140 main jets!?

Hello All, I found a garage find ( parked since 1988) 1976 kz 900 last fall. The bike was clean and modded with a 4 into one, electronic ignition, a 42 tooth rear sprocket and some nice chrome work. I have no other info on any internal mods.
The tank was clean so I pulled the plugs and loaded all cylinders with wd40 a couple times over several weeks, and found good spark +compression. With a squirt of starting fluid and some battery, she barked to life immediately.
Since then I've replaced the oil, gave the carbs a modest clean up,and new plugs. The original aftermarket air cleaner had disintegrated and I could not find a replacement element so I went with pods. Before the pods I could get the bike to run. Now...no luck. I assumed I needed to jet up and so took off the carbs and found mains marked 140 with 17.5 pilot jets on what I think are 2nd generation 128mm carbs. The bike has a Racer One 4 into one pipe.
Thats the bad news. The good is I think this is actually a Z1 based on the frame number - Z1F-502288 and manufacture date of 10/75.
Based on all I've read here the 140 mains seem huge! So I have a couple questions:
Should I assume some internal mods to warrant the huge mains?
What is the trick to removing an oilfilter cover thats been untouched for 25 years?

It's a really nice looking bike and I had such a boner for one these when i was a youngster that i can't wait to ride this monster. These have such a distinctive engine note it's a rush just to hear that music again. I'll share some pics when it's closer to being re-assembled.
Thanks for the help you've already provided and I appreciate any comments on this thread

I have 125's in my 33's. Buy a K/N filter for your air box and keep it. I'd like to see some pics.
Good Job.
Steve

Hoping a photo will compel some comments and I've also come up with another question - there are 2 nipples on the fuel tank...one main, one reserve. There are also 2 lines from the fuel rail. Does this require a double T set up? That is - T the fuel lines and then T again at the petcock?

Cant seem to get Pics to post

Both go to the carbs. Reserve is switched in the petcock.
Steve

stevets wrote: Hello All, I found a garage find ( parked since 1988) 1976 kz 900 last fall. The bike was clean and modded with a 4 into one, electronic ignition, a 42 tooth rear sprocket and some nice chrome work. I have no other info on any internal mods.
The tank was clean so I pulled the plugs and loaded all cylinders with wd40 a couple times over several weeks, and found good spark +compression. With a squirt of starting fluid and some battery, she barked to life immediately.
Since then I've replaced the oil, gave the carbs a modest clean up,and new plugs. The original aftermarket air cleaner had disintegrated and I could not find a replacement element so I went with pods. Before the pods I could get the bike to run. Now...no luck.

Hope you saved the stock airbox. You can get replacement filter elements by size. You buy the metal frame with the foam cell filter element around it and oil it. I have been running one for 30 years.

K&N filter. But once, use forever.
Steve

There was no stock airbox...it was a non branded aftermarket thing with what was once a reusable foam filter. Seems like it would have been fairly unrestricted and I'm not sure how much the pods actually increased the amount of air available. Again - 140 main jets! This thing was getting plenty of fuel and air.

140's are way too big.
Steve

Hey swest. I thought the same thing and thats why I started this post. And yet - today I finished putting everything back together and she fired right up! Used the idle adjust screw to set that and it is purring like a kitten. The bikes been sitting for 25 years and the clutch is seized. My first ride on the bike was an attempt at busting loose the clutch by doing the whole accelerate/decelerate thing but no luck.

Check under the sprocket cover. Grease the clutch release arm.
Steve

Dug in to remove the clutch today. When I put the impact wrench on the 30mm nut that holds the outer basket, the clutch broke loose and spun freely. I still disassembled the plates and my luck continues: everything was beautiful! Reassembled and put the first 4 miles on her since 1988.
Now it's "just" a matter of figuring out why she starts bogging at about 5000 revs.