TOPIC:

Hi I m new to site. I have a 1979 kz650be and want swap out my engine block with that of the same year and size . My engine no. Is kz650be103613 and the new is kz650be117007. Will this be compatible?

Here are the frame and engine numbers I could find and make sense of. Keep in mind I am not claiming this is 100% correct, rather what I could find and make sense of.

Yes, one KZ650B engine can be swapped for another KZ650B engine.

Additionally, I'm pretty sure you can use any KZ650 engine & some of the 750-4 chain drive engines. The 650s & 750E/H models use the same crankcase set. Depending upon what a guy went with, he may have to make some charging system & ignition system component changes. assuming you want to swap the entire engine.

Staying with the same year engine is the smartest idea. The problem with using an engine of a different year is that the charging systems changed a few times throughout the KZ650 models, so there can be a compatibility problem as far as the charging systems are concerned. Ed

Good upgrade swap to 750 when you first do it?

I'd do a 750 swap too. As long as you stay with the early 750E and 750H engines it will be a straight swap. The later year 750 engines received rubber mounts so the frame would have to be modded to suit.

The 750's come with a common 3 phase AC generator which is simple and cheap to manage. If your bike came with a separate regulator and rectifier, or that odd ball field generator setup, ditch the whole thing in the trash and buy a bulletproof SH775.

For rebuilding your current engine. The 650B has a roller cam chain with cam chain rollers/idlers, so your engine probably has the same top end stuff as the 77-80 KZ650 models (cylinder block & cylinder head). The 81-83 650-CSR has a Hy-Vo cam chain w rubber slipper guides. I forget if you could use any of the csr stuff. doh. For simplicity & assuming you just want to swap the cylinder block &/or cylinder head, you'd probably want to stick with parts from a 77-80 model with roller cam chain. Someone else can probably say for sure what you can do.

Thank you very helpful information. I'm interested in buying the parts I need , I'm working on full list. Definitely need. Cylinder head and block. i do have all the parts just need to set up a work station with solvents and start cleaning up .

I'm not an engine guy. my disclaimer. hee.
In another topic I think you said the engine melted or something like that.
Do you know if the crankshaft or piston connecting rods got damaged?

I've never done it, but if push came to shove I think I could do the top end. But if the crankshaft was bent or something,
I'd rather not split the crankcase. in which case I would probably think about replacing the engine. but that's just me. anyway, good luck.

Thank for feedback. I think the connecting rods and crankshaft are good however super dirty and I think I would have to split crankcase and I have never done that before I have rebuilt top end before.

My friend gave me the bike in 2003, it was in pieces and needed chain tensioner. I found the part and started putting it together. Rebuilt carbs. But had a hella of time syncing them so reached out to someone who could and got it running drove it around for 1yr or so and then I crashed and messed up my body and then I fixed the bike after the crash , drove it until it overheated an after that I set it aside to heal.