Head Installation Sanity Check

Ready to install my head tomorrow night, thought I'd run this by you guys. Its an 82 XJ650 YICS motor for a Maxim.

Head was disassembled and cleaned up by local shop. I lapped and reinstalled valves, all passed the liquid test (filling port with paint thinner). Engine block is cleaned up. Both manuals (FSM and Haynes) seem to agree on procedure, torque specs, and sequence.

In addition to the head gasket and cam tunnel, here is the hardware and parts (2 dowels are still in motor). Anything missing?



I didn't see any mention of gasket sealer but I've always used the Permatex Copper spray for head gaskets. Any reason not too?

Also, I see that this is usually adjusted before replacing the jugs. I loosened it when I removed the head to get the rear cam chain guide out of the way. The manual states the procedure but not much insight into what is going on in the motor. Any tips here?



And lastly, obligatory engine porn shots. You can ignore the random pile of cam parts, those are from old head and will not be used.

 

I don't see anything missing. The adjustment bolt holds the rear guide in place but also allows it to rotate. Follow the books, it should not be snug to the guide. I don't use anything on the head gasket but if I ever do it'll be on one side only (the head side).

Gary H.

 

I don't like to use anything on factory gaskets that are fibre based or have metal with fibre coating
Only on old 2 stroke copper gaskets do I used copper spray after annealing process.

 

The only reasons for using sealer on a fiber head gasket is if there are any nicks in an otherwise flat head, and those nicks would only have the potential for causing an oil leak, or you are in a situation where you have to reuse the head gasket.

 

Was that head surfaced by the machine shop?

 

If it wasn't it should have been checked for flat.

Gary H.

 

I checked it with a straightedge and feeler per shop manual when I first purchased the head since it was a used one from another member.

 

That cam tunnel gasket can be a bugger, watch the yics orings.
Not the head but sort of , inspect the shim buckets for nicks where the shim fits.

 

Shim buckets are good, looked for excessive wear etc. on them and the bores. I unfortunately don't know what bore they came out of as they shipped out of the head.

I'm questioning my straightness check now as I do not have a precision straightedge as shown in the manual.

 

Doesn't matter. They are all made to the same tolerance so they can fit into any of the bucket bores, otherwise they would be stamped for location at the factory.

 

wipe some oil on the buckets,put all the buckets in a bore then move each one a few times. if one feels tighter or maybe looser swap it to one that felt the opposite.
if you trust the tolerances it will work but you can do better than that

 

Oh, i don't see any valve stem seals, now's the time

 

Did those after the valve lapping!

Going to have head checked for straightness at shop and then proceed with install.

Plan is to coat in oil and fit in bores, see where they "feel" best. The original head still has them installed so I can get a feel for them. The suction cup lapping tool works well for this.

 

Finally got some time in the garage last night. Changed out the oil pan gasket, no plastic pieces, RTV chunks, etc. so good to go there.

Got the head on following the book but I have a couple areas where the gasket is "loose" between the cylinder and head. Its right where the cam chain tunnel gasket is, you can feel the feeler gauge hitting the cam chain tunnel gasket. Doesn't seem right so I thought I'd ask. I searched and found one other thread where the user had the same issue. His ended up being the nuts were only at 17 ft lbs. I checked with 2 torque wrenches and I'm at ~24.

Is this because the cam tunnel gasket is thicker or do I have another issue? I never did take the head back in to confirm that it was flat, just used a straightedge and my feeler. The head fit fine without the gasket and poked around with the feeler gauge.

Thoughts?

 

Is the tunnel gasket completely seated? The tunnel gasket shouldn't be thicker and should recess into the head gasket. Dumb question...all the acorn nuts have washers and you torqued the nuts in sequence right? Hope this helps.

Gary H.

Correction per Chacal's post: The oem tunnel gasket is thicker than the oem head gasket pre-installation.

 

Yes it was seated, I can see the tabs looking down the cam chain tunnel. All nuts have washers and were torqued in two applications, first to 11 and then 23.

 

Ran home for lunch and pulled the head to see what's going on. You can clearly see that the outer two cylinders sealed up by the ridge where the sleeve is and the center two cylinders show some sealing on the outer sides but nothing in the middle by the cam chain tunnel. I then mic'd the gaskets and the head gasket comes in around 0.048 and the cam chain tunnel at 0.062. These measurements were taken where they meet up but were fairly consistent around the gasket.

Should I be expecting that gasket to crush 0.014+ so that the head gasket will seal? Seems like a stretch.

Tonight I will put the head gasket back on without the cam tunnel gasket and see if the inner two cylinders will seal up. Will drop head off at a machine shop too to ensure its flat before wasting another head gasket.

 

Post a pic of the entire head gasket.

Gary H.

 

Your cam tunnel gasket slipped out of place. loosen the head before it warps.
Lift the head but not off and block it up.
You should be able to maneuver the cam gasket into place, then check the rubber seal on #4 stud. When everything is right it should go down and kind of clunk solidly.

 

I don't think so. You could clearly see all 7 tabs when looking down the tunnel. If it did slip, there would be a bigger gap between the head and jugs. You could feel the feeler gauge hitting the cam tunnel gasket when slipping it between the head and the gasket.

You can feel the difference in thickness when you set these side by side on the bench.

