Kz 650 oil cooler fitting questions

I tried to read everything there was about this, but they didn't seem answer this question. Why do you need a special rear fitting for the oil pan on a 78 kz650. Why can't you use the existing plug, tap a hole and put a barb in it and be done? Does this special part block off an oil return route, then send it to somewhere else? The front fitting is just out and up to the cooler. The front fitting is the same as the rear fitting on mine. It's not the 17mm, its the 18mm one. If their the same, why do you need a different part? Its really putting the zap on my mind. Thanks for your help! -Bobby

On the 650 and 750 motors the oil path runs through the crankcase on the left side, then down into a passage on the oil pan, then back up into a passage in the block. The GPz750's with factory installed oil coolers have the oil cooler connections on the front of the oil pan, so a lot of people use a GPz750 oil pan on 650's to make it easy to install an oil cooler.

I don't know anything about installing an oil cooler on a 650/750 without using the GPz750 oil pan, so I don't know if this helps answer your question.

I think the rear piece may restrick oil flow through the cooler so that it actually has time to be in the cooler to be cooled, and so it doesnt rob too much oil from the top end, but its just an idea.... can anyone verify this?
Scott

If you can't find a GPZ oil pan, I've used a new Zr-7 oil pan which is about a hundred bucks brand new. It bolts right up.

If this is wrong I hope someone corrects me. There is an oil diagram on kz650.info/ .

I believe the special fitting on the rear of the oil pan blocks off the oil route along the right side of the engine. The fitting re-routes the oil to the cooler, then from the cooler it is returned to the oil fitting underneath the points cover, where it goes to the bearings and head. The pressure should stay the same with this setup. All you block off is about 6-8" of galley between the two fittings.

If you just tap into the oil pan bolt without a restriction, then the oil travels to the engine and the cooler. I think you would have some pressure drop but how much I couldn't guess. And then the return from the cooler will be blending with hot oil from the pan...I can't see it working well myself. What if the pressure at that return bolt from the cooler is lower than that coming from the galley that should have been blocked off? Will it back up into the cooler?? I don't know...

Are you sure you want to experiment on your motor?

Thanks to everyone. No no, I do not want to expiriment with my motor. I wondered if it restricted the flow to keep up pressure. Thanks for finding the oil diagram OKC_Kent. When you put it that way it doesn't seem like a good idea to me anymore. Thanks for everybodys help, I'm going to do a search for a 18mm bolt to have turned down to the fitting it should be, as explained in another section. Thanks again!!!!!!!! -Bobby Merry Christmas!

Post edited by: Paladin, at: 2006/12/11 13:25

Here's how my Oil Cooler has been hooked up for over 15 years, with no problems. It was installed by a bike shop, so I have no idea on the technical side of how and why it was done this way. I do recall they mentioned that the first time they hooked it up with other line routing, that the cooler was not getting warm.

The Red arrow is pointing to the cooler feeder line, tapped into the pan just in front of the oil filter. There is a cast flat spot in the pan, as though it were made for this.

The yellow arrow is pointing to the return line fitting from the cooler.

The Blue arrow is pointing to what I believe is the 18mm bolt you mentioned.