Question about welding the engine

[fredintoon]

I have a small crack just above the cam chain tensioner. I brought the engine to a welder and he said that he would rather have me pull it apart or other components on the engine like the rings could get messed up.

I would have to pull it completely apart because the crack is on the bottom half of the engine just below were the head splits. Has anyone welded in this area before? Do you think there is a risk of damaging the cylinders/rings?

Hi bottle,
your welder won't touch the job because it's plain ol' impossible to make a good weld in situ.
The engine has to be dismantled so that the crack can be Vee'd out and the barrels degreased in a trichloroethylene vapour bath before the MIG weld is applied.

[ViperRon]

I agree with Fredintune that it needs to be removed. I do not see where a crack here is causing a leak unless it has cracked all the way threw to an oil port. The main use of this bolt it to apply even presure on the head gasket. If there is a leak from this spot then cold weld is more than likely continue to leak. The other issue is that to do a proper weld in that spot it needs to be welded all the way arround the crack to get any strength to the weld. After it is welded the surfaces will need to be re-shaped as typically you want the weld to puddle to ensure a complete weld with no voids. It can be welded only on one side but the V would have to penatrate all the way threw and then there is the risk that the two parts would bond together if it's not taken apart. You do not need the head and cylinder welded together. When you take the parts off you may want to clean and strip the paint off the cylinder in the area of the weld and about 6 inches out. The reason is the heat will damage the paint and it will be hard to remove the paint after its burnt. Being clean metal before welding makes it much easier to clean and repaint. One other issue is the welder can see what he is doing and get a better angle on the metal on a bench. To properly weld you need to be in a position to direct the heat of the weld equally.

I am also pretty sure there will be enough heat from the process that it will destroy the head gasket even if they can weld it on the bike.

[James England]

Where the red line is where the crack is on the bike... sorry I don't have an actual picture of it and I'm too lazy to go take one.

Mmm... I'm too lazy to comment further then, I'm afraid.....

[thebottle]

Yeah, it definitely leaks from here... quite a bit for not having any pressure. And the previous owner already tried the JB weld but it leaked through it so I guess I will be tearing it apart.

[crazy steve]

If the crack is all the way through (and it probably is if it's leaking), you might try removing the nut, pulling the broken piece out, then clean eveything really well. Goo it up with sealer, then reinstall it. Worth a try....

[thebottle]

Yeah, I would but I'm worried that after all the work it will leak through again... and I'm going to be repainting it so I don't want it to ruin the paint once again.

andreashweiss said he has a good cylinder jug for not much more then it would cost to weld this one so I will probably go that route. I was leaking a quart of oil every 1,000 miles on my last trip. I find it hard to believe that much would leak from such a small crack in a place with no pressure. Even though I have good compression I am guessing it was leaking from the head gasket so I most likely would have been taking off the top half anyway. And since I am tearing it apart I might as well get the valves ground, etc. I'm done taking shortcuts with it. It just about broke me having to work on it all the time my last trip. I'm planning on taking another trip this summer so I want to do it right.

I was only dissapointed that it couldn't be welded because I was hoping to be riding it by the end of this week, but I guess it will just be a couple more weeks before I get it on the road.

[mharrington]

If you can replace the jug that would be a permanent repair. The oil is pumped thru gallies to the top of the engine to lubricate the cams and such. When running back down to the pan its going over your crack. My bike would leave a puddle on the floor and dripped on the exhaust. The permatex sets up faster than JB. Thats important as even though I blew air into the crack to push back any oil it will weep back into the crack. The RTV began to cure before the oil could contaminate it. Regular JB takes too long. Good luck.

[trbig]

I've had an engine case welded on considerably after I messed it up in a crash. I did take the motor out for the guy, but no disassembly was needed. Aluminum has a much lower melting point than steel, and the amps that would be used to do the welding would not weld your steel rings to your steel cylinders. The grounding strap should just be kept close, not on the other side of the motor. And I don't know if you were talking about the oil on the outside of the motor or inside, but it would be a pretty fancy trick to get oil to ignite inside in a place that no new oxygen can readily get to to sustain it.

