make sure the readings on the meters match the ones in the service manual. Cheers!
You need to remove the valve cover and rotate the crank shaft to TDC then with a feeler gauge you check the clearance between the cam lobe and lifter bucket. There are 3 on intake cam and 2 on the exhaust. The clearance will most likely tighten as the valve seats and valve wear in. If the valve clearance gets too tight they will hang open and not seal for proper combustion. Valve clearance for my 2002 YZ426 are intake=0.10-0.15 mm (0.0039-0.0059 in) exhaust=0.20-0.25 mm (0.0079-0.0098 in) the 450 should be the same or very close
Possible water in the carb float bowl. Go over a whoop and a bit of water gets picked up and into the engine. Water doesn't burn well. The water is condensation from the gas tank. Try draining the carb and see if that helps. Also be sure the spark plug cap and battery terminals are on securely. Check the side stand kill switch to be sure it is securely mounted. Please rate my answer. Thanks!
ok first u need tire bar's proper tool's for the job if u use scrue driver's u will put hole 's in tube ....1 take out vave stem 2 un do the tube lock on rim 3 pop the bead 4 get sprey bottle with sopy water spray around the tire then put bar in and work 2 bar's around the tire untill come's off 1 side then do the same on the get other and pull
If you are going to dismantle a gearbox, Buy a manual. It is not something that can be accomplished without pictures (rebuild is even more critical.) They only cost about 20GBP and a professional gearbox rebuild will cost in the region of 400GBP- no contest is there.
Do not try to out engineer the engineers. Do not take a drill to your clutch. Just put 10w40 in the crankcase and see if that takes care of the problem. How good is your clutch cable? Lubricated it lately?
