Top End Rebuild

Retiredgentleman · Posted: October 18, 2008, 12:56 pm Post subject: Top End Rebuild

My oil consumption got to be rather excessive...............about 1 liter in 335 kms!! Bike was running real good, lots of power, but when friends driving behind me on their bikes, they were talking about the black stuff coming out of my exhausts. So, time for a top end rebuild. The carbon build up was so bad, I think there may have been a chance that the valve could contact the piston top.Here's a few pictures.

Retiredgentleman · Posted: October 18, 2008, 12:58 pm Post subject: Re: Top End Rebuild

Another picture.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

How many miles on the motor? That does look like quite a build-up. What all do you plan on changing out and replacing?

Retiredgentleman · Posted: October 18, 2008, 3:31 pm Post subject: Re: Top End Rebuild

Engine has 20,000 Kms on it. I'd say the valve seals are the main reason for the oil consumption. I have to find a valve spring compressor to get to the seals. The front cam chain guide has the rubber separating on one side and a piece coming off on the other side. Haven't had time yet to measure the piston or cylinders for wear. I also need to check the rings end gap. The rear cam chain tensioner looks to be in good shape.
So, will replace valve seals, front cam chain guide for sure. I expect that I will find pistons, cylinders, rings, and valve guides in spec. Not decided about the cam chain to replace or not?
Will also lap the valves and check for any pitting.
What kind of life span have others been getting with rings?

jayel · Posted: October 18, 2008, 5:25 pm Post subject: Re: Top End Rebuild

RG you been burning coal in that thing? or just making your own? did you check compression before you took it down? doesn't really matter since you're in that deep might as well ring it while it's open, read up on head porting the xs motor while you've got the top off it's going to be a long winter

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

I remember you mentioning you had to enlarge your points plate slot to gain more adjustment. That's a pretty good indicator that your cam chain is stretched out. You should probably replace it. On mine, I was nearly out of adjustment slot. I hadn't filed it yet but would have probably had to soon. With my new chain, the timing dialed in with the plate right about in the middle of the slot. If you marked your timing plate before you removed it and do install a new chain, that mark won't be good anymore. Do a static timing check before you fire it up.

xs1961 · Posted: October 18, 2008, 7:08 pm Post subject: Re: Top End Rebuild

.. messed-up...read next... Embarassed

xs1961 · Posted: October 18, 2008, 7:16 pm Post subject: Re: Top End Rebuild

mmm..So much carbon - I would expect to find signs of late devonian Equisetales and/or early terrestrial invertebrates such as amphibious Lepospondyli....Then again , maybe I'm thinking of an old coal mine in Leicestershire i visited recently.... Wink

xsjohn · Posted: October 18, 2008, 7:35 pm Post subject: Re: Top End Rebuild

Clean coal should solve that problem.............xsjohn

Retiredgentleman · Posted: October 18, 2008, 9:24 pm Post subject: Re: Top End Rebuild

jayel; Checked compression before pulling the engine and both cylinders were at 150 psi. The rings are probably in good shape. I'll know more after I take some measurements. Picked-up an inexpensive valve spring compressor to-day, so I'll soon have my hands on those pesky little valve seals.
Well, I've not been burning any coal..............those pictures are real ugly!
Looking on the good side, when I get the engine re-built, I'll feel good that I'm reducing pollution in the world.

jayel · Posted: October 18, 2008, 9:41 pm Post subject: Re: Top End Rebuild

going green is good RG, john ain't no such thing as clean coal, kind of like picking up a turd by the clean end but I think we're going to have to use it or go with the nuke plants I don't know why they just don't drop the spend fuel off in the ocean subduction zone and let it go back under the continent, last time I checked the al-qaeda navy hadn't got their deep diving submersibles working yet

davidnj2 · Posted: October 18, 2008, 11:18 pm Post subject: Re: Top End Rebuild

Hey RG, Might be a good idea to double check to see if you were pulling oil from the head gasket next to the camchain chamber. That's what happened to me on my first rebuild.

Retiredgentleman · Posted: October 19, 2008, 1:24 am Post subject: Re: Top End Rebuild

davidnj2;
That's always a possibility. Was your head gasket visably damaged or broken? How did you determine it was a leaky head gasket? Was the head not torqued down enough? My head gasket looks like its new, I can't see how it would leak with the head torqued down.

xsjohn · Posted: October 19, 2008, 8:25 am Post subject: Re: Top End Rebuild

Jayel...........Was kidding about the clean coal.........

