kz400 over heating?

[govmule84]

Man, I'm coming off all wrong. If was in the garage with you, I wouldn't be standing there yelling, I'd be shaking my head.

Demoto is most likely right. I think your rings are toast. To fully prove it, we need a comp check, but I think until the verdict comes out on that, you should either be planning on rebuilding or acquiring a new rig (not sure how much your KZ is worth to ya, and it's easy to get upside down on one of them.)

Good luck, sir.

[hotroute]

Helping people

You see this is why I don't reply to post on this site. Most of the answers that where gave to Boocifier where good reasons in one way or another. But you have the ones on here that all they care about is giving the reasons why others are wrong with their diagnosis instead of helping a fellow rider out.

Their is two types of home builders\mechanics, their are the ones that depend on other people to tell them how to fix a problem and those that figure it out on their own. I may be only 30 years old but, I have been building daily drivers and race engines since i was 13 years old with no help from a knowledgeable person. I have seen about every problem that a non electronically controlled engine can have. With that being said anyone that hasn't seen an engine overtighten "seize" and smoke from running hot hasn't been around long enough to give anyone an educated answer to any problem they have.

[govmule84]

"Overtightening" is not seizing. They are different words, and they mean different things. Precision in language, like precision in engines, is a necessary evil of the job.

If indeed the engine has seized due to a super-lean condition, THE RINGS ARE JUNK. Pistons are prolly smoked, too. Put your feelings aside for a minute, and also, if you please, put your ego aside. I understand that you've been building engines since you were wee. It does not necessarily mean you are doing it correctly, or you know everything you need to. I don't know everything either, but if it helps, I worked as a professional auto mechanic, and an automotive machinist, and I've moonlit on bikes since I started riding them. I'm ASE certified. (One of my certs is in engine repair!) My garage is consistently jammed with customers and their vehicles. I have made many, many mistakes - more than most people have an opportunity to. I mean this sincerely when I say that I am being persistent because this is a case where someone can save himself some headaches and wonder by simply approaching this problem in an orderly fashion. There IS a correct order here, and we need to verify oil quantity and dry and wet compression numbers before anything else can be done. If you've been building engines for a long time, surely you know that rings are garbage after multiple temperature-related seizures. Often, just once is enough to trash it. But, we do need to verify that the rings are bad before a teardown occurs - hence my request for wet and dry compression numbers.

With that being said anyone that hasn't seen an engine overtighten "seize" and smoke from running hot hasn't been around long enough to give anyone an educated answer to any problem they have.

I've seen it, just like you. The blue smoke is indicative of oil consumption. The trick is not to richen it up, it's to richen it up after you fix the newly introduced oil-use problem. The blue smoke comes from burning oil, which came from rings which galled and scored the cylinder walls, and self-destructed in the process. The engine may run again, but guess what? It's fucked up, and will never have compression as good as when it was running normally. We use motor oil and the stoichiometric ratio for a reason - keeping things lubricated and cool.

The things to check are all good things to have a handle on, but we need to figure out why it's blowing oil. There is not really a point in trying to tune a carb, diag a bad coil, or any of the other myriad of things that happened here, if the engine has no compression. You can have the hottest coils in the world, and a perfectly dialed-in carb, and they are useless to make an engine that can't suck, squeeze, or blow try to go 'bang!'.

If OP doesn't want my advice, I'll politely bow out. However, here's my challenge to all you "wrenches" out there: If I've misspoken, or you can find an automotive machinist who can find a flaw with a single thing I've posted, I'll nut up and admit it. But the fact is that you won't. If anyone here wants to back their diagnosis up with something that I've missed, or point out how they would diag this thing without verifying compression, I'm all ears.

ALL ENGINE PERFORMANCE DIAGNOSTICS START WITH COMPRESSION. I am not saying this to hurt feelings. This is an undeniable fact of internal combustion. We often skip it because it is a problem that is typically ruled out quickly. (IE, the bike is running, but not as well as it could.) Blowing blue smoke is a characteristic problem of a bike that is not displaying proper compression. If I'm wrong, and this thing has nice high numbers dry and wet, AND the valve guide seals aren't pissing any oil down the valves, I'll defer to some of the other guessers on this thread - but until compression numbers are posted and interpreted, you are all guessing. I'm a step worse than most of you - I haven't even taken a guess as to why it's running lean. Could be a million fucking things. But it's pointless to try and figure the A/F ratio out if the engine won't suck, squeeze, bang, and blow.

Any takers?

[MTW]

Have you found anything about your bike's running problem, Boocifer?

[CLAWKEEPER]

God damn! I'm off the internet for a f'in week and this shit has blown up! Thanks for the info i guess. I do appreciate everyone chiming in and providing a shit ton of info.
Here's an update:
First off, I changed the Oil Filter. Totally forgot to when I first got the bike about two months ago. Shit had been in there since '86 I assume. Verdict: pretty gnarly. crusted and caked oil
Next, despite my oil level window / glass seeming fucked, I at least was able to put in the correct amount of oil, so I know my level is currently good.
Then, I realized that my fuel / air mixture screws were completely tightened, maybe out 1/8 of a turn. I don't know what this has to do with overheating, if anything, but since backing that screw out, the bike idles a million times better and runs a lot smoother.
Thats it. That's all I have done so far since posting originally. Rode all day a couple days ago (two days in a row) and had NONE of overheating symptoms or smoke which I mentioned originally.

I'm thinking it can't be that simple, but maybe? Whos the asshole

[MTW]

A good starting point on the fuel mixture screws is 1 1/2 to 1 3/4 turns out.