Stumped! - bike suddenly won't start. Ideas?
Posted April 05, 2008 - 09:03 PM
Just some background... The bike is well used, but has a fairly fresh top end and a few mods... hotcam, Mikuni flatslide, pipe... It has thus far been very reliable, and usually cold starts on or before the 3rd kick, even in cold whether.
Today I hauled it to my local OHV park in the back of my pickup. When I got there, I cold started it (60 degrees out) before unloading from the truck (just in case). It started easily on the 2nd kick, as usual. I let it run for a minute and then rolled it off the truck while running. I left it running on the ground for about 5 minutes to warm up while I packed up my ramps and gathered my riding gear. I then shut it down.
About 10 minutes later, after getting ready to go, I got back to the bike. It started right up, as usual. I revved it a few times to make sure it was ready to go, and I began to drive off for my ride. I moved about 2 feet before the bike stalled. It felt like the kind of stall that happens when the bike isn't warm enough yet (after a cold start) and isn't quite running right. Once I loaded the engine, it stalled.
When I tried to start it again.... nothing. I spent an hour trying to get it running before packing everything up and heading home, very pissed off. Here's what I did, other than kicking a hundred times with no success....
1) Kicked a bunch of times, gave it a 5 minute rest, and went back at it.
2) Checked the fuel... full tank, gas was "on", full carb.
3) Thought it might be flooded... tried starting with wide open throttle with no success.
4) Turned off the gas, drained the carb, kicked through a bunch of times, and gave it a good rest. Then turned the gas back on and tried again.... nothing.
5) Changed the spark plug and confirmed a good spark. The plug smelled like gasoline, but wasn't wet... no luck.
6) Checked my kill switch and confirmed it was working. (no spark at the plug when the button was depressed, and spark when I let go).
7) Adjusted idle screw for faster idle... nothing.
8) Even tried the choke, which I have never needed before, even in freezing whether.
9) Kick, kick, kick!! Thought my leg would fall off. I got a few pops here and there, but it never fired up.
10) Swore profusely.
Any ideas? I tried again when I got it home with no success. Obviously there could be other causes for a bike not starting (carb adjustments, dirty air filter, valves out of adjustment), but I have a tough time believing that these things could change so dramatically from one minute to the next that the bike would go from running fine, to not running at all. In my experience, carbs don't un-adjust spontaneously, filters don't clog instantly, and valves come out of adjustment gradually over time. Why would it start right up when cold, and then when warm, and then not at all a moment later?
I appreciate any ideas you all might have. Thanks!
Posted April 05, 2008 - 11:29 PM
Could of course be something like the CDI going into terminal failure..You will need another "spare" for testing..Thats my ideas gone..barring of course a valve gap check.
Ps..I can imagine the state of your leg..LoL
Posted April 05, 2008 - 11:43 PM
I had a similar problem with my 2000 XR, which ended up being water in the fuel. You say you drained the carb float bowl? from the bottom drain plug? Try a few squirts of brake/carb clean into the back of the carb with the air cleaner off. (Always bring brake/ carb cleaner to the trail with you. Best $2 troubleshooting aid out there.) If you get fire, then COMPLETELY drain the carb bowl from the bottom and try a new tank of gas. If that doesnt fix it, then I would pull the carb and look around in there. If it doesnt fire off the brake/carb cleaner, then obviously something is squirrely with the ign.
Also, food for thought, I'm not a fan of those stock kill buttons. You have to hold them down til the engine stops to shut the bike down. If you have a good fall and youre at high RPM, that could potentially cause undue pain. A $17 off/on kill switch is a much better way to go IMO.
Posted April 06, 2008 - 05:11 AM
I'm of the opinion that a roll start on a long hill should tell you whether or not the bike will start at all. To get the rear tire to spin with no manual decompressor in the AZ cinders, get going pretty fast, stick it in third with the clutch in, and as you let the clutch out, kick it. It takes some finesse to get the timing right but the tire should start to spin. Once it's spinning, mash it into second and hope it fires.
Horri may be right that it's a bad CDI or coil. The XR's coils are known to die with age (maybe because they run in oil). A weak coil will still show a spark. Granted, coils don't usually go pop and die, but CDIs do.
