I sourced my jets from a local shop ( http://www.siriusconinc.com/ ) and don't have a part number. I paid CDN $3/ea. for them, but I have preferred customer status with them.
I've been told that the holes in the side don't matter.
Dave
-
Enjoy XS400.com? Consider making a donation to help support the site.
XS400.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
To Pod, or not to Pod? That is my question!
- Thread starter 16VGTIDave
- Start date
I sourced my jets from a local shop ( http://www.siriusconinc.com/ ) and don't have a part number. I paid CDN $3/ea. for them, but I have preferred customer status with them.
I've been told that the holes in the side don't matter.
Dave
Nuno
XS400 Enthusiast
I sourced my jets from a local shop ( http://www.siriusconinc.com/ ) and don't have a part number. I paid CDN $3/ea. for them, but I have preferred customer status with them.
I've been told that the holes in the side don't matter.
Dave
Yes I know, but it seems like Mikuni forget about Europe a long time ago.
In Rome if you ask for a jet, the shops answers that you have to order them and you have to buy the whole series. So I looked online and the cheapest shop I could find is in Germany and wants 8€ (10.3$!!) for one jet + shipment.
Long story short...I bought them from US (ebay), 7$ for two pilot jets, 7$ for two main jets, 6$ of shipment....without raising my ass from the chair (actually I sit on a loudspeaker..but that's a whole different story...
)p.s. = I sweared I'm not going to shave 'til the XS is not back on the road, I hate the long beard so I'm really rushing to finish it.
Nuno
XS400 Enthusiast
mhm...same problem as before.
The bike starts just fine but as soon as it warm up it won't idle anymore...as soon as I pull the choke everything goes fine and I can freely rev it.
and know you'd say : just put a bigger pilot jet.
Of course I will, the point is that I'd expect the carburation to become rich when hot, not leaner...that doesn't make sense at all
The bike starts just fine but as soon as it warm up it won't idle anymore...as soon as I pull the choke everything goes fine and I can freely rev it.
and know you'd say : just put a bigger pilot jet.
Of course I will, the point is that I'd expect the carburation to become rich when hot, not leaner...that doesn't make sense at all
- Vacuum leaks when hot? Check the carb mounts.
- Is the fuel boiling causing vapour lock? (unlikely, but a possibility)
- Collapsing fuel line or vacuum line to petcock?
- Dirty carbs or dirt in the float bowls? This is the usual problem, even if they have been cleaned 2 or 3 times.
- Are the carbs setup reasonably well? Try increasing the idle speed adjustment a turn or 2 (just be ready to hit the kill switch if it is too high!)
- Is the ignition system failing or breaking down when hot? A rich mixture is easier to ignite.
- How about low battery voltage?
You should be able to get it to idle even with the stock pilot jets, even if not well... Maybe it is time to get back to basics. Remember the triangle of engine operation - Air, Fuel, and Ignition. If you are missing one (or have too much) of these three, you won't be running!
Dave
- Is the fuel boiling causing vapour lock? (unlikely, but a possibility)
- Collapsing fuel line or vacuum line to petcock?
- Dirty carbs or dirt in the float bowls? This is the usual problem, even if they have been cleaned 2 or 3 times.
- Are the carbs setup reasonably well? Try increasing the idle speed adjustment a turn or 2 (just be ready to hit the kill switch if it is too high!)
- Is the ignition system failing or breaking down when hot? A rich mixture is easier to ignite.
- How about low battery voltage?
You should be able to get it to idle even with the stock pilot jets, even if not well... Maybe it is time to get back to basics. Remember the triangle of engine operation - Air, Fuel, and Ignition. If you are missing one (or have too much) of these three, you won't be running!
Dave
Nuno
XS400 Enthusiast
Battery is new and I put it on charge every night.
All the stuff you mentioned can lead to the bike to die but pulling the choke wouldn't fix it.
What I was thinking is that maybe the choke circuit is not working properly.
