Re-sealing the KTM LC4 rocker cover
It seems that nearly everyone with an LC4 will, at some point need to re-seal their cylinder head rocker cover. Most seem to develop a leak at the left front, above the exhaust port.
Why this is such a common location is the subject of many theories, but I can tell you that a head I have in the shop right now has enough of a gap in this location between the head and cover to see the light from a flashlight thru.
The problem with these heads is that you can’t “re-machine” the surfaces without altering the cam bearing clamp load or the relationship of the rockers to the valve stem tips.
The only “cure” that comes to mind if the gap is beyond the capabilities of a sealant is to weld the low spots and re-machine the surface to the original height.
The first time I re-sealed my rocker cover was less than 2500 miles ago, just before I left for Loadedpalooza… in September.
I used Permatex because it was convenient, then I hit the road less than 36 hours after I had done the job.
Now that it’s leaking again, and I have my bike apart for other projects, I decided to think about this process a bit and do a little investigating before approaching the job.
This time around I did some research on sealants and the methodology of the job. Why did it start to leak again? Was it the sealant, the process… did I damage the wet bead during reassembly? Was it the rush to finish or too limited a cure time before going for a ride?
A few things come to mind.
1. I didn’t disconnect the ‘Y’ radiator hose from the thermostat… I thought I could get “around” it. Disassembly was no big deal, but reassembly was a PITA trying to clear that hose and not disrupt my bead of sealant.
2. I did not allow the sealant an adequate amount of time to cure. Some brands require as much as 72 hours for “best results”.
3. I got lazy and used regular old Permatex gasket maker, the cheapest cheesiest stuff on the market, only one or two steps above bathroom caulk.
The product I originally intended to use for this second re-seal was Three Bond 1211. This is a high silicone rubber content sealant that is designed for this type of application and comes well recommended. It is available thru shops carrying Tucker Rocky and/or Parts Unlimited products.
Curious about the sealants properties and best usage, I contacted Three Bond International with a few questions, and to my surprise I got not only a rapid response but additional, and what I think is very valuable, advice… more on this later.
Stuff you need or may want to buy
1. Sealant is a good place to start. I’m not going to presume to tell you what to use… we all have our “pet” chemicals that we’ve had good to mixed success with. But you may be interested in what I’ve found out... read on.
2. You may wish to replace all the copper sealing washers that are under the five (5) “center” bolts holding the rocker cover on… but they can probably be reused a few times before they are complete junk.
3. Rocker inspection cover gaskets if yours are getting a little frayed around the edges.
4. Coolant… as chances are, you’re going to lose a bit.
5. The tools you’ll need are pretty much the same ones you use for a valve lash inspection/adjustment. A low value torque wrench for the rocker cover fasteners is pretty much mandatory, as the torques are quite low and easy to overshoot with out one.
6. Some sort of cap or plug to seal the thermostat housing while the radiator hose is removed. It has a tendency to seep for awhile until after the fluid level ah… levels.
To begin, we have to do the usual… which is of course, remove everything that’s in the way.
Once you’ve gotten to this point…
You’re not ready yet.
You’ll need to remove and/or disconnect a few more parts, such as:
2. Tank mounting “doughnuts”.
3. Miscellaneous wire connectors.
4. Fan assembly if you have one.
5. De-compressor cable.
6. Upper ‘Y’ radiator hose.
7. Engine top breather hose.
Not disconnecting the ‘Y’ hose from the thermostat housing was a mistake I made the first time I did this… I didn’t want to screw around with coolant.
Trying to maneuver the cover back in to place without disturbing the fresh sealant, with the ‘Y’ hose in the way just made the reassembly job much harder than it needed to be.
You’re ready to start in earnest when you get to this point.
Now you’ll need to turn the motor over until you are near TDC-C… just like checking valve lash. This is necessary to take any loads off the cam, rockers and valves.
It’s not necessary to de-tension the cam chain tensioner, unless you intend to remove and reseal the water pump as well. Chances are that the next time I do this job, I’ll be pulling the head for valve seat touch-ups, replacing the water pump seals and ah… some other stuff.
4-19-06 Addendum: LC4 Pilot has written an excellent DIY guide for rebuilding the water pump. Click here to review it.
