Another "Won't Start" thread

[bralkan]

When I open the choke the bike just turns over and doesn't sound like it is sparking. I took the plugs out and they are sooty and have un-burnt fuel on them.

If I close the choke it sounds like it wants to spark and it would if I just opened the choke. But, as I said, opening the choke kills it completely.

Any ideas? Carbs?

[bralkan]

When I open the choke the bike just turns over and doesn't sound like it is sparking. I took the plugs out and they are sooty and have un-burnt fuel on them.

If I close the choke it sounds like it wants to spark and it would if I just opened the choke. But, as I said, opening the choke kills it completely.

Any ideas? Carbs?

Went out there this morning - took out the plugs and cleaned them really well with compressed air. Put them back in, kept the choke closed and cranked on it. Finally it started it. I let it sit for a minute, keeping it at about 3k rpms. I opened the choke to see what it would do and it killed the engine.

Any ideas?

[yoda]

It's overfuelling with choke on. Dont open the choke fully.

[drewpy]

Went out there this morning - took out the plugs and cleaned them really well with compressed air. Put them back in, kept the choke closed and cranked on it. Finally it started it. I let it sit for a minute, keeping it at about 3k rpms. I opened the choke to see what it would do and it killed the engine.

Any ideas?

can you keep the bike going with revs when warmed up?

[bralkan]

can you keep the bike going with revs when warmed up?

It seems to stay on if I keep my hand on the throttle. I tried again tonight and it would idle with the choke open.After awhile I closed the choke and it idled for a good while before it cut off (what I would expect for not running more than 10-15 minutes). It would start right back up.

One question though, is the choke supposed to have more states than just open and closed?

(it is a 1980 XS400 special ii, but with points (long story).)

I have another question too - I have a working headlight but It won't turn on with the bike. Instrument panel lights up and the tail light works. There are no directionals (as in none are connected). I have a multimeter but I am not sure exactly which wires I should be testing for current and at what voltage. Anys uggestions?

Thanks for the answers to the nub questions.

[drewpy]

It seems to stay on if I keep my hand on the throttle. I tried again tonight and it would idle with the choke open.After awhile I closed the choke and it idled for a good while before it cut off (what I would expect for not running more than 10-15 minutes). It would start right back up.

One question though, is the choke supposed to have more states than just open and closed?

(it is a 1980 XS400 special ii, but with points (long story).)

I have another question too - I have a working headlight but It won't turn on with the bike. Instrument panel lights up and the tail light works. There are no directionals (as in none are connected). I have a multimeter but I am not sure exactly which wires I should be testing for current and at what voltage. Anys uggestions?

Thanks for the answers to the nub questions.

on mine its a 2 stage affair with a ball/sping combination in the cartbs acting on indents on the choke rod.

I usually start it on full, take it right down to 1/2 way, and fully in after a minute. My bike will "drop off" the revs if left for a min or so at the lights, its down to modern fuels and old design. just blip the throttle when the engine starts shunting. you could also have a blocked pilot screw which will affect the tick over (yours might be sealed, its on top/in front of the main carb body)

got an xs400d circuit diagram, which should share the colours of yours

[Cy Welch]

It seems to stay on if I keep my hand on the throttle. I tried again tonight and it would idle with the choke open.After awhile I closed the choke and it idled for a good while before it cut off (what I would expect for not running more than 10-15 minutes). It would start right back up.

One question though, is the choke supposed to have more states than just open and closed?

(it is a 1980 XS400 special ii, but with points (long story).)

I have another question too - I have a working headlight but It won't turn on with the bike. Instrument panel lights up and the tail light works. There are no directionals (as in none are connected). I have a multimeter but I am not sure exactly which wires I should be testing for current and at what voltage. Anys uggestions?

Thanks for the answers to the nub questions.

Is your XS400 a G or SG? If so the choke should be a pull button with 2 stops assmuming that you have the right carbs for the year. I start mine on full choke and like Drewpy change to 1/2 choke after a short time but I find that I have to feather the throttle for a little before it will hold at idle. I generally (in the current cold weather) leave it on half choke for about 2 blocks and then turn the choke off. I do have to blip the gas at lights at least until the day is warmer and/or the engine gets fully warmed up. I worry about the excessive RPMs from full choke (like 4000) so I fight with it at half choke as soon as it starts as I can keep it under there. I wish it didn't have the stops as it seems to be best just a little off the full choke, but not quite to the half setting.

[bralkan]

Thanks for the info on the choke and the wiring diagram.

I got it working and I think I have a way to get the headlight to work.

I have a new problem though:

I have been running it without airfilters (been having to work on it to much and it had been dieing before it was worth it to be them back on). I put them back on today and the bike sounded great when I started it. I pulled out the driveway and it was going great. As I round the first turn out of my driveway I try to accellerate but no matter how much I opened the throttle the RPMs went down and down until the bike cut off. I push it back home (100s of feet) and I can smell lots of gas. I pull the filter and boots off and gas poured out the carbs from the air intake.

Anyidea why it started flooding?

[bralkan]

I let the bike sit and went back out to crank it. Each crank pours gas out of the air intake on the carbs.

Is the petcock fubar?

[bralkan]

I let the bike sit and went back out to crank it. Each crank pours gas out of the air intake on the carbs.

Is the petcock fubar?