You may also have a goober in your carb somewhere.
Posted April 06, 2008 - 07:33 AM
Horri... yeah, the leg is pretty sore this morning!
Ch47 Pilot.... I did actually do a complete carb drain from the bottom plug in the field, but of course couldn't really swap out all the fuel. I may give that a shot if a bump start doesn't work. By the way, I like your idea about the kill switch, too.
"O", FYI I do have a decompression lever and I use it. I can't imagine trying to start the pig without it! I thought of trying to bump start in the field, but I didn't have a hill near where I parked, and with my rubber leg (after all the kicking), any finesse that I may have had was long gone. So, I bagged the idea and headed home.
It occurred to me last night as I was pondering the problem that I think I experienced this before in a different way. I recalled that some time ago I decided to start the bike in my garage just because I hadn't had it running in a couple of weeks. I remember that I couldn't start it after about 20 kicks. Being that it was just a whim anyway, and I didn't have time to look into it, I just left the bike alone, figuring that I was just "off" or something. The next day, I went out to start it again, and it started on the first kick. I never really thought about it any further, but I bet it was the same deal as whatever happened yesterday. I haven't tried starting it today because I'm still in my boxers.
Anyway, thanks guys. I'll report back after fiddling with it today. If you have any further ideas, I'd love to hear them. Thanks again!
Posted April 06, 2008 - 10:53 AM
It died a moment later, but started right back up again and is now idling in the driveway like nothing ever happened yesterday.
What is up with that?!?!
Anybody got any ideas on what may be happening here? Please also have a look at my prior post (just before this one) and consider the prior instance of this event that I recalled.
Thanks everyone! Any input you have would be appreciated.
Posted April 06, 2008 - 10:57 AM
Posted April 06, 2008 - 12:44 PM
A::No I don't..I've had a few bikes that refuse to start and then half an hour later fire right up..I generally put it down to flooding and a bad hair day..No rhyme nor reason for it..My 82 XL500 is quite prone to the problem but it has a oddball carb and non stock air filtering so I put it down to technical issues which I should look into but never do.
Posted April 06, 2008 - 03:15 PM
Posted April 08, 2008 - 07:48 AM
Posted April 08, 2008 - 11:06 AM
Posted April 09, 2008 - 10:32 PM
After it started on the first kick on Sunday morning (after the Saturday no-start that sent me home sobbing), I got the bike out for a ride. Based on Sunday's ride, and some fiddling I've done with it since, I seem to have found a pattern.
First, I was able to duplicate Saturday's events right away... I couldn't start the bike by normal means after it was warm. Here's what I learned, though. Usually I hold my compression release lever in when I start the bike, and it has historically started every time, hot or cold. Now, it seems that once the bike is warm, it won't start with the compression release pulled. I need to use it to find TDC without getting stuck, but then I have to kick without it to get the bike to start.
Not being a genius at this stuff (only mechanically inclined), I figure this may be an indication of valve adjustment having changed, or perhaps an indication of a decrease in compression. I draw these possible conclusions because I figure that in the past, even with the compression release lever pulled, it would still start, hot or cold. Now, it seems there's not enough compression to get it to fire when the engine is hot and the lever is pulled.
Posted April 10, 2008 - 03:09 AM
Now, it seems there's not enough compression to get it to fire when the engine is hot and the lever is pulled.
On my 600 sometimes the idle is too low and the auto decomp on the cam kills the bike. Cranking up the idle all the way helps it start every time, even when really cold.
I doubt the valves are the issue. If they're out so far as to kill the bike it won't want to ever start or run, and if it does it sounds like a sewing machine on NOS.
Posted April 10, 2008 - 05:31 AM
Posted April 13, 2008 - 04:10 PM
Posted April 14, 2008 - 10:37 PM
does your bike have an oil pressure switch and is it working properly on my 95 xr600 it is by the front sproket and should have one wire going to it
Well, I see the wire, so I assume I've got one. Not sure if it's working properly or not, though. How would I know from the outside... or can I know from the outside?
Posted April 15, 2008 - 06:41 AM
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