First Generation Ascots > Tech Section
Motor locked up on freeway
NinjaFinch:
Hey all, long time lurker in need of help. Please don't hurt me.
So I have an '82 FT500 that I got last year with ~6k mi on it. It's completely stock mechanically, and I've been keeping up with maintenance. Until yesterday, it didn't really give me any major problems.
After a weekend of long-distance riding, I was heading home on a fairly straight stretch of highway at ~110 km/h. Then without any sort of noise or stuttering, the engine just stopped like someone hit the kill switch. It rolled for a bit and by the time I realized what was going on, it locked the back wheel (in 5th gear) at somewhere between 60-80 km/h. Luckily, being Saskatchewan, the highway was pretty empty when this happened. Got it off to the side of the road and despite my best efforts, I couldn't get it going again. Ended up going home on a wrecker.
One change of pants later, I tried to poke around a bit more with no luck. As it is, it still won't start. Changed the spark plug since it was due for that anyway, and it's getting both gas and spark. Air filter looks almost new. Despite the wheel locking up, the starter will engage the motor and the crankshaft turns normally. Oil was low, but still within the hash marks on the dipstick. All electrics beside the left turn signal (different issue) work normally. Gassed up about 20 mi prior, and tried the petcock in both on and reserve. Where should I look next?
murdo:
Wow, I'll bet that got your attention. Lucky I've never had a high speed seize like that.
If the engine is turning over on the starter, does it have compression. Take the plug out and put a finger over the hole and engage the starter, it should blow your finger off the plug hole. If no compression then you will need to remove the cylinder head and see what has happened.
NinjaFinch:
Yeah, first mechanical failure I've had to deal with on a bike. But if the fact that I could keep it righ side up isn't a testament to the value of the MSF course, I don't know what is.
Just tried the thumb-on-spark-plug-hole trick, and I could feel it motor pushing air past my finger. I'm guessing that says there's some compression? But if everything else is good, it's probably not enough.
I checked the valves on the exhaust side. One was perfect, the other was a bit tight (>0.05mm). No idea about the intake side yet, I'll have to tackle it after lunch. Just hoping it's not permanently knackered.
firecaptp7:
According to what you’ve written …
You’re riding down the road when suddenly the engine stops running as if the kill switch was turned off. But you’re still moving forward? Did you immediately pull in the clutch lever? And the rear wheel was still locked up?
First question? Why did the rear wheel lock up? When you pulled in the clutch lever did it roll free? Or is it still locked up? If so that’s a separate issue from the starting problem.
Second question - You now have fuel, spark and compression but the engine won’t start?
Trying to understand.
NinjaFinch:
I didn't pull the clutch until after it came to a stop. It was when I was trying to get it off the side of the highway that I pulled it and it rolled no problem. For the second question, I have fuel for sure, some compression (gauge doesn't fit, so I can't tell how much, or if it's even enough), and spark.
Thinking about it now, the spark colour is dramatically different from what it used to be. But for every argument I can find that says 'weak spark' is a thing, I find another in all caps saying it isn't. I don't know who to believe anymore, but I'm testing the ignition system later today. Hopefully that yields something.
Edit: According to the ignition pinpoint test that's elsewhere on this site, my CDI is putting ~6V to the coil vs the expected 36-42V. Ignition Pulse Generator is ~493Ω vs the expected 500-570V, which is out of limits but also doesn't seem too far off. Still need to test the alternator, but I feel like one or both of the two might do it.
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