Exhaust modification and Main / Pilot jets

I have recently been working on my sons Xj650 (1980). It wasn't running well at all. So I first cleaned the carbs, checked valves and compression (both OK) Checked and adjusted fuel in floats (wet). When I cleaned the carbs I noticed the main jet was #107 and the pilot jet #45 ( manufacture recommended #110 and #40). Today I was learned from a friend that the muffler or exhaust on the bike is not factory - which based on reading numerous posts, that likely accounts for the change in main / pilot jets ? The problem is I don't know how to confirm the correct jets were used. Attached are photographs of the exhaust now on the bike - any chance anyone would recognize them and be able to let me know if the #107 and #45 main / pilot jets are correct - or at least point me in the right direction ? Thanks

 

Commonly you go about 3 main jet sizes bigger when you attach an aftermarket pipe, due to its ability to flow more freely.

 

Looking at the pic. The bike still has the stock airbox. This is good.
It is hard to tell for sure, but the exhaust appear to be a 4-1 (single muffler). If that is the case. The bike was rejetted, and the 107 main is on the lean side.

Is the air fiter a stock paper filter, or aftermaket highflow (K&N, Uniflo, redish in color)?

What do the plugs look like. tan (paper bag brown), or white?
If possible post a pic of the plug ends.

Getting a bike jetted properly is mostly a trial, and error process.

Read this post
The Information Overload Hour
Approx 1/3 the way down where it talks about pods will give you a starting point to understand jetting the carbs.

Ghost

 

Looks like a MAC 4-1, those mains are too lean, maybe get some 114 or so.

BIG thing i've just recently found with the MAC's, the baffle is held in the pipe by ONE (1)! *RIVET* mine has come loose and the baffle rattles around like a stone in the pipe.

I seriously think MAC should be charging $100 for that POS exhaust, not $400.

The reason I bring that up, loose baffle means that the exhaust can escape around the outside of the baffle and be unrestricted, making you run even more lean.

 

MiGhost to answer your question, the air filter is not the "paper type" but a "UNI" brand foam filter (picture attached) it is however the same shape and box as the factory one.

As far as plug condition I have attached 4 sep. pictures of the plugs - unfortunately while the plugs are new, and the bike hasn't been out of my garage, the bike has been run frequently in the garage while working on it over the past few weeks - so they aren't new any more. Plugs from cylinders 2 and 3 look rich while 1 and 4 -mostly 4 looks lean ? At least compared to when I cleaned them and putt them back before testing again.

Plugs aside, I assume the more pressing issue before looking at the plugs is the issue of Jets and the change of the exhaust / air filter ?? So these are the JETS that are presently in the bike:

Elevation: Live at or very close to sea level (less then 500 feet)

Main Fuel #107 (Factory #110)
Pilot Fuel #45 (factory #40)

Main Air #66 (factory #50 ???)
Pilot Air #195 (Factory #195)

So, if I understand the posts regarding jets and modifications a good starting point would be:

MAIN FUEL Modifications:
1) As the exhaust change to a 4-1 pipe add +4
2) Air filter NO change ??
3) -2 for overall modifications / result +2 on Main Fuel Jet = #112

Pilot Fuel: " Increase the pilot fuel jet size +1 for every +3 main fuel jet size increases.

1) As Main fuel jet increase of +2 results in +1 increase of pilot jet = #41

Main and Pilot AIR jets = No adjustment needed ??

All this to say start with:

Main fuel #112 (Factory #110 / current #107)
Pilot Fuel Jet #41 (Factory #40 / current #45)

Leave Air jets alone -- I'am I missing something ??