engine seized momentarily due to oil possibly

True. I am thinking more pistons. I am honestly planning on taking the head off, I am just a little scared at the whole putting it back together part. Gaping, timing, ect.
I guess the only way to truly know nothing is wrong and to put my mind at ease is to take the top off. I will start tmrw as today I planned on taking the carbs apart and readjusting the jet needle to run it a little more lean, as stated earlier I believe it's running way to rich right now. I will post back with the results and pictures if I do find something questionable. I would rather know for sure and quit wasting your guys time. I was just wanting to hear if I needed to or not and I truly need to.
Any tips or advice on taking the head off before hand as this is my first time?

Also, anyone have any input on my second problem? Whether or not I should re-jet my carbs(if I need to) or get the oem air box. I feel I should get the oem air box, especially since the oil breather recycles unused fuel back into the carbs and I have no idea on how to re-jet the carbs (bigger or smaller) or if I even need to. I see pictures of my bike with the pods, so I know it's possible. I will honestly do whatever is cheaper rather than easier.

And, the whole hose question, does that hose by the choke lever go to the other carb or simply hang off the carb?

Instead of removing the head, rent a bore scope to check the cylinder bores. Pop a cam cap off one at a time to check those surfaces.

Trwkz750 wrote: True. I am thinking more pistons. I am honestly planning on taking the head off, I am just a little scared at the whole putting it back together part. Gaping, timing, ect.
I guess the only way to truly know nothing is wrong and to put my mind at ease is to take the top off. I will start tmrw as today I planned on taking the carbs apart and readjusting the jet needle to run it a little more lean, as stated earlier I believe it's running way to rich right now. I will post back with the results and pictures if I do find something questionable. I would rather know for sure and quit wasting your guys time. I was just wanting to hear if I needed to or not and I truly need to.
Any tips or advice on taking the head off before hand as this is my first time?

Also, anyone have any input on my second problem? Whether or not I should re-jet my carbs(if I need to) or get the oem air box. I feel I should get the oem air box, especially since the oil breather recycles unused fuel back into the carbs and I have no idea on how to re-jet the carbs (bigger or smaller) or if I even need to. I see pictures of my bike with the pods, so I know it's possible. I will honestly do whatever is cheaper rather than easier.

Hey just want to give you some words of encouragement on taking the top end apart. I just recently had to do the same thing on my KZ400 and, like you, this was my first time ever doing it. I was actually rather suprised at how easy it was to both take apart and put back together. I'm somewhat mechanically inclined but no more than the average person who is willing to try. The key for me was having the manual in my hand while doing it. I mean getting grease, oil and fuel all over it. Anyway, it took me only about 1 hour to get the thing apart. Might be a little more involved on a 750..IDK. But I think it's worth a shot to put your mind at ease.

So far as the pods go.. It's usually the case that when pods are installed the motor starts to run lean, not rich. So unless the PO had rejetted, the pods shouldn't cause it to run rich. I put pods on mine as well and had to jump up on my main jet size by quite a bit. I had previously stated in a topic that I jetted up to a 140 which is one size larger than stock (for a 74kz 400). But in the end I've gone all the way up to a 150 main jet just to keep the bike from running so lean. It might be a little rich now.... but from what I've read and heard, I'd rather be rich than lean. Lean seems to lead to a lot more damage than rich. So I errored on the side of rich.

hope some of this helps.

Service manual available for download:
kz750twins.com/?p=15

Good Fortune!

Most motors will run at least 1/2 hour with no oil at all, snake oil salesmen have been using that fact to sell their oil additives for decades. If rod or main bearings seize, they don't lock up the motor, they either spin, or in the case of rod bearings, they bend then break the rod, usually leaving a big hole as they exit the case.

Running lean creates lots of heat, so it could have overheated if it's lean (which seems likely). The key is the fact that it freed up when it cooled down, that's piston seizure.

I had a 750 twin that had seized then released when it cooled down (the one in my avatar actually). It did this prior to my purchase of it, so I just swapped the motor for an 82 750M motor I had. I sold that motor to someone local, after I told them the story, and last I heard they'd been riding with the same motor for three years.

@kidkawie
Thanks for that information about the bore scope. I will try to get my hands on one to (hopefully) reduce the amount of time spent on the head. It will definitely help in my opinion.

