Expansion chamber broke

[justintendo]

and big timmy, i bet your pipes are gorgeous! got any pics to check out? if i lived nearby i would drop off a swede for a pipe! do you still do any 2 stroke work?

 

[Big Timmy]

You Bet! your not welding or heating to a melting point. You're brazing on top of the brazing as long as its clean it will proceed forward on its own thats what the flux does and allows you to keep working your way forward.
Nice to have someone ring in and take the mystery out of my hands. Thats what the forums are all about, fixing this stuff yourself and learning. It comes with many benifits out on the trail as well because you know you can fix it again if needed and your out on the bike again with more confidence while riding. Its called prestige. It also doesn't hurt to have an extra 50.00 bucks in your wallet either.

 

[justintendo]

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.

i have an early cr500 4 speed in pieces that we used to drag alot of newer stuff with..nothing serious, just kids on a mining road. utterly smoked a new cannondale 4 stroke many times..always did well against yzfs too. the 4 speed was tough in the woods sometimes but really was a solid runner on that road and the mini baja desert we had in western pa. only bike that i was proud of the wheelies i could do with it! running with other bikes, most reactions were "what the heck is that thing??" alum tank and the itcs in the back made it all that much sweeter as the taunts about dual shocks and fins ringing usually ended up getting pretty quiet by the end of the day!

 

[Xcuvator]

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 ones were made of 4 pieces. 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.

I love to hear old Maico talk. They were the best turning bikes of the day without a doubt. The transmission and clutch were my biggest problem. I was trying to go to college, work full time, practice/train, ride in the woods and race MX and didn't have the funds to buy the parts I needed. I remember splitting the cases during the week and installing the transmission/clutch parts that I could afford that week to get ready for the weekend.
But those were the days!

 

[Dave Mills]

Thanks Big Timmy for your expert opinion. I bet it does have may more spiderweb cracks. I have never brazed before, so I will be dropping it off at my welding guru with your instructions. I wonder if George at Uptite got the tooling to make the 500 pipes yet.

 

[Big Timmy]

The old Maico's had designed the first leading axle fork legs back in the day. I installed a few sets of Wheelsmith lower leg extensions back in the day to upgrade and increase travel an inch back then. The triple trees had very little offset between the steering stem and the legs to account for the extended lower legs with the axle mounted forward and up about 4 inches from the bottom. Everybody followed this design because it steered so quickly. Although forks are mostly upsidedown nowadays short or shorter offset Triple trees today are all the rage still. Technology from this initial Maico flat triple clamp off set and leading axle design. It requires less effort to turn having the weight back closer to the steering head. Go figure. Back then all forks had the axle straight down on the bottom of the lower legs, and almost V shaped massively off set trees, including Husqvarna for several years. The Maico fork was superior to anything else at the time from about 1970 to about 1980 and they made the forks themselves in house. They weren't outsourced. I have a stash of them. Triple clamps and all. My 77'Maico has a set of conventional 12 inch travel 45 mm marzocchis on it from a Can-Am Rotax 600 that I'm taking back off when I restore it though.

 

[Xcuvator]

The old Maico's had designed the first leading axle fork legs back in the day. I installed a few sets of Wheelsmith lower leg extensions back in the day to upgrade and increase travel an inch back then. The triple trees had very little offset between the steering stem and the legs to account for the extended lower legs with the axle mounted forward and up about 4 inches from the bottom. Everybody followed this design because it steered so quickly. Although forks are mostly upsidedown nowadays short or shorter offset Triple trees today are all the rage still. Technology from this initial Maico flat triple clamp off set and leading axle design. It requires less effort to turn having the weight back closer to the steering head. Go figure. Back then all forks had the axle straight down on the bottom of the lower legs, and almost V shaped massively off set trees, including Husqvarna for several years. The Maico fork was superior to anything else at the time from about 1970 to about 1980 and they made the forks themselves in house. They weren't outsourced. I have a stash of them. Triple clamps and all. My 77'Maico has a set of conventional 12 inch travel 45 mm marzocchis on it from a Can-Am Rotax 600 that I'm taking back off when I restore it though.

