Turns over but wont start, Backfires.

[Tricod]

Well, Ive had this bike for a bit now. Seems to only work half the time. It was running fine up until yesterday. I changed the Oil and now it wont start. It turns over sometimes and then backfires. It only turns over if the choke is in all the way. It just runs the starter if I have the Choke pulled out. Ive read some things about it possible being the carbs but the past owner had a complete rebuild on them about six months back. The Backfiring is coming from the exhaust. I was hoping someone could maybe give me some hints/ tips or what not. Thanks

Brad

[skids]

Re: Turns over but wont start, Backfires.

Check to see if the plug wires have been switched, set the petcock to prime to initially fill the carbs if it hasn't run in a while, check to see if the vacuum hose is disconnected that either operates the petcock (standards) or the octopus (specials), see if the airbox is saturated with gas.

[Dennyz]

check the pickup wires.

[prometheus578]

I'm having a hard time with this one. Did you do anything else other than change the oil? Backfiring, as the others have stated is usually an ignition prob. I also was going to suggest switched plug wires.... did you change plugs, too?
The starter prob has me thinking.... are you saying that sometimes it cranks... other times... the starter just spins but not the engine? One possable solution might incorporate all the probs. I've seen some starters, when not getting enough juice, spin, but not push the gear forward to engage the crank. Ok, here's the drill. Charge the battery, or take it to a shop, have them charge it, and load test it to see if it will really put out 12 volts and not just read a 12 volt surface charge with nothing to back it up with. With the battery out, clean the cable connectors, and all electrical connections. (I had an 850 with intermittent electrical probs. Was the fuse box, which is notorious on 1100's. Pullled the fuses and used a rifle bore brush and brushed the clips that hold the fuses. Prob solved) I suspect an intermittent connection at the battery or the fuse box. Would explain the sometimes yes, sometimes no, juice to the starter. Would also explain the intermittent spark to the plugs. You're cranking and cranking with no spark, filling the exhaust with unburnt fuel. Along comes the random spark... fires the cylinder... and ignites the unburnt fuel in the exhaust system. Hence, the backfire. The choke in/choke out is just an incidental, confusing the issue. Better still.... bring your bike up here. I'm in the middle of my seasonal layoff and haven't wrenched on a bike in 3 months. Note to Dennyz: The owner of Cycle Mart died last month. (I may be looking at a looong seasonal layoff!)

[dbyers]

This may not be the issue but I had a simular problem with water in the gas. I drained the tank and the carbs then replaced the plugs just for good measure. It backfired once more and then started right up and is running smooth. Good luck!

[Tricod]

Hmm,
Now you all got me wondering. Ill go out and check the pickup wires in a bit that could be something, however I havent Touched them ever on this bike. I pulled the airbox last night and it was drenched with fuel. Not Good. I also drained the the Tank and the carbs thinking it may be an Issue that others had mention in past post and per some of your comments. Plugs are clean and in good condition. prometheus578- your comment on the battery I check it out and charged it up. The battery is perfect. Its only about 1 month old as is so im not to worried its the battery. Guess Ill go check the wires put it ll back together and give it a shot.

Brad

[John]

If you found fuel in the airbox, then that usually means that one or more float needle and seat are leaking. Check your oil level again, and check to see if it smells like fuel. If it does, then you'll need to drain it again,and replace with new oil, and determine which carb has the problem. With the airbox off, just put the bike on the center stand, and turn the fuel on, and wait a few minutes. Watch the carb air inlets to see if fuel is trickling from any of them. A good test is to start it, and using a spray bottle with some water in it, spray the header pipes to see which
one(s) are not getting hot, or as hot as the others. That will be the problem cylinder(s). Your bike being a special, then the seat assembly has an O ring sealing it from the carb body. These are known to get brittle and also to develop a flat edge that won't seal, and cause the very problem you are experiencing. Also the octopus, or fuel distribution valve, could be leaking by the diaphram, but the needle and seat are the last item in the fuel delivery system.

[Tricod]

Thanks all for your replies. Ive narrowed the problem down for sure to the starter system. The problem is that im very new to this kinda stuff and learning as I go. And by the way thank you all for your help Ive learn a lot already. But now I have to show my ignorance.

When you all say check the pickup coil what in the world are you talking about. Ive checked my Clymer Manual and everything on this site I can find. Everything seems to mention it but no one ever seems to talk about what or where it is. Mostly where. I jut cant find. Or most likely Ive been looking right at it and don’t know that’s what it is. So I what hoping someone could open my eyes a bit.