There are two kind of choke: the first one reduce the amount of air, the second one increase the amount of fuel. If I don't get it wrong the one on the Mikuni is of the second kind.
What I mean is that I may have an oring not sealing properly so basically my choke is always ON (that's why the bike starts so well) and when it gets hot (time to close the choke) I act on the choke and somehow push back the oring in position.
This "intuition" came to my mind because when the bike is hot and I want it to idle I don't fully pull the choke, I just have to move it a bit and everything goes fine.
Make sense? Should I go back to EFIs?
Battery is new and I put it on charge every night.
All the stuff you mentioned can lead to the bike to die but pulling the choke wouldn't fix it.
What I was thinking is that maybe the choke circuit is not working properly.
There are two kind of choke: the first one reduce the amount of air, the second one increase the amount of fuel. If I don't get it wrong the one on the Mikuni is of the second kind.
What I mean is that I may have an oring not sealing properly so basically my choke is always ON (that's why the bike starts so well) and when it gets hot (time to close the choke) I act on the choke and somehow push back the oring in position.
This "intuition" came to my mind because when the bike is hot and I want it to idle I don't fully pull the choke, I just have to move it a bit and everything goes fine.
Make sense? Should I go back to EFIs?
The start function (what we are calling the choke) adds air for a faster engine speed (at a low setting) and fuel (if operated more) to compensate for a cold engine. If your throttle plates are adjusted completely closed, then the engine won't idle when you fully release the choke. That is why I suggested increasing the idle speed adjustment. This will also get the carbs partially above the idle (pilot) circuit and onto the main circuit to allow for more testing.
Also, if the pilot screw o-rings are not sealing properly, you won't get enough fuel to idle well no matter how large a jet you install. Though it doesn't sound like this is the problem.
Have you been able to determine if the engine is running lean (popping, sharp and crackling exhaust tone) or rich (black smoke) when you release the choke?
Let us know what you find!
Dave
Nuno
XS400 Enthusiast
that's not the case for a simple reason: I start the bike with no choke at all and it starts fine.
anyhow there is no black smoke, the engine seems to run pretty well when cold and also when hot IF the choke is activated.
The problem is that it should start with the choke and then run without it....my bike starts without and runs with!
Sorry, I forgot that you had already mentioned that.
I just watched your video again. It sounds to me like your bike is running lean when you rev the engine. I know that your exhaust is wide open and very loud. But the TONE is what I'm referring to. It sounds harsh and "crackling". A rich mixture would have a deeper tone without any crackle or popping. If you run the bike in darkness, can you see blue flames out the exhaust when you rev it?
Back to the idle problem - I'm grasping for straws, but I keep thinking that you have a vacuum leak or 2 when the engine is cold. A rich pilot mixture and vacuum leak would have the engine running when cold (what is cold for you, 20C?). If the leak then closed up when the engine warmed up, it would stall from lack of air. Especially if the throttle plates are closed too far to compensate for the vacuum leaks when cold. This would also explain why you need to open the choke to get it to idle when hot.
Try adjusting the throttle stop for a higher idle to see if you can keep it running without the choke. Then you could adjust the carbs a bit and see if you can get it to idle at a lower RPM, check for vacuum leaks, etc.
That is all I can think of.
Dave
Nuno
XS400 Enthusiast
how many of us has seen the video?
how many of my friends has heard the bike live?
how many times did I try to carb that thing???
Well....nobody has been so good to hear one of the cylinders was not firing (in Italy we'd say "it was going by 1")...faulty spark plug. It works outside of the cylinders but not once it's inside... just put another plug and everything is fine (except that now the bike is awfully rich).
Your pilot jets should have the holes in the sides. If you have or use the non-bleed type it will run poorly on idle
Attachments
Nuno
XS400 Enthusiast
Your pilot jets should have the holes in the sides. If you have or use the non-bleed type it will run poorly on idle
no I ordered the right one.
Now that the bike seems to be running fine I can make the fine adjustments. It's such a relief...
