'77 XS360 jetting question

[got20z]

Hey guys.
I'm working on a 1977 xs360 and recently purchased a 2 into 1 exhaust for it. Besides the exhaust change, the bike is completely stock otherwise. I was looking for some carburetor jetting advice for this setup. I wonder if this will be enough to require any major rejetting or not. Right now the bike is still apart.

I recently built a xs750 and had to do major rejetting but I did not have stock a airbox and it was a 3 into 1 exhaust. I know this is a much different bike so thanks in a advance for any posts of your experiences.

 

[xschris]

I would start with stock and go from there. You may only need to set your idle mix screws a bit richer. The xs360 carbs run a lot richer than xs400 carbs. I run xs360 carbs on two of my 400 bikes and even with uni pods on the H-pipe and a free flow 2-1 I still kept stock size jets. I would keep you stock air boxes. The bike will run it's best with them.

 

[got20z]

Thanks for your post. Sounds like a good place to start and if you have that setup with stock jets that gives me some hope for mine. It couldn't be any worse than the work it was to get the 750 to run well. Can't wait until riding weather!

 

[NewHavenMike]

I went through this last year alllll Summer lol. Stock main jet on my 360 was #135. I purchased a couple steps up and a new stock size size, I marred one of the originals up and had some crappy aftermarket jets.. Get authentic Mikuni jets!! The real ones will have a stamp on them. The best way I can describe it is it looks like a little square with another square inside it. Jets-R-Us has what you need.

In the end, I kept thinking I had to go up because I had an aftermarket exhaust.. I ended up settling on one step down from stock, #132.5. Now I have at least 10 different jet sizes.

I may end up giving the stock jets a try this Spring. Testing new jets was a long process for me. I would install them and sometimes Id be able to tell right away that the jet was too big or too small. Other times I had to ride the bike for a couple weeks. I remember one of the longer tests I did, I was riding around with these jets. I think they were 120 something maybe 130, I was alright on the street and cruising at 45mph. When I got on the highway, I couldnt go faster than about 70mph.

I was forgetting the fact that main jets are used under full throttle and high speeds. You really need to run the bike out to redline to find the right jet..

 

[got20z]

Thanks for sharing.. Sounds about exactly like the time I had with my other XS last year.

Please post back if you toy around with stock jetting again this year.. I probably won't have my 360 road ready until April.