I understand there are a few gearheads running about this little old place. Rather than go to an actual motorcycle forum, I decided to go to you - cause I wuv you SO much!
Let's say, hypothetically, that you have a motorcycle. Let's say you go through a series of events as such:
1. You crash your motorcycle. Only cosmetic damage is apparent.
2. Upon return from the emergency room, you hit up the bike. You find that it runs, but does not idle properly. You turn the idle screw, effectively 'turning up' the idle, until it runs properly - and it does run properly.
3. You leave the bike in a bikeport for about three weeks while you await the parts needed to make it look pretty again - and while you wait for your f!$@ing knee to heal up so you can bend it again.
4. After installing all the cosmetic bits (including a turn signal, which means you've played with some of the wires in the 'lectric system), the bike refuses to turn. She'll crank, but she won't ignite.
5. Naturally, being the good icrontian that you are, you check your fuel by turning the petcock. Sure enough, good clean fuel comes out. You drain the carbs and allow them to refill, then check again. Yep, she's got fuel.
6. Hoping it's not spark, you spend a frustration-filled day trying to figure out how the ever loving hell to get your spark plugs out of that freaking tiny motor - upon removal, you attach both plugs to their wires and ground them against the engine. You turn the engine - yep, you've got spark.
7. Noting that the engine is acting suspiciously like the killswitch is on, you pry open the killswitch and check it with a multimeter - nope, the circuit is still complete. Killswitch ain't the deal.
What would you do, icrontic? Naturally, my next move is to check the air, but as I've replaced the filter recently, I reckon it's sitting pretty. Assuming the air is good, some googling shows people suggesting 'testing the timing' and doing a compression test - I've no idea how to do the former, and need to buy the tools for the latter.
I have a hunch that messing with the idle screw did some uncool things, but the idle screw works post-mixing, right? Is it remotely possible that this could have screwed things up?
What next, icrontic?
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Myrmidon
Gonna lifesteal so much moneys Member, Supporter, Expo Attendee
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While said spark plugs were out, did you crank with a finger covering 1 cylinder to make sure of compression, then the other?
Two stroke or four? How many cylinders? Single carbs, multiple carbs? How bad was the drop and was the bike running on its side for awhile?
Or just type of bike... heh.
Does it even kick at all when turning it over? I always like to try a little bit of starter fluid just to see if it will kick.
Also, the carbs may have gummed up a bit or possibly a float is stuck and the carbs are flooding the motor. Were the plugs really wet when you took them out, bone dry, brown, white?
As for pseudonym: I have attempted starter fluid - I blew some ether into one of the cylinders via the spark plug hole, replaced the plug, and tried to start it - no luck. Of course, by this time the battery was getting a little weak. As for the plugs themselves, the ceramic was nice and white, and the gap area had turned black from carburization and stuff. I didn't smell it for gas, which I should have done. It didn't seem wet.
It's a Honda VF500F - 1985. It's carbureted, two cylinder, multiple carbs. The bike WAS running on its side for a while - the crash was simply putting the bike down on its side, but since it's been three weeks since its last run and since I drained the carbs, I don't think they're flooded - I don't really know about the cylinders themselves - when cylinders get flooded, how does the stuff get out?
Generally you flood the motor when the motor is turning over but not firing and gas is just pumped into the combustion chamber, when this happens you soak the spark plugs and the cylinder while also ruining the air fuel mixture. Generally the easy fix for this is to pull the plugs, turn the motor over without the plugs to allow the cylinders to clear out, clean and dry the plugs, and then attempt to start the motor again. My thought was that if the carbs aren't acting right, they might be putting too much fuel in the motor, and flooding the motor. So possibly an internal carb problem (float etc)
Also, since you had it on the side, generally these motors have to be told when to fire the spark. Your timing is most likely (guessing here) based off of a stator on the crank somewhere. There is then a sensor there that senses the stator when it goes by (its just a magnet) and that signals the motor to fire. If this has been knocked loose and is in a strange position it is possible that it is misaligned and firing the spark at the wrong time, but even in this case I would expect the motor to at least do something.
Now this is an older bike so that may not apply, your timing may be set mechanically and therefore my suggestion is null and void. There is also a possibility there is a problem with the coil which is what the spark plugs are connected to. Does the bike have a distributor? This could have been knocked out of adjustment.
I just read that this thing requires valve adjustment too every once in awhile, which would be a mechanical change, this could be causing a problem if something was knocked out of place.
Also, you say its a 2-Cylinder? Doesn't everything with a VF500 designation use Honda's 500cc V4 motor?
1) I'd check over the bike REALLY well. See if anything is loose, cracked, broken etc.
