Stong fuel smell.

Cow_Man wrote:

Hi, I just bought a 78 KZ 650. Overall in great shape. It doesn't have a owners manual. I noticed that the fuel valve does not have a shutoff position. It had RES, PRI, and MAIN. My garage has a strong smell of fuel and the bike would not start till I pulled and dried the plugs and cleared the cylinders. Then it started great and did after till it sat overnight again. Am I not setting the valve right or do I need a new one??

P.S. I don't find any fuel on the ground.

Thanks<br><br>Post edited by: Cow_Man, at: 2007/11/25 09:00

The following history is particularly worrisome:

"the bike would not start till I pulled and dried the plugs and cleared the cylinders."

As already suggested, this could indicate fuel is overfilling a carb floatbowl. The overflow is supposed to allow excess fuel an escape via nipple on bottom of carb floatbowl. Usually a rubber tube connects to the nipple and directs excess fuel underneath the bike. Absent proper overflow operation (perhaps clogged), excess fuel rising inside the floatbowl may go up into the carb throat and flow both ways from there -- back toward the air filter and forward toward the engine intake. Fuel reaching the airbox may drain into the crankcase via the tube connecting the oil breather to bottom of air box (pods eliminate this avenue into the crankcase). Fuel reaching the engine intake may (as earlier posted) wash down around the piston into the crankcase. And it only takes one defective carb to cause this problem.

Normally, perfect float needle/seat interface with correct float performance should stop fuel flow into the carb upon reaching the prescribed level inside the floatbowl (regardless of petcock condition or petcock setting). Inadvertantly leaving the petcock on "prime" should not cause a problem. But excess fuel into a floatbowl with a clogged overflow often spells trouble. So perfect petcock closure when parked can sometimes mask the underlying problem. In fact, fuel may be intruding into the crankcase while riding the bike.

Regarding garage having a strong fuel odor, there are several suspects, such as -- deteriorated gasket in tank cap, cracked fuel tank, leaking connection between tank and petcock, leaky petcock, leak at any fuel line connection, cracked fuel line, cracked in-line filter, loose fitment due to worn fuel pipe, fuel dripping from carb float bowl overflow tube (very common), and probably others. Perhaps some float needle/seat interfaces are leaking and some carb floatbowl overflows are clogged. Also, absence of garage fuel odor does not guarantee absence of fuel intrusion into the crankcase.

Perhaps a dose of Seafoam or other carb cleaner in the fuel tank might improve the float needle/seat interface. But I doubt it's ability to remove a clog in the overflow.

After petcock repair, would continue checking for any gas smell in the oil.

Good luck with the repairs.

Forgot to mention Mikuni 29mm smoothbores do not have a carb bowl overflow (no nipples or drain tubes from floatbowls). Fuel leakage past float needle/seat interface rises up into carb throat, then forward to engine intake and and backward to airbox (or pods). Imo, when using smoothbores with airbox, it's best to disconnect the S-shaped oem tube which connects oil breather to bottom of airbox. And replace the S-shaped oem tube with a longer hose running from the breather vent nipple to underneath the bike. There are other fixes such as an aftermarket filter attached to the vent nipple, but a filter may clog and prevent venting, so I prefer the longer hose method.

However, while the above may avoid fuel flow from airbox through vent into crankcase, it sadly does nothing to prevent excess fuel from reaching the engine intake and washing down past the piston into the crankcase. So those using smoothbores are well advised to be extra diligent about assuring perfect float needle/seat interfaces, and cleanliness of fuel entering the carb (to help keep the float needle/seat interface in pristine working order), and also to assure the petcock is completely closing when turned off while bike is parked. And to regularly smell-test the oil.

An easy test of the float needle/seat interface is to turn off the petcock, then drain the bowls, then use the clear plastic tube test (with vacuum petcock on prime or mauual petcock turned on) to see that the fuel level stays at the proper level. If the fuel level gradually rises above the proper level, the float needle/seat interface is probably leaking and allowing too much fuel into the floatbowl.

P.S. Clear plastic tube test on smoothbores (no bowl nipple) requires fitting the tube to the drain plug hole. While there may be better methods, I use a tapered rubber grommet pressed into the drain hole with the clear plastic tube fitted inside the grommet hole.

