The Zephyr Zone

had the same thing happen many years ago. Tried all those fixes and no good. We contacted Kawasaki in Japan and described the problem. They sent one very expensive oxy welding rod and that did the trick, you need the same alloy rod as the engine cases.... something about magnesium and silicone. Don't know if that could even happen nowadays

Fishrider wrote:
3) Do an engine swap. There is, at least, one engine on Ebay right now. I am sure if I poked around I could find more. If I did this I almost would be tempted to crack the engines to see which is in better condition and pull parts, but that is a lot more work. There is always the old 6 speed swap, but that is even more work. Sourcing even more parts and spending lots more money.

I feel your pain Fishrider, if it was me, i would stick another engine in, but try to listen to it running if you can because you really haven't had much luck with this bike so far

Swampy wrote:I feel your pain Fishrider, if it was me, i would stick another engine in, but try to listen to it running if you can because you really haven't had much luck with this bike so far

I am leaning towards this option. Although, I very much doubt I will be able to hear the engine before shipping. The upside is, if I have to crack an engine, I can pull pieces parts from both to hopefully make a whole. Not much of an upside though. The one on Ebay that looks alright admits to having starter issues with 9K miles on it. SO trading problems.

Does anybody know of a website that shows motor comparisons for older bikes, or does anyone know which motors were a direct fit or easy (relatively) fit for a Zephyr 750C? Any newer motors that might fit?

Anyone want to come over and bang out this project in a weekend? LOL

http://www.bikeexif.com/kawasaki-zephyr-750

The Zephyr 750 engines are identical in mechanics to the 82-86 gpz750 motors as well as pretty much every 4cyl kz750 motor from 80-86. They all came in different colors, rounded and squared off fins and valve covers, different power outputs (83-86 gpz being the most) and clutch actuator types (pushrod clutches would mean changing your clutch cable as well). Your carbs, exhaust, charging system and ignition would swap right over with very little effort.
The later zr-7's would also work, but require modifying the ignition timing system as they have a different timing rotor that would require some custom work to retrofit.

Swapping engines is the theoretical path of least resistance, as you can't just put the bottom case from another motor on yours as both halves of the cases are lined bored as a pair. You would need the cases from another engine and then gut yours and put it all in the new case.

The only other thing worth trying is there are Aluminum brazing rods that can be bought at your local box store or from Amazon that you could possibly use to make the repair, they are "low temp" but they require good amounts of heat to get the thick engine case warm enough for it all to work properly. So MAP gas or an acetylene torch will be necessary.

I would hate to see you part the bike out. I would desperately love to buy it, but I am several states away.

Hope this helps!

My thoughts on brazing or welding the case insitu ..... I reckon the chance of success is limited due to oil impregnation in the 'pores' of the aluminium. To be a success the case would need to be extensively cleaned to remove all that ingrained oil prior to attempting a braze or weld. And to my thinking that would mean high pressure steam cleaning.

Thanks for all the info Freddy. I don't want to part it out, but it has now become a project bike. If I decide to take it on, I can't very well just slap in a new engine. I am a bit of a tinkerer. So we will see... Honestly, the bike is in super condition except for the motor. Makes me want to strip it though, and piece it back together exactly how I want it. Could take awhile. I'll let you know what I come up with.

I was looking at this crankcase as a decently cheap alternative. https://www.ebay.com/itm/1984-KAWASAKI-ZX750-ZX-GPZ-750-KM325-ENGINE-TRANSMISSION-CRANKCASE-CASES/351069880260?hash=item51bd653fc4:g:-DAAAMXQNo5TZBKv It has the same starting serial: KZ750EExxxxx as my Zephyr crankcase. Although, Zedder does not list any of the crankcases as cross referenced for other models. Would I really be able to drop in all my parts and covers into this crankcase? It looks extremely similar, and it has the same number. What differences might I encounter?

Since the engine case is black, it is either from a gpz or kz750e. I am not 150% sure, but that engine case should work just fine.
I personally know that the transmission, secondary shaft and crank will fit with zero issues. You will have to buy all new crank bearings as the line bore diameter from one case to another are not the same. The engine case will be stamped/marked with a code to let you what outer diameter bearing shells are required. Your zephyr crank will be marked with required inner diameter....so on and so forth.
The black engine case will have lower mounting points that the Zephyr frame does not have. You might have to tweak you oil cooler pipes a very small amount to clear the case bracing for these mounting ears.
I am not entirely sure that the rear mounting ears on the kz case are exactly the same as the Zephyr. The zephyr uses rubber mounts where as the kz used solid steel ones. They may have slightly changed them....they may not have. (My Zephyr zr550 engine case is identical to the old kz/gpz550 engine cases. They didn't even bother to remove the no longer used lower engine mount ears from the Zephyr engine case. So its possible they didn't change the 750 mounts either.)
I for a fact know that Kawasaki only offers the cylinder base gasket from the 2000+ zr750s when you order one for the vintage engines, so there is also zero issue with bolting your top end on to this case.
The oil sumps are 100% interchangeable as is the transmission shift mechanism cover.
Partzilla lists the clutch cover gaskets as being different between the kz and the zephyr. But any time Kawasaki changed the material of a gasket, they changed the part number, just like the cylinder base gasket. So that is a total unknown whether the clutch covers are interchangeable. But at the very worse, you buy a gpz clutch cover with the pull type clutch release mechanism.
The only issue that I do know of, is that one of the three mounting points for the pulsar coil bracket on the kz motor is in a slightly different spot than the Zephyr bracket. I had to slightly elongate the top mounting hole to get the Zephyr bracket to fit the kz motor. There may be more of these minor discrepancies that you will run into.
Simply put, If I was in your spot, I wouldn't hesitate to buy this case to do the swap.