Two questions

charwood89 wrote:

...getting about 120 psi evenly across all four...dropped a teaspoon of oil in like suggested, and the compression did jump. All the way to 180-200 psi. I'm not sure of what to make of that.

Even with properly adjusted valves, the extended road trip with over-heating issues (possibily caused by improperly jetted carbs aggravated by pods) might have damaged the valve faces and/or seats. However, the dramatic compression increase with oil added indicates the valves are still sealing okay, and likely undamaged.

Perhaps condition of the pistons/rings/bore suffered a little from the over-heating.
I'm unaware of psi service limit range for '82 KZ750. Standard psi on Z1/KZ900 is 145 psi, and 128~156 psi on KZ1000, with service limit of 100 psi. So an even 120 psi across all four would still seem okay (at least in the large fours).

With compression matters mostly ruled out (valve clearances being to spec, with decent even compression), would proceed as suggested by others to assure ignition timing is correct, and then focus on carb and fuel issues.

Rule out fuel starvation by (1) assuring ample clean fuel supply to carbs (no clogging in tank cap vent, petcock screens, or inline filter; (2) assure service floatbowl fuel levels correct, especially not too low, via clear tube test; (3)assure internal carb set-up best suited to pods, including jets, jet needle clip position, etc. All directed toward reducing an excessivly lean mixture.

Sometimes pods just don't play nice throughout the full range of carb performance.
By chance happen to have a standard air box in the parts bin?? :laugh:

Good Luck!

She runs. Started up without hesitation and idles pretty nicely. Running a bit rich with the 135 mains I think, since it stumbles just a little below 2k.

Yeah, I'm getting almost exactly 120 across all four. That's only 3/4 what I got when I first purchased the bike, but there's been no noticeable decrease in power. My compression guage is pretty low-quality, so that's suspect, but I wouldn't be surprised if the overheating led to some ring damage. I'll see how it rides on the highway this weekend.

As for the blowback, it's almost nonexistent when the bike is actually running. There's almost no puffing through the carbs except occasionally at a cold idle and sometimes when engine braking (I think the rich mixture has something to do with that.) It's always made noise in such instances, so I'm not too worried.

I guess I was just being paranoid about an old bike. The valves probably don't seat perfectly, and the compression isn't high as it once was, but hey... the thing cost me $300 and it runs like a champ.

Thanks again for all the patience and advice.

Casey

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She runs. Started up without hesitation and idles pretty nicely. Running a bit rich with the 135 mains I think, since it stumbles just a little below 2k.
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If to rich with 135 then perhaps try 130. Are the plugs a bit on the black side ?

charwood89 wrote:

Oops, dumb error on the compression test. I forgot to open up the throttle while cranking. I'm getting about 120 psi evenly across all four.

Here's the really weird thing. I dropped a teaspoon of oil in like suggested, and the compression did jump. All the way to 180-200 psi. I'm not sure of what to make of that.

:blink:

I'm sure: your rings are hosed. A jump of 60 - 80 psi is huge.

650ed wrote:

One question does occur to me regarding the jump in compression in any engine when oil is added to the cylinder: all else being equal, what is the affect of the oil on cylinder head volume?

Not too much. The combustion chamber volume on my 750 is about 55 CC (which I think is the same as mL). I think that works out to be about 5.5% of a quart which is the ballpark of about 1.75 ounces. I'd be surprised if a squirt of oil is more than 10% of that.