@recez
Thanks for the encouragement. I lived on a farm my adolescent years in life, as a result I am a little more mechanically inclined than the average person but now live in the city and am limited by tools. Took me a couple years before I had enough tools to work on a motor. I'm very happy I bought this bike, the cheaper parts make fixing up my bike realistic rather than some dream.
I found the manual online the day I bought it luckily. It has helped already. I can't believe that they even have step by step instructions to fix and repair the bike in the owners manual! Wish they still did that....
Also, you can tell a previous owner has been in the carb before, what would be a way to check if they jetted the carb, a micrometer or something? I think the air pods explain everything related tonmy fuel/air problems, now I just need to decide if I am going to re-jet or go oem.

@steel
Ok. Thanks for the information, honestly hearing someone's own words on a situation (and even better, experience) help me understand it more and allow me to be better able to identify, evaluate, and cross reference problems when I encounter them. It also gives me (more) encouragement! I was kicking myself in the butt for buying this at first, but now (with all your guy's help) know this motorcycle was a rare find and it has changed my life!

@everyone
Today I will (try to) get a bore scope and open up the top end. Thank you for talking me into it, I knew I needed to but honestly was a little freaked out. Lol. I will let you know how everything goes later this afternoon!
Thanks again for your help and support!

Harbor Freight sells a bore scope pretty cheap, and they're fun to play with

You could even start your own colonoscopy business and make some money with it. :laugh:

steell wrote: Harbor Freight sells a bore scope pretty cheap, and they're fun to play with

You could even start your own colonoscopy business and make some money with it. :laugh:

Just make sure you clean it well before looking at your bore!

kzz1king wrote:

steell wrote: Harbor Freight sells a bore scope pretty cheap, and they're fun to play with

You could even start your own colonoscopy business and make some money with it. :laugh:

Just make sure you clean it well before looking at your bore!

Hospitals use the same instrument to look up the rear and down into the stomach........ I always wondered if they REUSE the hardware. I don't care how well they claimed they cleaned it..... :ohmy:

Trwkz750 wrote: @kidkawie
Thanks for that information about the bore scope. I will try to get my hands on one to (hopefully) reduce the amount of time spent on the head. It will definitely help in my opinion.

@recez
Thanks for the encouragement. I lived on a farm my adolescent years in life, as a result I am a little more mechanically inclined than the average person but now live in the city and am limited by tools. Took me a couple years before I had enough tools to work on a motor. I'm very happy I bought this bike, the cheaper parts make fixing up my bike realistic rather than some dream.
I found the manual online the day I bought it luckily. It has helped already. I can't believe that they even have step by step instructions to fix and repair the bike in the owners manual! Wish they still did that....
Also, you can tell a previous owner has been in the carb before, what would be a way to check if they jetted the carb, a micrometer or something? I think the air pods explain everything related tonmy fuel/air problems, now I just need to decide if I am going to re-jet or go oem.

@steel
Ok. Thanks for the information, honestly hearing someone's own words on a situation (and even better, experience) help me understand it more and allow me to be better able to identify, evaluate, and cross reference problems when I encounter them. It also gives me (more) encouragement! I was kicking myself in the butt for buying this at first, but now (with all your guy's help) know this motorcycle was a rare find and it has changed my life!

@everyone
Today I will (try to) get a bore scope and open up the top end. Thank you for talking me into it, I knew I needed to but honestly was a little freaked out. Lol. I will let you know how everything goes later this afternoon!
Thanks again for your help and support!

you should be able to locate the stock jet sizes in your shop manual. I know that the kz400 shop manual lists the stock sizes in the carb section. Once you locate that, the jets have the size(number) etched into the top or the side. It's really hard to see sometime so you might need a magnifiying glass to help you out. But once you pull out the main jet have a look and compare... if it's the stock carb but the main jet is different then the manual says then I would guess the PO had rejetted for the pods. Good luck with it. Most people will tell you not to use pods on the CV carbs... which is pretty sound advice... but for me I like the pods and was willing to do alot of trial and error (rejetting and re_syncing) until I found something that worked well.. So far just uping the main jet size has worked for me.. My bike is running good... in my opinion

I just had this problem recently. starter clutched locked up and was pulling started. I took the chain and sprocket off. and just kick start every time.

Thanks for everones help in the past, lookong back at my posts made me laugh, its funny how far i have come
I,now have the 750(someone stole my engine block while apart) and now a 81 kz550 ltd.
Still want to finish my 750 but now have to buy new parts since a couple parts were stolen...