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Gentlemen,
Another query by Bald Eagle.
When I did the rebuild on my second bike (my track bike), I installed Yoshimura stage 2 cams. When I put the cylinder head back on, my rear cylinder went perfect. No problem. But, I have been having issues with my front cylinder head gasket.
The problem is I am having oil weep from the cam chain and cam gear area.
It wasn't weeping there before I did the cylinder head removal. So the cylinder head should not be warped. I've put a straight edge on it and there is no sign of a gap in that particular area.
I've emailed my guru in England and he said that the head gaskets have been sitting on the shelf too long and possibly not sealing properly in the cam chain/cam gear wall.
I've re-done this head gasket twice now, and still have the oil weeping.
Tightening down the cylinder head gasket, there is a sequence that I have followed religiously. But where it is weeping, there are two smaller bolts that tighten the cylinder head wall down to the engine wall, which have their own torque sequence (much less than the cylinder head bolts). Do you tighten those down in the first sequence? Or do you do the cylinder head bolts first? I don't think the manual tells you what order the smaller bolts are meant to be done.
I have another cylinder head gasket to be put on. I'm going to get the cylinder head skimmed to make sure it is level first.
But has anybody had this issue or have any feedback that might resolve my weepy head?
I can ride the motorcycle, it's not pissing oil, but it's just pissing me off.
Once again, thank you for any insight.
As far as torque, typically any smaller fasteners, get tightened last in my experience. Even if you torque them to spec first
the higher torque/clamping force for the larger head bolts will snug the head down a bit further and you will need to retorque the
smaller fasteners again anyway.
I would even try a skim coat of Hondabond sealant in those thinner areas of the head. Carefully key the aluminum mating surfaces with a
red scotchbrite (getting none of it in the cylinder, chain area), then wipe clean with IPA/acetone/non-chlor brake cleaner. Apply a skim coat of
hondabond to both sides of the head gasket and assemble as normal.
As far as torque, typically any smaller fasteners, get tightened last in my experience. Even if you torque them to spec first
the higher torque/clamping force for the larger head bolts will snug the head down a bit further and you will need to retorque the
smaller fasteners again anyway.
I would even try a skim coat of Hondabond sealant in those thinner areas of the head. Carefully key the aluminum mating surfaces with a
red scotchbrite (getting none of it in the cylinder, chain area), then wipe clean with IPA/acetone/non-chlor brake cleaner. Apply a skim coat of
hondabond to both sides of the head gasket and assemble as normal.
Not saying it's wrong, but I do question the use of a sealant on a head gasket. In my limited experience, I have never seen or read about this being done.
Yeah, not ideal I do agree but if it's not on a coolant or pressurized oil passage or near the combustion chamber, I wouldn't necessarily rule it out after OP having tried twice before with similar leaking results.
The alternative would be some oldschool Permatex spray copper just in that area, again not ideal but it's not in a pressure critical area where you want the viton (or whatever honda uses) to do the sealing.
Also (and i think this really goes without saying but) be sure to use OEM headgaskets.
Once I get the Cylinder Head off, I will take a closer look at the gasket. The cylinder head gasket is made up of two plates, which have a glue between. On the outside of the gasket there is a seal that welds the gasket to the cylinder head and the engine block. I believe that where the two metal surfaces of the gasket are connected, that's where the oil is weeping through. This is an original factory Honda gasket and has likely been on the shelf too long.
I just hope the new one I just purchased works this time. I will give an update when I take the head off.
I have to deal with this but playing with two strokes in my yute The cylinder had gaskets and base gaskets were copper which you could anealed with a torch and reused.
Four stroke stroke gaskets are often as described above. If you can use a solvent like acetone to separate the upper and lower "plates" (laminated gasket), clean and rebound them together, and your mating surfaces are within spec, reuse will likely be successful witn a hitemp silicone sealant allowed to cure to the head before pretensioning ("torqueing") the threaded fasteners to the spec stress psi certified by manufacturer as checked on a Skidmore calibration rig to convert to conventional torque wrench readings, as well as the fastener alloy content and condition, thread execution (hot., cold rolled or machined), and install procedures (galvanized, cadmium or other corrosion inhibitors; dry or how lubed; order of installation, etc.).
Personally, I gave up on manual torque 🔧 regardless of their indicators (click, tension needle sweep scale, or digital) for
I also design strain gauges that going into the head of certified ASTM A490 bolt so you don't have to check for loss of tension with a wrench at all it's just visual.
Hydraulic bolt tensioning has gone from heavy bridges to everyday manufacturing with automated systems eliminating all but hand labor for installation of the bolts and even then that is eliminated.
ASTM A325 fasteners and eq are the bread and butter of the fastening industry.
Snap-offvbolts are interesting and eliminate reliance on technique
Update on the cylinder head gasket issue.
Purchased a "straight edge" to see how bad the indifference was in the cylinder head. Not really happy with it being high where the gasket was leaking...could fit a 0.0015 feeler gauge in the gap without any resistance. But I decided to put a new head gasket on and do the recommended head bolt torquing sequence, leaving the last two screws where it was leaking as the last sequence. The required torque setting for the bolts was 9 ft-lbs, which is 108 in-lbs. So I set my in-lbs to 100 to be on the safe side. And the bolt snapped.
It never felt right when I was tightening it up.
So I had to take the head off, and the head gasket is now useless. So I have to purchase a new head gasket.
The good news is that I found a guy who can resurface the cylinder head for me and I will be going to see him tomorrow. Hopefully once that is done and I get my new head gasket I'll be back on track.
Will update you on this continuing saga at another time.
Sooo...drove all the way down to New Bedford, an hour away, and the guy said he would resurface the cylinder head while I waited. Great! But when I was 5 minutes away he called to tell me that his power was out. Not great.
So I left the cylinder head with him and he said he would ship it to me when it was done. I thought it would take a week or so to get it back. But the very next day it was delivered to my door. And he did an excellent job. When I put the straight edge on the cylinder head in multiple places, it is dead to nuts.
So now I am just waiting for delivery of my new cylinder head gasket.
By the way, the bolt that snapped was the original bolt and I am replacing it with grade 10.8 bolts. Exactly the same size as the original.
Still not comfortable with setting the torque on this bolt at 9 ft-lbs/108 in-lbs.
But I will let you know how it goes.
I think the biggest plus in this entire saga is that the cylinder head is now perfectly level.
Talk to you later!
You gotta love this story.
OK, the gasket arrived. I installed the gasket making sure the FT is on the flywheel and the cam shafts are aligned, etc.
Everything goes great. I checked for clearance, rotated the engine 360, with the engine in the off-position I used the starter to pump oil through the system. It seems perfect.
I go to start the engine and I hear the valves touching the piston. I shut it off immediately.
I called the machine shop and asked how much he took off the cylinder head and he said about 0.015.
I have high-compression pistons (11:1) and stage 2 cams.... off comes the cylinder head again.
Yup, sure enough the intake valve is just kissing the piston.
I rechecked all the timing marks before I took it apart and there is no fault there. I guess that's how close these intake valves are when you have high-compression pistons and stage 2 cams.
I didn't have this problem prior to the 0.015 resurface.
The other cylinder is fine.
I am now looking for a front cylinder head, which seems to be rare to find. Anyone got one out there???
06-12-2023, 01:02 PM