Even More disassembly
If you are not familiar with finding TDC-C, here is an outline of the process
Now that you’re at TDC-C, you can unbolt the cam cover. Careful not to lose the copper sealing washers under the four (4) long center cover bolts and the one (1) short one above and behind the spark plug hole.
And this is what it looks like.
One thing you need to attend to right now. OK… two things. There is a large snap ring that retains the outer cam bearing. This has a tendency to move up out of its groove in the head. Make sure that you press it back down and seat it into its groove before you reinstall the rocker cover… if you forget, you can damage the machined groove in the cover and head.
Addendum 5-30-07. It will be easier to compress this snap ring back down if the open end is at 3 or 9 o'clock.
Number two… some LC4s have two (2) locating dowels at either end of the camshaft… and some only have one. The first time I did this job, I thought I had lost the left side dowel down the cam chain tower, when in fact 2003 640 Adventures have only one dowel… surprise surprise.
It appears that in 2003, KTM changed the two bolts that hold the rocker shafts in place from 6mm to 8mm and deleted a hollow dowel nearest the cam gear. The black headed 8mm bolts are easy to spot.
And now the fun part, also known as the part I hate the mostest worstest… removing all the old sealant. Nothing to say except take your time, try not to scratch anything… and get all the old sealant off.
I use a combination of tools, a square edge carbide gasket scraper, a single edge razor blade, an X-acto knife, a plastic razor blade and finally a little acetone for those hard to scrape spots on the head.
Did I say take your time? OK… just checking.
After you’ve removed all the old sealant, use a solvent such as a carb or brake cleaner, lacquer reducer… you get the idea, something that doesn’t leave any residue, to wipe down the sealing surfaces. You may want to do this several times especially if you use synthetic oil… the surfaces need to be completely oil free and dry
Don’t forget to clean all the rocker cover fasteners now… instead of after you have the cover back on.
Is the cam snap ring seated in its groove? Do you have the correct number of locating dowels for your application?
While you’ve got the rocker cover off
1. Check the rocker arm lateral end play. If either or both are out of spec, you can re-shim them using the various sizes of available shims from KTM and get your “elephant’s feet” centered over the valve stem tips again… and possibly eliminate that pesky noise that’s been driving you crazy for the last 5000 miles. Lateral play for the rockers is 0.20mm to 0.30mm.
2. You can also look for pitting and unusual wear on the cam; the rocker cam followers, the elephant’s feet and the valve stem tips. The elephant’s feet will have oval or “rounded rectangle” shaped wear patterns… this is normal as long as they have no real measurable “depth” to them. If you are unsure, replace them.
As I said earlier, I intended to use Three Bond 1211… until I talked to Tony Tsukui, the Branch Manager at Three Bond International in Torrance, CA.
My first question was about “when” to use the product… in other words, should I assemble the parts before or after the product becomes “tack free”? Tony told me in no uncertain terms that Three Bond silicone sealants should be assembled before they become tack free.
I told Tony what my particular application was, and this is where I think contacting Three Bond was one of my better ideas.
Tony recommended that I not
use the 1211, but instead using a relatively new product called 1216E, which was developed for Honda, specifically
for rocker cover applications. It is sold in Honda dealers as “Hondabond HT” sealant.
Tony indicated that, in the rocker cover application, the 1216E now surpasses the sometimes difficult to find Three Bond 1215 as the sealant of choice
, which is the product recommended by KTM.
Tony sent me a small sample of the 1216E and I put a bead of it next to a bead of the 1211. The white 1211 is almost a liquid when applied where as the grey 1216E is very thick. After two days to cure a bit, the difference is quite noticeable in that the 1216E sets up to a much firmer, stronger consistency, where as the 1211 is softer and more pliable.
Just for fun, I also applied a bead of the same Permatex product I used the first time I re-sealed the cover. It was very easy to dislodge the cured Permatex from the metal plate I applied the sealants to… both Three bond products had much better adhesion.
Tony also sent me a data sheet on the 1216E. The “blow out” specs are much higher than anything else I could find similar data on. This could possibly cure those rocker cover leaks that have a “bit of daylight” showing thru the seams due to heat or owner/tech over-torquing warpage.
