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Matty05

Changing pilot air jet

9 posts in this topic

Who has changed their PAJ?

I have been reading flat out about PJ to PAJ relationship, seems that Taffy's old info is the only info that is really available anywhere.

His chart is basically:

PJ - PAJ

38 - 60

40 - 70/75

42 - 85/90

45 - 100

48 - 110 to 125.

The YZ450's come with a 100 PAJ and 45 PJ, our WR450's come with a 45 PJ also but with only a 80 PAJ. Is this to do with ACV crap again?

I originally thought I was too big with the 80 PAJ, but I realize too small now.

Basically what I understand now is the bigger the PAJ, the more fuel the PJ will flow. I have to use a 52 pilot jet to have correct pilot circuit, but I wonder about getting big PAJ will change much? I will have to wait and see.

Clark, I read some old posts, you had an improvement going bigger PAJ didn't you? :thumbsup:

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Clark, I read some old posts, you had an improvement going bigger PAJ didn't you? :thumbsup:

I played with it in the hopes of getting rid of my bog, but it didn't do much. For my altitude and temps, leaving the entire Pilot circuit stock is what works best. I rode in 30 degree temps today around 9:00 a.m at around 5500' ASL with a 45 PJ and the bike ran like a striped ape. I had no decel popping or anything that would indicate a lean condition anywhere in the rev range. It eventually warmed up to 48 by noon and I got back down to 4700' ASL with no issues whatsoever. My current jetting specs are on the first page of the jetting database. It's the best the bike has run in cold weather to date! :bonk::thumbsup:...SC

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YAMAHA PILOT AIR JET PART NUMBERS other than stock are:

7A9-14943-27-00 JET (#100)

7A9-14943-17-00 JET (#75)

Sudco sells all the sizes and has an adjustable version to cover the entire range ( They call it the slow air jet but we know it as the PAJ ). Look at page 95 of their catalog for all the part numbers link:

http://www.sudco.com/catalog105/095.pdf

You wont find a significant impact with a change to your PAJ unless you bypass the ACV circuit. I tired it 3 years ago with no sucesss before JD jetting kit was available. :thumbsup:

What issue are you trying to fix with your jetting? :thumbsup:

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You wont find a significant impact with a change to your PAJ unless you bypass the ACV circuit. I tired it 3 years ago with no sucesss before JD jetting kit was available. :thumbsup:

I tried the bypassed ACV circuit, as you know, but only dropped 1 jet size (52 down to 50). I got JD kit, the bike is great, but I felt it definately went better with the ACV disconnected. Still popped on decel, even though PJ set correctly.
What issue are you trying to fix with your jetting? :thumbsup:
It does run good with the 52 PJ and stock 80 PAJ, but the YZ use a bigger PAJ then the WR's for the same PJ size. Seeing as I have to use a way bigger PJ, I am thinking there must be some benefit of going with a bigger PAJ too.

Just hoping to stop popping with ACV disconnected, or get same feeling with ACV connected.

Waste of time? :bonk:

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I played with it in the hopes of getting rid of my bog, but it didn't do much. For my altitude and temps, leaving the entire Pilot circuit stock is what works best. I rode in 30 degree temps today around 9:00 a.m at around 5500' ASL with a 45 PJ and the bike ran like a striped ape. I had no decel popping or anything that would indicate a lean condition anywhere in the rev range. It eventually warmed up to 48 by noon and I got back down to 4700' ASL with no issues whatsoever. My current jetting specs are on the first page of the jetting database. It's the best the bike has run in cold weather to date! :thumbsup: :thumbsup:...SC

Cheers mate, I like how you say it warmed up to 48!!!!! Shit that's cold! :bonk:

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i tried bigger on my 04 wr 450 with excellent results,the stuff i ordered from sudco (slow air jet) wasn't correct. so i found a drill bit about the right size(i had a 80 and a 100 paj and looked for a bit that would change it about the same difference(larger) between those two,as i have no idea what measurement system they use) so i ended up with what i estimated to be a 120 paj which i ran with a 48 pj @ 2,000-5,000 ft pretty much yr round only having to change the mj from 165 to 170 in the winter. this was with the AIS connected. it was one of the best changes that i made to the jetting on that bike. consider though that i had a few mods on this bike;power now,powerbomb w/ pc4,yz airbox. but as cheap as it is,it'd be worth trying :thumbsup:

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i tried bigger on my 04 wr 450 with excellent results,the stuff i ordered from sudco (slow air jet) wasn't correct. so i found a drill bit about the right size(i had a 80 and a 100 paj and looked for a bit that would change it about the same difference(larger) between those two,as i have no idea what measurement system they use) so i ended up with what i estimated to be a 120 paj which i ran with a 48 pj @ 2,000-5,000 ft pretty much yr round only having to change the mj from 165 to 170 in the winter. this was with the AIS connected. it was one of the best changes that i made to the jetting on that bike. consider though that i had a few mods on this bike;power now,powerbomb w/ pc4,yz airbox. but as cheap as it is,it'd be worth trying :thumbsup:

That's what I wanted to hear!

What difference did it make? Pilot circuit way less erratic I suppose? :thumbsup:

I will have to ring around tomorrow and finally order some if I can find em!

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Basically what I understand now is the bigger the PAJ, the more fuel the PJ will flow.:
The PAJ controls vacuum at the PJ. A bigger PAJ should flow less fuel because it draws less vacuum. This is reflected in the chart; as you increase the PAJ, you must also increase the PJ to account for the reduced vacuum.
but the YZ use a bigger PAJ then the WR's for the same PJ size.:
I believe the WR's have an air-bypass that supplements your stock pilot air jet, unlike a YZ with a #100 PAJ

That said, the adjustable PAJ at sudco looks like just the ticket if you're into experimenting. :thumbsup:

Keep us posted.

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