Replacing base o-rings, Do I need anything else?
 

I have a leak in my base o-rings on my 2009 FLHX so I bought the Cometic top end gasket kit with .030 head gaskets (guy that built the engine for PO used this and talked to him). Got the book, videos from Youtube, Yamabond 4 for around the base when install new o-rings (builder recommended it), all the tools (nothing special except ring compressor and torque wrench) and beer. Am I missing anything else?

My only hiccup looking at everything is the getting the rods in the right spot for disassembly and assembly.

-Should I do 1 cylinder at a time and then move the wheel in 6th gear so I'm on the compression stroke of the opposite cylinder or do both at the same time?
-Should I replace rod/tappet housing base gaskets as there are no leaks?

The bike has 25K on it and about 15,000 since it was built from a stock 96 to 103 (4 years ago) with Woods cam, big sucker, heads ported and polished, Fat Cats, Wiseco high compression pistons, manual compression releases, DK head breather bypass, ect. The original builder said not to mess with the heads at all unless they look fried and then to call him. I only notice the base o-ring leak and a veeerrry slight loss in power. I think I got some bad gas with water in it on a trip.

Also, there isn't much air coming out of either breathers or sucking in. I don't know if it's supposed to be this way and if that has had an effect on anything and the Big Sucker breather bolts are free and clear. It doesn't really use any oil and my oil pressure gauge is running a little past 32 (probably 38 and comes down when stopped) when it's normally at 32 (have some pictures riding down the road with it pegged at 32). I did an oil change after I noticed it (Mobil 1 and K&N filter) but no change there as I thought maybe the filter was plugged somehow. Oil coming out looked fine and nothing on the drain plug magnet.

Thanks in advance.

So, let's see if I have this straight:

1) "The builder" you mention performed the last build, which is now leaking at the cylinder base O-rings.
2) Same builder is now recommending that you do or have the work done at your expense to correct the leaking O-rings.
3) Same builder is recommending that you use Yamabond on the O-rings.

Did that builder use Yamabond in the O-rings when he built the motor? I have been through four builds of my 2000 TC motor where the cylinder O-rings were replaced. Never used Yamabond or anything else on the O-rings, only made sure that they were free of excess oil when the jugs were pushed down into position onto the cases. Never, ever had a leak in 13 years with any of these builds. HD service manual does not recommend using Yamabond or anything else on the O-rings. Why are you so ready to do this?

I would send the jugs to a quality machine shop and have the base surfaces measured for absolute flatness and have them milled the minimal amount to achieve absolute flatness if necessary and forego the Yamabond or any other band-aid when you put your motor back together.

Thanks for the reply. The builder, who had a shop here in Iowa and a great reputation, did this for the previous owner years ago and did not use Yamabond 4 at that time. He said he personally has a 117 with no o-rings and just Yamabond on it with zero problems in 40K miles. He retired and now lives in FL but the PO gave me his number if anything would ever come up. He suggested an ultra thing layer on the case, not actually on the o-rings, and I thought this might be a little extra insurance since it didn't have it before and he wasn't doing that at the time when he built my motor for the PO. I would still install the o-rings no matter what. I don't think it's necessary but he said he started doing it the last couple years he was building. Both cylinders just started leaking at the exact same time and have always been dry as a bone up until a few weeks ago while I was on a trip. Please feel free to give me more opinions as I'm open to suggestions. I like wrenching myself and hate to pay someone for something I can do on my own. I certainly don't trust the stearlerships. Thanks again.

I appreciate you taking my feedback in the (helpful) spirit that it is offered and I respect and applaude you for doing the wrenching yourself. If you do not intend to have the cylinder bases inspected/measured by a machine shop, you can save a lot of time and money (cylinder honing and new rings) by lifting the cylinders and pistons off as an assembly. Once the heads are off, cut some 1/2" PVC pipe to about 4" length for spacers and cut a groove lengthwise such that the spacers will fit around the cylinder studs. With the assistance of a competent buddy, lift the cylinder up just enough to get clear access to the piston pin (and NO MORE, less the oil ring become unseated), insert the four PVC spacers around the studs to support the cylinder. Carefully cover the exposed holes in the case with clean rags to avoid dropping anything down into the cases. Then remove the piston pin circlip from the right side and then drive the piston pin out from the other (left) side. Carefully and slowly lift the cylinder and piston assembly off of the rod and the studs, being very careful not to let the oil ring become unseated at the bottom of the cylinder bore.

Do the second cylinder/piston the same way. Do not rotate the cylinder or piston in relation to each other, thus not disturbing the piston ring/cylinder coupling, bag them to maintain cleanliness, and set them aside in a safe place out of the way.

Put a minimal amount of motor oil on the O-ring and slide it over the bottom of the cylinder bore, making sure not to twist it and that it is seated correctly at the base of the cylinder.

Carefully work the cylinder/piston assembly down over the cylinder studs until the hole in the piston land lines up with the rod bore and drive the piston pin through the hole in the piston land. Replace the circlip removed during disassembly with a NEW one. Check the O-ring to make sure that no excess oil is present, wipe it off with a clean rag if there is. Remove the rags covering the bores in the cases and slowly slide the cylinder down until it firmly seats into the case and then secure it in place with two short head bolts using ~1.5 inch long 3/4" diameter PVC spacers. Do the other cylinder the same way and then reassemble the motor, making sure not to rotate the crankshaft once the head bolts and spacers are removed until both heads are correctly torqued into place.

Never used Yamabond or anything else on the O-rings ... Ditto ... Yamabond is great for sealing case halves and the like but NOT FOR RUBBER PARTS

I appreciate the how to. What is the benefit of doing it that way vs just pulling the cylinder off and reinstalling with a ring compressor (I have one)? How am I saving a lot of time by doing it as you have instructed because I'm still tearing everything down? If I can't get that wrist pin out, which can be a bitch from what I've seen and read about, I don't have a puller and don't want to mess anything up because then I'm really in a word of hurt. I'm sure I could make some type of puller but don't want to F it up. Thanks.

EDIT: I was also going to clean off the piston tops when I had the jugs off because I'm sure they are nasty but I guess I'll see.

It wouldn't be on any rubber parts, just metal.

Oh, and I've rebuilt many 2 strokes (motorcycles and snowmobiles) but not a 4 just for reference.

You save time and money by avoiding cylinder honing and new rings once you disturb the rotational relationship between the rings and the cylinder bores.

I did exactly as I described in my prior post last December and had no issues with removing the circlips nor the piston pins. Use the appropriate sized deep well socket and a dead blow mallet to drive the pins out and back in. Works like a charm.

Carbon can be safely cleaned off of the piston top by bringing it to TDC, taping off the piston top to the cylinder top with duct tape, and then using a wire wheel on a drill, air grinder, rotozip, or Dremel tool to blast the carbon off. Did mine with a drill and a wire wheel. Clean as new.

Your motor, your money, your call.

Hey, I appreciate it and why I asked. I didn't know that I would need to put new rings and hone if I simply slide the cylinders off. When I've done 2 strokes you can simply cross hatch if they are worn but they usually are not (on snowmobiles anyway). I'll give your way a shot. Any advice on the push rod install other than having the cylinder you are working with on the base circle?