78 XS650 Special - won't start with good spark

[Bethinkin]

After many suggestions to help get this bike up and running, I spent the weekend adjusting the valves, chain, ignition, and finally the carbs. I found that the last person to work on the valves had them set wrong. Instead of .004" (.10mm) clearance on the intake for example, they have 0.04mm of clearance. That is a big difference.

I adjusted and triple checked. Ignition points were good and the bike was idling well. I pulled the carbs, cleaned and put in a new gasket.

My tach was broken, so I rewired a new one from a newer model. I had to splice and change the wiring a bit to get it all to work.

So, after putting it all back together tonight, I can't get it to start. It cranks just fine. I have a good spark, but it doesn't come close to catching. I pulled the carbs again to make sure I didn't block something to the new gaskets aren't covering something. They looked good to me. But I feel like it isn't getting the fuel it needs. The lines are flowing as well.

Would it be a fuel issue? Did such a large adjustment to the valves mess it up, or is there a wire that needs to be hooked up that I missed (kickstart isn't working either). Any insight would be great. I'm feeling stuck.

 

[TwoManyXS1Bs]

A "quick 'n dirty" diagnostic method:

- Attempt to start the bike.

- Immediately pull the plugs.

- Inspect/smell the plugs.

If noticably wet, and strong fuel smell:
May be flooded, rich, too much fuel.
Leave the plugs out, throttle open, kick thru several times to dry it out.

If noticibly dry, and no fuel smell:
Not getting enuff fuel, or any at all.
Check choke usage, check carbs and fuel delivery.

If slightly damp, with fuel smell:
Probably getting enuff fuel, but this is a gray area.
Leave the plugs out, throttle open, kick thru several times to dry it out.

- Before doing the above kick-thru's:
Clean the plugs.
Plug them into the plug caps.
Set them on the head so that the bodies are grounded, and rotated so you can see the electrode gap.

- During the "clearing kick-thru's", observe spark at plugs' electrodes.

- If no/poor spark, fix ignition, replace plugs as necessary.

- Reinstall plugs, attempt restart.

Many of our bikes seem to have their own startup personality. And, there's several startup methods favored by the members, depending on tuner skills, odd-numbered Thursdays, and something involving chicken blood. If everything's correct, may just be a starting ritual...

 

[Bethinkin]

Checked the plugs. They seemed pretty dry. I've checked that fuel is flowing from the tank, and it is. Also, for what it's worth, it added a little fuel down the spark plug hole on each side and got the bike to fire up for half a second, until it burned off.

I could be wrong, but I feel like I'm chasing a fuel issue. So probably something to do with the carbs. The bike valves are much louder since the adjustment, is that normal?

 

[5twins]

Set at .004", your intakes may make a lot of noise. Most of us use .003". I know .001" doesn't seem like much but it can really cut down the racket.

Your chokes might be plugged or blocked by the new gasket. There is a feed passageway on the top edge of the bowl where the gasket sits. Some new gaskets have the hole stamped but the punch-out not removed .....

It's also possible the choke jets themselves are plugged. Here's how to check them .....

In either case, with the choke blocked, it will not function and cold starts will be very difficult.

 

[fredintoon]

Hi Bethinkin and welcome,
OK then, it ran before you adjusted it?
And it briefly ran after you tricked gas down the sparkplug holes?
Gotta be the carbs.
Overlarge lifter clearance is noisy but it'll still run OK.
If it's a wiring-related thing it must be the electric starter that's not working, the kickstarter is purely mechanical.