Engine Just Blew??

Jeff.Saunders wrote:

Have you replaced the cam cap bolts? Allen head bolts sit too high and the valve cover can hit on the tops of them. If this happens, the gasket isn't being compressed properly.

Still using stock cam cap bolts but thanks for the tip.

If not already done, might consider a leakdown test to determine which if any of the cylinders might be allowing a particularly inordinate amount of blowby into the crankcase, and also whether there might be a headgasket sealing issue (blown internally allowing combustion from #2 or #3 into crankcase via cam chain passage.)

Since reassembly, head has of course been re-torqued once or twice after cool down.

Any evidence of cam lobe hitting against inside of valve cover (espcially due to the thinner gasket)?

DIY cutting valve cover gasket seems to me like it would be very difficult.

Wondering if fitting double gaskets might help.

And of course the correct model 1979 KZ1000 valve cover gasket is being fitted (not the earlier Z1~'78 model). See image below.

Just thoughts.

Good Luck!

[Click on image for larger view]

All very good points Patton. The cams did contact the valve cover after changing to the thinner gasket. I cut away more material on it and it seems good now even with the thin gasket. If I remember correctly, the thinner gasket measured about .040" and the old one I had was closer to .080".

I'm hoping there are no internal engine issues as it runs fantastic and shows no signs of anything being wrong. I'm hoping that the rings haven't fully seated yet and that the blow-by will get better. If all else fails I will tear it down again. :S

Definitely retorqued the head and have used correct gasket for pollution style head. I think a thicker gasket is worth a try and then maybe venting the cam cover itself if that one blows. I am in search of a good quality gasket thicker than the blue ones. I also used Gascacinch for the first time recently helping a friend rebuild his bike (80 LTD 1000)and that stuff is awesome! Really easy to work with and sealed up really well. I think I'll try that on the next gasket.

I will re-check the cover for evidence of cam lobe contact while I'm in there. I needed to re-check the valve clearances anyway. :laugh:

79MKII wrote:

mark1122 wrote:

u should consider increasing the crankcase vent area, if u havent already. with bigger pistons u have more crankcase preasure. this is a common problem for leaks on the old Z's.

I think you're right. I'm hoping the pressure drops as the engine breaks in and has less blow by?? I still only have 180 miles on the 1261cc rebuild. I have since added a vent to the oil fill cap and thought it was the trick - guess not!

Is there a common mod for the stock crankcase breather to open it up?

U should be fine with 2 vents.
u could just try some atv silicone on the gasket. just put on a very thin line on each side of the gasket,and set the cover on. do not torque the bolts until the silicone has dryed. just snug them up a bit to seat the cover into the silicone or it will sqeese out.
This is what i did to modify my breather cup.
look on pg 6 of my project.
kzrider.com/index.php?option=com_kunena&...it=20&limitstart=100
i went for a hard ride the other day and my lower case to block started to seep oil. I will retorque and pray. this is why they go to dry blocks.

My valve cover gasket should be here today or tomorrow. Now I have to decide exactly what to do to try and stop the madness. I was talking about the silicone all over the gasket thing just last night. It's just weird that I never had to do anything like that before.

I also have a new can of gasgacinch and that's supposed to be pretty good stuff. Here's the really strange part though - I helped my friend rebuild his top end ('80 LTD 1000 with chronic base gasket seepage)and we used gasgacinch for the first time on everything. It worked super great on the base gasket, head gasket, and all other gaskets EXCEPT the valve cover gasket. He had a blow out right above his front left cam end plug. We just replaced it with another gasket and it's slipping out in the same area. It's not leaking yet but it appears to be only a matter of time. The bolts are tight, the surfaces are clean, the gasgacinch was applied and it still looks like it's going to slip out. There were no upper end components changed that would cause a valve cover seating issue and it doesn't leak anywhere else. I had never seen this problem before in over 25 years of owning KZ's and now I can't rebuild one without the valve cover gasket blowing out!! :S

all i can say is the silicone has worked for me.

every 1 of my cover gaskets leaked after my first full build 3 years ago.i used aftermarket gaskets. i took all of the covers off and applied the back Permatex rtv silicone, and no more leaks.
Often i can take off a gasket and re-use it with more silicone.
i just don’t torque it tight until it dries. just snug it up.
also i don’t use a lot. the more u use the more chance of squeeze out , into the motor.
How is the gaskasinch for removal?
i have heard it used successfully on head and base gaskets.

It was surprisingly good on removal of the valve cover gasket. It dries into a rubber-like film and most of the gasket came right off. A couple little spots had to be scraped off with a finger nail. Once you get it started it will peel off pretty easily in one piece. I was afraid it would be totally glued on the head but it wasn't. Pretty neat stuff.

Doesn't the black RTV make it nearly impossible to remove the gasket? I'll have to be in there for valve checks/ adjustments and don't want a major cleaning job. It comes off OK with the RTV all around? The black permatex is what I used on the end plugs by the way.

i havent had the cam cover off as yet. the other covers came off ok. it sounds like it is similar to the Gaskacinch.it comes off fairly well but may stick in the odd spot.
i used it on my cam end plugs as well. they do seep a tiny bit the odd ride. maybee it is temp related, but it only seeps sometimes?? just enough to notice.
i just retorqued the head.it seemed ok.i brought it up to 40ft. lbs. from 38 this time.
the APE studs can go up to 42ft. lbs.
i also did a cold compression and leek down test. i got 190 to 205psi. and 1 to 5% leakage . #2 cyl was the low 1 on both tests.
i also noticed #2 plug was leaner.
i need to buy a carb sync tool some day. it does run well very though.

My plugs leak a very small amount too - I plan to redo them when I change this gasket.

I have only vacuum synchronized 3 sets of carbs now, but the difference on all 3 bikes was totally amazing. Instantly idled higher, smoother, and ran much better. Really amazing. I bought a motion pro mercury manometer years ago and finally opened the box and tried them out last spring. Well worth the money.

I plan to re-check the compression and carb synch when I get some more mileage on this new engine. I'm only at 180 miles right now.

By the way, when is it safe to assume that everything has broken in enough to switch to synthetic oil??

they say 1000 to 1500 miles. the only down side i have heard about synthetic , is that it can make a motor leak. Jeff Saunders @ z1e says he has heard that enough times to beleive it.

Up here in Scandoland Finland there i9s a very strong preference for minarla oil. The one and (almost) only way to go is Mobil Delvac MX. It just seem to make these old motors run smoother and tranny+cluct just works better. I´va also heard of many guys using Delvac in much newer bikes.

do you have the two piece head gasket?i started leaking oil out of the front of the head by # 2 exhaust when i put my motor back together and it was getting passed the center o-ring,then blowing back through the cooling passages under the cam tunnels and going everywhere.if this has already been covered forgive me .

leon holmes