Tune-Up for YZ 85

[jarl66]

Hello everybody,

I have a 2004 YZ85 (all stock) and I am having a problem with it. When I start riding the bike, it starts very slowly not picking enough power/speed right away, even if I open it up. After 4-5 seconds it picks up and flies, but the start is very slow(no matter if I have been riding for a long time). I think it might be a carb adjustment (probably the low needle), but I don't know what is what in the carb or how to turn it to adjust it. Any detail information on how can I fixed this will be greatly appreciated.

jarl66

[crazyrydermx]

You probably have some work to do with the pilot circuit. If you have absolutely no clue of what the parts of the carb are, it is going to take a little explaining because it is a complex part. So first I will ask some simple questions before the big explaining begins...
How well does it idle? By simply turning the air screw you may find that to be enough. If you look at the carb there will be a brass screw in which can be turned using a flathead screwdriver. Play around with this to where your bike idles a bit faster. This will slightly help your problem.
Make sure all things necessary are cleaned/new, such as spark plug and air filter. Is the pipe stock?
Is this your first two stroke? You may just be below the powerband and if you aren't used to a two stroke motocrosser, you may think that it is a problem when in reality, it is just an engine characteristic due to the properties of two strokes. As many people say with a two stroke motocrosser, on these bikes you must ride the pipe. Below the powerband the power is useless, so what you want to do is keep it in the powerband. When you release the clutch, how much throttle are you giving it and how do you release it?

[kwmotocrosspunk]

Originally Posted by crazyrydermx

Is this your first two stroke? You may just be below the powerband and if you aren't used to a two stroke motocrosser, you may think that it is a problem when in reality, it is just an engine characteristic due to the properties of two strokes. As many people say with a two stroke motocrosser, on these bikes you must ride the pipe. Below the powerband the power is useless, so what you want to do is keep it in the powerband. When you release the clutch, how much throttle are you giving it and how do you release it?

i think this is it, i had an 99 yz 80 and it had no power in the bottom end, but as soon as the power band hit it took of like a rocket

try changing the gearing in the drive sprocket to give it more bottom, and you could also throw in a V-force 3 reed valve, i had one on my 80 and it really livened it up, i also changed my gear and that instantly helped it

[jarl66]

The idle is ok. I also have a YZ125 that runs great. Everything in the 85 is stock including the pipe and the air filter/spark plug are new. I am aware of the powerband, but I feel it a little slow when you are starting to ride the bike. As an example, if I am riding my 125 slowy in first gear, I can hit the gas and I have to hold on to the bike. With the 85, in the same scenario, it will take few seconds to responde, not immediately like the 125, it is just too slow and powerless for few seconds until it picks up.