Jetting on a 77' XS360

[ciaostupido]

Hi there. I recently purchased a 1977 XS360 for my first bike. I've worked on small displacement 2 strokes and mopeds before so i get some of the theory behind it. Anyway does anyone know what jets, mainly idle and main jets I should be running on a stock xs360 with Mikuni BS34 Carbs?

I ask because recently I've been doing some much needed maintenance to this lil' guy. It sat in a barn in Nh for the first 1/4 of its life. Then the previous owner got it running abit roughish but running. Now i have it and have been slowly bringing back to the 21st century. I replaced the friction discs in the clutch. But my problems started after I replaced the intake boots.

I had ultrasoinic'd the carbs like four times. The main jets in the float bowls weren't coming out so I had to extract them. Now the first round of jetting I followed the xs360/400 service manual and ordered 135's off of MikesXS. Little did i know those jets aren't genuine Mikuni jets and caused the bike to run suuuuuuuuper lean.

So I got proper Genuine Mikuni jets and installed them, the 135's. Also another discrepancy I'm trying to figure out is the Idle jets. The manual calls for 17.5's, but Mikuni doesn't make 17.5's without the air bleed holes anymore. They only make the 42.5's range that the XS400 jetting specs use. So I put in some Mikuni VM 17.5's that have the air bleed holes but the bike is still running lean and my idle does go up from time to time unless I blip the throttle.

Soooooo should I run an XS400 jetting spec on these carbs? I heard they were jetted lean from the factory. So that would mean I would go up to either a 137.5 or 142.5 main, and a 42.5 idle, as thats what the manual calls for on all the models of the XS400's but calls for obsolete 17.5's on the XS360. Anyone with any experience think this is the way to go?

Also what should I do about the fact that Mikuni doesn't manufacture any 17.5 Idle jets with no air-bleed holes anymore. Should I run regular vm 17.5's, or go up to the 42.5's with the non air bleed holes?

Any help would be awesome, as im starting to turn into this guy:

 

[xschris]

17.5 non-bleed is what you need for a stock bike. I know if you run non-bleed in the xs400 carbs it will not tune right, I made that mistake once Have you tried yamaha or a search on the net? These use a different type of jet than the later bikes use. Not like the bleed and non-bleed VM's. I posted a few pics The xs360 one is on the left in the first and second pic. After you find the correct jets make sure all the holes in the carbs are clear with compressed air (125+psi) and all the rubber o-rings/seals are new ( needle jet o-ring and butterfly shaft seals) Then sync them with a manometer.

 

[xschris]

The 77 yamaha xs750 was another bike that used those style jets. http://www.ebay.com/itm/77-Yamaha-X...Parts_Accessories&hash=item336d4b3893&vxp=mtr Found these on ebay.

 

[ciaostupido]

Right so there are no fresh new ones I can buy, just old used ones?

And yes I have re-synced these carbs and cleaned them multiple times with an ultrasonic cleaner, compressed air, ect. Also replaced the needles and needle valves, ect, ect..

 

[xschris]

There is nothing bad about used jets as long as they are not damaged. If you soda blast them they will look and work like new. I do this with all the carbs I sell and use with no issues.

 

[ciaostupido]

Weeeellll.. .I guess thats my only option then XD. Is there any benefit to running 142.5's and 42.5's jetting like the xs400 has? or is that wayyy to rich on the 360's cylinders?

 

[xschris]

The xs360 carbs are NOT like the xs400 ones and run much richer with stock jets. My 80 has xs360 carbs with stock jets and settings. The bike has a free flow 2-1 exhaust and k&n's on the H-pipe. Runs and starts great all with stock jets. You CAN'T use non-xs360 pilot jets in these carbs. The ends are different and the size is not the same. I just stopped at my local yamaha dealer and they had some N.O.S mikuni pilot jets for it. They where $12 each I got them just to have as they are no longer around and used on very few bikes.