Well I assume it is something in the float bowls. I drained the float bowls hoping it would come out. I plug them up, opened the petcock to prime for a few seconds, and put it back to run. I cranked it and it gave me a "put put" once. I took out the plugs and one side is covered with suit and the other is ok. Why would one side be so rich?

I am letting it air out and will try and crank it later.

edit: I got it to turn on momentarly. I let the RPMs get low and it cut off. I went to crank it back up and it wouldn't. After a few no-starts I took the plugs out, they look ok other than the unburnt fuel. I'm letting it air out again. The carbs intimidate me a bit - looks like I am taking them to the mechanic to look at?

[jrhendryx]

Well I assume it is something in the float bowls. I drained the float bowls hoping it would come out. I plug them up, opened the petcock to prime for a few seconds, and put it back to run. I cranked it and it gave me a "put put" once. I took out the plugs and one side is covered with suit and the other is ok. Why would one side be so rich?

I am letting it air out and will try and crank it later.

edit: I got it to turn on momentarly. I let the RPMs get low and it cut off. I went to crank it back up and it wouldn't. After a few no-starts I took the plugs out, they look ok other than the unburnt fuel. I'm letting it air out again. The carbs intimidate me a bit - looks like I am taking them to the mechanic to look at?

from reading what my manuals have to say on my xs500, it seems as though running the bike without the air filter can damage its ability to process the air-fuel mixture properly, since it was designed to compensate for the loss of airflow created by the filter element.

it might be that your carbs will need to be readjusted among other things? it could be in your best interest to get a vacuum gauge and figure out how to do this.

good luck.

*edit*

this occurred to me while reading your above post again.

perhaps the reason that there is so much fuel is that the bike overcompensated for the extra airflow by allowing more fuel to enter the engine. now that the airfilter is in place, the bike is running too rich because it is still giving the same amount of fuel it would if it was processing all of the air it would have been without the filter. when you kick in the choke, the air/fuel mixture becomes rich enough that the engine cant even create a detonation, and it dies.

im not any kind of good mechanic, and am still trying to learn this myself, but it might be worth looking into.

[drewpy]

Well I assume it is something in the float bowls. I drained the float bowls hoping it would come out. I plug them up, opened the petcock to prime for a few seconds, and put it back to run. I cranked it and it gave me a "put put" once. I took out the plugs and one side is covered with suit and the other is ok. Why would one side be so rich?

I am letting it air out and will try and crank it later.

edit: I got it to turn on momentarly. I let the RPMs get low and it cut off. I went to crank it back up and it wouldn't. After a few no-starts I took the plugs out, they look ok other than the unburnt fuel. I'm letting it air out again. The carbs intimidate me a bit - looks like I am taking them to the mechanic to look at?

check your petcock is not leaking through the pipe. can you pull off the pipe from the carb and only a small amount of fuel runs out?

next is your float height and float needle, you can get keyster kits from sirrius online and you can just replace the float needle ( as they wear and flood the carb) or if feeling adventurous, replace all the jets supplied.

[Cy Welch]

check your petcock is not leaking through the pipe. can you pull off the pipe from the carb and only a small amount of fuel runs out?

next is your float height and float needle, you can get keyster kits from sirrius online and you can just replace the float needle ( as they wear and flood the carb) or if feeling adventurous, replace all the jets supplied.

For 1980 carbs you can also get kits from MikesXS which come with new seats. What I found on mine (gettitng the same overflowing gas problem) was that the O rings on the seats (1980's us a push in seat) had been eaten by modern gas (along with ALL other rubber parts in the bowls). The kit from Mikes comes with the plugs (required in 1980 carbs) floats, needles and gaskets, with these my carbs have been working pretty flawlessly. I still need to get the replacement blind plugs and idle mix screws and drill the originals out and retune the idle, but other than it being a bit lean at idle (and non-adjustable without some drilling) it's running pretty good now.

I don't know about the earlier models, but the 1980 has a relay in the headlight circuit. There are two things that can go wrong with it, one is the relay can go out, and the other is the diode that activates the relay burns out (often when the relay went). I have had both go wrong with mine and it's not too hard to fix if you can get the relay (you can order the OEM part from bike bandit) and the relay can be found on ebay most of the time.

You can see an earlier pic of my bike in my avatar, but the paint job has changed. I'll be changing my pic as soon as the weather allows me to get a good pic of the new paint job, which IMHO looks awsome.

[bralkan]

check your petcock is not leaking through the pipe. can you pull off the pipe from the carb and only a small amount of fuel runs out?

next is your float height and float needle, you can get keyster kits from sirrius online and you can just replace the float needle ( as they wear and flood the carb) or if feeling adventurous, replace all the jets supplied.

It does leak out when I pull the pipe off - I figured it was left over fuel in there. Now that I think about it though, it would keep coming - kinda sputtered out. I guess this means I need to replace / rebuild the petcock?

As an aside, I am going to clean the tank and add an inline filter.

[drewpy]

It does leak out when I pull the pipe off - I figured it was left over fuel in there. Now that I think about it though, it would keep coming - kinda sputtered out. I guess this means I need to replace / rebuild the petcock?

As an aside, I am going to clean the tank and add an inline filter.

yep sounds like pet cock gone, which will flood the carbs.

Always use an inline filter.