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Strange running problem

2K views 12 replies 8 participants last post by  Tripps 
#1 ·
98 bird. I had an issue with the bike dieing within 1-5 miles from home. Changed plugs and coils, no luck. Bought a used ignition on ebay, seller has 99% reputation, said taken off good running bike, still no luck. Took it in toy buddy's shop, mostly a Harley mechanic, but he's pretty good at figuring things out. Checked fuel pressure, it's good. Put a new rectifier from Rick's, took carbs apart, anything he could think of. It will start and run good, after about a minute it gradually dies, whether idle, of even trying to keep rpms up, still gradually Peter's out. Will not restart, but after 15 minutes it fires right up, but dies again. We're both stumped, at a dead end. Any suggestions appreciated.
 
#3 ·
Yes, battery good, cranks well every time. Wondered about vacuum petcock, because it acts like it runs out of gas. Coils do that when hot, but replaced coils, and really doesn't have time to get hot.
Chased a hot problem on a Triumph Rocket for a couple years, went away as soon as I changed the coils.
Blocked vent is a great suggestion, as I can imagine pressure equalizing after 15 minutes.
 
#4 ·
Right after it dies see if you can open the cap. If you can't then betting it's what fizzy said about a vacuum lock. To confirm pop the cap fire it back up and see if it dies. If not then there's your culprit.
 
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#7 · (Edited)
Does all electrical quit, like no power when it stalls?.
If you have power, take the fuel tank off and use another means of fuelling it, start her up and let her run.
See if it stalls.
You need to separate if it's a fuel, or electrical problem.
How many miles are on it?
Does it have an alarm fitted?
Did you do any work on it before the problems first started?
Keep a multimeter on the battery to see what happens when it dies.
As you already know, air, fuel and spark, it should run and seen as it is a carb model, then the electrics are pretty straight forward.
As I put, you need to see if its fuel or electrical.
If it was a fuel issue though, then a closer inspection of the carbs and main jets mite be in order, and just a thought, but put a new piece of vacuum line on the petcock just to rule it out, and if it was fuel problem then is your tank clean?, check you fuel tap and petcock, you mite have a problem with it, and since it's a 98 model then I would change the petcock seals anyway by now, and properly inspect the fuel strainer in the tank that the petcock is attached to.
 
#9 ·
Thanks guys. Already ordered petcock rebuild kit. He already had carbs apart, seemed fine
Does seem to be fuel, as no power loss, no discernible loss of cranking power after multiple starts. No alarm I noticed, but did ask shop to check for one. Am in Maggie Valley this week riding, I'll probably pick up bike next week and pursue these suggestions.
 
#12 ·
98 is carburetor, I don't think it has a cps, no computer. I'm going to let my mechanic install the petcock rebuild, seems like a gas issue, starts fine then dies, like it runs out of gas. After 15 minutes it will start again, maybe gas trickles in again.
 
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