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Message started by Moarpower on 04/17/23 at 19:27:45

Title: Cylinder Base gasket Failure
Post by Moarpower on 04/17/23 at 19:27:45

Hey guys.

Finally, after months of waiting for parts, I got my 87 running beautifully with a 96.5mm piston and dr650 cam.

Unfortunately I need to tear it down again to replace the cylinder base gasket as it failed.

It was a new gasket from an Athena gasket kit. Coated paper gasket that felt flimsy, but I went for it anyway.

I have ordered OEM base gaskets a cover gaskets now so just waiting for them and ill be tearing the engine down again :-[

Is the OEM gasket also a paper gasket? i remember when I tore it down it seemed a lot harder and thicker than the one I bought ? It was more like a compressed material. Id prefer to use the same thing again.

SHould I apply any sealant to the new gasket ?

Title: Re: Cylinder Base gasket Failure
Post by Ruttly on 04/17/23 at 20:11:08

Dry gasket, no sealant

Title: Re: Cylinder Base gasket Failure
Post by Moarpower on 04/17/23 at 20:55:08

022524243C29500 wrote:

Dry gasket, no sealant

Thanks. Do you know if the OEM gasket is just a paper one? I want something a little more heavy duty I think

Title: Re: Cylinder Base gasket Failure
Post by Dave on 04/18/23 at 09:42:21

The OEM gasket is paper - but it does have a line of sealant applied to one side.

https://www.ebay.com/itm/194267382311?epid=1623414517&hash=item2d3b3d0227:g:N0YAAOSwAKBhCALV&amdata=enc%3AAQAIAAAA8MKCTx8i7SAJx4DD%2BvTvWDhYNUEYl79102emlPuOjyts64XRuMi05oZBVo5j8J0VAGtbvBNghEcoHZCRFcovcPQQS7bVCTLyjI%2BYlYv00sXwltOS8fYJ024p5fT7Tt1qmU52PHdsDCqqqs7E8LZDAl0eVx1fA29nMOSJHAznhi6%2BqGGex21hbU%2Bz1Jb9J9CswhDmldp4SErRP%2FdJngk6R5g9HWsMzy6HmN22qIS%2BomOfVsNA%2BGhqIIe8UcwYKS9ZY8QG7jN7UhFY%2FYQGdmTLjV4V9aZu764bG04cVK0LJJ7e3omYKJNdBIuZTp%2BuBF2Ttg%3D%3D%7Ctkp%3ABk9SR8yV4tPyYQ

Title: Re: Cylinder Base gasket Failure
Post by DragBikeMike on 04/18/23 at 11:47:54

Did your base gasket fail like this? In this same location, left/front corner?

Title: Re: Cylinder Base gasket Failure
Post by DragBikeMike on 04/18/23 at 12:05:56

Are you applying any sort of lubricant to the head nuts, studs, and copper wahsers.......or........are you applying silicone sealant to said nuts, studs and/or washers?

If you are applying sealant, or if you aren't lubricating the fasteners, you are not getting the studs stretched to the proper stress. The difference in stress is dramatic. This post provides valuable info.

http://suzukisavage.com/cgi-bin/YaBB.pl?num=1576269113/12#12

I believe the problem manifests at the base gasket rather than the head gasket because the head has a couple of additional fasteners closing the joint, and also the multi-layered steel (MLS) head gaskets use embossed beads that tend to keep the joint closed (to a point).

What head gasket are you running? Is it a solid copper gasket or a (MLS) gasket?

I currently run solid copper gaskets that I purchase from Copper Gaskets Unlimited in Phoenix, AZ. They are reasonably priced and can be used over & over. You can also get them in a variety of thicknesses. That being said, the stock composite gasket should hold up just fine if your fasteners are stressed correctly.

Congrats on your successful 96.5. This is a minor hicup. You will fix it straight away. BTW, that DR cam, I have mentioned in the past that it doesn't need the oil holes in the lobes. I take that back. I believe I have stumbled across the real reason those holes are in the cam lobes. I suggest you get those holes drilled. Sorry if I streered you the wrong way but I'm learnin new stuff all the time.

Title: Re: Cylinder Base gasket Failure
Post by Moarpower on 04/18/23 at 16:31:35

Thanks, guys.

Yes, it failed in that same area. I did use sealant on the washers as I reused them on the installation this time, but I won't on the next one. Ill try to source new ones. Are they generally reuseable or should they be replaced each use ?

I am using the OEM MLS head gasket. Hopefully, I have a spare for the teardown.

Dave, when you say stressing do you mean torquing to the correct spec?

