YFZ450 won't start in the cool NE Ohio weather.

[DarkRider3]

Here's the problem. My YFZ is more stubborn than 90 year old that thinks the world owes him something. My bike is MX ready, but I'm not the most mechanically sound with it. I know the basics.

Specs:
Yosh tri -oval full system
Jets: 48-pilot, 185 main, can't recall the leak
Airscrew at 2 turns
compression piston
falicon crank
quick shot

I have gotten it running, but not without exhausting the battery. That means if I stall out too quickly theres no chance of a restart. Temps here in NE Ohio are going to be steady in the upper 40's to low 50's over the next few days. I would love to hit NEMX tomorrow if I can get it running. Any fellow YFZ riders out there with some know how? I would appreciate it.

[Ride1Rob]

What exactly is the bike doing? Just turning over? Any backfiring? There are 3 basic things you can do to make sure it's getting the essentials... Check for spark, check for compression, and check to make sure it's getting fuel. Being that you said you got it running those are more than likely good. I would have to go with your jetting. Was it doing this before the weather got cooler? Give a run down when the bike began to act up and if possible what led up to it. This may help in determining what the culprit could be.

[DarkRider3]

Ok, here's whats going on. Last night, after leaving the battery on the charger for 2 hours it fired right up. Got home from work and was hoping to head up to NEMX and it hates me again.

Here are the symptoms.

1. It turns over several times with no signs of life.

2. There will be an occaisional pop.

3. AT this point, my battery can only sustain about 5 minutes of trying to start before dying out.

4. I shot a few sprays of starter fluid into the air filter, this seemed to do very little.

5. I just upper my main to a 190 from the 185, and the air screw is at 2 turns out.

6. There will also be an occaisional backfire, not a loud one, just a loud pop.

Hope this helps a little.

[DarkRider3]

It took a little time and some patience but it finally started tonight. I missed out on NEMX, but at least its running.

I think that the bike is just cold blooded and needs to be warmed before riding.

[Ride1Rob]

A 190 is REALLY high! You need to back that main jet down. If you pull your plug I'm sure that it's black. You're dumping too much gas into the carb and it's flooding itself out that's why it's so hard to start when it's cold and after it's been running. When you're riding and you stab the throttle it doesn't want to fall flat on it's face?

[rt20ps]

Make shure your valve lash is in spec and clean your pilot jet. Those two things usually clean up a hard starting YFZ.

[DarkRider3]

I know a 190 is high, and when I got it running last night it was a bit rich. As the temp dropped into the 40's it rAn even better.

My bro ran a 200+ main last winter in his 450r.

My carb is very clean, just cleaned last week. When it was running last night it didn't fall on it's face at all.

[cmpearce]

i don't have a yfz but, i had the same problem on my predator.tight valves are usually the culpret.mine was to rich of a fuel mixture and it was gumming up the valves.i ran some sea foam intake cleaner through it (advance auto has it) and leaned the jetting.befor it didn't want to start in 45 degree weather ,now it will start below zero

[DarkRider3]

I truely believe that my problem is a cold headed/cylinder. Once I get it warm and running it rips with no problems. I will try the cleaner though. Thanks for the tip.

[DarkRider3]

I truely believe that my problem is a cold headed/cylinder. Once I get it warm and running it rips with no problems. I will try the cleaner though. Thanks for the tip.