2) Check the choke like Ryder said.
3) Messing with the idle should have done nothing to throw the bike off. To be sure you could turn it down and try starting again. The idle screw should have only adjusted the mechanical position of the butterflys and nothing else so it shouldn't hurt anything
4) It was the idle screw right? And not a mixture screw on the carb? Thats possible but I don't know the carbs. Possibly could have thrown the carbs out of synch but again, it should still fire, just run poorly.
5) Make sure the carbs are clean and functioning well. This may require a rebuild.
6) Find out how to check the timing on the bike.
I'd do as much as you can that doesn't involve taking the thing apart at first. Then move to carbs, fuel system, etc. I have a sneaking suspicion that it is the timing though. Fits the runs hot but not cold, hard to start, doesn't spark, required more idle theory.
Also, these guys might be of some help.
http://www.vfrdiscussion.com/forum/index.php?
I was under the impression that the VF500 was a 4 cylinder as well, but for the life of me I can't find the other two damn spark plugs (though the bike isn't apart), I only see two carburetors, and the exhaust pipes only seem to lead to two places. But I'm a guy that makes HUGE GROSS ERRORS, so it could definitely be a four and I may be overlooking lots of stuff.
My workaholic got into me - I did your compression test, I definitely have compression. I noted that the spark plugs smelled like gas (and in one case a hint of ether, heh), but they were both bone dry. Doing the compression test, I'm pretty sure the pistons were just blowing air - didn't feel any mixture on my fingers.
I also took a look at the choke LEVER - not the actual choke mechanism down in the engine, mind you. The lever was on the handlebar that hit the ground, so I was thinking the lever mechanism might have come loose - it hasn't. I have yet to take a look at the actual beast.
I like the timing idea, but I REALLY don't like having to deal with it. I'm uncertain how the timing mechanism works, and I've never NOTICED a distributor - but like I said, I overlook things easily.
And yeah, I dig vfrdiscussion... it's where I bought a few of the parts I needed. But I like icrontic so MUCH! :D
EDIT: It's definitely a 4 cylinder. I'm an idiot.
Looking at my shop manual, I see two procedures - ignition timing and valve timing. Ignition timing is done by coils that have to be straight-up replaced, while valve timing is done by god-knows-what (I hate these things, they don't explain HOW it works, just how to take it APART). Is it more common for ignition timing to get off, or for valve timing to get off in a crash?
#2.. Ignition timing.. also.. under a side cover (probably round near bottom of engine) unless part of the engine case itself was cracked or broken in the accident. Timing is not the issue.
You had it running after the crash, correct? This is now just a problem after the 3 week dormant period.. correct?
How hard did anything get jarred? Was this an impact crash or a slide?
I would do this:
Get the other 2 plugs out, check for spark, check those cylinders for compression also.
Put 4 plugs back in, make sure connections are tight, set choke and attempt to fire. (charge battery while you are doing other things, you can leave battery charger connected while cranking too.) Only crank for 4 to 8 seconds total with the choke on. Remove choke and crank again, if it does not fire in the first 8 seconds.
If it fails to fire....guess we worry about that then.
I tore down the whole fuel line from tank to carbs, and the gas is definitely flowing in. I checked out the air box and the filter, while not pristine, still passes plenty of air. I want to hit the ether test again with a good, fat spark - they definitely looked a bit on the weak side. If the ether test flies, I'm pulling the carbs - and terrified to do it.
But what if the ether test doesn't work? I want to say compression pressure or timing, what would you think?
It just seems like if it cranked once after the accident it shouldn't be so hard to crank again. Just my opinion.
I'll go sit back down now ...good luck!
I ALWAYS keep it in neutral when it's parked, but yes, I did check that - in fact, she'll start in gear with the clutch in, too.
Damn good advice, though - I've been the bonehead pushing his bike home with nothing wrong but the killswitch more than once! :)
Anyways.... after reading about the bike.... I WANT it!!
/jealous.
I still think something is knocked out though, just don;t know well enough to know. Taking everything apart is the LAST RESORT!
All spark plugs are good - that scares me. That means ELECTRIC is good, too.
Air filter looks gorgeous. If there's not air getting in, I'd be surprised.
All cylinders have compression.
Flooded and emptied the carbs, and suddenly the bike started right up, and subsequent times had no problem either. She sounds like she's missing a little bit, but I think that's because the spark plug wires are nearly broken. I'm worried the problem will be back tomorrow, though. What do you suppose? Just blockage in the carbs that got forced out?
Carbs were clogged with a mystical substance that resisted my cleaning attempts.