I had 4 XS650’s over the last 35 yrs so I can appreciate your sentiments but that is not why I am writing.
I just modified my XV1100 SH (1996) Virago to accept a H-D K&N RK-380B air cleaner assembly. I am thrilled w/ the modification and my OEM jetted carbs are great from idle to 3/4 throttle. After that the bike feels as if it has a miss. I believe that I have to replace the main jets. Another Virago tech forum member did a similar but not identical mod and had to open his main jets two sizes larger. My Hitachi HSC40’s have stock sizes of, Front #122, Rear #128. Does that mean that I should go, Front #126, Rear #132 ? I appreciate your advice.
Your jet size estimates sound correct. When you change an intake or an exhaust you’ll generally go up on the main jet anywhere from 1 to 3 sizes. 2 is probably about right for your bike, but personally I never make jetting adjustments in increments more than one jet size. If I was you I would pick up a 124, 126, 130, and a 132. I’d go up one size on the main jets then give it a ride. If it still stammered at open throttle I’d go up one more size.
Most (imported) transversely mounted air-cooled V-twins like your Virago run the rear cylinder richer than the front to keep it cooler because it doesn’t get a whole lot of air flow. Kind of an interesting solution to a specific problem. Just part of the reason the big twins never have a competitive edge in any racing circuits.
Anyway, thanks for reading the blog. Let me know how it goes.
Lots has happened since the message below.
1- It turns out that the Factory service manual was wrong. I do not have Hitachi’s I have Mikuni’s. This is very good because of widespread availability of various jet sizes.
2- After becoming extremely effective and proficient at removing and installing carburetors I have finalized the jetting. 140 for the front cylinder and 137.5 for the rear, that’s 6 sizes up. I opened the pilot jets up to 42.5, that’s one size. If you read your attached post you can be amused that you threw me one. I thought that my jets were in ass-backward but after I inquired on the Virago Tech Forum I found that not to be the case. I was severely chastised. The front cylinder is richer of the two.
3- My Photobucket slide show is complete. Here’s the link http://s156.photobucket.com/albums/t23/ … 20Cleaner/
Please view it and provide me w/ some honest critique.
4- I synced the carbs w/ a homemade “Manometer” constructed for <$4.00.
That’s it. If anyone can use any of this info then pass it on.
Great looking bike you have there.
I find it very odd that the front cylinder would be the richer of the two. I’m going to do a little reading on that out of curiosity, I can’t think of why that would be. Glad you got it sorted!