Only Runs on Full Choke

[spayne83]

I fired the bike up for the first time in a few weeks and took it for a ride. It fired right up cold and ran until it warmed up. Then it died and would try to start but just backfire and die. Then I tried running with full choke and it would stay running but backfire after what I guess would be 4000 rpm. With half open throttle it would run ok, but would die if I let the throttle close. I put a strong mix of Seafoam and gas in the tank (1/2 a bottle of Seafoam/1 gal gas) as I assume that the carbs are dirty, but would that explain the problem running, and why it takes full choke? I know that I will need to clean the carbs, but could that be the only problem.

Also I ditched the PCV hose and added 3 qts of oil (I'm pretty sure it was dry) and there was a pool of oil on the middle gear and sprayed on my foot. Was the oil too full, or is that what happens without a filter on the PCV?

[XS1100_OEM4ME]

Vacuum

I fired the bike up for the first time in a few weeks and took it for a ride. It fired right up cold and ran until it warmed up. Then it died and would try to start but just backfire and die. Then I tried running with full choke and it would stay running but backfire after what I guess would be 4000 rpm. With half open throttle it would run ok, but would die if I let the throttle close. I put a strong mix of Seafoam and gas in the tank (1/2 a bottle of Seafoam/1 gal gas) as I assume that the carbs are dirty, but would that explain the problem running, and why it takes full choke? I know that I will need to clean the carbs, but could that be the only problem.

Also I ditched the PCV hose and added 3 qts of oil (I'm pretty sure it was dry) and there was a pool of oil on the middle gear and sprayed on my foot. Was the oil too full, or is that what happens without a filter on the PCV?

Sounds like a vacuum leak or clogged fuel flow. I would check all the vacuum lines and carb manifolds for leaks, then check to see if good fuel flow from the petcocks to carbs, if all is good, pull the carbs and see what is up IMHO

[oldyam80sg]

A good thorough carb cleaning is in order.

[Rasputin]

If you had to add 3 quarts of oil I would make damn sure you know what you are doing. If you drained the oil, you would not need much more to fill it completely.
There are drain plugs under there for the middle drive as well as the engine, not to mention the oil filter.
Do you have a manual?
Oil on your foot is a pretty good indication that something is wrong!
Pool of oil...middle drive related.... makes one wonder what may be wrong here.

[XS1100_OEM4ME]

Oil

If you had to add 3 quarts of oil I would make damn sure you know what you are doing. If you drained the oil, you would not need much more to fill it completely.
There are drain plugs under there for the middle drive as well as the engine, not to mention the oil filter.
Do you have a manual?
Oil on your foot is a pretty good indication that something is wrong!
Pool of oil...middle drive related.... makes one wonder what may be wrong here.

I didn't catch the oil part of your post at 1st You have bad leak, drain plug missing, blown or loose oil filter seal or a hole in your motor

[spayne83]

I am an idiot

Yeah, I noticed that the vacuum line to the 4th cylinder is not capped, but it was before.

As for the oil...I am an idiot. I ASSUMED that because it was not leaking oil anymore that the engine was pretty close to empty. I drained the oil and had almost 7 quarts! I swear that I am not really that stupid, just wanted to make sure that I didn't run the engine dry and didn't even think to check the oil level first. I am pretty sure that it was the more than double capacity oil that was causing the oil spray from the PCV.

[motoman]

Yeah, I noticed that the vacuum line to the 4th cylinder is not capped, but it was before.

As for the oil...I am an idiot. I ASSUMED that because it was not leaking oil anymore that the engine was pretty close to empty. I drained the oil and had almost 7 quarts! I swear that I am not really that stupid, just wanted to make sure that I didn't run the engine dry and didn't even think to check the oil level first. I am pretty sure that it was the more than double capacity oil that was causing the oil spray from the PCV.

............what happens in Cantafordya stays in Cantafordya........oopppss, too late.

[donebysunday]

Yeah, I noticed that the vacuum line to the 4th cylinder is not capped, but it was before.

As for the oil...I am an idiot. I ASSUMED that because it was not leaking oil anymore that the engine was pretty close to empty. I drained the oil and had almost 7 quarts! I swear that I am not really that stupid, just wanted to make sure that I didn't run the engine dry and didn't even think to check the oil level first. I am pretty sure that it was the more than double capacity oil that was causing the oil spray from the PCV.

Don't feel bad, back in the early 80s on my 79 SF I did my oil in a hurry, bought as I still do from Yamaha by the case. How I do not know, again I do not know, wanted to get to my watering hole. Half way there 2 mi. I see blue smoke behind me, get there smoking. Turned around and went home smoking went to drain the oil and all this oil came out close to double. Put in the correct amount and went back. All was well after.

[Schming]

Yeah, I noticed that the vacuum line to the 4th cylinder is not capped, but it was before.

As for the oil...I am an idiot. I ASSUMED that because it was not leaking oil anymore that the engine was pretty close to empty. I drained the oil and had almost 7 quarts! I swear that I am not really that stupid, just wanted to make sure that I didn't run the engine dry and didn't even think to check the oil level first. I am pretty sure that it was the more than double capacity oil that was causing the oil spray from the PCV.

There is no PCV on these bikes, just a cranckase breather, so if its disconnected from the airbox it would be a good idea to put a breather filter on.

