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Engine dies only when warm
- Thread starter crashcourse
- Start date
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- Tags
- engine
crashcourse
XS650 Addict
Okay, I'll replace that cap. Would they have that at a local motorcycle shop, or do I have to order it? I looked at an auto parts store and they don't sell just the cap. And as far as I know, the carbs still have the stock jets.
Actually, that 8.3 ohms may not be too high if your caps are originals. Originals were something like 10K ohms. Still, you want them matched, I would replace both. Most of us use the NGK 5K ohm replacement. Get the LB05F, not the "E" version .....
The "F" version fits on that threaded stud sticking out of the top of the plug. They grip and hold better than the "E" version that snaps on the terminal nut. Any motorcycle shop should have them or could get them for you.
The mix screw spec for your carbs is 3 to 3 1/2 turns out. Anything under 3 turns will probably be too lean.
The "F" version fits on that threaded stud sticking out of the top of the plug. They grip and hold better than the "E" version that snaps on the terminal nut. Any motorcycle shop should have them or could get them for you.
The mix screw spec for your carbs is 3 to 3 1/2 turns out. Anything under 3 turns will probably be too lean.
crashcourse
XS650 Addict
Replaced the spark plug cap, still no improvement. I thought maybe I didn't clean the idle jet well enough, so I sprayed some carb cleaner in while it was running (following instructions), and then it just pooped out. So I cleaned took out the mix screw and actually cleaned the jet, but it still wouldn't start.
Turns out, now there isn't even spark. Either something failed randomly or I jostled it loose or caused a short or something. I started backtracking from the plugs, and the ignition coil seems okay with the right resistances. The red and orange coils have twelve volts across them, are they supposed to? It seems like that would just run current through the coil instead of making a spark. Can anybody confirm if this is a problem, or should I keep looking?
Turns out, now there isn't even spark. Either something failed randomly or I jostled it loose or caused a short or something. I started backtracking from the plugs, and the ignition coil seems okay with the right resistances. The red and orange coils have twelve volts across them, are they supposed to? It seems like that would just run current through the coil instead of making a spark. Can anybody confirm if this is a problem, or should I keep looking?
Red and orange coils? Or do you mean the wires? On the coil you should have red/white and orange. The red/white wire supplies battery voltage to the coil. The orange wire goes to the TCI box where it gets grounded to make the coil spark. The TCI box needs battery voltage on the red/white wire too. You can check that under the side cover at the connector for the TCI box. I've seen them have coil power but not TCI box power.
If you turn on the bike and don't start it the TCI box has a circuit that sences that and turns the TCI box off.
I might check the fuses, if the fuse box is still stock, it's very likely a trouble spot. As the clips that hold the fuses age they get weak. Weak clips don't carry the power as well and can overheat, this excess heat weakens the clips even more.
Replacing the fuse box fixes this. The way most fix them is to replace the box with individual inline fuse holders. The ones that use the blade style fuses are much better than the round glass ones. I get mine from Radio Shack. They have a cap the hlep keep crap out of the fuses. Cost less too.
If you turn on the bike and don't start it the TCI box has a circuit that sences that and turns the TCI box off.
I might check the fuses, if the fuse box is still stock, it's very likely a trouble spot. As the clips that hold the fuses age they get weak. Weak clips don't carry the power as well and can overheat, this excess heat weakens the clips even more.
Replacing the fuse box fixes this. The way most fix them is to replace the box with individual inline fuse holders. The ones that use the blade style fuses are much better than the round glass ones. I get mine from Radio Shack. They have a cap the hlep keep crap out of the fuses. Cost less too.
crashcourse
XS650 Addict
Yeah, wires was what I meant. Okay, so they are supposed to have power, and I'll check that the TCI is getting power. Also I'll check for shorts to ground more thoroughly.
At the very least, I am getting to know my motorcycle more and better every day.
At the very least, I am getting to know my motorcycle more and better every day.
crashcourse
XS650 Addict
Is there supposed to be continuity between the red/yellow and orange wires at the TCI box when the bike is off?
Edit: And thanks to everyone for their input, I'd be lost without ya'll.
Edit: And thanks to everyone for their input, I'd be lost without ya'll.
Red/yellow at the TCI box? The diagrams I have don't show a red/yellow wire at the TCI box.
Yamaha never gave any test readings for the TCI box. The only way they say to test the TCI box is to put on one that is known to be good.
I think the only red/yellow wire on your bike feeds fused power to the safety relay. And thats to send power the headlight when the bike starts.
Yamaha never gave any test readings for the TCI box. The only way they say to test the TCI box is to put on one that is known to be good.
I think the only red/yellow wire on your bike feeds fused power to the safety relay. And thats to send power the headlight when the bike starts.
crashcourse
XS650 Addict
It's dark in my parking garage and the wire might be too dirt to tell the color, but I'll look again. Could anyone test theirs for continuity?
crashcourse
XS650 Addict
For those interested, here's an update.
