MISSIONmoto Mike
XS400 Member
Hello, this is Michael from MISSIONmoto.org I'm a new member on the forum.
I lead a WA state nonprofit 501c3 that takes donated bikes, we fix and sell them to support missions and youth programs. MISSIONmoto.org. Before posting, I'm pretty sure I read all the threads I thought my have an answer for me.
We’re finishing a donated 1979 XS400F project. I've already spent money on new jets, and I think they are wrong...I should have reached out for help earlier because PO may have had wrong types of jets to begin with and I just ordered bigger sizes of the wrong ones. You never know what surprises await you with abandoned, donated projects.
Bike has pod air filters and 2 into 2 short exhaust- no crossover.
We've got 160 compression on #2, 155 on #1
Set the valve lash correctly
Set points gap and timing correctly
Intake manifolds look rough on outside, but no cracks on inside
New, correct NGKs
Set float height to around 26.5 to 27 per manual but I did see another manual say 30+. No gas leaks now, but what is the correct measurement?
Carbs were meticulously cleaned with cleaner, ultrasonic, and compressed air.
Has Mikuni carbs, but can't confirm the exact type. Takes the round main jets.
Bike would fire right up, but only run with full choke.
1. #2 carb has the air/fuel mixture screw broken off in it. It’s the little screw that sits on top in between carb and intake. I was reading a post where it mentioned these can break if over-tightened. Sure enough, when I backed out #2 the little sharp internal end did not move at all. I’ve got to get it out and replace it. Any advice and what’s it called exactly and where I can buy one?
2. When pulling the main jet, there was a thin metal washer pressure fitted on top of the main jet. All parts diagrams I've seen show a smaller washer going in first, then the main jet going in through the middle of it for seating. Our washer only clicks in on the top, won't seat in the tube. The Main Jet was a 132.5 Big Round type. Legit?
2. Removed the metal screw plug and removed the 42.5 idle jet
3. Thought I'd better go two up on both the mains and pilots. So after looking at all Google images and ebay listing images, paying attention to large round vs. small round mains, and looking at the tips of the idle jets paying attention to tapered vs. flat ends
I ordered 137.5 mains and 47.5 idles from Niche-cycle off ebay. Had identical look and feel to my old ones.
4. Popped all jets in, mounted carbs and filters, bike ran worse than before! Could not even get it to stay running. Pulled carb and jets and the weird thing is after closer inspection the hole passages on the new main and idle jets look noticeably SMALLER than the old ones even though the size markings say they are two sizes bigger!!!
We are lost. Can you help us? I can send you pictures. I don't know XS models well and can't tell if PO put different carbs on or wrong jets in, or maybe I ordered the wrong jets or the new jets got marked with the wrong sizes at the factory?
Real bummer because we just finished a custom paint job and got the seat fabrication done and most electrical done. Can't sell the bike now; everyone loses until we can.
Thanks, Michael 206.427.1955 in West Seattle
I lead a WA state nonprofit 501c3 that takes donated bikes, we fix and sell them to support missions and youth programs. MISSIONmoto.org. Before posting, I'm pretty sure I read all the threads I thought my have an answer for me.
We’re finishing a donated 1979 XS400F project. I've already spent money on new jets, and I think they are wrong...I should have reached out for help earlier because PO may have had wrong types of jets to begin with and I just ordered bigger sizes of the wrong ones. You never know what surprises await you with abandoned, donated projects.
Bike has pod air filters and 2 into 2 short exhaust- no crossover.
We've got 160 compression on #2, 155 on #1
Set the valve lash correctly
Set points gap and timing correctly
Intake manifolds look rough on outside, but no cracks on inside
New, correct NGKs
Set float height to around 26.5 to 27 per manual but I did see another manual say 30+. No gas leaks now, but what is the correct measurement?
Carbs were meticulously cleaned with cleaner, ultrasonic, and compressed air.
Has Mikuni carbs, but can't confirm the exact type. Takes the round main jets.
Bike would fire right up, but only run with full choke.
1. #2 carb has the air/fuel mixture screw broken off in it. It’s the little screw that sits on top in between carb and intake. I was reading a post where it mentioned these can break if over-tightened. Sure enough, when I backed out #2 the little sharp internal end did not move at all. I’ve got to get it out and replace it. Any advice and what’s it called exactly and where I can buy one?
2. When pulling the main jet, there was a thin metal washer pressure fitted on top of the main jet. All parts diagrams I've seen show a smaller washer going in first, then the main jet going in through the middle of it for seating. Our washer only clicks in on the top, won't seat in the tube. The Main Jet was a 132.5 Big Round type. Legit?
2. Removed the metal screw plug and removed the 42.5 idle jet
3. Thought I'd better go two up on both the mains and pilots. So after looking at all Google images and ebay listing images, paying attention to large round vs. small round mains, and looking at the tips of the idle jets paying attention to tapered vs. flat ends
I ordered 137.5 mains and 47.5 idles from Niche-cycle off ebay. Had identical look and feel to my old ones.
4. Popped all jets in, mounted carbs and filters, bike ran worse than before! Could not even get it to stay running. Pulled carb and jets and the weird thing is after closer inspection the hole passages on the new main and idle jets look noticeably SMALLER than the old ones even though the size markings say they are two sizes bigger!!!
We are lost. Can you help us? I can send you pictures. I don't know XS models well and can't tell if PO put different carbs on or wrong jets in, or maybe I ordered the wrong jets or the new jets got marked with the wrong sizes at the factory?
Real bummer because we just finished a custom paint job and got the seat fabrication done and most electrical done. Can't sell the bike now; everyone loses until we can.
Thanks, Michael 206.427.1955 in West Seattle