Expansion chamber broke

[Dave Mills]

I went riding this weekend in the CA desert. I warmed up the ol' 85 500XC and took off down the road. I was fired up, the bike was running great, and pulling extremely hard. I even hit 6th gear and it was still pulling hard. Then it started to sound "different". Low and behold, i had cracked the header portion of the expansion chamber (almost 3/4 of the way around). Done for the day. The old Husky just sat there looking menacing after that. On a brighter note, my buddy asked if I wanted to ride his new 2013 YZ450F with a Yoshimura pipe, I said, "Sure." Believe it or not the the new Yamaha was kind of disappointing. No offense to anyone out there that owns this model, but it was very surprising. The old Husky was way more powerful, and even went through the whoops better at speed. I do have the Husky set up for me, but I thought the modern suspension would way overshadow that. And the power, wow! What a difference! I don't know how that works, as the new 4Ts are rated at 54+ hp. I saw a test in Dirt Rider that had the Husky at 44 or 46 hp. The new bike actually felt slow in comparison. It was great all twisted up, but low to upper mid seemed slow. The top end was good, but I can't even compare that to the 500XC. I haven't been brave enough to rev it out all the way yet. Anyway, any good ideas on pipe welding or rubber mounts that will work from a Japanese bike would be appreciated.

 

[84scrambler]

Do you know why it cracked ( rusted inside or did it take a hit at sometime or another?) If its not rusty I would let a professional tig welder have at it. If it is rusty try searching for a newer one , as far as the mounts I would think the factory ones would be sufficient as long as they are all in place.

 

[Motosportz]

Do you know why it cracked

usually on these vintage bikes it is from vibration.

 

[Big Timmy]

If its the flange area of the pipe have it Acetylene Torch welded, Tig weldings not necassary. The weld will be more ductile and maleable if done with a torch if done correctly. If any brackets or mounts are added or repaired always weld a rounded edge patch of like thickness to the pipe first then "Braze" the thicker mount to the patch plate so it spreads the load over a larger area. Otherwise if the bracket happens to break it will pull a piece of the pipe out with it. The fact you are welding a thicker section of metal to a thin section more than likely will leave an undercut weld and that becomes the weak spot. Yes vibration is the culprit. it's an 85' it owes you nothing at this point.
I've built over 300 hand rolled cone expansion chambers over the years since 1975 and I always torch welded my own with a small jewelers torch with a triple 000 size tip. I Tig welded most of my production pipes. I've repaired more than I can count. With the popularity of 4strokes nowadays the expansion chamber being hand made is a lost art nearly. I make more money doing drag car equal length stepped headers if the price is right. Thats a lost art as well but I do stuff you can't buy off the shelf.

A good example of the brazing technique and why its done is like on a set of good race car headers the flanges may be 3/8 thick with thin mandrel bent primary tubes shaped to fit the exhaust flange holes. The tubes pass all the way through the thick flange and get welded solidly to the gasket side and then ground flush and cleaned up with a diegrinder just like the gaskets. The outside of the tubes on a good set of headers will always be sealed and brazed to the flanges on the outside of the flange. I do this to all my headers with a Tig welder set up on DC straight polarity. Just like I'm welding the steel itself but use a silicon bronze filler rod instead, I turn the voltage/temp down so it won't really melt the metal itself and braze the tubes to seal them from the outside all the way around each tube. It looks just like a regular Tig weld does but No actual welding or fusion of the two dissasimalar metals has taken place. Its just got some meat around it to stiffen it up since the shear point would be where the thin 16 or 18 guage tubes stick out from the flange which is 3/8 thick or so. This can be done with an acetylene torch as well and brazing rod but the brazing bead of material will turn out much wider.

