My 75 won't start.

[ssjody]

When you pull the carbs off were they full of fuel? I know it's a basic question but unless I missed it there has been very little mentioned about fuel flow. Pull the fuel line and see if you're getting fuel. Throwing a capful of gas in the carbs might not be the best choice. Spray some ether in it and see if it reacts to that.

 

[Tone]

Yes, I neglected to mention that carbs were full of fuel. I have in line filters also so you can see the fuel flowing when the taps are turned on after the carbs are installed.

 

[gggGary]

I'm not picking on you, but agree odds are pretty high at this point there's some "assumed right" that isn't. It'll be a JC why didn't I see that moment.

cuz we're clutching at straws;
PMA or stock rotor? (PMA's dont have a keyway, can move on the crankshaft.)
reverse the points (not plug) wires and try?
condensers tested?
Have you changed or dried the plugs with a torch?
plugs that work fine out in 1 atmosphere can act differently under high compression.
I prefer spray carb cleaner to poured gasoline when doing "will it run" testing.
ON VM34's yes the idle stop is the only diff most L-R sets, and yes if installed on the wrong side the slides go in backward and it won't run.
Are you 100% sure the gas last poured in the tank really is gas?
Any chance a nefarious actor messed with the bike?

 

[JJames]

Please don't comment any further you are not helpful.

Hey! You're talking to my guy all wrong. It's the wrong tone.

 

[Jan_P]

Hey! You're talking to my guy all wrong. It's the wrong tone.

Thank you Sir ... for the Support ..Many Thanks
To move it on .in a constructive note
I have been doing this for 40 years on exactly this motorcycle .All the time with substandard wiring
Probably world record kicking it
feel free to question. my suggestions I may well be wrong It happens .But there are others sources for information internet search
And 2 methods
Figure it out at the Desk or Do some experiments.

I am out per orders and as in the military " Yes Sir " but there are others here that can solve it in a spirit of Cooperation

 

[Paul Sutton]

When I first got my Virago it ran well then up and died one day. I checked everything. It turned out the bike's VIN had expired. Yamaha issued a new VIN and the bike started first go...

 

[Tone]

Bike is now going, I checked the Vin, that was still current, so no problem there. Moved onto the tyres, pressure was good there, so I moved onto the chain, it was a little loose so, I tightened it but it still wouldn't start, so I checked the oil level in the forks, and there was the problem, oil was low, topped it up and the bike started right up and ran like a dream. It does splutter a bit though, probably the fork,seals. I'll replace them tomorrow, that should fix the splutter.

 

[JOHNDADDY]

Bike is now going, I checked the Vin, that was still current, so no problem there. Moved onto the tyres, pressure was good there, so I moved onto the chain, it was a little loose so, I tightened it but it still wouldn't start, so I checked the oil level in the forks, and there was the problem, oil was low, topped it up and the bike started right up and ran like a dream. It does splutter a bit though, probably the fork,seals. I'll replace them tomorrow, that should fix the splutter.

Frickin Hilarious! Oil level in the forks. That's funny.
Check your headlight fluid.
Dowel a cylinder to make sure TDC is TDC.

 

[jaybar6]

the exhaust could be blocked. take one silencer off and start it.

 

[JOHNDADDY]

Kill switch?
Or kill switch bad?

 

[Tone]

Frickin Hilarious! Oil level in the forks. That's funny.
Check your headlight fluid.
Dowel a cylinder to make sure TDC is TDC.

That's stupid, there is no fluid in headlights. Headlights are full of worms, everyone knows that.

 

[gggGary]

dang I didn't want to mention cuz it's so obvious but thought for sure a corroded Tillman junction would be the prollum.

 

[Tone]

dang I didn't want to mention cuz it's so obvious but thought for sure a corroded Tillman junction would be the prollum.

I've never heard of a Tilman Junction, where is it, what does it look like, how do I clean it, is there a gap to set, what about timining it, will a philips screwdriver remove it or will I need an Eziout?? ? Sorry to ask so many questions but I'm hoping to become a 'real' mechanic.

I'm pretty sure it was the the fork oil though, after topping it up it started up straight away, it's still sputtering a little but new seals should fix that. Never the less I'd still like to have a look at this Tilman thing. If I have to open it to clean it that won't be a problem, I'm very good with Eziouts if my philips screwdriver fails.

Look at that, I'm even starting to talk like a 'real' mechanic now. I know all the words Tilman, junction, eziout, philips, gap, timing, fork, oil, topping up, sputtering. Is the prollum part of the Tillman?

 

[JOHNDADDY]

Tone, can you take and post a pics? Or have a friend do it.
One of your points and another of your spark advance unit
and one of your timing marks at TDC?
Please.

 

[jaybar6]

Kill switch?
Or kill switch bad?

I hate the kill switch, it takes 0.5volt out of the ignition coil!

 

[650Skull]

Arctic picked it.

 

[jaybar6]

I read some where that air resistance requires 10,000 volt to jump the gap, hence lightening is more than 10,000 volts. The spark plug gap requires more than 10,000 volts as there is the compression to over come. 8.7 ratio. half a volt out of 12 volts, what's that about 5% reduction? with the induction effect, turns ratio and all that, what voltage is required?

 

[Its been a long time]

Good idea to power the ignition system via a (fuse and) relay to get battery voltage onto the coils. I use the red/white wire to switch the relay. Gives the best possible spark from the coils.

 

[jaybar6]

Good idea to power the ignition system via a (fuse and) relay to get battery voltage onto the coils. I use the red/white wire to switch the relay. Gives the best possible spark from the coils.

Yes, there you go. that is the solution. I was going to bypass the safety switch and run the coils straight from the ignition switch,..

 

[Its been a long time]

Yes, there you go. that is the solution. I was going to bypass the safety switch and run the coils straight from the ignition switch,..

I've refurbished all the switches on my 650 and got the voltage drop across them way down from where it was. But there's still crusty 48 year old bullet connectors and wiring. The ignition system on these bikes wasn't wonderful back in the 1970's. So to get it as good as it can be, I installed the ignition relay when I fitted the Boyer Bransden kit. Big fat sparks now