 

The tunnel gasket looks stock. Start a conversation with Chacal. Ask for the thickness dimension of the tunnel and head gaskets in his catalog. Hope this helps.

Gary H.

 

i went through the same thing this spring, the cam tunnel gasket on mine slipped. remember when you took it apart, the tunnel gasket was smashed. what else could it be.
did you ever torque it down?

 

The OEM head gasket (uncompressed) measure about 1.30 - 1.45mm thick (outer edges, not in the metal ring area).......it's hard to get a stable measurement because the internal "spring metal" that is sandwiched in-between the fiber layers is not uniform.

The cam tunnel gasket has a molded rubber skin with "o-ring" shaped protrusions on both the top and bottom of the gasket, and of course once crushed won't ever really return to their nominal dimensions. A new OEM cam tunnel gasket measures about 1.55mm thick.

 

Wow someone doing the exact same thing I am... Other than the fact I am doing it insitu rather than pulling the motor. I am scratching my head with the case to cylinder oil passing studs and the cylinder to head oil passing studs. It seems to me I need 4 dowels for both the case to cylinders and another two for the top of the cylinders and the head. I only have two oring/gromets in the gasket set (Athena) and the original ones on the bike. I have dowels for two holes, not four.

 

Check the thread you started on this issue for an answer.

 

Gary H.

 

Bad Post

 

Spent some more time on this tonight. I reinstalled the head with just the head gasket and not the cam chain tunnel gasket, torqued it down the same. This time, I was not able to insert my feeler gauge anywhere around the head. When I pulled the head back off, there were nice rings on all 4 cylinders where the cylinder sleeve was. I'm pretty confident there is an issue with my cam chain tunnel gasket.

Not the one I have. Looks more like a standard gasket.

Another good point, mine is measuring 1.65mm after being installed and torqued down. I didn't measure it before but it obviously was the only thing getting compressed in the middle of the head so I suspect it's out of spec.

I still don't see how it slipped. There are 7 tabs that hold it in place and I could visibly see all 7 in the the head. Also, if it had slipped and overlapped the head gasket, I would see that damage on both gaskets and there would've been a serious gap on that side.

I will do my due diligence and have a machine shop double check my flatness check on the head before seeing if there is any recourse with the vendor. I may not have any being a hobbyist but that's the risk you take doing it yourself. I'm here to slowly restore a bike in my spare time to relieve stress and get some man/beer time, learn some new things, and share some knowledge, nothing more.

 

+1. I believe most of us are here for the same. Miller Lite Tallboy? I prefer the Genuine Draft, but I drink my fair share of the Lite.

The problem very well could be the tunnel gasket. Do you still have the old gasket? If so try dry fitting it with the new gasket.

Gary H.

 

Regular Miller Lite, you know, the "Fine Pilsner". Used to brew/drink a bunch of craft beer but haven't had any time for that lately. Pretty easy to add a case of miller to the shopping list

I still have the original head and head gasket, but no cam tunnel gasket. Looking at the head surface, it almost appears like there wasn't one in there. I don't recall pulling it out either. The PO was the second owner and he never pulled it, but who knows what PO #1 did. I've known the second for 27 of my 36 years and went with him to test drive this bike when we were 21 so I trust his word.

 

It would have leaked like a sieve if there wasn't one in there!

 

Imo if the other vendor has a feedback section on their website tell them it doesn't fit, cut your loss and order a tunnel gasket from Chacal. I doubt the other vendor will refund your $. They might give you store credit though.

Gary H.

 

Is the head gasket you have 1.20mm uncompressed?

Gary H.

 

The head checked out within spec by the shop. The original gasket was in a set I received from Chacal and once again he has gone above and beyond expectations in assisting and backing his products (not that this is a surprise but its worth mentioning). Ill update this again once everything comes in and I get some time to put it together.

Going to shift my focus to the frame this week and hopefully get the mill back in next week.

 

Received all my new parts today and the install went off without a hitch. There is definitely a difference in the OEM tunnel gasket vs. the one that came in my kit. The OEM is exactly as Chacal describes above and compresses much easier.



Side note, the OEM head gasket is very similar to the aftermarket Victor Reinz I received in regards to construction and thickness, but it does have some preapplied sticky compound around the chain tunnel area.

I totally understand this now. While the OEM gasket is much better, it is a little tricky to keep it seated until the head drops down. I did a quick inspection inside the tunnel to look for all the tabs before I torqued everything down.

Need to get cams in and shims and it will be time for paint and back into the frame. Big thanks to Len for getting me squared away on the parts!

 

so, in conclusion, the problem was your cam tunnel gasket? I actualy just re-built my head and I seem to have the same exact issue as you.

However, I did order the top end re-build kit from Chacal. It may be that my tunnel gasket was not OEM?

Did the bike run and start up fine without any compression loss? I was under the impression my issue was engine block warpage, but it may be that the tunnel gasket is bad.

Thanks for the great info.

 

Also,
i would like to add that I replaced the gasket recently, and that it failed completely. The gasket was burned through cylinders 2-3 going to the cam tunnel area.
Therefore, I think that it may be the same issue, as the same cylinders in your post were not sealing.

Eventually, I had a terrible gasket leak, but I ran the engine. It may have lead to over heating....