VF500 Starting Issue

HiroProtagonist

Been Around the Block
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

https://youtu.be/JeI7CEoaFXE
 
leave the petcock off and try it. on the other hand if there is a vacumn tube that opens the fuel flow, it may not be connected. this will not allow the fuel to flow at all. So the once over is basically fuel vaporizing up into the carbs from the bowls giving you the one fire. Wait 30 and more vaporizes to give one more fire.

JMO
 
A red spark is a very weak spark. Red is the coolest color, then to orange, yellow, blue, white. Not sure if you'll get ignition at that compression. I'd run through the ignition and test those coils. They may be overheating or something and on their way out.
 
SO:
I took off the air box and fired it up. I was seeing the slides bob up and down and seeing what appeared to be fuel coming up the jets near the needles, so I'm prettttyyyy sure it's getting fuel.

Would the vacuum tube issue stop fuel from coming up the jets or just stop it from getting to the float bowls?

My next steps that I've thought of:
[list type=decimal]
[*]To eliminate it being a flooding issue, I have drained the floats completely, and left the petcock off. I'm going to turn it on for a very short amount of time (just enough to get some fuel in each bowl) and try to fire it.
[*]Once I do that, I'm going to turn it on and fill up the bowls. Then I'll open the drains and make sure each bowl has gas. (Should not be that, though, as I know that at least 3 of them had gas, so at least 3 of them should be firing.
[*]Check all 4 spark plugs to see if they're getting weak spark. I check a front one yesterday with the actual plugs intended for the bike (I was testing before with a spare plug because taking these plugs out is the worst thing ever) and it had a nice white spark
[/list]

Any advice on the next steps after this? From what I understand I should have eliminated flooding, made sure fuel is getting to the carbs, and spark. Guess I just have to clean the carbs again? Maybe check the diaphragms?
 
Start at your plugs and work your back to test for resistance. Check the plug connector to the positive connector on the coil, and check the positive to negative connector on the coil. If you have resistor caps on your plug wires, check with and without the caps. As far as the CDI, I'm pretty sure they work or they don't.
 
irk miller said:
Start at your plugs and work your back to test for resistance. Check the plug connector to the positive connector on the coil, and check the positive to negative connector on the coil. If you have resistor caps on your plug wires, check with and without the caps. As far as the CDI, I'm pretty sure they work or they don't.

Judging by this you believe it's electrical?
 
That's where I'd start based on what you described by your spark. If I understand correctly, you're also getting fuel.
 
it realy sounds like a cdi igniter box

viffers dont have a typical cdi system so they dont always do the just work or dont

and one side of the ignition does more than the other in it drives the tach as well as something else

it is also had to test these reliably

give these guys a call they can point you in the right path

http://www.v4spark.com/
 
Awesome. I'm trying to decide whether to start with carbs or electronics. I cleaned the carbs so I'm just not sure how much further to go. HOWEVER, leaving it overnight with the carbs drained and the petcock off resulted in it completely not starting at all!
 
run it from a test tank and eliminate the guess work about the tank and vacuum petcock for now
 
Roger. Am I crazy or is the vacuum switch not in the petcock - I drained the floats with the tank off and fuel still in the line, and the fuel didn't go into the bowls until I turned the bike over
 
It was the carbs! The pilot jets were just a tiny bit clogged - still able to see through them, but the hole was a little bit too small. Cleaned those out and it runs! Just need to run some techron through the gas to hopefully wash the rest of it out
 
The 500cc V4 is notorious for the carbs clogging after it's been sitting. There are a LOT of tiny passages in there, and the carbs need to be immaculate on the inside, or you'll run into hesitation, strange running, and performance issues.

First thing you should always do when you're not sure if it's fuel or spark is shoot some ether (starting fluid) down the carb throats and try to start it. If it catches and starts running, you know you've got decent spark - decent enough to run at least. Saves a lot of headache diagnosing things.

Also, very VERY few motorcycles actually use CDI ignition. (Capacitor-Discharge Ignition). The V4s are TCI - Transistor Controlled Ignition. Basically you have two identical spark boxes on the 500V4. One of them drives the electronic tach. If you have running issues where it feels like two cylinders drop out, check your tachometer. While the bike is running (poorly) does the tach read zero rpm, or alternatively bounce around crazily? If not, swap the spark boxes. Does it do so now? If it does, you've got a bad spark box. (Check the harness, the connector with the extra wire is the one that drives the tach, and now you know which spark box is bad).

I had the VF500C, which is the cruiser version with the same engine. I'm not sure about the F, but the C did not have a rev limiter box. The bigger V4s have two boxes, one with a white connector and one with a red connector. The red connector box has a rev-limiter built in (cuts two cylinders at 12k rpm). They are interchangeable, and you can run the bike with 2 red or 2 white boxes. With 2 white, you won't have a rev-limiter. With 2 red, all 4 cylinders cut out at 12k. Note that the bigger V4s have a 10k redline.

Boxes from different 1st gen V4 bikes will swap in and out without issues. HOWEVER, the advance curve may be slightly different between boxes. You can still do it, but in that case you should replace them in pairs. I didn't notice any performance issues running my V65 Magna (VF1100C) with V30 (VF500C) spark boxes, and I keep a pair as emergency spares in case of a failure on the road. Also, since the larger bikes have a lower redline, you may want to avoid the boxes with red connectors, as they'll cut out sooner. Then again, maybe not:

The 500 V4s have fragile wrist pins. Don't spin them past redline. My first bike was a V30 I got in boxes, because of that issue. Broken wrist pin, scored cylinder wall, but fortunately it broke at idle and the PO shut it down immediately, so a honing fixed it enough to be a runner again. (It burned a little oil, but I could live with that).

Also, dunno if it makes a difference but the V30 Magna and V30 Interceptor (VF500F) have the exact same motor... but the Magna has 500rpm lower redline. 11,500 on the magna, 12,000 on the Interceptor. There is no difference to engine internals, the only difference is printed on the tach itself. Just keep away from redline if you want your motor to live!

Charles.
 
Sorry to bump, but that's really good to know! I've hit redline once, and the engine immediately cut out, so I'm guessing that I have a rev limiter (it's an 86 and they made some changes on that). I'm just gonna pick up a set of new jets, because it's still running wonky. Finally put a working tach in (turns out the tach was shot!) It's a blast to ride, but crazy how quick it turns in. I'm used to 18" front wheels, so the tracking on the road is taking a bit of getting used to.
 
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