Any quality set of headers is always done this way with Tig/silicon bronze at the outside of the flanges or they are Junk. Its a sign of quality and one of the main reasons I can fetch and demand as much as $3000.00 or more easily for a set of custom drag car stepped slip fit collector headers. I won't make a set of them for less. For any custom application or chassis configuration. Period. If you cant buy them off the shelf than you will pay the price. Or the project stops at this point of the game. If its a street legal application Hot rod, I usually run the exhaust fully to the rear bumper with Mufflers for my customers all in S/S mandrel tubing and charge another 2 to 3 thousand dollars for that. Plus material costs. But it just may be the trickest thing on the entire project.

Or you can take it to a local Muffler shop and have them do some compression crushed bends for you and it could be the most screwed up thing on your entire project, take your pick.

 

[84scrambler]

Sounds like you done a few, Big Timmy. I like custom stuff too..

 

[Big Timmy]

With cheater lenses in my welding hood and a set of reading glasses I can still weld just about anything. For Example, I used to make Aluminum oil bags for Harley flat trackers and used to Oxy/Hydrogen weld them. An Oxy/hydrogen's nuetral flame ( 1800 degrees fahrenheit) is much closer to the melting point of the aluminum (1214 degrees) so it was more controllable than a neutral Oxy/acetylene flame ( 2300+ degrees fahrenheit) Yes you can torch weld aluminum. The thing is the filler rod is hard to come by ( I got a bunch of it) and the special flux makes such a brite light you have to use Cobalt blue lenses to see WTF you are doing. They don't make Cobalt Blue lenses anymore. This Oxy/Hydrogen torch welding procedure allowed the tank to expand and contract without cracking as it was soft and annealed and went through many thermal cycles with the hot oil but the mounts to hang the bag always got Tig welded on as they were thicker. This is an example of contradiction of what I posted earlier but I am talking about aluminum here.

There are different teqniques for all types of procedures. One can make alot of money doing repairs on things done incorrectly by someone else. Then one can build things with old school knowledge and never have anything need repaired by someone else. That may be the reason I'm poor and work for the Govt. LOL! The only repair work I do nowadays practically is from the Drug Cartels cutting my 38 miles of fence down to run a stolen truck full of drugs into the US. It's what you call, Job Security.

My Brain barely functions at work. If it wasn't for some of these forums I would have "No Outlet". I'm glad I can share some of these things with someone. Hope it helps out. Its like I've said before, many people can operate a welding machine, then again many should leave the welder alone and call in an old fart to do the work itself. The preparation is the name of the game. The welding is the easy part.

 

[suprize]

hunt around for an "exhaust man" and get him to whip up a new pipe like ol mate Big T said. I reckon the old aircooled pipes are fatigued and seem to always crack. im with you on the new bikes...apart from the brakes I reckon weve been sold some b*ll about the handling, I still feel more comfortable on the husky than the ktm in most off road situations.

ok, the power valves are great on the 2 strokes and the fork / shock action is better but sometimes I wonder. the husky just barges through stuff while the ktm gets all nervous and requires you to pick a careful line..

we had a "natural terrain" mx last year and few mates soon ditched their ktm 350's for the ol yz and kdx and were faster on them.

 

[Dave Mills]

Thanks Big Timmy. I too work for the govt. and need an outlet. I will try to post a pic and tell me what you think. If I find out that I have a higher GS level than you, then I will disagree with you, and look elsewhere for the answer I want. Kidding aside, I appreciate the input!

 

[Motosportz]

the husky just barges through stuff while the ktm gets all nervous and requires you to pick a careful line..

Good description of old -v- new.

 

[2premo]

George at Up-Tite makes a mean 500 pipe

 

[fran...k.]

snip They don't make Cobalt Blue lenses anymore.

Kind of off topic but this tim man tech is the rage on welding fourms. http://www.tinmantech.com/html/tm2000.php I had no idea how much the new lenses for this cost and I can't assure you the one I found is the best for aluminum as I just use the electric coated sticks for gas welding aluminum but hardly any of the flux. 4043 rod seems to work, I know I have the dedicated flux somewhere. I have moved on to steel thicker than motorcycle stuff. I don't have one but the ac tig gets more advanded every 5 years or so.


