Bike just wont start!

[edavi394]

Hi, I have been trying to breathe life back into my 79 xs1100 special off and on for a month now. I just got sound to rebuilding the carbs and putting them back on the bike today. I thought at first it was going to start right up. I turned the tank to prime to fill the carbs with gas then turned them to the on position. And hit the button. It fired over and tried to idle but died after about 2 seconds. That’s the closest it has come. I tried for 10 more mins. Cranking then waiting a little bit then cranking some more. Every once in a while it sounded like it would fire on one cylinder but that’s it. Any ideas on why this won’t run? When it was parked it was running great now nothing. The bike only has 10k miles on it and I would love to put a lot more if I can ever get it to start.

[psycoreefer]

Do you have spark?
Are the plugs wet?
Is the air filter clean - no junk in the airbox?

Hows the battery? When I got mine it was hard to start and if I cranked it more then a few times the battery would drop down to 10ish volts. It would still crank fast enough but the TCI needs more then 10v to fire the plugs. You could try throwing it on a charger.

Check those things and let us know what you find.

[78yamahaman]

I too have been having a similar problem. I have a 79 special that I am trying to get running. I also have a 78 too but thats another story. My 79 will start but it is very hard to do. It seems like when I try to give it gas it only makes it worse. Once the bike is started and warmed up it seems like it runs fine. Any ideas? When I first put the carbs on after I rebuilt them I had to use some starting fluid to get it to turn over have you tried that?

[thewiz]

here's the deal, dude ...

Just takes four basic things to make a gas engine run. Fuel and air mix, spark, timing, and compression.

Since you say that it had run before it was shut down, I'd start with the spark and fuel.

Pull a plug, re-attach it to the wire, then ground it to the head AWAY from the plug hole. Then crank the motor and look for spark. Repeat this on each cylinder while noting if the plug for that cylinder is wet when you pull it out. If the plugs are wet or oily looking, replace them with new ones. If they are brand new, spritz 'em with some electrical contact cleaner and hit 'em with a little wire brush to clean 'em up and stick 'em back in there.

Try this and let us here know what happen and what you've observed ....

[prometheus578]

edavi and yamahaman....both symptoms show it's carb related.
(provided that both bikes are getting spartk to all cylinders)
sadly, you both must repull your carbs and recheck your work.
common... it's not the first time that this happens. cleaning carbs is simple... so simple, that oft' times, people take short cuts and miss something.
both your idle circuits are plugged.
(if you need starting fluid to start the bike... that means it's not getting fuel at idle)
when you try to give it gas and it dies... this also means it's not getting enough fuel... and when you open the throttle, the extra air starves the engine.
follow what wiz and psychoreefer stated to ensure that all cylinders are getting spark, and then pull the carbs... but this time, you'll need to actually clean them.

[edavi394]

Hi, thanks for your replies. I didn't think to check the spark plugs because I knew I had just replaced them the last time I had the bike running. The plugs are in good shape however I did find that the middle 2 cylinders are not fireing. As for re cleaning the carbs they are spotless inside and out there is nothing in them except gas I spent about 15 hours making sure there was not dirt rust or anything else. Thx for the tip though

[Flatlander]

Carbs........Probably......Most likely!
But under the small chance that you have done a compression test to find out were you are at with your motor and added some oil, (no more than a tea spoon!) you are probably running into the problem that happens. The plug gets covered in oil and dosen't spark properly, like a fowled plug would act like, the spark runs up the porcelin instead of making the jump. Keep pulling the plugs, clean, and retry. After you get the motor to run it will probably take several minutes of running to completely burn the oil/carbon/high fuel mixture to get it to run just like it use too.
Just my 2 cents.
Good luck and if running it on the stand dosen't do it, head down the road for a couple of miles giving some high revs.......were they like to run.......high revs and under a load.

394, you posted just before I did, I'm a slow typer.

[jeffe]

Originally posted by edavi394
did find that the middle 2 cylinders are not fireing.

If middle 2 are not firing it probally means a spark problem to them.

[edavi394]

yes i thought so since I tested those 2 plugs in one of the cylinders that was fireing and they worked. I havent got a chance yet to pull the tank off and see if the wires are loose or bad ect. I hope the coils didn't go bad.

[edavi394]

does anyone know what year and model coils interchange with the 79 special? just incase i have to replace mine. thx

[edavi394]

also is there a fuse or something else it could be besides the coil or wire? the bike ran great when parked and I find it hard to beleave that the 2 coils went bad just setting there especialy when one side still works on each one

[psycoreefer]

the center two plugs should be on one coil, the outside two plugs on the other. If you have one inside an one outside plug on each coil then you have them hooked up wrong.

[edavi394]

hi thx for the reply I was just going to ask that. the 2 outside ones are on one coil and the inside on the other. from the diagram it looks like they go the other way but when I pulled my tank back off to check them out they were hooked up the way you stated. so i wasn't forsure what was right.

[thewiz]

Up on top ...

under the tank there is a triple bullet connector that has a gray, an orange and a red and white striped wire in it. Disconnect, hit 'em with some dielectric silicone grease and re-seat them.

But first, for kicks, take off the left engine side cover and expose the PU coils. There some small wires in there held in a clamp that lead to the pick up coils which are prone to breakage. Pull on them and see if the insulation stretches and then if they will separate all the way. If you do a search on 'pick up coil wires' you can find the whole process of checking and fixing them IF that turns out to be it. There is another way to check 'em with a multimeter too ... but first give these couple of things a try.

[edavi394]

Hi, ok here is what I have done so far. I checked the connection on the wires (grey orange and red&white) they seem good so I switched the grey and orange around to see if I could get the other coil to work and the one to stop it made no differance the coil that was working still foires and the other does not. so i changed them back the switched the red with white stripe (even though they hook together) I thought maybe one side was getting a better conection. still no differance the one still fires either way and the other does not. so I guess that means the coil that goes to the center 2 cylinders is bad. is this a correct assumesion? I did not take off the side cover for the engine since all the wires are working on the top side I did not trace it back further. did i miss something by doing this?

thanks