Glad you were able to find the problem and fix it Nuno. Thanks for the update!
Dave
Dave
Nuno
XS400 Enthusiast
Not at all! There are many possible causes for the problems you had. You just had to work through them until you found it. We have all gotten stuck thinking we knew what the problem was, and been unable to fix it because we were ignoring other possible causes.
Live and learn!
Dave
Live and learn!
Dave
Nuno
XS400 Enthusiast
A little update...I've spoken with one of those old-chaps with huge workshops and tons of bikes inside...you know, that kind of man. Well his advice is that pods can't work fine on CV carburetors for a simple stupid reason...their rubber mount covers a hole on the intake of the carburetor and that hole is where air flows in to create the depression to lift the needle. I hope my tech explanation make sense...
anyhow, the solution would be just to cut a small window on the pod rubber mount in order to let this hole free to breath. He showed me and that's true, the rubber goes straight onto this small hole in the middle of the intake port.
It makes sense if I think to my last ride on the bike...it didn't lack power UNTIL it had power...it seemed like if no mattered how much I twisted the throttle, I couldn't get more than 40% of power....that might be the needle not being lifted enough and so on...
Anyhow, I'm gonna switch to a pair of Mikuni or Keihin in March so I'm not really going to spend much time on it...
...except that at the end of February I'll have to ride the bike from Rome to London and I don't have a whole month to get there so I'll let you know if this mod works or not.
If you don't get any more updates I'm probably stuck somewhere on the Alps
anyhow, the solution would be just to cut a small window on the pod rubber mount in order to let this hole free to breath. He showed me and that's true, the rubber goes straight onto this small hole in the middle of the intake port.
It makes sense if I think to my last ride on the bike...it didn't lack power UNTIL it had power...it seemed like if no mattered how much I twisted the throttle, I couldn't get more than 40% of power....that might be the needle not being lifted enough and so on...
Anyhow, I'm gonna switch to a pair of Mikuni or Keihin in March so I'm not really going to spend much time on it...
...except that at the end of February I'll have to ride the bike from Rome to London and I don't have a whole month to get there so I'll let you know if this mod works or not.
If you don't get any more updates I'm probably stuck somewhere on the Alps
I don't suppose you took any photos that would help us non-Tech types visualize where exactly this all happens. Would love to see your modification.
Have a nice ride to London - sounds fantastic. If you don't get stuck in the Alps, maybe you could revive this photo thread so we could share a bit:
Perhaps make the challenge "xs 400 in front of mountain" or "xs400 on edge of cliff" ...
Have a nice ride to London - sounds fantastic. If you don't get stuck in the Alps, maybe you could revive this photo thread so we could share a bit:
Perhaps make the challenge "xs 400 in front of mountain" or "xs400 on edge of cliff" ...
Nuno
XS400 Enthusiast
I had this conversation in December and that's the last time I saw my bike...then moved to London.
Anyhow....I found this pics online
Look at the arrow on the right part of the second picture...that's the central top "window" in the first picture. As you can see it goes straight under the membrane that should lift the needle.
I don't know if all the pods cover that hole but in my case they do and, looking at the second pic, it sounds reasonable that I can't get full power
Anyhow....I found this pics online
Look at the arrow on the right part of the second picture...that's the central top "window" in the first picture. As you can see it goes straight under the membrane that should lift the needle.
I don't know if all the pods cover that hole but in my case they do and, looking at the second pic, it sounds reasonable that I can't get full power
Interesting thought, but I think it depends on the brand of pod filter - not all of them have a lip that would block those holes (which explains why I didn't need to cut holes, and my bike worked, unjetted without them. Jetted, it worked even better.)
Nuno
XS400 Enthusiast
Yep, sure...your thought plus mine makes more sense than "The bike will never work fine with pods" that sounds like a dogma without any reasonable explanation.
p.s. = "mine" ... not mine.
Last edited:
Nuno
XS400 Enthusiast
The result of the experiment is....100% positive