The whole bike just stopped working a few posts up, the last time I worked on it. Took me until last night to find time to go over the bike thoroughly enough to find the loose connector blade that was preventing it from starting. Besides making me feel very silly for taking so long to find, I was very glad to just get it started. So now I'm back to where I was a month ago: it will start but not run.
My Uncle thought maybe it was an air leak between the carbs and the intake manifold, since it acts like its lean maybe it is sucking in too much air? He said to spray a fine mist of water over the to see if it would make that side's cylinder sputter and that would tell me where the leak was. I did, but didn't notice any difference. Any other ways to look for leaks? I'm going to check my valves too - it might be sucking air from the exhaust pipe if those valves aren't closing. Any other bright ideas?
The whole bike just stopped working a few posts up, the last time I worked on it. Took me until last night to find time to go over the bike thoroughly enough to find the loose connector blade that was preventing it from starting. Besides making me feel very silly for taking so long to find, I was very glad to just get it started. So now I'm back to where I was a month ago: it will start but not run.
My Uncle thought maybe it was an air leak between the carbs and the intake manifold, since it acts like its lean maybe it is sucking in too much air? He said to spray a fine mist of water over the to see if it would make that side's cylinder sputter and that would tell me where the leak was. I did, but didn't notice any difference. Any other ways to look for leaks? I'm going to check my valves too - it might be sucking air from the exhaust pipe if those valves aren't closing. Any other bright ideas?
Classic
rackin' up the miles
Spraying wd40 around the carb manifolds is a more accurate indicator of a leak. Rpm will increase if there is a crack or opening.
crashcourse
XS650 Addict
So, I had some time yesterday, and here is what I did: Sprayed the WD 40, didn't notice anything on either side. But, I did notice that the vacuum line was starting to crack and was really hardened, so I replaced that and crudely synced the carbs with a dial vacuum gauge I borrowed from work. It was running better, but still net really great, and dying at idle after it got warm. Then I remembered that I had taken the petcock apart last fall when it first started giving me trouble and thought maybe I didn't get it back together right. So I pulled off the gas tank and petcock, took it apart and checked how everything was supposed to be from an assembly drawing in the manual. Everything was in place. To double check that the vacuum valve was working, after I put it back on the tank I set the petcock to "ON" and sucked on the vacuum line and no fuel came out, but when I set it to "RES" and sucked on the vacuum line fuel came out just fine. That may have been cause there isn't much gas in the tank.
Then just to see what would happen, I put it back together to take a short ride and see if anything had really changed. But when I got going, huge clouds of billowing white smoke came out of both tailpipes. I figured if I was in a tank it would have been enough smoke to make a daring escape.
So: the smoke probably means I'm burning oil. This might be because there is too much oil in the engine, but I'm due for an oil change anyway so I can drain some and see if that changes things, or look for gaskets or shavings in the oil itself. If letting oil out so it isn't overfull doesn't change things, or if I find gasket material or metal shavings in my oil, what do I do next? Is there an additive I can use to seal the leak into my cylinders, would it be the piston rings, burned valves, or something else in there going bad? Would burning lots of oil explain it not idling after it warms up but still acting lean?
Thanks in advance!
Then just to see what would happen, I put it back together to take a short ride and see if anything had really changed. But when I got going, huge clouds of billowing white smoke came out of both tailpipes. I figured if I was in a tank it would have been enough smoke to make a daring escape.
So: the smoke probably means I'm burning oil. This might be because there is too much oil in the engine, but I'm due for an oil change anyway so I can drain some and see if that changes things, or look for gaskets or shavings in the oil itself. If letting oil out so it isn't overfull doesn't change things, or if I find gasket material or metal shavings in my oil, what do I do next? Is there an additive I can use to seal the leak into my cylinders, would it be the piston rings, burned valves, or something else in there going bad? Would burning lots of oil explain it not idling after it warms up but still acting lean?
Thanks in advance!
crashcourse
XS650 Addict
Alright, in case anyone is still paying attention, or if this happens to anyone in the future, here is how I fixed all of the above problems:
The oil was full of gas because I didn't have my floats adjusted right. The bike wouldn't run because a small passage in the float bowl was clogged. It's the one that has the long brass tube going down into it. After I adjusted the floats, cleared the blockage, put it back together and added new oil and fresh gas, it runs like a dream. And I am done riding the bus to work! I still need to do some fine tuning to sync my carbs properly, but it is so great to have my wheels again. Thanks to everyone who had any input, and especially to 5twins and his carb guide!
The oil was full of gas because I didn't have my floats adjusted right. The bike wouldn't run because a small passage in the float bowl was clogged. It's the one that has the long brass tube going down into it. After I adjusted the floats, cleared the blockage, put it back together and added new oil and fresh gas, it runs like a dream. And I am done riding the bus to work! I still need to do some fine tuning to sync my carbs properly, but it is so great to have my wheels again. Thanks to everyone who had any input, and especially to 5twins and his carb guide!
