83 650 Nighthawk Starting Probs

[Kjkenney]

Been a while since I've been around but I'm at wits end here...bike was running in the fall great, would start every now and then to keep it happy in the cold months. Getting ready for the warm weather and did some carb cleaning to remedy a non fire issue on cylinder one. Now it's back together and when cranking it acts like the kill switch is in the off, no fuel flow and can't feel vacuum off carb boot. Bypassed the switch just to test and no change. Tried push starting it and I get a couple grumbles and it stalls. I'm feeling like something electrical went wrong just with the way it's acting like something is telling it not to run. Anyone have any pointers on what to check in something like this? Is checking the components like the Cdi, pulse generator et al the next step? Again this was running great solid for about 200 miles after rebuild in fall. Thanks in advance

[Folsoml]

You say you can't feel the vacuum? What is your compression like? Are you getting spark to the plugs?

Those would be the first things I'd check.

[Kjkenney]

I honestly haven't checked with a gauge since I rebuilt, I recently just did the finger over the spark plug pop test with good results, but I know that can be subjective and not guarantee anything. I need to borrow a gauge again and check for sure. Spark is not there either which is odd....when the bike cranks in the off position, does it just turn the starter and attempt to do nothing else? Such as generate a spark..I may be focusing too hard on the wiring portion but po was creative with some wiring before I purchased it and I've had other gremlins with it. The fact that both are absent can't be a coincidence can it? Thanks for the input!

[Kjkenney]

OK I'm silly, spark test in the day fools my eyes..haha as far as compression, will the hydraulic tappets cause issues with the valves if they fail to pump up? I'm wondering if I need to take them out, bleed them and use the kerosene. I used oil the first time which I've seen opinions both ways, but would rather have it the way sir Honda wanted them. They definitely were clicky at times

[Folsoml]

If you were not able to see the spark in the daytime, that suggests to me that it is weak...

but po was creative with some wiring before I purchased it and I've had other gremlins with it.

...or intermittent. With "creative" wiring from a PO, it will be difficult to give advice. I would go through the wiring harness (or what's left of it) and clean all the electrical contacts. Make sure they are good and tight--the contacts themselves, not just the plastic plugs.

I'm not terribly familiar with the Nighthawk 650. What are the "hydraulic tappets" you speak of?

[Kjkenney]

It's the dohc model, so it has the hydraulic valve adjusters situated under the rockers. Upon rebuild I had to bleed the liquid out and refill them but used oil to refill them. I referred back to the manual later to see that Honda used kerosene to do so, because of a lower density. I could hear them clicking but it did not impede on the ride of it so I didn't think much of it. I'm wondering if this is affecting the valves and I'm losing air through them. I think you're right, I really just need to check the compression and do a leak test and go from there. Weak spark worries me as well

[Folsoml]

Here is a thread on another forum about a direct to coil modification that can be done:

http://www.cb750c.com/modules.php?name= ... pic&t=2740

This will work on your bike as well. You lose a small amount of voltage when the power for the coils has to travel through the entire wiring harness to get to the coils. You can get a stronger spark by going directly from the battery to the coils.