bike cuts out and dies

[Guest]

so ill be riding down the road and my 81 gs450t will just randomly stop running, simular to running out of gas, rpms will drop fast with a loud ass backfire, like a gunshot. at first i just thought it was a carb issue, so i took the apart cleaned the with boiling lemon juice, and replaced all the rubber and any work looking parts with parts from another carb i have for the bike. the bike still cuts out the same. my spark plugs have a very weak purple spark most of the tie, but rarely will have a thick white spark. the bike is running super rich with the air screw set to 2.5 turns out. i keep fiddling with the air screw, the bike still runs real rich, you can smell it in the exhaust. when y bike dies, i always take the plugs out ad check if i have spark. sometimes there is no spark in one cylinder when it cuts out. sometimes they still are sparking when i pull them out but weak sparks. i cant figure out if its the carbs that are too rich that are fouling the plugs or if its that i just have an electrical problem and all the gas isnt being burned every rotation and eventually just floods out. ive bought new plugs, and done lots of sanding and regapping. im thinking its electrical because my gear indication lights are going out one by one but some if the will randomly come back on. so the bulbs arent out. i thought i may have had a bad ground so i got a wire to connect the ground points of the rectifier and whatever that black box is next to it, to the battery negative. what are some ways to improve spark? should i try out a new plug? right now i have ngk b83s plugs. during a ride, once she gets warmed up, it dies out alot, once it died every half mile for a few hours, after it dies i check the spark, sand the contact a bit and let it sit for 5- 10 mins and it will start again. today i took the airscrews to 6.5 turns out and took out the air filter pad, and it made it the 15 minute ride home without dieing. i just dont know where the root of the problem is, is it the fuel richness causing the bad spark(fouling the plugs)? or is it an electrical issue causing a weak spark letting fuel build up in the cylinder flooding it out?

[bonanzadave]

Put a meter on the battery and run it up to 2-3k rpms. Is it 14vdc or better ? If not, you have a charging issue and your coils are getting less than adequate voltage

[tom203]

Yes, try doing this Quick test

http://www.thegsresources.com/_forum/showthread.php?164993-Charging-System-QUICK-TEST/page2&p=1272192#post1272192

[hockey911]

Im in a similar boat as you right now.... ill be just driving down the road around 55mph and it feels like i ran out of gas, i can keep it running for about a mile or so, pull over, wait a few minutes and its running like nothing ever happened.... I often get a loud backfire pop when im sitting idling, the battery on mine is new......


For both of us any suggestions, im thinking ground or stater

[bonanzadave]

For both of us any suggestions,

Do the easy stuff first. If either of you have not replaced the spark plug caps in recent years.....do it.....now.

[alke46]

[QUOTE=bonanzadave.
Do the easy stuff first. If either of you have not replaced the spark plug caps in recent years.....do it.....now.[/QUOTE]

Ageed, I had a similar situation and after checking the ohm readings at the plug caps, that is what I had to replace. New caps, end of problems. Good luck to both of you guys.

[Wraith]

Wow!
OK, point number one - you need to go back to the start, set everyting back to standard settings, stop trying to check, clean, adust or change everything all at once and scientifically check, test, eliminate or hold steady each bit one at a time. Your problem could be a lot of things but the only way that you track it down is very methodically!

Point two - if you know that it's running rich then you must sort that before seeing what other problem(s) you have. I suspect that your 'gunshot' is simply running rich, as is the change when at different running temperatures. Also, get the carbs and screws properly sorted, again from scratch and methodically, rather than tinkering and "fiddling". Then you've got a baseline to work from even if it isn't the main problem (which it could be). (Never heard of cleaning carbs in lemon juice...! do you have to add sugar? Seriously, get some proper carb cleaner!). Is it really rich on the carbs or is it an air problem like a dirty filter or hole in the airbox or rubbers? Could be a fuel starvation/blockage/tank venting issue? Petcock/filter?

Three - you know that you have a weak spark which occasionally goes strong, and you know that sometimes there's no spark (or a very weak one). I can't tell from what you've said if the spark is good with new or clean plugs and then gets worse as the engine is run or if there's a problem from the get go. Your problem could well stem from wet plugs, but you should be able to tell this visually (and by smell) as soon as you take them out and it should run better once they're dry again. But a problem like that should occur repeatedly and predictably (if you don't keep on changing everyting all the time). Don't keep altering the plug gap and you shouldn't need to sand them all the time, either. What colour are they and what does that tell you? Can you 'plug chop' them to get some idea? Occasionally you can get bad plugs (and batches of 'em too!) so you could try a different plug make. Certainly try brand new plugs - perhaps if you've messed and gapped them a lot then just get a new lot, check the gap once (they're normally pres-set to the right gap anyway) and leave 'em alone. Could also be spark plug caps, so replace them too just to be thorough.

Four - if it's still doing it after the carbs are sorted then it could well (or must?) be some problem in the ignition circuit. I'm loathe to say coil (at least directly), but then again they do have a certain habit of going sudddenly and then maybe recovering after cooling down. I'd prefer to look for a failure in the electronic ignition (or points - but I think that you're electronic, aren't you?) or maybe simply a loose connection/wire - sometimes you can get heat effects in a wire, especially if its insulation is breaking down or rubbing against something hot. It could also be an HT lead breaking down or having a fault/damage in it (or water in?).

Five - Electrics could be a problem. I don't understand how you've tested the ground/earth wires but you'd need to check everything that's on the ignition circuit, earths and live feeds, for bad connections or rubs, loss of insulation, burns and the like. Is there a link to anyting like turning the bars one way or turning the wheel or, well, anything? That would indicate a rubbing wire or loose connection. However, if it's stopping/dying like it's running our of gas (rather than suddenly) - by which I assume you mean spluttering first - then I wouldn't normaly think electrics.

Look for patterns and check it one thing at a time.

Good luck!

[Wraith]

Have you got anywhere?????