Which way are the air jets sopposed to go in the carbs?

I just inherited a 82 750 seca from my father in law's passing and I've been trying to get it to run right. I decided to look at the carbs since I found a forum on this site that said that there is a misprint in the Haynes manual which I have. The Haynes manual says the smaller jet is supposed to be on the side closer to the cylinder head and the post that I read said the other way around.

Here is a link to the page I read. The particular post is towards the bottom.
http://xjbikes.com/Forums/posting/mode= ... c/f=4.html

By the way, I am new today to this site but I've been poking around here for a couple weeks now. This place is awesome. Thanks ahead of time for the help!

 

The smaller air jet is the main jet. So iirc you are correct that the small jet is on the motor side of the two. Will have to check my manual tomorrow to confirm.

Dave

 

The smaller jet should be in the more "middle" position. The smaller jet should be farther from the middle. the Haynes is wrong in the placement

 

what are teh chances that someone took the jets out and put them in different places???

the jets go back in the same place you took them out.

if they are plugged. i used boiling water to clean. and a bristle from a wire brush.

 

I can tell that the carbs have been taken apart before and I suspected that whoever did the carb job probably referred to the manual. If the manual is incorrect, then i suspected the jets were wrong.

I did take them apart last night and discovered that the jet with the smaller opening was in the side that would be closest to the engine and the larger one was in the middle. If I understand you correctly, that is wrong, so i did the switch and now the exhaust is really smokey and it wont idle (i have to hold the throttle to get it to stay running). It does sound better to me though (has a deeper richer tone to the engine sound).

If the valves are now in the correct position and the bike runs worse, what does that tell me? Too much gas getting in? I checked the pectock and it looks good. Bad float needle gasket? There was some gunk in the carbs but the jet holes were clear.

Thanks for the help

 

Welcome to the site !!

Your link didn't work for me.

 

Sorry about the bad link, this one should work

http://www.xjbikes.com/Forums/viewtopic ... plugs.html

 

the larger jet goes in the middle. it's the main jet. it's also the jet that your throttle needle slides up and down in. it's used for wider open throttle circuits

the smaller jet is your pilot jet. used for idle to low throttle circuitry.

i don't have my yamaha anymore but i beleive there should be an air pilot jet also. it's on the backside of the carb air intake. if it has it.

i don't know if there's any other jets. other then what would be in the top part of the carb under the cap. the parts fischer shows pilot air jet is in the front. main air jet is in the middle. doesn't specify a jet number though.


you probably won't be able to read the numbers on the jets. but you should confer with the manual to make sure you have the right numbers. unless the manual has the wrong information on that part also. then you'll have to ask other members.

parts fischer shows the main being a 120 inside the float bowl. it's not listing the pilot or an air pilot

 

The main AIR jet goes directly above the main FUEL jet, and likewise for the pilot AIR jet.........it is located directly "above" the pilot fuel jet.

The main AIR jet is fitted to the "center" hole in the area under the vac piston diaphram and is the SMALLER of the two air jets. The pilot AIR jet is fitted in the forward-most hole and is the LARGER of the two air jets.

The above info only applies to Hitachi carbs; Mikuni carbs (used on 550's, 650 Turbo, 700-X, 900, and 1100 models use a different arrangement).

 

do you have jet numbers chacal???

so he can make sure he's got the right stuff in the right holes or if he needs to order the right stuff.

 

Yes, for all the 1981-83 XJ750 models, you should use:

#205 pilot air jets
#80 main air jets

#40 pilot fuel jets (Canadian and Euro model XJ750 models use #43 pilot fuel jets)
#120 main fuel jets (750P police bikes used #118 main fuel jets)

 

This is the diagram from Yamaha

Tell me if I am not allowed to post this here, and I will remove it. I don't know the rules about posting manual pages.

As you can see, Pilot is on the butterfly side, main on the airbox side.
As chacal posted, main is the smaller of the two air jets

Cheers
Dave

 

Ok, thanks a lot guys. I found out that the jets in the bowl were switched too. I have everything just like chacal described. I took the carbs apart and checked everything extensively and cleaned all the parts. Only found one bad bowl gasket, so I ordered a new set.

Confirmed that there is a misprint in the Haynes manual (its a wonder people don't do it right). Will let you know how it turns out. Thanks again!

 

Yay team, color me impressed! You ALL got this fellow headed in the right direction with timely information and, might I say, a useful picture. Big kudos to Chacal, Snowwy and Azrael. Bravo Zulu!