Petcock Problemo!!

Okay, my lovr/hate relationship with my mildly cafe'd 78 KZ650 D continues. Had the bike finally rejetted by my friends dad (ol Factory trained tech)snd bike ran great for about 70 miles. Now bike will only go down the rode if the petcock is in the prime position. I am using the stock tank/petcock combo which is vacum type, and I can see in the in line fuel filter there is no gas getting in unless it is in prime position while running. I thought maybe that this was due to insufficient venting,so I took a spare gas cap I had and drilled a 3/32 hole in to experiment. Still same problem. The weather here in Pennsylvania is getting warmer(80+) so I am inclined to think it has to do with heat and expansion in the tank. Am I maybe getting to much venting...HELP!

A hole in the diaphragm or vacuum line leak.

I'd check the rubber diaphram inside the petcock as the Alcohol/gas mix is not kind to rubber bits.Your's may have developed a hole or tear.

I think www.z1enterprises.com sells new diaphrams.

Thanks for the info guys. I ordered a new diaphram and and gave the vacume line elbow a fresh hit of thread sealer for good measure. We'll see what happens.

rsrcafe wrote:

Thanks for the info guys. I ordered a new diaphram and and gave the vacume line elbow a fresh hit of thread sealer for good measure. We'll see what happens.

If the inline filter was a paper one, that can be a problem. They tend to seal up after just a little while. Sometimes playing with the petcock will make it flow a little while.

Have you checked the petcock flow by itself? Hook up a small hose to the vacuum port and you should be able to open it by sucking on it. Or you can use a small disposable syringe to pull the vacuum. Then you can check the flow.

Here's a video I made showing how inline filters seal up, but can be blown through with a little pressure. The one had wouldn't even flow on prime (that's where it starts on the video).

LOL - Great Video loudhvx, but I had to laugh. With those latex gloves on and the way you used the bottle to force air into the tank it reminded me of doing artificial respiration on a patient. Well, I guess you breathed new life into your filter! :laugh:
:laugh:

:laugh: Yup.

But it was only a temporary resuscitation. I pulled the plug later that day.

Now I use metal-screen filters like this.
www.denniskirk.com/jsp/product_catalog/P...04&leafCatId=&mmyId=

Thanks for the rest of your info. I have to tear things apart this weekend and get it figured out. I am pretty sure the filter is okay(metal type from K&K)but I have a spare on hand. I'll let you know what fixes the problem.

Okay, I tried a new diaphram and still no luck bike still shuts down under load unless on prime. I did see when I took the old one out that there was a black "seal" that sat on top of the diaphram over th 4mm o-ring side. I don't see it on the kawasaki parts break down. It looks like a top hat ( real technical I know) and althought there doesn't seem to be any holes in the seal it looks real worn. could this be the culprit? If so any OEM number?

I also drained the tank a second time and tried to check the petcock flow above the filter on the vacume line. I used a syringe and on prime I can open the syringe ( no surprise). On the On position I pull it open, and the syringe gets sucked back to the closed position. Is this normal? I have a service manual and it spends about 1 paragraph talking about the fuel valve and has no diagnostic info whatsoever. HELP!!

You have to make sure the vacuum to the petcock is good. Apply vacuum with a piece of hose, apply suction with a Mighty Vac tool, or your mouth if you don't have one. Fuel should then flow out in both the ON and The Reserve position. You are then pulling the diaphragm back, and the O-Ring on the plunger to allow fuel to flow, basicly same as when in Prime. If working correctly when vacuum is taken away fuel should flow only when Prime is selected, apply vacuum and fuel should flow in all positions. There is a screen above the petcock in the tank, did you remove the whole assembly and check it?

rsrcafe wrote:

Okay, I tried a new diaphram and still no luck bike still shuts down under load unless on prime. I did see when I took the old one out that there was a black "seal" that sat on top of the diaphram over th 4mm o-ring side. I don't see it on the kawasaki parts break down. It looks like a top hat ( real technical I know) and althought there doesn't seem to be any holes in the seal it looks real worn. could this be the culprit? If so any OEM number?

I also drained the tank a second time and tried to check the petcock flow above the filter on the vacume line. I used a syringe and on prime I can open the syringe ( no surprise). On the On position I pull it open, and the syringe gets sucked back to the closed position. Is this normal? I have a service manual and it spends about 1 paragraph talking about the fuel valve and has no diagnostic info whatsoever. HELP!!

You are putting the syringe on the vacuum connection, correct? The vacuum port is the smaller pipe.

There should never be air flow through the vacuum connection on the petcock. The syringe should always get pulled back in regardless of the petcock position. If it doesn't, then there is a leak.

Sorry bit of a Hijack but where does the extra vacum line on the gas petcock connect to on an 82 kz1000.