Mikuni bs34 constant velocity.

[sdhadley94]

On my 81 xs400 special, I have 2 factory mikuni carbs. Thing is, it was running rich but still managed to score the plugs as if it were lean and rich. Cruising speed was a no problem. But anything over 35-40mph at around 1/8 to 3/4 throttle seemed like the bike had to catch it's breath before taking off. Mains are at 142.5
And the jet needle is a Y316S set at the middle position. How do I tune these jets to make my bike do 60 at least without bogging down?
Will post pics later. I'm stumped on what to do so any and all help, helps! Lol thanks guys

 

[xschris]

Needles should be 5GZ9 or a 5Z1. Mains should be 135 for the 80-82 sohc xs400 also. If you running stock exhaust and intake these will work. Have you synced the carbs with a manometer? Or set the valves to spec?

 

[sdhadley94]

I forgot to add that I have pods, stock air filters wouldn't stay connected to the boot. I have yet to do the sync. At the moment I'm having a hard time getting an idle without the choke on all the way. I have 3 main sets, 112.5, 125 and the 142.5 it had the 142.5 on it when I bought it and it ran, just sluggishly. And the valves, no. Imy new to bikes in general so I'm a little intimated honestly

 

[xschris]

With the wrong needles and pods, that will cause a lot of your issues.What pods do you have. The stock air boxes are held in place by a metal strap on the battery box. What pilots are you running and what are your pilot mix screws set at? You need the set your valves and then do a carb sync before moving on to jetting.

 

[sdhadley94]

According to the pdf service manual on this forum, I have all the right jets except for the jet needle. And the pods are from some eBay seller they're made by 2 fast? Honestly never heard of them but they gave the bike a sweet throaty sound around 4k.

 

[sdhadley94]

With the wrong needles and pods, that will cause a lot of your issues.What pods do you have. The stock air boxes are held in place by a metal strap on the battery box. What pilots are you running and what are your pilot mix screws set at? You need the set your valves and then do a carb sync before moving on to jetting.

Last night I seated them and brought them out 1.5 turns. I was gonna go from there after work and see if I can get a better idle out of it.

 

[xschris]

Post pics of the pods my guess is they are those crap gray cone type ones. Not everything in the manual is correct for all bikes. That part you listed is in the front of the book and for the 77 D model bike. Also it states the float height as 32mm which it should be 26mm. Your bike looks to be a 81 that had 135 mains. Since your bike is now not stock, getting it to work well will be a lot of trial and error. That wrong needle will give you a lot of 1/4 to 3/4 throttle issues.

 

[sdhadley94]

I've brought the pilot out 2 and it idles perfectly at 1450 and no backfire and I went ahead and lowered the needle (put the clip in the 4th slot) I'm a little lean but I managed to get rid of a lot of the lag.. so honestly I feel like if I raised the needle to the third slot it might do away with the power loss completely. Idk like you said trial and error. I'll probably end up getting the right needles and a set of 135's. But here's a picture of the pods

 

[sdhadley94]

They are grey and from ebay.. so maybe the same ones lol