Anyway, after reading all the data on the products, talking to Tony and performing my less than objective, touchy feely test… I went and bought a tube of Hondabond HT/Three Bond 1216E
I don’t worry too much about trying to lay down a “pretty” bead of silicone… I just make sure that the entire sealing surface has a layer of around .030” to .050” thick, and then I wipe off the excess on the outside and inside edges and inside the bolt holes. The adhesion qualities of the 1216E means that I’m not too worried about any silicone inside the cover coming loose and clogging an oil “artery”.
Now that the sealant is applied, you can reinstall the cover. You have, depending on the temperature, approximately one hour to assemble the cover back onto the head from the time you started applying the sealant. You did remember to clean all the fasteners… right?
If you own an “Oil in the frame” LC4, then you have a braided stainless hose used to carry engine oil to the frame down tube. These have a tendency to be a little tight. Rather than remove the hose, I zip-tie it to the water pump bypass hose to keep it out of the way when reinstalling the cover.
reinstall the rocker cover making sure it goes down square and even onto the head…
Don’t rush this part of the job, it’s the reason you’re here in the first place!
Apply light pressure to the cover while you reinstall all the fasteners and thread them all the way in by hand.
Note the lengths of the bolts. The longer of the two left side and right side center bolts go in the holes where the dowel(s) are or would be, as the threads start deeper in the hole.
Using KTMs assembly pattern, torque the fasteners in the following order:
1. Tighten the four (4) long center bolts to 6ft.lbs in a cross pattern.
2. Tighten the two (2) right side rocker shaft retainer bolts to 11ft.lbs.
3. Tighten the remaining “exterior” bolts to 6ft.lbs.
4. Don’t forget the bolt with the copper sealing washer behind and above the spark plug hole!
This may seem like a low torque value, and you may think to yourself “If a little is good, then too much should be just right”. Consider that as the engine heats up, the clamp load can increase as much as 300%, so even a small increase in torque value could exceed the limits of any sealant to remain in place.
TA DA!!! Congratulations… you’ve done it!
Reassembly is pretty straight forward. You will need to check and possibly adjust your valve lash… instructions on how to do that are right here
Don’t wipe off any excess sealant from the outside, let it set up and leave it the hell alone. With some sealants, peeling this excess off can damage the quality of the joint seal.
If you applied the correct amount of sealant, you will have a firm 1/32” to 3/32” bead of sealant all the way around the cover.
As you only drained the cooling system from the thermostat up, you should be able to refill with coolant and be good to go with minimal need for burping the system.
It’s still a good idea however when you first start the bike to leave the radiator cap off and check the coolant flow and level. Re-check after the bike has cooled back to room temperature.
It’s recommended that the sealant be allowed to cure for at least 48 hours and preferably 72 before you start your bike
. For engines with a bit of “gap”, the longer you allow the sealant to cure before being put into service the greater the likelihood it will hold a seal.
I can’t think of anything else to add… sorry there are no pics of the applied sealant on the cover, I was preoccupied.
4-19-06 Addendum: LC4 Pilot has written an excellent DIY guide for rebuilding the water pump. Click here to review it.
9-8-06 Addendum: There has been talk of using Loctite 515 as a sealant for this application. Loctite 515 is an anaerobic sealant (dries in the absence of air) with a "gap fill" of up to .015". This gap fill limits the use of 515 for rocker covers that have little to no warpage.
If you must use an anaerobic, I would recommend Loctite 518 which has a much better gap fill of .050".
Personally, I don't like anaerobics in this application because they don't provide an inner and outer "squeeze out" that adheres and dries to provide a "secondary barrier".
Considering the amount of hot oil thrown at the rocker cover/cylinder head seam... I'll take all the barriers I can get.
Like all things... do what you want, use what you want. Run with scissors if you'd like... I'm not your mommy.
9-21-06 Addendum: Warewolf has recently resealed the rocker cover on his 2005 Euro/AU 640 Adventure and has posted some of the variations he's encountered. Those with Euro/AU bikes, or even '05 and later US bikes would do well to review it here.
To print a copy of this guide, go to the top of the page and click on "Thread Tools" then click on "Show Printable Version"
I'd like to sincerely thank Tony Tsukui and Colleen Kasai of Three Bond International for the invaluable information they provided, only a small percentage of which is included in this guide.