Nicked up my Magnum Crank Case -What do do?-

[Cary Cooke]

Completely restoring a Stihl 038 Magnum II and all was going well till I dropped the case on a Vise and it Nicked up
opening for cylinder. I dont want any compression leaks so I would like to fix. I do work for a fabrication shop so I could tig the spot up and grind down but I dont know anything on magnesium if that is what it is? Should i use the epoxy JB weld then form it back into shape? Just looking for suggestions thanks in advance.

 

[stihl ms]

Oh man, maybe you could try sanding any high spots carefully first. Then try putting a small amount of rtv in that area when you assemble the case. Somebody with more knowledge will chime in.

 

[s sidewall]

As said, remove hi spots and motor seal, or do a base gasket delete.

Steve

 

[Deleted member 117362]

Like Steve said. Use Motoseal even if you use a gasket. Let it cure before running your saw. Removing a cylinder after using Motoseal makes it seem like you could run it without bolting cylinder down, that said, I do bolt them down.

 

[alfbolin]

I would only try the tig as a very last resort. Too many variables. I am not familiar with Motorseal but that does not mean it wouldn't be perfect for the task at hand. In the past I have used a dremel with the tiny cutoff wheels To cut a couple of very small , fine grooves in the base metal before adding epoxy type filler to a void area subject to pressure to keep the repair material in place. There is a metal based filler sold at some welding supply houses that is sort of a non ferrous metallic based jb weld type stuff that is machinable and blah , blah, after curing that works pretty good at filing divets but something a little more pliable after curing would likely work better. I am imagining Motorseal to be something of that nature. Tig could likely be done if one had a sample piece of the same material to set up the settings with. Hard to tell what is going to happen til you light up on most any non ferrous unknown base. Sometimes the damage from that learning curve can be pretty adverse to the repair goal.

 

[alexcagle]

That's not really that bad, IMO.
File off the high spot, or tap it back down gently, then use a bastard file to make sure it's flat as possible.
Just use Yamabond #4 on the base gasket, and fill the spot. Warm it overnight. Done.
If you use it on a gasket delete, you can start it up almost immediately.

Motoseal sucks on chainsaw cylinder gaskets, if you ask me.
It will dissolve when exposed to gasoline.
I had zero luck with it, and yes, I used it as suggested. It may be good for gaskets, but it won't seal a gap like that, or on a base gasket delete as well as Yamabond #4.
You can get it on eBay for around $13.00 shipped. It is awesome stuff.

 

[Cary Cooke]

That's not really that bad, IMO.
File off the high spot, or tap it back down gently, then use a bastard file to make sure it's flat as possible.
Just use Yamabond #4 on the base gasket, and fill the spot. Warm it overnight. Done.
If you use it on a gasket delete, you can start it up almost immediately.

Motoseal sucks on chainsaw cylinder gaskets, if you ask me.
It will dissolve when exposed to gasoline.
I had zero luck with it, and yes, I used it as suggested. It may be good for gaskets, but it won't seal a gap like that, or on a base gasket delete as well as Yamabond #4.
You can get it on eBay for around $13.00 shipped. It is awesome stuff.

So does Yamabond#4 harden or is more like a gasket sealer type materiel?

 

[Cary Cooke]

Also if I use some kind of sealer you are saying to remove gasket? Thank you all for helping

 

[Deleted member 117362]

Yamabond #4 Yamabond 4 Motorsports is a silicone based liquid gasket that fills gaps on a flange surface and prevents leaks. When cured, this product forms a rubber-like body that resists heat and seals joints subjected to high temperature. Gear and engine oil resistant, Yamabond 4 Motorsports sets in 60 minutes. Not for use on copper or copper-based alloys.

 

[Deleted member 117362]

Motoseal

• Ideal for use on frequently disassembled engines and two and four cycle engines
• Fully seals within 20 minutes
• Forms a tough flexible bond that is highly effective on irregular and uneven joint surfaces
• Withstands temperatures to 350F continuous, 400F intermittent
• Resists gasoline and other damaging fluids

 

[Cary Cooke]

Motoseal

• Ideal for use on frequently disassembled engines and two and four cycle engines
• Fully seals within 20 minutes
• Forms a tough flexible bond that is highly effective on irregular and uneven joint surfaces
• Withstands temperatures to 350F continuous, 400F intermittent
• Resists gasoline and other damaging fluids

Hmmm well there has already been a contradiction on the resisting of gasoline? Might have to way out the options a bit more

 

[Gugi47]

Somebody suggested here. Take it to a welding shop for TIG welding.
That is 100% and no problem after.
Good luck.

 

[Deleted member 117362]

Hmmm well there has already been a contradiction on the resisting of gasoline? Might have to way out the options a bit more

I could put a small amount of motoseal on a piece of metal, let it cure and soak it in fuel mix to see how it reacts, then post a picture. I know when used on base to cylinder bond, it is hard to remove and must be scraped off with effort. Sure, someone has had other experiences with it and may not care for it.

 

[Deleted member 117362]

Also if I use some kind of sealer you are saying to remove gasket? Thank you all for helping

Either way. Some people want a base gasket delete, some cut the base and use gasket. Doing that you must check squish, good idea anyways.

 

[rocketnorton]

that would be the easiest tig job on chainsaw parts ive done. worst part would be filin or machining weld down flat/square.
Id suggest gasket & 1104 or similar, 24hr set, vac/pressure test, if u don't wanna weld

edit. just reread the op. it is mag. you'll need mag rod. needs CLEAN b4 weld. much like weldin alum, otherwise.

 

[deezlfan]

My worry would be getting good flat surfaces after it was welded. Suppose that anyone with the skills to weld it probably has the equipment to make it flat too.

I wouldn't use RTV. Contact with fuel turns it to jelly. MotoSeal and the other crankcase sealers work just fine.

 

[alexcagle]

I was using motoseal for about 3 months, until some came in for service, and I noticed leakage on several.
Never have had Yamabond leak, and that's in hundreds of cylinder base gaskets, including some base gasket deletes.
I'm not saying motoseal doesn't have it's uses, but I've found Yamabond 4 much more user friendly in a chainsaw.
Motoseal does have a nice smell though...

 

[Cary Cooke]

That is what our best tig welder said is that it is such a small area and such a porous material that it would burn off at first more to start a puddle before he could build it back up and he thought we might think of another route before tigging.

 

[Cary Cooke]

Ok guys here is my honest opinion and what I am thinking of doing until someone gives me good proof of why not to do it this way but i was going to clean it, scuff it up, and build it back up with JB Weld then machine it back down flush and then use yamabond #4 on it. Im not sure to do just use Yamabond and squish or to use a gasket and yamabond together. This vid got me wanting to try the jb weld (original)

 

[burnses]

ill give ya the farm fix and the supreme sleep at night all the time fix....not that the farm fix is lame just different....you likely have a burr that will keep the cases from flush but you have a gasket but still should lap file or get rid of burr or high spot on gasket surface of case half...the jb weld deal will work just fine I would use hyomar as a gasket dresser...I don't like it on everything but it moves and stays soft....finial answer...bolt the cases together and have your or a machine shop fly cut the deck or cylinder mating surface till the "dent" cleans. use a thicker gasket or mod piston top for squish to correct. Next person to build will be totally miffed and confused but who cares...no weld im not a pro welder but can be hard to do edges like that with mag....might have to make some small adjustments and will likely lower the cylinder bout .030-.050 it looks like to clean that gash...that's just my take on it good luck

the can