I thought the actual fork legs were made by the same company that made BMW legs (they look very similar) during the late 60s early 70s. Someone back then told me they were made by Sachs.

 

[Tinken]

I wonder if George at Uptite got the tooling to make the 500 pipes yet.

We do.

 

[fran...k.]

Ask your welding guru what hot short means and if it applies in this situation.

It wouldn't be horrible to cut that section out and fit something else in there without quite as abrupt a turn. Kx500 and honda cr500 have significantly more room before the tire than these bikes.

 

[Dave Mills]

We do.

What are your prices?

 

[Tinken]

Depends on the pipe, can you take a couple pictures so I can run them by Ty?

 

[Big Timmy]

Good idea fran...k,
I myself would agree that the term "Hot short" would apply in this thin, stressed, stretched, brittle section as the actual welding of the cracks as I said before would lead to cracking again. Add to that the possible undercut from a full penetration weld of these cracks with a Tig weld possibly left behind as it is so thin and it would likely crack again adjacent to the weld due to its inherent brittleness already. The heat affected zone after welding with any dilution of the actual unknown properties of the parent metal with a filler rod would cause it to crack and become even more excessively brittle after welding. Back stepping the weld or keeping the puddle of the weld arc or torch application of that heat on the weld itself and laying it down incrementally and letting it cool between incremental deposition of that weld would be a good idea. Just don't let it get so hot all at once. Another words If you can't touch it with your bare hands (welders hands) which are nearly burn and heat resistant, (more than some may think), right after welding a bit, Its too damned hot. Its kind of hard to explain. It can become less ductile if handled improperly. Another words you've got to know your SH(T or just avoid this and braze it, you can avoid all this possible damage of getting it to this point of heat that will actually cause more harm than good because it cools faster than it can nearly take on heat. This problem can be from its long life of thermal cycles from all the years of riding and it being hot and getting air blown at it, getting splashed with water and just out right age fatigue as we talked about before. There are just too many variables that have taken place since 1985 that this headpipe has been through. So avoid all this BS by doing the simplest thing possible. Brazing. Simply put, actual "welding" heat period can make it more brittle as it will or can cool too fast causing this brittleness. Even on something brand new the first time it got welded.

"Hot Short" on a metalurgical level is a common problem though especially on some exotic non ferrous metals made up of many alloys high in Nickel, Manganese, Copper, certain alloyed Aluminums, certain Stainless Steels, Monel and I believe Inconel as well. It can happen to common mild steel though also especially high martinsitic steels. Welding Old Train Railroad track would be a good example of this low in the base flange area on that track.

"Hot Short" is the cracking of the metal adjacent or even in the middle of the weld after improper welding technique or any welding technique right or wrong, once it reaches its threshold temperature on a molecular level during its cooling and recrystallization or solidification process after being melted and molten. Its kind of an intergranular thing. As the molecules reallign themselves unfavorably. To my Knowledge anyway. Now put that in your pipe and smoke it. I've said enough on this matter.

Best idea would be replace the section first. The radius is so tight to replace this area you would need an exhaust "Donut" ring to cut the section you would need. They certainly don't make a madrel bend that tight of a radius in that diameter but stamped half "Donuts" are welded circumferentialy from two halfs and could be had in a tight enough section available to replace this piece nearly exactly. I've had to resort to using them a few times on race car headers to get around varius obstructions. I've used them on Custom Harley pipes as well in recent applications for 2 into 1 systems. check out "The Chassis shop" I buy fittings and hardware from them all the time when I can't find specialty fabrication fittings etc. anywhere else. I think they have them. If they don't! Then try "Stainless Headers Mfg.Inc" these guys sell everything imaginable for the fabrication of SS and Mild Steel exhaust components and related hardware. I know yhave Exhaust "Donuts" check them out. They have some trick stuff. They are the best supplier and also build some of the most exotic headers you could imagine.

Or buy a new pipe and enjoy its new found powerband as the stock pipes are always a compromise.

