Can I leave the tach drive open on an 8 valve 750?

[koolaid_kid]

The KZ750 is an 8 valve engine, very similar to the GS models. It has a tach drive in the center top of the head just like the GS. I have a KZ750 head which has been ported that I would like to try on the GPz. The problem is that the GPz engine has an electronic tach, so there is no tach cable. Can I just leave the little drive part hanging out there, or does it need some kind of cap on it to replace the cable and prevent oil from leaking out?
Thanks in advance.

 

[Suzuki_Don]

I would advise you to cap it off to be on the safe side. I started my bike and had forgotten to reattach the tach cable and I got oil over everything in sight. All over the front of the engine, over the frame downtubes at the front, the rear of the front mudguard, etc.

Cap it off, just cut out a couple of round pieces of gasket material so they will fit inside the housing and screw an old tach drive screw attachment to hold them in place.

 

[Agemax]

should be ok, if it is the same as a GS it will have a seal in the tacho drive to stop it from pumping the cable full of oil. disconnect the cable then fire it up.....see if it leaks!

 

[kochic]

Has agemax said, disconnect the cable and see if it leak.My gs1000 the hole is plugged and on my cb650 i just removed the cable.If the seal is good you should be ok.
You can replace the seal it look like a valve stem seal.
Marc

 

[Suzuki_Don]

should be ok, if it is the same as a GS it will have a seal in the tacho drive to stop it from pumping the cable full of oil. disconnect the cable then fire it up.....see if it leaks!

It depends if you are going to take the actual tacho drive out (the part that spins the cable). If you don't take it out then it is going to be spinning around. OK no oil will come out but the spade shaped part will be spinning around and could catch on something. And if you take it out then the seal will not operate and oil will go everywhere.

My opinion only.

 

[koolaid_kid]

should be ok, if it is the same as a GS it will have a seal in the tacho drive to stop it from pumping the cable full of oil. disconnect the cable then fire it up.....see if it leaks!

You have a valid point. It has seals similar to the GS; I replaced them on my 81 KZ750. I think I did it because it was leaking onto the front of the engine. After replacing, the leak stopped.

 

[koolaid_kid]

It depends if you are going to take the actual tacho drive out (the part that spins the cable). If you don't take it out then it is going to be spinning around. OK no oil will come out but the spade shaped part will be spinning around and could catch on something. And if you take it out then the seal will not operate and oil will go everywhere.

My opinion only.

Another valid point. The GPz cams do not have the worm gear to spin the tach drive, but they do have a piece of blank stock there which looks like it would be machined for the worm gear if it were to be a KZ instead. I will have to install the exhaust cam and see if it clearances the tach drive in the KZ head. If it interferes, I would have to remove the tach drive and put a sealed cap on the outside. Hmmm.

 

[koolaid_kid]

Has agemax said, disconnect the cable and see if it leak.My gs1000 the hole is plugged and on my cb650 i just removed the cable.If the seal is good you should be ok.
You can replace the seal it look like a valve stem seal.
Marc

What did you plug it with? That would be the cleaner way to do it, IMHO.

 

[kochic]

I have removed drive from the engine, removed the shaft and the ''stem'' seal, cut the portion where the cable screw, enlarge a little the hole where the seal was and put a locktited small frost plug in it.And put it back on the head.
Both my gs have this mod.One have a electronic tach and the other a rev limiter.
I can post pics if you want, but not today its really look like a good autumn riding day.If you want pic i will take them tomorrow morning.
marc

 

[Guest]

I dont run a tach on my 850 and thought the same, shouldnt leak right? Na, leaked.
I took the tach cable to the hardware store to size up a homemade plug.
Needs painted but it dont leak.

 

[koolaid_kid]

Well, I just pulled it out of the head. The part that will remain has male threads, so I will need to find a metric cap instead of a plug. Sounds like a trip to Ace.

 

[koolaid_kid]

Well crud. It has M18 threads and my Ace carries M16 and M20. Grrr.

 

[bwringer]

Well crud. It has M18 threads and my Ace carries M16 and M20. Grrr.

I believe most O2 sensors are 18mm X 1.5 -- perhaps you have a spare O2 sensor plug lying around from your cage-based endeavors?

No idea if the thread pitch matches, but it's worth a try...


I'll poke around -- I think I have one of these plugs somewhere.

 

[koolaid_kid]

Please do that. I will need both parts, the one that is made to weld into the pipe and has female threads (looks like a really short pipe), and the plug itself which has male threads. I have purchased them before for my wideband installations in my cage, but I don't have any spare female threaded parts at this time.

 

[Guest]

I dont recall the thread size when I was doing mine but I do remember it wasnt a perfect fit and used a good bit of teflon tape. Its not tlike there's a buncha pressure behind the fitting.
As long as it dont leak.

 

[koolaid_kid]

Ding ding ding! We have a winner. Threads are indeed M18x1.5 and match exactly an O2 bung. Verified with an O2 bung I have welded into a pipe already.
Thanks bwringer and everyone else who contributed.