[ccogswel]

spayne83. You say the bike will run with choke until it gets warm then will only run at half throttle at or above 4000 rpm. If this is true what you have a plugged up pilot circuits in the carbs. Your pilot circuit runs from idle to about 3500-4000 rpms then after that your main jet takes over to redline. Theres some tech tips on how to clean carbs. Pretty basic on all years of our bikes and can be used on most carbs from small engine dirt bikes and atv's as they are all more less the same. You have your started circuit which is your choke. Then you have your pilot circuit which is your pilot jet. It sits down in a hole next to your main jet. That pilot jet has a very small hole at the tip of it. They usually get gummed up from old gas. That hole is smaller then a sewing needle to give you a idea. Anyways take the carbs off and the float bowls. You'll see your main jet sticking out. If you look right next to it inside a hole you'll see your pilot jet. Just make sure you use a good tipped screw driver that fit's it tight. Cause most times they are in there real tight or just been in there for long time and a pain to get out and you don't want to strip the head cause then your left having to use a easy out and ruining your jet just to get it out. Look at some of the tech tips and look at some of the pictures to get a idea of what all is inside in case you haven't been in them before. Hope this helps. Good Luck!

[Schming]

spayne83. You say the bike will run with choke until it gets warm then will only run at half throttle at or above 4000 rpm. If this is true what you have a plugged up pilot circuits in the carbs. Your pilot circuit runs from idle to about 3500-4000 rpms then after that your main jet takes over to redline. Theres some tech tips on how to clean carbs. Pretty basic on all years of our bikes and can be used on most carbs from small engine dirt bikes and atv's as they are all more less the same. You have your started circuit which is your choke. Then you have your pilot circuit which is your pilot jet. It sits down in a hole next to your main jet. That pilot jet has a very small hole at the tip of it. They usually get gummed up from old gas. That hole is smaller then a sewing needle to give you a idea. Anyways take the carbs off and the float bowls. You'll see your main jet sticking out. If you look right next to it inside a hole you'll see your pilot jet. Just make sure you use a good tipped screw driver that fit's it tight. Cause most times they are in there real tight or just been in there for long time and a pain to get out and you don't want to strip the head cause then your left having to use a easy out and ruining your jet just to get it out. Look at some of the tech tips and look at some of the pictures to get a idea of what all is inside in case you haven't been in them before. Hope this helps. Good Luck!

x2 Great Descriptive Explanation, Good on Ya !!!

[spayne83]

spayne83. You say the bike will run with choke until it gets warm then will only run at half throttle at or above 4000 rpm. If this is true what you have a plugged up pilot circuits in the carbs. Your pilot circuit runs from idle to about 3500-4000 rpms then after that your main jet takes over to redline. Theres some tech tips on how to clean carbs. Pretty basic on all years of our bikes and can be used on most carbs from small engine dirt bikes and atv's as they are all more less the same. You have your started circuit which is your choke. Then you have your pilot circuit which is your pilot jet. It sits down in a hole next to your main jet. That pilot jet has a very small hole at the tip of it. They usually get gummed up from old gas. That hole is smaller then a sewing needle to give you a idea. Anyways take the carbs off and the float bowls. You'll see your main jet sticking out. If you look right next to it inside a hole you'll see your pilot jet. Just make sure you use a good tipped screw driver that fit's it tight. Cause most times they are in there real tight or just been in there for long time and a pain to get out and you don't want to strip the head cause then your left having to use a easy out and ruining your jet just to get it out. Look at some of the tech tips and look at some of the pictures to get a idea of what all is inside in case you haven't been in them before. Hope this helps. Good Luck!

I don't know if I was clear. I have to have the choke on the whole time to keep the bike running. Even after it is warm, if I take the choke off then the bike will stumble and die even with an open throttle. I tried plugging the vacuum leak on #4 when riding and it does not seem to make a difference. So ultimately it is a matter of the carbs being dirty and needing to be cleaned? Not a matter of the carbs being out of sync or a vacuum leak? Looks like I have to do that next weekend.

One question, there is bunch of rusty parts around the carbs, so I want to take off the carbs and soak that stuff in Apple Cider Vinegar, but I saw that there are steps that you would want to do in order so that you can put it all back together correctly. I just want to know how far to disassemble to clean the external hardware before I clean the carbs?

Thanks for all the help guys.

[ccogswel]

The only external things you can take off the carbs are the float bowls and the diaphragm tops. Each bowl and top has 4 screws hold them on. Know if you really want to be meticulous and clean the carb bodies then you have to break the set individually. Which will require the choke rod (be careful of carbs 2 and 4 as theres a really small spring and ball bearing that will fly out. After you get the choke rod out then remove the choke plunger. Then remove the top along with the diaphragm and big spring. Keep all parts separate from each carb or do one at a time. Then remove the idle mixture screw. Keep a eye out for a smalls spring, small flat washer and one really small rubber o-ring. After that remove the float bowl the float and be careful of the float posts are they can break real easy if your not careful about getting the float pin out. Then all you have to do is remove the air jet in the back of the carb and the pilot and main jets. Then what I do is take one of your top or float bowl screws and screw one into the place where the the main jet sits. This is the emulsion tube. Just screw it in a few turns and gentle tap on it. That tube should come out through the top side. And if memory serves me that screw should fit in through that hole that way you can take your 4 way screw driver and keep tapping on it till it is completely out. Just pay attention when you put it back in as there is a small set pin for it to go back in one direction only. The only thing left would be your throttle plates and stuff. But if you are careful with carb cleaner if that is what you try to use just don't spray to much around the throttle shaft seals as you don't want them to swell up. You can also use brake cleaner in those areas with good results and no worries about the seals swelling up on you. Hope this helps to give you a idea on how far you want to go. Good luck!