Thought I would share my experience of replacing a head gasket on my scoot. I had a fun 4 days (yes, 4 days) and learned a lot about Harley top ends.
First, a disclaimer: I am not a certified mechanic. My processes are not the end-all only way to do anything. I know just enough to be dangerous. Don't take anything I say as "Gospel", but rather just one person's experience in trying to save some money by doing work himself. If you're not comfortable or competent enough to attempt this or any task envolving disassembly of any motorcycle, DO NOT DO IT
Now on to the goodies:
I noticed a small oil leak coming from the rear of the number two (rear) cylinder between the jug and the head. I had a bad head gasket. I went to the dealership and got the gaskets (head gasket, 2 breather o-rings, rocker box gasket, upper pushrod cover o-rings, and 2 rocker box cover gaskets). It cost me around $40 for the complete set. The service tech at the dealership said that I had to replace the cylinder gasket (between the jug and engine housing). I was unsure about that, since I wasn't removing the jug. I will get back to that point here shortly.
I started by removing the seat and tank, which is really easy on a fuel-injected bike. The fuel fitting from the fuel pump is similar to that on an air chuck, so it basically just pops off. The number two cylinder (on my bike) has a temperature sensor in the center of the head that has a wire coming out of it, so I disconnected that from the molex plug just infront of the oil tank. I then removed the rocker box cover and rocker box.
Note: Be sure to follow the Harley Service Manual when you remove the rocker box. The manual says to remove the large screws last and in small increments and in a cross pattern. This is important because when you loosen these bolts, you are draining the pushrods and lifters of oil and you don't want to warp anything or create another problem somewhere else.
Once the rocker box is off you only have the 4 head bolts holding the whole mess on. Disconnect and remove the spark plug.
Remember when the service tech told me to replace the lower cylinder gasket? I found out why. The 4 head bolts actually hold both the head to the jug, but also the jug to the engine casing. If you are VERY
careful and don't move the jug around much and don't disturb the cylinder gasket, YOU SHOULDN'T HAVE TO REPLACE THE LOWER GASKET
. I choose not to replace that gakset, even though I was told to. You make your own decision if/when the time comes.
I cleaned up the top of the jug where the head gasket goes and this is what it looked like:
You can see the oil residue on the right side of the jug where I had the oil leak. You can also see 4 head studs and 2 breathers.
And then took a pic of the inside of the cylinder looking at the top of the piston:
After I took a straight razor and cleaned both the upper of the jug and the lower of the head (the two mating surfaces of the head gasket) I replaced the head gasket and 2 breather o-rings. The manual says to put the o-rings UNDER the head gasket, BTW. Replaced the 4 head bolts and torqued to spec.
VERY IMPORTANT PART COMING UP, DON'T TAKE A BATHROOM BREAK RIGHT NOW!!
The head bolt torquing process is a little involved. You have to torque to an initial spec, in inch-pounds. Then a secondary sepc, in foot-pounds. Oh, and in a crossing pattern to spread the force over the gasket evenly.
Once that process is complete, back off each of the 4 head bolts in 1/4 turn increments in a cross pattern. Don't cheat, you'll regret it later.
Now it's time to bolt the head down for good.
Hand tighten the 4 head bolts. In a criss-cross pattern, torque to initial spec, in inch-pounds. Again, in the same criss-cross pattern, torque to final spec, in foot-pounds. Finally, in the same criss-cross pattern, add an additional 85-95 degrees of sweep (another 1/4 turn) to each bolt. The manual was very specific about this process, so it's one from which I didn't deviate.
Once the head is torqued down, replace the rocker box gasket and reinstall the rocker box. Follow the Harley specs for bolt order and torque specs.
New rocker cover gaskets (two in my case) and reinstall the rocker box cover.
Don't forget to reinstall the spark plug, and temperature sensor from the rear cylinder.
Here's where my 4-hour job turned into a 4 day job.
When you removed the rocker box from the head, you lost all oil pressure in the pushrods that pump oil into the head to lubricate the rockers. I was told that the lack of oil would result in valvetrain chatter once the bike was started again. I was also ensured that the chatter would go away once oil pressure was re-established in the pushrods and lubrication was back in the rockers. I let the bike idle for 5 minutes, and the chatter persisted.
I let every word that my mom didn't like me saying fly as my bike was, at that point, a big, shiny paperweight.
My dad saved me when he suggested that we prime the lifters and pushrods before starting the bike.
We primed the lifters by forcing oil into the engine casing through the return line in the oil cooler that I installed over winter. We took engine oil from the oil tank and forced it into the line from the cooler back to the engine with a large plastic syringe. This forced oil into the lifters and pushrods and primed the rockers before the bike was started. We only forced about 500cc of oil into the case. Once that was completed, and the lines to the oil cooler were reinstalled, I fired it up, and she purred like a kitten.
I reinstalled the seat and rode her away.
If any part of this is unclear or if I seem to have skipped a step, it probably is or I probably did. Ask me questions. That's why I wrote this up--to spread the knowledge. I've learned a lot from this forum, this is just my small part to pay it foward.
I need to thank the usual people for their help in the entire process:
K3VL4R, you've proven, yet again, that there is little you can't/won't try on a motorcycle. Thanks for all your help.
My brother Jake was a big help in getting everything apart-small hands.
My buddy Jake let me borrow the coolest torque wrench on the planet. A Snap-On electronic torque qrench that vibrates when you get near the input torque, and beeps when you are there. Then it displays the actual torque that was put on the bolt. Pretty sweet. Now he just needs to buy a bike for himself...
Finally my dad and his girlfriend. It was in her garage that this whole mess took place, and it was his suggestion that got my bike back to life.