jetting advice

[whiteYZ]

Just wandering what you guys recommend. 2007 yz450f. Stock was 160 main 45 pilot 1 1/4 turns out on the fuel screw. I put a boyesen quickshot on which they recommend going out another 1/4 to 1/2 turn out and a full dr. d race exhaust system which they recommend going to a 162 or 165 main. I am at about 1000ft above sea level and its around 45 degrees out.

My current setup is 162 main 45 pilot and 1 1/2 turns out. Bike runs real crisp but pops on decel kinda bad. Also since the bike only had about 4 hours on it I reused the exhaust gasket so I am thinking that is bad. So maybe an air leak???? But let me know what you recommend jetting wise. Thanx

[Bigcr]

Test a 165 and a 170 main. My '07 (stock pipe) really likes the 165. However, others on this site have had success with the 170. It's an easy swap, so you might as well try both.

[whiteYZ]

160 to 170 is kinda a big jump isnt it?

[whiteYZ]

i forgot to mention needle was also dropped down one position from stock.

[Fastest1]

The fuel screw and pilot jet will control the pop. go out on the fuel screw and see. if it doesnt have an effect go up on the pilot size.

[bsmilee]

go up on the pilot jet, my friends 06 yz 450 did the same thing and we went up on the pilot and it doesn't nearly pop that much. Remember that a little deceleration pop is fine.

[rexbond007]

i went to 48 pilot and 165, took the popping out right away. left the needle stock for now.

[ethan]

I have an 06 and when I started it the first time it was way too lean. I went to a 170 main and 48 pilot off a rec. from this site and it ran perfect. The stock 07' exhaust is a little different, but with the Dr. D I would go to at least a 165 and 48. I also wired my AC pump and changed the leak jet to a #70. These changes made the bike run perfectly. I personally do not see the need for the AP cover.

I don't know why the bikes come jetted so lean from the factory, but they do. I feel that if you can start your bike when it is warm without the hot start lever, then your pilot ciruit is too lean. You should need to use the hot start to start your bike when it is hot, otherwise your jetting is not right.

[yz007f]

You dropped the needle which will lean out your pilot alittle even a main jet change will effect the pilot a small amount. I always found with these bikes you can richen the needle by dropping the clip on the position and they run alot better. Yamaha keeps the bikes on the lean side for the emissions they have to meet when they leave the factory.

yz007f

[whiteYZ]

right now I am at 162 main 45 pilot and 2 turns out on fuel screw and one grove down from stock on the needle. Seems to be running perfect. Do you think that it is to lean. I have minor decel popping now and bike is really snappy.

[bigjohn450]

i too have machine gun popping on decel my bike is new about 30 min on it im like 4500 ft above sea level jetting is stock im running super lean pulled the main its a 165 what pilot do you guys recomend?

[grayracer513]

48 for the colder weather. 45 should be fine in the summer.

[grayracer513]

Just wandering what you guys recommend. 2007 yz450f. Stock was 160 main 45 pilot 1 1/4 turns out on the fuel screw. I put a boyesen quickshot on which they recommend going out another 1/4 to 1/2 turn out and a full dr. d race exhaust system which they recommend going to a 162 or 165 main. I am at about 1000ft above sea level and its around 45 degrees out.

My current setup is 162 main 45 pilot and 1 1/2 turns out. Bike runs real crisp but pops on decel kinda bad. Also since the bike only had about 4 hours on it I reused the exhaust gasket so I am thinking that is bad. So maybe an air leak???? But let me know what you recommend jetting wise. Thanx

i forgot to mention needle was also dropped down one position from stock.

160 to 170 is kinda a big jump isnt it?

The jetting recommendations given are for "STP", or Standard Temperature and Pressure. That means 70 degrees at sea level. The increase to 1000 feet only puts the jetting off by 1%, so it's more or less inconsequential. However, the drop from 70 to 40 degrees calls for a change from a 165 to a 170.

Going from a 160 to a 170 would seem to be a big jump, but the bike should be quite lean with a 160 in it at that altitude, and should be happier with a 165. Colder weather demands richer jetting because the colder air is denser.

When you say the needle is lower, do you mean th eclip is lower, or the needle was actually lowered by raising the clip?

I run my '06 with a 45 pilot, stock needle in the 4th position, and a 165 main in SoCal at altitudes from sea level to 3700 feet.

[whiteYZ]

i mean the clip was dropped so the needle was raised. Tonight I put a 50 pilot 168 main and the fuel screw is at 1 3/4 turns. Seems better. HAvent gotten to ride yet though. I am hoping i can dial it in with the fuel screw, and have also added full dr d exhaust race system.

[whiteYZ]

Well I rode it alittle today and have to only have set fuel screw out at 1 turn to achieve max rpms before sounding lame, also have tach so that helps. So I am thinking I may need to drop to a 48 pilot. Sound right???? Also switched from 168 main back to 165 because of the fact that it is supposed to break record temps tomorrow at 65 degrees and I plan on doing a full day of riding, also assuming my needle being raised thus richening it would make the 165 suffcient. What do you guys think???? Am I anywhere close?

[grayracer513]

I ... have to only have set fuel screw out at 1 turn to achieve max rpms before sounding lame, also have tach so that helps. So I am thinking I may need to drop to a 48 pilot. Sound right????

Yes, it does.

[whiteYZ]

do you think I will be ok for a day of riding tomorrow with the 50 pilot in grayracer?

[grayracer513]

It might run a little dirty off idle, or get cranky about starting, but it shouldn't hurt anything.