Secondly I have a tube coming from the Crank case about 1/4" inch in Dia. That im not sure what it is or where it goes. I have crankcase breather tube that goes to the airbox connected so its not that one. I was hoping someone could help me out there.

Thanks in Advance.


Brad

[Ken Talbot]

Brad, the tube you're looking at goes to the vacuum advance mechanism behind the pick-up coils. It should connect to a brass nipple on the engine-side of the throat of carb #2. The pick-up coils and advance mechanism are located inside the cover on the lower left side of the motor. There is a link here to an article about diagnosing and fixing a problem with the pick-up coil wires.

[Tricod]

Well for one I just answered my own question, I found the Pickup Coils. Now I have a new question. But first let me say that Ken The the vacuum advance mechanism tube was already in place and I Knew where it goes. Kinda dumb of me to know where the Vacuum advance is and not know the pickup coils are an inch away. But hey thats me . The tube im speaking of starts just to the left of where the crankcase breather tube (the one about 3/4" Dia. ) and goes to, I dont know where. Im not sure what it is or where it goes. But Its underneith the Airbox next to the crankcase breather tube.

Second why would there be a zipp tie holding the pickup coils as seen here in the picture. And what can I do to fix whatever it was trying to fix.



Thanks again.

Brad

[TopCatGr58]

Hey there Brad,

First, that little hose is a vent for the middle gear, and it just sits suspended up under the gas tank, there usually is a clip that it fits into. Some folks have put a small fuel filter or something similar on the end of it to keep dust and such from entering it.

Secondly, on close inspection of your picture, the zip tie looks like it goes around the pickup coil wires, to keep them from rubbing against the rotating shaft. It doesn't appear to be actually holding the P.U. Coils themselves! I'd checked to make sure that the timing plate rotates when you apply suction to the vacuum advance mechanism, and that the zip tie isn't preventing it's travel!? These wires are the ones that can fracture from constant flexing over the years, and are repaired by replacing them with test lead wire or similar braided flexible wire! Another suggestion was to loop the wire around the shaft once before attaching it to the P.U.Coils, so that they only flexed a little in tightening their coil around the shaft, vs. getting bent all the time when using short wires!

[Tricod]

Thanks TopCat,
The zip does actually prevent the P.U. Coils from rotation and seems to lock the vacuum pump in the fully up position. I expect that the pump is broken or some such and this was the fix by the past owner to get it to reach higher rpms. Unfortunately I am unable to check it until I get the bike running again. Hopefully tomorrow. Or until i can replace the ignition coils which is what I suspect the problem is based on some test with the ohms meter.

Sorry all for the frantic matter with which I have posted. I just got my License a few days back and I was excited to get out and ride legally for a change, but of course, the bike dies.

Thanks

Brad

[prometheus578]

Brad, knowledge come with experience, and experience can only be gained by tinkering. You've already aquired a Clymer's.... you're way ahead of the bunch. And if the book doesn't sufficiently explain everthing for you, there's a million years of experience on this site for you to tap into. There's no such thing as a dumb question, and everyone here, at one time, had zero experience, too. Truth be told, if my niece's wedding wasn't just called off for a medical emergency, I was going to be down in Broomfield next week, being an hour away from Ft. Collins, and would have tried to link up.
There's very few things on a bike that can't be fixed with a Clymer's, a set of metric sockets and a #2 Phillips screwstick.
I'm amazed that people pay the shop $75 an hour for me to fix what they could have done themselves in about the same time. But hey, it keeps me and the dogs fed.
Three hours to rebuild the 4 carbs, an hour or two to diagnose and repair whatever ails you, and you'd be talking $375, not including parts!
You've saved bucks, gained knowledge of your machine, and gotten the sense of ownership that only can be gained by getting your hands dirty.
( I know... it's 2:00 in the morning and I'm rambling... off to bed)

[randy]

Tricod,

I'll bet that zip-tie is holding the pickups too far advanced to idle properly. Clip it and try it. if it runs, and you find that the vacuum advance canister is no good, I have a working spare you can have. Test the canister this way: remove the vacuum hose from the canister and rotate the timing plate all the way up. put your finger on the end of the vacuum fitting on the canister and let the plate go. If the canister is good, the timing plate should hold. If the plate returns to it's resting place, the canister is toast.

HTH

Randy

[Tricod]

Randy,
Thanks for your offer, that’s very generous of you. Fortunately after some testing I found that the Advance canister works fine. Upon some inspection I found that the tube from it to the #2 Carb was cracked and wasn’t putting any pressure. I replaced the tube and now it should work fine.

Now off to get the bike working.

Brad