RG.......have you lifted the barrels.........if mine at 150PSI I wouldn't lift them.........new valve seals and lap and try it....you might be able to tell if the valve seals were funk if they are hard....gets harder to get the used rings to seat if disturbed especially when it sounds like they are doing good now......

xsjohn

Retiredgentleman · Posted: October 19, 2008, 12:32 pm Post subject: Re: Top End Rebuild

John; I had to lift out the barrels..............with all that carbon on top of the pistons,it has to be cleaned, and I wouldn't want all that crap falling down into the rings.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

For cleaning the carbon off, I use paint stripper. Paint it on, let it sit 10 minutes or so, and wipe it off. Several applications may be needed but it will literally melt away most of the carbon. What's left will be softened and can be easily scraped off. This also works well for gasket removal. Clean the carbon off the heads and test the valves for leaks before you disassemble them.

When you get to the re-assembly part, read over the "Leakless XS Assembly" thread over at the Garage, there's some good tips in there. In particular, adding a small bead of sealer to the head gasket around the cam chain tunnel and 4 outer oil flowing stud holes. This is just some added insurance against the problem David encountered.

Retiredgentleman · Posted: October 19, 2008, 1:15 pm Post subject: Re: Top End Rebuild

5twins; Thanks for the tip on the paint thinner ( and I only thought it was for sniffing Smile

Yes, I will do a re-read of the leakless assembly from the garage.
For the rocker box assembly onto the head, do you use "threebond 1104", and what do you use for the casing halves, even though I don't plan to open up the casings.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Paint Stripper, not thinner. I don't think thinner would do anything.

It appeared my points and advance housings were originally installed used the Yamabond (same as 3-Bond), but I didn't use it upon re-assembly, just oiled the gaskets with motor oil. I also didn't chance the seals in the housings because they weren't leaking. What I did do is buff both ends of the cam where it fit through the seals with a Scotch Brite pad while the cam was out. This gives the seals a fresh, clean surface to work against. The way I figured it, these covers are something you can access and remove when the motor is still in the frame. If a problem does arise, I can service them. So far, they've remained leak-free.

For the lower case halves (I didn't have mine apart either) and the top cover over the valves and cam, Yamaha recommends Yamabond (3 Bond) and that's what I used. You'll also want to use it on both sides of the base gasket. No sealer was used there from the factory but on rebuilds, you always put it there.

Be aware that the original good gray colored Yamabond (and 3 Bond) has been discontinued. There is a new version out but it's clear and silicone based. I won't use it and would probably use something like Holimar instead if I had none of the original good stuff left.

Applying the original Yamabond can be messy and difficult. It comes out of the tube in a rather large and stringy bead. You need a short bristled stiff brush to spread it around and "paint" it onto the surface in a nice thin coat. One of those metal handled acid/flux brushes with the bristles cut down works well.

xsjohn · Posted: October 19, 2008, 1:41 pm Post subject: Re: Top End Rebuild

I would have scrapped the carbon off the pistons and blown the junk away with air.......but.........welcome to a new break in..........xsjohn

Retiredgentleman · Posted: October 19, 2008, 5:06 pm Post subject: Re: Top End Rebuild

Yes, I meant to say paint stripper (not thinner), minor brain lapse. I have a feeling that oven cleaner would also work well.
I have a tube of the original grey 3-bond 1104, not sure if it will be enough. "Holimar", do you mean Hylomar? Last time I did a top end rebuild, 23 years ago, I used Hylomar and its an excellent product...............no leaks on motor. I may buy a tube of Hylomar.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Yes, that's what I meant. I used to use it on my old BMWs as it was what they recommended. It's supposedly made under license from Rolls Royce. I always thought it was cool to tell people I used Rolls Royce gasket sealer on those bikes Smile

The key to using gasket sealer is to apply a THIN coat so you really don't need a whole lot left in the tube. Some guys seem to think that they need to use that whole tube on one motor. They goop it on like ketchup on a hot dog Smile

Retiredgentleman · Posted: October 19, 2008, 11:40 pm Post subject: Re: Top End Rebuild

davidnj2;
After some investigation, it does look like oil was being sucked across the head gasket from the camchain tunnel. There is oil on the cylinder side of the head gasket, but none on the head side. Now that I think about it, the domed nuts on the head seemed to undo very easy! Shocked

I now suspect that the PO had the head off and did not properly re-torque the head. This seems to justify 5twins, saying we should run a bead of sealer around the cam chain tunnel on the head gasket.
The valve seals don't appear to be badly worn.

davidnj2 · Posted: October 20, 2008, 12:13 am Post subject: Re: Top End Rebuild

Hey RG, Sorry for taking so long to reply. My head gasket leak was quite obvious as the gasket was drenched thru to the cylinder. I had retorqued at 100 miles to 35lbs but I had used an after market from mikesxs. I tried permatex copper-kote on a new mikesxs gasket on the second build but now am thinking I just should have splurged on getting a Yamaha gasket. Only time will tell

Retiredgentleman · Posted: October 20, 2008, 12:41 pm Post subject: Re: Top End Rebuild

Good info there David. You probably got it right the second time.
So guys, if you were buying gaskets, oil seals and o-rings, would you buy from mikesxs,650 central or other suppliers?

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