1979 KZ650 ... major issues, please help!

Hey guys!

When I bought this bike a couple months ago (my first bike) it ran great. The last couple weeks it got worse and worse, mainly after I took it an hour and a half into the mountains (it started acting up on the ride home).

It would lurch and bog down at above 6k rpms, so it wouldn't go over 80mph. (But I hit 100 on the way into the mountains)

Rode it a few more days, WOT could bog down. Then a few days ago it bogged and died when I accelerated too fast. Wouldn't start up and I had to push it home 3 miles.

Took the carbs apart and cleaned (although the previous owner told me this wouldn't be the issue, because he already cleaned and rejetted... and he was right, everything was pristine). Popped carbs back on and it still wouldn't start. Oh also put new spark plugs in.

My buddy came over and looked at it today. We couldn't get the plugs to spark, so he looked at the ignition points and say they were super corroded so he sanded them a bit. We got sparks to the plugs, and got it running again.
But it runs really poorly. I can slowly give it throttle (in neutral) and it will rev alright, but if I quickly give it throttle it bogs down and dies. I also could not actually ride it, as it would bog down when I let out the clutch.
And now I can't start it again

Oh and this is all kick start by the way, the electric ignition never worked when I bought it.

Would it be worth it to buy a Dyna S ignition? Because even when I got it running, it still was not running well, which makes me think it's not the ignition's fault.

Any ideas? I'm clueless.

Thanks in advance!
- Steve

Check the valve adjustments.
Steve

SWest wrote: Check the valve adjustments.
Steve

Do you have a link for a guide to do this? I searched a bunch, but didn't find anything suuuper helpful.

Also did some more searching and thinking... decided to leave my petcock on prime, and that actually worked! Got it started up and it even stayed idling when I took the choke off. Still sounded kind of rough, but I'm gonna play with that more tomorrow.
I noticed the petcock was leaking when I would switch from prime to on, earlier today, so I probably need to swap in a new one.

The leaky petcock does need to be tended to, but that usually shows up as a problem at low rpm, and is most often in conjunction with leaking float valves in one or more carbs.
You really need a factory service manual for your specific model. While you are looking for one, you can go to the home page of KZR and download factory manuals for the 1977 and 1981 KZ650. There will be some differences from your model, but I'd bet that the valve adjustment procedure is the same for all years of that engine.

Where is the petcock leaking? If your bike has a vacuum petcock, then it can for sure run terrible if the diaphragm is defective. if the thing is torn or damaged, it can lead to a vacuum leak. on the carb with the vacuum port. One test is to remove the vacuum line & cap the vac ports with good automotive vac caps, then ride around with it on PRI. and check for fuel leaks.

martin_csr wrote: One test is to remove the vacuum line & cap the vac ports with good automotive vac caps, then ride around with it on PRI.

Did this, and it runs like a champ! Up to redline with no hiccups!! So stoked.

Only thing I notice now is it idles around 2k, that's rather high isn't it?

Also, does anyone have a link to the Pingel petcock for my KZ650? I'm not sure which one to get.
Or should I just get this rebuild kit? www.z1enterprises.com/petcock-kit-vacuum-200-2014.html

In case anyone is reading this in the future and wondering, here is what Pingel customer service told me to get for my 79 KZ650:
www.pingelonline.com/fuel-valve-adapters/a1802c.asp
www.pingelonline.com/motorcycle-fuel-valves/6211-ch.asp

But I'm gonna buy the rebuild kit from Z1 and hopefully that works. If not, I'll splurge on the Pingel.

43028-1015 diaphram kit is only around $11.00. That is the original Kawasaki part which will always be a better bet than the K&L aftermarket which may be and most likely is Chinese. The other orings in the kit I don't exactly get where they fit. You have an oval oring attaching the petcock to the tank, no need to even remove the petcock from the tank to replace the diaphram. No orings in the petcock. I believe the rebuild kit is standard overpriced aftermarket chinese replacement, where original parts are still available for 1/2 the cost.

RonKZ650 wrote: 43028-1015 diaphram kit is only around $11.00. That is the original Kawasaki part which will always be a better bet than the K&L aftermarket which may be and most likely is Chinese. The other orings in the kit I don't exactly get where they fit. You have an oval oring attaching the petcock to the tank, no need to even remove the petcock from the tank to replace the diaphram. No orings in the petcock. I believe the rebuild kit is standard overpriced aftermarket chinese replacement, where original parts are still available for 1/2 the cost.

Ok I'll try that one, thanks!

If the oem diaphragm is available, get that.
As for K&L, their kits are made in Japan, and the parts I've gotten have been oem quality. IMHO.
Others have reported problems. In some cases it could have been installer error or an incorrect part.
I thoroughly refurbish the Kawasaki parts on the motorcycle before installing the K&L rebuild stuff.
I've never had an issue w K&L. petcock kit. Fr br caliper piston & kit. fork seals. etc. Some guys have even been able to solve an availability problem by using a K&L master cylinder piston on their bike that was intended for different KZ models.

..... K&L substitute part & oem comparison.

I would replace all the rubber bits in the petcock as long as it is apart.. Also, it is a really good idea to carefully polish the seat that the little oring is supposed to seal against, and also the face of the lever where it presses against the big, four-holed oring. Not only will this help insure good sealing, it will make for smoother operation as well. I think any quality aluminum polish will do. Polish by hand and clean up carefully.
Here is the parts diagram. www.partzilla.com/catalog/kawasaki/motor...9/kz650-b3/fuel-tank

The diaphragm assembly (23) should consist of a diaphragm with a metal post in the center, an oring on the post, and the plastic spacer with the vent hole. Be sure to get the vent hole properly oriented when reinstalling it. It also looks like some of them had an oring on the lever. If the kit does not come with the spacer, no worries as it is easily reusable.

After cleaning & inspecting the petcock, I used brass wool to polish the mating surfaces, especially where the diaphragm o-ring contacts the petcock body. steel wool would probably be good as well. Some guys probably don't bother doing this stuff, then blame the aftermarket part after it leaks.