VF500 Will Fire Once but Won't Start

Hey all,

Just got a VF500 and I'm having the oddest issue. The bike turns over fine, gets a solid spark (red not blue, but solid all the same) and will turn over once, but then not turn over again until I let it sit for quite a while (30 minutes plus).

I cleaned the carbs and they were pristine from the moment I opened them. I would assume that the engine is flooding but this seems extreme.

Here's a video of the issue

 

sure fuel is getting to carbs ?

 

I'll check again, but 99% sure. Wouldn't that cause the opposite problem, though? If fuel wasn't getting to the engine wouldn't it never fire?

 

Rather than firing once and then absolutely not firing, I mean

 

Bump!

 

Nobody has any ideas? I feel like this can't be that obscure a problem!

 

Heard tell that it could be Spark Ignitor related. Thoughts?

 

the shit can damage an engine, but try spraying starting fluid into the air intake while cranking. if the engine runs on all cylinders, your carbs are probably clogged or not getting fuel.

 

Turns out that the pilot jets were clogged! I could see through them, so I assumed they had been cleaned enough, but it turns out they needed more cleaning. I ran a bristle from a steel brush through them and the bike fired right up.

Next step is my bent idle screw. Any advice on a replacement?

 

so what is this, about the thousandth time someone asks for help getting his bike running and claims his carbs were clean, and it turns out his carbs were clogged ?? all too common, Colin, you're just the latest in a long, long string.

 

I will totally accept that. Was mainly hoping for some pain spots of the carbs to check or possibly other things to make sure were okay. I don't know what to tell you, those CV carbs are delicate and it's hard to tell if they're 100% clean unless you happen to have an ultrasonic cleaner on hand or boil them in CLR. The test of spraying the starter fluid was exactly the direction I was hoping for - something to stop me from chasing down a million different problems and at least narrow it down.

Honestly, I'm pretty sure I still haven't completely gotten everything. The RPMs still won't drop quickly, and the bike gets pretty darn hot even in cold Seattle. It's up at the top of the range most of the time and the fan is on quite a bit.

I'm probably just going to pick up a stock jet kit for it for peace of mind.

Either way, thank you for your help! Sorry that it was such a simple fix - I switched to Mikunis for both my CB350 and my CX500, so I didn't end up having to fight the battle to clean them.

 

running too hot needs correcting. could be as simple as a bad radiator cap or cooling system flush.

 

Roger.

My tach is shot as well. I'll probably start a new post about it, but in case you have ideas. All 3 wires leading to it are getting good connection (yellow has almost no resistance to the yellow coming out of the coil, green has almost no resistance to ground, and black/brown has almost no resistance to temp sensor black/brown)

The tach wobbles against zero at idle, but as soon as I throttle it just hangs out at zero.

 

Update on the running too hot - the fan only kicks on when the temp sensor is about 3/4 of the way up. Does that mean my thermostat is shot?

 

I'm going with no. But it wouldn't hurt to test it.

Sent from my XT1031 using Tapatalk

 

Cool. SO, another update! I put a new gauge assembly on (my old tach was shot), and the new temp gauge is showing it hanging out more in the middle. I'll post pictures soon to get opinions on whether it's still too hot, but looks like it might have just been the old sensor.

 

the fan coming on at 3/4 scale is normal and OK.