As to the Husqvarna exhaust pipes, not just the two stroke ones either, Just tig welding wih 70s6 and getting all the way to the end of all the cracks has held up. Perhaps crashing pust stresses and repairing and in some cases blowing out dents just relaxes those stresses. It certainly would help to have an inert gas inside the pipe and heat up to burn off carbon inside before actually tig welding. I was blowing the dents out with carbon dioxide and plugs soldered in the ends so it wouldn't have really been any extra steps. You don't want co2 for tig welding because of the carbon and other things but for a little back up it has to be better than air. Oxy acetylene will work, certainly makes more distortion than tig. I have done that but for the amount of crack you describe the tig would make the nicest result. A torch and bronze rod with flux and proper use of gravity can make a good repair as well without getting the distortion of going to welding temperature but looks and paintability will certainly be effected. I have not put into service this type of repair though

 

[fran...k.]

snipOn a brighter note, my buddy asked if I wanted to ride his new 2013 YZ450F with a Yoshimura pipe, I said, "Sure." Believe it or not the the new Yamaha was kind of disappointing. No offense to anyone out there that owns this model, but it was very surprising. The old Husky was way more powerful, and even went through the whoops better at speed.

I havn't ridden one but count me on the not side.

 

[Dave Mills]

It's true Fran...k, It was much slower. The new bike had much firmer suspension, but it is mx suspension, and wanted to kick sideways in the desert whoops. The new Yamaha was very smooth, where the Husky will vibrate your fillings loose, but I really only notice it when I'm stopped.

 

[fran...k.]

That business is just for amusement. Both the pipe that came on the 82.5 silver streak thing and my 1988 te 510 had a few inches of crack. Neither pipe has seemed to re crack, Probably waved a torch around a bit on the two stroke one to kind of stress relieve it. I didn't even use a backing gas for the four stroke one, that pipe is thinner than one would expect. Under BMW those exhaust rubber mounts got down under $4 from halls just a little longer. I like the mounts for a 1998 wr125 husky and have used a few in re designed applications. I also have used sections of hoosier racing tires, the tread section in other applications though not sure it is something to boast about.

 

[Big Timmy]

Kind of off topic but this tim man tech is the rage on welding fourms. http://www.tinmantech.com/html/tm2000.php I had no idea how much the new lenses for this cost and I can't assure you the one I found is the best for aluminum as I just use the electric coated sticks for gas welding aluminum but hardly any of the flux. 4043 rod seems to work, I know I have the dedicated flux somewhere. I have moved on to steel thicker than motorcycle stuff. I don't have one but the ac tig gets more advanded every 5 years or so.


As to the Husqvarna exhaust pipes, not just the two stroke ones either, Just tig welding wih 70s6 and getting all the way to the end of all the cracks has held up. Perhaps crashing pust stresses and repairing and in some cases blowing out dents just relaxes those stresses. It certainly would help to have an inert gas inside the pipe and heat up to burn off carbon inside before actually tig welding. I was blowing the dents out with carbon dioxide and plugs soldered in the ends so it wouldn't have really been any extra steps. You don't want co2 for tig welding because of the carbon and other things but for a little back up it has to be better than air. Oxy acetylene will work, certainly makes more distortion than tig. I have done that but for the amount of crack you describe the tig would make the nicest result. A torch and bronze rod with flux and proper use of gravity can make a good repair as well without getting the distortion of going to welding temperature but looks and paintability will certainly be effected. I have not put into service this type of repair though

That would be the point of brazing in the first place as this area more than likely has a network of cracks the eye can't see and broke because of the edge of the weld being under cut at the weldment. This being the weak point. All steel has a yield point and useable stress life to the point of fracture. Catastrophic failure is a bummer. Whether its just the bike sitting there for the day and having to ride a Yamahaha. Or doing a pole vault when the pipe hits the ground. The brazing would avoid getting the fatigued metal up to the point of actual weld temperature. Distortion isn't a factor IMHO. Avoiding getting the parent metal to welding temperature by brazing even if done with silicon bronze and no flux with a Tig welder if you must, as an option. The point is to avoid that critical melting/welding temperature. As the inside is full of contamanents. I have never in 40 years seen a bottle of CO2 anywhere near a Tig welder and have never used it as a purging gas either. I don't even use it to Mig weld ever.. Its for dispensing soda pop...The brazing would be better than actually welding the crack as thin as the material is and would cover any related roadmap type cracks unseen and stiffen this area up so it wouldn't break again like a collar.

