XS750SE Pilot Circuit Diagram/Photos

Neemox

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Hey all, I have a 1978 XS750SE that I have owned for a long time, and neglected for a long time. In an attempt to get things back to normal, I recently threw away the pod filters that were on it when I bought it, and got a replacement airbox to put things back to stock. It never ran super well with the pods, and it became a bit of a project that I put on hold for too long.

It's been sitting for a couple years at this point. I changed the gas, Tightened the deadbolts to spec, check the valve clearance's and replaced two shims to bring everything back in line. That's about where my engine knowledge ends, as everything else I've worked on is fuel injected.
I replaced the boots for intake and airbox, I opened the carbs up and soaked them in B-12 dip and also made it a point to clean out the pilot circuit in the float bowl. I checked the jets and seems everything was left stock even though it had pods.

I bench synced the carbs, and am planning on timing and carb sync once I can get the thing to a nice warm idle. Which is where I'm stuck. The bike actually fired up real nice on full choke, and ran forever at half choke, around 950 RPM. Even after letting the bike warm up for 20 minutes or so, if I tried to kill the choke, it just sputtered and died right away. I restarted it and tried to kill the choke while giving gas, and I could keep it alive as long as I stayed on the gas, but if I let off for a second, it would die right away.

Reading here, it sounds like I failed to get the entire Pilot circuit clean? So my question is, is there a solid clean/rebuild protocol for these carbs? My understanding is they only really used these for two years? All of the picture/videos/write-ups I am seeing are for the earlier 1977 carb, and I'm admittedly a little lost. I have the clymer but it doesn't go into enough detail either.

Any help at all getting this bike back to normal is sure appreciated.
 
Thanks for the info there. I definitely feel like not too long ago there were more resources for the triples, but I'm sure not finding them now.

The parts manual regretfully doesn't quite get details enough to tell which of the critical passages I'm missing for the pilot circuit
 
Thanks for the info there. I definitely feel like not too long ago there were more resources for the triples, but I'm sure not finding them now.

The parts manual regretfully doesn't quite get details enough to tell which of the critical passages I'm missing for the pilot circuit


Yes, i see the UK one has folded as well. There is a German one https://www.triples.de/pages/main.html i have linked towho have a forum. Will need to use translate, they may be able to answer, or have the info your after.

It might pay to download anything off that Minek page before it to goes the way of the others. There used to be a great one, then it folded and gave all the info to the guy that ran the UK Site. unfortunately he never reposted 1/4 of it and now the UK one has folded all that info has been lost
 
You will need to remove the brass and check it's open, plugged pilot jets would be my guess here. Use spray carb cleaner and be sure it will go from pilot to spray out the idle holes at the butterfly.
I did pull the pilot jets and carb cleaner sprays through them great, fun little pattern coming out the side. I did not ever see spray at the butterfly bore though, so perhaps those are the passages I am missing. Do you know how many of the holes in the throat should be tied to the pilot circuit? 1 is for the choke, right?

Thanks in advance!
 
FWIW, my XS750G was a pig to start cold when the exhaust baffles were rusted out. I concluded that the jetting was so weak from the factory that it didn't take much of an upset on the inlet or outlet to screw it up.
<edit, the last of the 750s was the F, the 850 was the G>
 
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There is also a (very small) hole straight through pilot jet, that's the one that gets clogged.
a pic of your carb?
Well, if there is a hole in the end, it is definitely clogged. Great info here. Thanks. I'll pull the carbs again and get pics in the process
 
Cutaway of a couple types of pilot jets.
They're all pretty similar.
mikunipilotjetsmoddedam2.gif
 
There are 2 or 3 holes in addition to the idle outlet that has the mixture screw in it. All are fed by the pilot jet. Spray cleaner in the pilot jet, with the butterfly open. You should see fluid coming out all the holes.

If you don't see a good pattern, with your finger covering the idle outlet with the screw out, blow cleaner backwards thru the mix screw. Cleaner should discharge thru the holes and where the pilot jet was.in the bowl.

If still no joy, find some thin multi strand copper wire. Take one thin strand, put a 90deg bend in it and probe the transition and idle ports from inside the carb throat. Blow cleaner backwards again.
 
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