Post edited by: Patton, at: 2007/12/17 09:37

Hi Patton, I was away from the puter for a while and just read your message. This gives me just what I was looking for I think. I really don't trust those vaccum valves even though it tested alright. I think I will replace with a manual shutoff.

If I get the clear plastic tube test right I will need to use it like a barometer and curve it up beside the bowl to read the level it is at inside the bowl?

Thanks for all your good help.

Cow_Man wrote:

...If I get the clear plastic tube test right I will need to use it like a barometer and curve it up beside the bowl to read the level it is at inside the bowl?....

That is correct. Am uncertain of the exact float height specification for your bike, but a common level is 2-4 mm below top of float bowl.

Are all four cylinders firing? After short warm-up, may use household spray bottle to mist water onto exhaust headers. The water should sizzle and immediately vaporize upon contacting the header pipe. The water will just roll down and drip off the header from a non-firing cylinder.

It could be helpful if able to narrow the problem down to one particular cylinder.

Does crankcase oil pass the "sniff test" (meaning absence of any gas smell)?

Good Luck!

Hi:
This is old post, but I'll reply anyway ...

I have a 1978 kz650 B1 I will be trying to restore but it is missing a petcock. The part number is 51023-1023 but I'm having trouble finding one (as you say they aren't making them anymore). You say
> The petcock for the Police bike is a 51023-1375
I a replacement, but I measured the distance between the holes on my fuel tank, the distance is 40mm. The 51023-1375 I found on ebay, link below, the detailed measurements in the diagram show 34mm so it will not fit.

Does anyone know of a source for a petcock replacement for a 78 KZ650 B1 - I just need to fix and work, it doesn't need to be OEM, and I would prefer to get away from the vacuum petcock if possible.

I searched for this and did find one here:
Pet Cock

The diagram to the far right shows the dimensions.

toddler wrote: ................I have a 1978 kz650 B1 .................

There's no such thing as a 1978 KZ650-B1. The KZ650-B1 is a 1977 model. You will find that it is VERY important to know exactly which model KZ650 you own because there are big differences in the bikes (especially in the charging systems) from one year to the next.

Also, the KZ650-B1 did not have a vacuum operated petcock and the carbs did not have the vacuum port to operate such a petcock. Ed

I would search for a genuine Kawasaki 51023-1375 petcock to see what the spacing is. I thought it was 44mm. not sure.
The 70s KZ650 bolt hole spacing is usually 44mm >> measured center-to-center.
That chinese petcock you linked may not actually match the stock part. maybe it does, but maybe it doesn't, and I wouldn't trust a made in china diaphragm to be of very good quality.

....

You correct it is not a 1978 B1 it is a B2. Unfortunately I have a 1977 KZ650 service manual, I thought it was a 1978 manual, the B1 in the manual that look like mine. Now I know why the petcock in this manual is not the same as I used to have on the bike.

Actually, based upon the serial number from my old registration it is a 1978 B2 made in Japan
EngineID KZ650BE076568
SerialNum: KZ650B037186
According to the following link
KZ650 Engine and frame numbershttps://kzrider.com/forum/5-chassis/536286-kz650-frame-and-engine-number-confusions


It was originally blue, but I got took the bike apart and got the frame and the bike painted red (flame). See that attached pictures
As per the attached picture it is a vacuum carb.
The petcock part number I found is 51023-1023, but I couldn't find one.
First step is to replace the oil, MacGyver a fake gas tank, use a boost for battery, just see if I can get the engine running before I spend too much money on it.
Questions:
I got my serial number off my old registration - where is the actual serial number? (I couldn't find it).
Anyone provide any tips on MacGyver'ing a pseudo tank ...? ...
My brake master cylinder likely need to be replaced as well - anyone know what other bike makes/models that would have a master cylinder I could use as a replacement? The existing is in bad shape, and I've never rebuilt one before.
Still would need a replacement petcock is all goes well - I did measure it, center-to-center is 40mm

The serial number is stamped into the headstock of the frame, right behind the headlight. There should also be a white sticker there with the number and date of manufacture.

I made a temporary tank fron a used lawnmower tank ($5), plus a short length of fuel hose and a plastic cutoff valve (also from lawnmower shop) and customized a couple of wire shirt hangers so I can hang the tank from the hand grip in the bike. Less than $15 total cost. If you want to go even higher tech, you can get a cheap IV hanger on fleabay to hang the tank on. Some even have wheels!