That all being said, that crack is all the way through the metal. The top of the crack is being exposed to oil. You are talking of welding only one side (Bottom side) of a crack. You may be able to get this structurally stronger with a weld, but with the top still being exposed to oil, it's still going to leak out between the cylinders and head. Plus, if welding up the sides of the crack to the top of the cylinders where it meets the head, you're likely to get a set of cylinders welded to the head.

Your best bet to fix those would be disassembly, getting it welded properly, then regrinding the mating surface, but a new(sed) set of cylinders honed with some new rings seems like it would be cheaper/easier. Even better, a whole motor?

Just my 3 cents worth.

Mmm... I'm too lazy to comment further then, I'm afraid.....

And Mr. England.. that was pretty dang funny.. lol.

[ddragon63]

I've had an engine case welded on considerably after I messed it up in a crash. I did take the motor out for the guy, but no disassembly was needed. Aluminum has a much lower melting point than steel, and the amps that would be used to do the welding would not weld your steel rings to your steel cylinders. The grounding strap should just be kept close, not on the other side of the motor. And I don't know if you were talking about the oil on the outside of the motor or inside, but it would be a pretty fancy trick to get oil to ignite inside in a place that no new oxygen can readily get to to sustain it.

Normal I don't like sticking my nose in peoples opinion but as I make a living in the welding industry I have to correct a part of your statement... Aluminum take a TON of energy to weld properly. you are correct that Aluminum itself has a lower melting point than steel Roughly 660 deg is the melting point of rough aluminum. BUT there are layers of Aluminum oxide in Aluminum that you have to break off and melt during the welding process. Aluminum oxide melts @ around 2000 deg. if you do not have enough energy to melt these layers of oxide during the welding process you will not get correct penetration of the filler material into the base metal. Thus the weld will crack out as soon as it is subject to any kind of stress or heat change.

As an example the base metal here is an aluminum engine block. Lets say its 1/8 of an inch. It will take about 160 to 180 amps of Hi-frequency AC current to properly weld that with a TIG welder. 160 to 180 amps standard AC current is enough to weld 1/4 to 5/16 steel with an 7018 AC stick electrode.

I'm not trying to be an a@# here I'm just trying to state the facts of welding processes. Carry on

[trbig]

I'm not trying to be an a@# here...

Sure you are! But I stand corrected. Carry on.

[ddragon63]

As I've stated before if I were doing the repair as is in place I would use an "Aladdin" type aluminum oxy/ace gas filler rod. This way your using heat instead of current to fuse the filler material into the base metal. You would then be basically brazing the crack. This type of filler rod melts @ about 575 deg and has and elastic strength of over 30,000 psi. Food for thought.

[CaptonZap]

I'm not trying to be an a@# here I'm just trying to state the facts of welding processes. Carry on

And I'm not trying to be an echo, but in the interest of full disclosure, the temperatures you quoted are in Celsius.
Carry on, oon, oooon. CZ

[ddragon63]

And I'm not trying to be an echo, but in the interest of full disclosure, the temperatures you quoted are in Celsius.
Carry on, oon, oooon. CZ

Yes it is.... Thanks for the disclosure

[mharrington]

What if- The jug was removed and then welded/trued up flat and correct. Can the rings be reused? They would be going back into their perspective bores. IIRC piston rings are hard to find for our bikes. (And $$$)

[trbig]

Yeah, in that case I personally would just re-use what I had unless it was high mileage already. Even if high mileage, good oil changing will help things a lot, so you're better off doing a ring gap check to make sure where you stand wear-wise. BUT.. you aren't going to get those rings in the same position they had been running, so I would still get a light hone done to the cylinders before re-installation.