Jetting Problem

I think I posted this in the wrong forum the first time sorry


I have a 1985 XJ 700 Maxim when I got it it did not run the best and I got it dirt cheap and now it is about 90% restored but I have a jetting problem I think. the Previous owner put on after market exhaust but never re jetted the carbs even though they said they did but the jets were 107 main and 36.5 pilot any way after a-lot of cleaning it ran pretty good but no top end power so I up the main jets to 110 and now it will do 120mph with no problem but my idle is off and I am getting some back fire I tried to get it synced but it still does it do I need to up them also to maybe a 40 from 36.5. ???

 

Try giving it some additional Richness at the Pilot Mixture Screws. You might be able to tune it out.

At some point there is no adjustment left on the Pilot Mixtures. You might be wide open and needing the additional Richness that upping the Pilot Jet will provide.

Look at them Plugs and see what the engines telling you. If the Plugs are too clean for their own good ... Order the hotter Pilot Jets. You'll need them if you have the Pilot Mixture Screws beyond 3.5 Turns out and the situation hasn't improved.

 

as far as I can tell there is no pilot mixture screw on my carbs they are Hitachi my service manual says there is also but I cant find it where it says it should be. but there are 2 jets under the diaphragm could one of them be it. cause the plugs are getting white so it is running quite lean.

 

No. They are on the outside, in front, nest to the enrichment valves and to the side of the pillar that the choke rod travels through.

If you cant see them look for a small, round, blind plug covering them.
The Screws are below the "Anti-tamper" Plugs.

The soft brass screw head is concealed by the Plug thats fitted into the housing.

You will have to drill them out.
Drill a small hole through the center pf the plug taking every precaution not to break through and have the drill damage the screw head.
Then you screw-in a drywall screw into the Plug and grab on to the drywall screw with some vice grips and impact the vice grips to extract the Plugs.

 

thank you for the info I will let you know how it turns out.

 

Don't push the drill through the Plug.
Let the drill work with minimal pressure.

I cannot over-emphasize the need to be careful NOT to damage the Slot on the Screw ... practically touching the base of the Plug.

If you can do the job without drilling all the way through the Plug ... all the better!