I will get those holes drilled in the cam. What issues did you find without having them drilled?

Title: Re: Cylinder Base gasket Failure
Post by Ruttly on 04/18/23 at 18:31:21

Think I might want to try plasigauge on both of those surfaces. Make sure it’s not bad machining in that same area , now that they found more than one leaking in same area. Sealant will only cause gasket to tear and migrate.

Title: Re: Cylinder Base gasket Failure
Post by Moarpower on 04/18/23 at 18:40:49

Thanks Ruttly, ill not be using sealant this time

Title: Re: Cylinder Base gasket Failure
Post by verslagen1 on 04/18/23 at 23:10:59

11333D2E2C332B392E5C0 wrote:

yes you can reuse the copper washers used on the head nuts.
but you should sand the smooth and anneal them.
to anneal them, just heat red hot over the stove burner and let them air cool.

Title: Re: Cylinder Base gasket Failure
Post by Dave on 04/19/23 at 02:55:02

1B1D126E6C6B6F5F0 wrote:

What head gasket are you running? Is it a solid copper gasket or a (MLS) gasket?

BTW, that DR cam, I have mentioned in the past that it doesn't need the oil holes in the lobes. I take that back. I believe I have stumbled across the real reason those holes are in the cam lobes.

Yes........do tell us what you learned! :-?

Title: Re: Cylinder Base gasket Failure
Post by DragBikeMike on 04/19/23 at 11:35:57

Moarpower, when I say "stressing" I am referring to the process of preloading the stud by rotating the nut. The thread pitch is 1.25 so every full turn of the nut advances the nut 1.25mm. As you turn the nut clockwise it keeps advancing onto the stud until the nut contacts the washer. Once everything is in intimate contact, any further rotation of the nut will start to pull on the stud. Eventually, as you continue to rotate the nut, the stud will start to stretch. As the stud stretches, it develops stress (measured in pounds per square inch of stud cross section). The stud acts like a spring. As you stretch it by rotating the nut clockwise, the stress continues to increase. As long as you don't exceed the yield strength of the material the stud maintains the preload (stress) developed by increasing the length of the stud (stretch).

The torque value is simply a crude way of making an educated guess as to how much you stretch the stud. As the stud gets longer (stretches), and the load goes up, more & more friction is developed in the threads and washer, which makes the nut harder & harder to turn. The torque value takes into consideration the friction based on the materials being used, thread form, surface finish of the threads, and whether or not there is lubrication on the threads and washer. Take the lubricant away and it will take a lot more rotational force (torque) to achieve the same amount of stud stretch. When you use that silicone sealant instead of oil, you reach the specified torque long before you have rotated the nut a sufficient amount to stretch the stud to the desired preload (stress).

Take another look at that old post where I did the tests on the stud. You will note that every time I torqued it up and then released the nut, the stud retuned to exactly the same length. That's because I did not exceed the yield strength of the material. If I had continued turning the nut and stretching the stud more & more, eventually I would have increased the stress in the material past the yield strength. Once I exceeded the yield strength of the material, the stud would not have returned to its original length when I backed off the nut. So, the specified torque value not only ensures that you stretch the stud to the desired preload, it also ensures that you don't overtighten the fastener to a point where the material yields. Once you take a fastener past its yield point, it will never return to its original dimensions, and will never return to its original strength. Take it past yield and it's junk. So, be careful.

Dave, what I learned is that the left-hand main bearing (roller bearing) gets all of its lubrication from the top end drain. The drain in the exhaust valve pocket dumps oil onto the LH main bearing and the LH balancer bearing. My LH main bearing failed after only about 6000 miles. Being the curious sort that I am, I dug up my original LH main bearing and inspected it. It also had failed. I didn't even know.

My DR cam without holes has held up admirably. It has a ton of miles on it and still looks great. The rocker arms look great too. That implies that the oil holes in the lobes aren't necessary to maintain adequate lubrication to the lobes and rockers. However, as the cam rotates and the lobes dip into the well below, they throw most of the oil off toward the rear of the head (intake side). As the rotation continues, the lobes rub on the rocker pads where the remaining oil gets rubbed away, leaving almost nothing to get thrown toward the forward side of the head. So, it seems to me that those holes in the lobes are intended to provide a nice squirt of oil to the exhaust valves and then continue on down the drain to lube and cool the LH bearings. Page 4-9 of the factory service manual confirms this.

I still have a lot of work to do on this issue. Very close to getting the thing running again. Then will be doing extensive tests on the lube system. I'm pretty sure I have it figured out but as I said, I'm always learning new stuff. For now, I think it's best to put those holes in the cam lobes. You don't want one of these.