05 wr450 running lean and has hard time starting/idling

I have an 05 WR450 with an FMF pipe, uni filter, grey wire mod, smog delete and some holes in the air box. The plastic hot start nut broke and everything seems to have gone downhill from there. We replaced the hot start return spring and plunger and put on an aluminum nut now which is much stronger. Yesterday we cleaned the carb and checked the float height and everything seemed ok inside the carb.

Main jet was 165 and we put in a 168

Pilot is 150

I really have to pump the gas alot before firing the bike and it will not idle at all. We started to think there was a vacuum leak and sprayed some carb cleaner around the carb and the rpm's spiked right around the carb-engine rubber boot. I am going to replace the boot, but mine looked fine with no visible cracks.

Do you think that the small vacuum leak there is going to cause all these problems or should I pull the carb apart again to check for more sand or dirt in there. We were pretty thorough with the cleaning so I'm fairly certain theres no more dirt there.

I just ordered the boot but trying to figure out some other things to check as well.

50 pilot jet is large, most run a 45 or a 42. If roms spiked when you spray stuff on the manifold, you may of found the culprit. It does not take much of a vacuum leak to make it crazy.

If the bike will still not idle:

The first areas to inspect are the pilot jet and fuel screw. First, I'd pop in a brand not (not just 'clean') pilot jet. Nerxt, I'd check the condition of the fuel screw and oring, ensuring the spring and washer are there also. Next suspect would be the splide, inparticular the vacuum release plate and seal. If you remove teh AIS, I'd check the vacuum port it connected to.

50 pilot jet is large, most run a 45 or a 42. If roms spiked when you spray stuff on the manifold, you may of found the culprit. It does not take much of a vacuum leak to make it crazy.

If the bike will still not idle:

The first areas to inspect are the pilot jet and fuel screw. First, I'd pop in a brand not (not just 'clean') pilot jet. Nerxt, I'd check the condition of the fuel screw and oring, ensuring the spring and washer are there also. Next suspect would be the splide, inparticular the vacuum release plate and seal. If you remove teh AIS, I'd check the vacuum port it connected to.

We tried a 45 pilot and it was much worse. The fuel screw has the spring, washer and o ring all intact and they are all new. I am wondering if we messed something up with the slide, but want to get this new boot on first. Will check the vacuum port when I get home.

Don't forget to check for a cracked slide - these things are famous for doing that. Will affect how the engine runs for sure...

Don't forget to check for a cracked slide - these things are famous for doing that. Will affect how the engine runs for sure...

Cracked where? Any pic of where i should check?

Did you pull the slide out? I bet you put it in upside down if you did!

Been there, done that. Got it running pretty good too before I found the problem! :lol:

But seriously, any vacuum leaks will throw your jetting way out. :thumbsup:

50 pilot jet is large, most run a 45 or a 42.

Yeah, on a 250F... :lol:

48 pilot is the norm. :thumbsup:

Did you pull the slide out? I bet you put it in upside down if you did!

Been there, done that. Got it running pretty good too before I found the problem! :lol:

But seriously, any vacuum leaks will throw your jetting way out. :thumbsup:

Should have that new rubber boot tomorrow but will try and pull the carb off again today to check the slide. Is there any way I can make sure the slide is upside down or not? Any pictures for reference?

My friend was the one that pulled the slide out so I dont even know what it was supposed to look like as it came out.

IIRC... it really looks like it should go in upside down and is an easy mistake to make...

or so i have heard...

450 or a 110.... that is a big difference......

IIRC... it really looks like it should go in upside down and is an easy mistake to make...

or so i have heard...

450 or a 110.... that is a big difference......

Which is why I want to take my 450 out. The 110 is my girls bike and will really just be for messing around at camp. We are going out to the sand dunes in pismo and don't think the 110 with a knobbie with my fatass on it will do too well.

Which is why I want to take my 450 out. The 110 is my girls bike and will really just be for messing around at camp. We are going out to the sand dunes in pismo and don't think the 110 with a knobbie with my fatass on it will do too well.

mine either.....(fatass part)

What ended up being the problem here?

He had a torn carb boot leaking air

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