I used to take my hand made Quad pipes off the bike and throw them in a brick BBQ with a bunch of cardboard and charcoal and just let it cook in the fire until it went out. Then shake out the carbon from the Blendzall film that would build up inside. I'd Just let it cook out for a few hours and let it cool slowly, scrub it down with scotchbrite and a water hose again and clear coat it with salad oil once back on the bike again while getting hot. It would stress relieve the entire pipe and I Never painted them at all. Its much easier to see any cracks without paint. The pipe would be destressed as well and I never had a single weld or bracket break on my CR500 engine I shoehorned in a Trx 250 R Honda Chassis. Keep in mind this engine combo had no counterbalancer either. Talk about vibration. I had to build a complete 4130 round tube frame after the tuning fork effect got to it after many laps around the Lodi Cycle Bowl. Subframe was the worst after a season of Flatrack and TT as it was the end of the tuning fork so to speak. I wish I still had that thing but the guy I sold it to put himself in a wheelchair for the rest of his life.

Back to the 85 Husky. The best option would probably be to buy a Mandrel U bend or J bend for building headers from Summit racing or Jegs for about $20.00 of the proper size and proper radius and replace the headpipe altogether. I keep all sizes in stock in my shop all the way from about 1 1/4" up to 3" diameter. It would be the simplest way to keep stress from causing anymore cracks and easy to do. The idea is to fix it cheap and maybe do it yourself instead of paying some guy for his Tig welder only to have it crack again. Either there or somewhere else about an inch away.

Fran...K, Thanks for the link to the Emerald green lenses those are cool. What a price huh? These being actual glass would allow grinding grit to stick like a magnet if left on the bench. Which I would probably do.That would sure piss you off if someone did that to your new 235.00 glasses wouldn't it! The town I live in had a large Phelps Dodge Copper smelter that closed in the early to mid 80's. I find some of the old Cobalt lenses around sometimes at garage sales. I also find the good old "American bridge and Iron" old gold welding lenses too that they haven't made for years for nearly nothing. Even though I now use the modern auto tint helmets I still have my old Huntsman 870 P helmets that I keep laying around. These gold lenses are about 60.00 or more if you can find them. A buck apiece here. Not like the plastic BS they have today.

Keep up the posts. Its good to here others professional opinions on welding and keeping these old and new bikes running. I don't do much research on the subject of welding on the internet but some of my studius Border patrol agents who work as welders on my crew at work do sometimes and tomorrow is one of those teaching days. Tig welding being the main focus. Only because a few guys won't be there and are off. I teach and do training as it applies because I enjoy teaching those who are willing to look at the internet and show me the pictures off there phones. It shows incentive and interest and I will go out of my way behind closed doors one on one to peak that interest.. Others I won't show anything but my trucks tail lights to. The "Lincoln square wave" with the pulse feature activated will get fired up and the training will commence. For the selected few. The rest can kiss my A$$.

If I ever get all my medical bills caught up I'm going to embark on the restoration of my Old Maico MC 400. I need a project and it's next on my list.
Achtung! It's not how we do it in Schveden.

 

[Dave Mills]

Here are some pics of the crack

 

[Big Timmy]

It looks like 3 big cracks to me and I'm wearing my reading Glasses. Clearly the Metal of this headpipe pictured has exceeded its fatigue life and probably looks more like a road map of cracks going all different directions. The paint is hiding more than you think. As I said, I would torchweld it and use a brazing rod to cover the area to patch it up and beef that area. Try to do it on the bike to get it started then remove it to complete.

