Engine problems, now in technicolor!

I sounds like a clogged carb jets and passages. Was the bike sitting for a period of time with gas in the carbs?
That is the number problem I have found with used bikes.

Big news... I managed to get it rolling today and took it for a spin around the block.

Here's the scoop.

It still idles highish around 1,500 with full choke on. When I rev it now it will do one of two things, bog and "chuff" through the carbs, or pick up nicely.
Occasionally it will stick or even rev on its own will up to 4500RPM and hold, or sometimes slowly settle back down.

Once rolling the bike gets somewhat decent bottom end pull, sometimes it bogs a bit but for the most part it is OK and smooth. Unfortunately once it gets up around 5-6k it will bog hard and just hang so I have to shift up to accelerate. I don't have a big stretch of road to work with and it's not insured so it's hard to tell much just from that quick stint. I guess I just wasn't used to the clutch, it has strange engagement at the moment, it feels like it's gently grabbing even with the lever pulled in and will usually engage VERY smoothly.

Questions:
Diaphragms looked ok when I had them apart. I know the carbs are getting fuel OK.

The reason for the valve job was low comp. The bike HARDLY ran at all. I wasn't able to find 650 rings (surprise surprise) so I had to make due with just the valves.

I reshimmed as well. I will probably take off the top end to re-check cam timing and valve clearance.

WG may be completely right, I am still fairly green.
I plan to use stock jets/airbox. I am having enough "fun" fiddling with this getting it tuned as is...

After running for a while and a bit of riding, it seems much more healthy, but there appears to be plenty of work left still.

I have no time to lose!

I kind of wonder if it didnt have some of this problem prior to the valve job?
if it ran like crap before makes me think the carbs may have been messed with before you got the bike.

have you checked the compression after the valve job?

Oh the bike was pretty bad prior to the valvejob. That's why I started a top end rebuild but got stalled trying to find rings. Compression is much better now, not stellar, but definitely runnable.

That's why I took the carbs apart and blew out the jets and passages with an airgun and aerosol carb cleaner.

Tuning them should be in order. The carbs/jets are stock and the needle is set in the middle clip I believe.

I'll be checking coil resistance and ignition timing with a light as soon as possible.

I'd still like to know why the mains feel like they are barely flowing, it has no ability to rev over 6ish.
Could a poorly timed ignit advance cause that??

Timing could be a big part of it.. Think of it this way. The ignition system supplies spark to ignite the fuel. The fuel ignites and creates pressure that moves the piston. If you are getting spark at the wrong time before or after the piston has traveled to the moment that maximizes the effect then it won't perform well. I would think that the faster the parts are moving the more critical it is to get spark at just the right moment. Don't get me wrong it COULD be fuel delivery. It seems more likely that it would be ignition related though. Poor timing, weak spark or even intermittant spark (grounding wires, arcing points etc). Points are crappy to start with so making sure they are correctly adjusted, clean, and perfectly timed is job #1. Gettin 9,000 RPM is asking a lot of points, it always amazed me that these bikes could do it.
Anyway, just my opinion. let us know what you find.

Ron

I was helping a friend with his cb 650 that had sat for a good while and he couldn't keep it running. After changing fuel filters plugs and air filters we found that almost all of his vacum lines were either hard and cracked or pinched off. It ran pretty good for a honda after we replaced all of the lines. Listen to these guys though they do know a hell of alot and wont stray you wrong.

I'm not a mechanic so I cant offer any real help but have you done a plug chop and checked the color and texture of the plugs ?

TwoSeven wrote:

I'm not a mechanic so I cant offer any real help but have you done a plug chop and checked the color and texture of the plugs ?

I'd try that TwoSeven, but it really dies past 1/3-1/2 throttle so running a WOT plug chop test just won't work.

As for the ignition AR15Ron, it's actually an electronic ignition, later KZs (80s and on mostly) didn't come with points anymore. I'll have to go over the rest of the carbs... like Gosling suggested.

ok, I mentioned the plug chop because its good to see what they look like when it dies. It may be something simple like a rich carb causing the plug to cold foul.