KZ 750 H3 - Valves and Compression

WBPDX wrote:

...procedure for checking or changing the valve shims for the FOURs....

Allow engine to completely cool. Overnight is best.

Remove points cover.
Remove fuel tank.
Remove valve cover.

Measure with feeler gauge between bucket and cam (lowest side of cam is supposed to have factory prescribed gap between it and bucket).

Use 17mm wrench on fake "nut" (the larger nut located underneath the points cover) for turning the crankshaft by hand (clockwise in its normal direction of rotation) to align the low side of cam with the bucket being measured. Don't go backwards. If go too far, keep turning forward again. And don't use the smaller bolt head that screws into end of the crankshaft (which holds the advancer in place) because doing so risks stripping the threads or breaking the bolt.

Keep clearly written notes of the existing gap measurements for later reference.

As known, other things besides jetting may cause evidence of too lean condition inside cylinder, such as too low fuel level, insufficient fuel supply, improper spark plug heat range, air leak, air filter issue, etc.

Thumbs up on rehabbing the carbs. But once is enough (when in the home stretch), even with delectably soft new intake hoses. :lol:

Good Luck!

Thanks, that's what I thought as far as the process, but it is good to see it all together.

Removing the cover has been a BEAR. The screws holding the coils are absolutely stuck. I tried everything. I came inside to charge up my drill batteries for drilling off the caps, and to grab my impact gun... What should have been a quick project is turning into an all afternoon afair, as usual. :laugh:

I found the UPPER mounts for the coils, and saved myself a bunch of time. Wiring was hiding them!

Here is what we have for valve clearances. I think I need a finer feeler gauge set? The smallest I have in either of my two sets is .038mm

Anywho.

I am providing corresponding compression numbers as well.

120 PSI:
.038mm Intake - Less Than .038mm Exhaust

60 PSI:
Less Than .038mm Intake - .152mm Exhaust (WOW!)

45 PSI:
Less Than .038mm Intake - Less Than .038mm Exhaust

110 PSI:
Less Than .038mm Intake - .06mm Exhaust

These are ALL really bad, aren't they? Is the spec .08-.18mm? If so, I have ONE valve that is within spec!

Bikebandit lists having a ton of shims in stock... is that where I should order since Z1E is out?

Patton wrote:

I concur with suggestions of OKC_Kent about reading up on the procedure. Especially about correct re-assembly, and how best to avoid stripping out threads in the cam bolt holes.

Good Luck!

Be very careful torquing the cam cap bolts. many have been stripped. I think the spec is about 8 ft-lbs or 100 inch-pounds. I suspect most were stripped using a torque wrench with no accuracy at that low range. Get a transmission torque wrench with 200 i-p full scale and you won't strip them. I got one at Harbor Freight tools pretty cheap.

duplicate

WBPDX wrote:

Is there another source for the shims other than Z1E?

The smaller shims for the fours are available everywhere, it's the larger shims for the twins which have no new sources. Do a search for "valve shim kits" and you will find them. They sell kits that have a ton of shims of all sizes.

WBPDX wrote:

These are ALL really bad, aren't they? Is the spec .08-.18mm? If so, I have ONE valve that is within spec!

If the thinnest gauge you have is .038mm and you can't get it under, you don't know what the clearance is. It could be zero. Until you install thinner shims and get an actual clearance reading, you can't calculate the shim you need.

.038mm gauge is thin enough to set valves, the smallest speced clearance is about .05mm. The thinnest gauge I have bought is .001" which is .025mm if I did the math right. The .038mm gauge is .0015".

WBPDX wrote:

Bikebandit lists having a ton of shims in stock... is that where I should order since Z1E is out?

I think they have good prices, I have bought stuff from them. These shims are pretty common, you might be able to go to the dealer and swap some instead of buying a bunch.

Thanks for all the info. I think I need a manual before I pull the head. I'm not sure on the orientation of the cams for pulling it, or how the cam chain comes apart.

I did NOT re-tourqe the camshafts. Luckily HF is 5 blocks away... I'll get a smaller-scaled torque wrench and check.

I just re-checked the clearances, I found one mistake I think... and I wanted to try giving the motor more time to cool, and checking to see if the buckets spin:


120 PSI:
.038mm Intake SPINS - Less Than .038mm Exhaust SPINS

60 PSI:
Less Than .038mm Intake Does NOT SPIN - .152mm Exhaust SPINS (WOW!)

45 PSI:
Less Than .038mm Intake Does NOT SPIN - .068mm Exhaust SPINS

110 PSI:
Less Than .038mm Intake Does NOT SPIN - Less Than .038mm Exhaust SPINS

As if all this wasn't fun enough, when I took off the points cover, there was a busted up spring, and what looked like part of the advancer assembly sitting loose, wedged in the cover! The messed up thing is, I can't find ANY of these parts in the fiches. Whats going on here?

So I've decided that if I am going to do this, I need to order my parts TONIGHT to have a chance of finishing it by the time I need the garage cleared out.

Right now my shopping list is:

-Manual
-Shims
-Carb boots (maybe)
-Advancer (eBay)
-Complete gasket set (Or just headgasket and valve cover)

How intelligent would it be to buy a used head for shim-swapping, and in case I have a REAL valve problem? For the cost of 8 shims, I can probably buy a used head...

What are the odds that my rings are worn, and is there a source for reasonably priced standard size rings?

WB, Offer this for consideration. buckets which don't spin probly have no clearance. (obviously they aren't frozen, as there is no measurable clearance), no change in compression w/ oil added indicates valve seal prob,or head gasket, but does not eliminate possibility of stuck rings. Valve w. excessive clearance could be, a chunk of carbon stuck to valve face, or bent valve.or simply a loose valve. a leak down test would help isolate. before tearing down, You might consider a potentially hazardous proceedure I call, "steam cleaning". in short, you get running, bring to temp (all cyls at least warm) and spray water into intake tract. the injested water turns to well, steam, hopefully breaking loose carbon and blowing bits free. proceedure always gets watr into oil, requireing a oil change. Buying a used head simply to scavange shims is a poor opt, as chances are you'll only get more of what you already have. points to ponder, G

WBPDX wrote:

...my shopping list is:
-Manual
-Shims
-Carb boots (maybe)
-Advancer (eBay)
-Complete gasket set (Or just headgasket and valve cover)....

Imo, chances are reasonably good that setting valve clearances to specs may resolve the compression problem, and without any need to remove the head.

I would like to, and intended to try the 'steam' cleaning or 'water tortue' as us Volvo guys call it... or\and using Seafoam in that manner. BUT, now my issue is my valve cover gasket is all busted to heck. I think I may try to temporarily reassemble tomorrow for water tortue, and a leakdown test.

For now, I am going to order:
- Manual
- Valve cover gasket

To at least get the party started.

Thanks for all the info guys.