The Intense concentrated heat applied from a Tig welder isn't going to help this situation at all because you will just be chasing cracks in all different directions. By the time you've done that you will have gotten it so hot you will have burned all the carbon out of the steel. It's messed up already bad enough. Thats a very sharp radius there next to the flange. An extreme highly stressed area.. I see atleast 3 cracks that are showing. If you took it off and grabbed it with a big Channelock it would twist right off.

Braze it or you will have weld burned through all the way that will be a bitch to die grind out of the inside of the header entry after filling those gaps. It will affect flow characteristics of the exhaust if not removed correctly and smoothed out after welding or brazing either one. No way around it. Paint adhesion isn't an issue if you have a network of spiderweb cracks that look like its shattered glass.

A quality new pipe may be on the list soon but it is repairable. Stock type split stamped pipes like you have are always a factory compromise and you got how many years out of this thing? it owes you nothing. It may be a wall hanger if you do buy a custom pipe just to keep the original before it gets smashed or damaged worse.

Keep in mind the inside is coated now with a thick layer of contamination (Hydrocarbons) and the biggest problem any weld can have is inclusions from contamination and Hydrogen entrapment, which can lead to embrittlement. Which is clearly your problem now. I hope my input and information helps. Personally I'd go get some prefluxed brazing rod from your local weld supply or Ace hardware store and keep it simple and do the repair with a simple acetylene torch. Its easy! Its just not worth paying somebody to Tig weld this problem as it would be wasted money IMHO.

Thanks for the photos they have alot to say about your situation. Tim

 

[Xcuvator]

I really like this level of expertise and discussion here.

Big Timmy,
I used to ride old Maicos in the Tillamook burn here in Oregon and carried a solidox ( I can almost hear the laughter) welding kit for repairing the the low track pipes on more than one Maico rider's pipe. I'm not sure what the solidox flame (propane flame enhanced with O generating smoke from burning tablets) temp is but it got the job done.

 

[Big Timmy]

I must have made 50 Maico Down pipes at least, only 3 sections total, a belly and 2 cones each for the old down pipe Maicos and a mandrel bent head pipe. I used to weld 3 pieces of 1/4 roundbar following the tapered cones on the bottoms of them to take the bashing. I'm talking all the way back to the 72' square barrels. I started cutting the frames and bending the shock mount tubes forward on the frame and moving the shocks forward on the frame and swingarm like the later models had. Then building new aluminum airboxes to fit the modified frames. That old Reynolds 531 tubing they built those frames out of was good stuff to work with. The best looking pipes were made of only 4 pieces and the head pipe and stinger. Those pipes I made had a second section angled off the belly to point them upward just past the frame hanger mount like the old Wheelsmith pipes used to be shaped like. I also made many aluminum brake pedals, brake stay arms with Spring loaded chain guides, footpegs, Aluminum coffin style Maico gastanks, both early and later style, etc. even a few gas tanks for CZ's. I also converted many of the early Radials to an up pipe design.

Those were the days man. I could take my Maico apart and have about half as many parts in the entire bike compared to a Japanese dirt bike of the same era. Everything back then on a Maico served double duty service for something else. They were very well thought out. Less to go wrong. I made a living for years repairing broken cases and other parts from Japanese dirt bikes. I could go out in the garage right now and slam my Old Maico cases with a good size hammer and it wouldn't do anything to em. Fricken bulletproof. Try that with a modern dirt bike engine.

 

[justintendo]

i use to fix my pipes likes this with braze rod and torch...i was somewhat ignorant of how good it was being a brass repair and all but always seemed to hold great for me...its pretty easy if you have the torch. have everything clean as possible just dont overheat! that pipe will disappear quick! napa in my town has 3 ft coated braze rods at a reasonable price. if you have a scrap piece of pipe to practice on that would be ideal..