 

[Big Timmy]

I thought the actual fork legs were made by the same company that made BMW legs (they look very similar) during the late 60s early 70s. Someone back then told me they were made by Sachs.

That very well could be. All the ones I have and have ever seen say "Maico" cast right into the side of them. Even the earlyiest ones that had external spring under the accordian fork leg boots. "Sachs" may have made them, I never heard that before but it wouldn't surprise me. They built motorcycles for years back then and didn't themselves use the leading axle design on their own little 100s and 125s though.

Of course the Ohlins forks for along time were cast "Husqvarna" also back when they started putting the axle forward of the lower legs, didn't they.

Guess where the idea came from? Pretty much "Maico" I think. More so than necessity because they worked.

 

[Xcuvator]

That very well could be. All the ones I have and have ever seen say "Maico" cast right into the side of them. Even the earlyiest ones that had external spring under the accordian fork leg boots. "Sachs" may have made them, I never heard that before but it wouldn't surprise me. They built motorcycles for years back then and didn't themselves use the leading axle design on their own little 100s and 125s though.

Of course the Ohlins forks for along time were cast "Husqvarna" also back when they started putting the axle forward of the lower legs, didn't they.

Guess where the idea came from? Pretty much "Maico" I think. More so than necessity because they worked.

All excellent points, especially regarding the external Maico springs. But don't forget the BMW forks had the leading axle forks going back to the 60s too though. :-)
Now to try to get back OT, I have noticed that some people refer to any torch welding as "brazing". I assume when you refer to brazing you are referring to the correct definition which means using brass filler rod? I was taught that welding with a steel or other filler rod is referred to as oxy acetylene welding, or has the definition changed?

 

[fran...k.]

Oh my goodness, what I was intending on getting at by stating hot short is that brazing has limited strength as the temperature gets higher. At least with the copper alloys I think of first. I do not know if that header pipe is hot enough to be an issue or not.

My way to alter that most likely would to use a section or few of pro circuit dirt bike pipe. (I did save to file some of above should I want to chase after pipe some day)They are two stamped halves welded together. It might even be possible to use/modify parts for metal hand rails.

 

[Big Timmy]

and big timmy, i bet your pipes are gorgeous! got any pics to check out? if i lived nearby i would drop off a swede for a pipe! do you still do any 2 stroke work?

I haven't done a 2 stroke pipe for many years now. I quit for along time as I got out of dirt bike riding and went through a phase of 8 and 9 second fast door slammer building and drag racing, building custom bikes again, as it took less space in my shop than a full tube chassied drag car and I could always get my money back on the bikes, unlike the drag cars or hot rods. I got back into dirt bikes a few years back again for an upperbody work out as I have had a few shoulder injuries at work. Its a great stress reliever too. it's something i can work on here at my house instead of going over a few blocks where my shop and other house is. I have a bike lift over there but haven't ever even brought or rode the bike over there. For anything. Its just something to walk out my door and play with in the garage here at my house and not have to plan a day over at my shop. I only have so many days off now that I got a real job... Govt. work sucks. Its beat me down and burned me out.

As for pictures of some of my old pipes they are all in a drawer over at my shop or in a pile somewhere. They are in the form of actual photos or polaroids as digital cameras were'nt even invented back then. LOL!

I do have the 2 stroke wizard program for 2 stroke chamber design and its pretty cool. I had learned how to calculate the port timing which is much like the events of a cam shaft and design of an expansion chamber in a straight line cone configuration like an old school race chainsaw has, by Mike or Doug Kukendahl ( can't remember his first name now) who designed all the RM Suzuki pipes for the factory back when they started calling them RMs instead of TMs. He tuned for "The King Kenny Roberts" and made all of Kennys 2 stroke pipes. I got introduced to him by John Cowgill who owned Quad Dynamics in Stockton, California back in the mid to late 80s and I used to make many production pipes for him for flatrack quads mostly. Many custom engine swaps though as well. Also made Quad swaybars, nerf bars, swingarms, flattrack adjustable lowering links for the rear suspensions. bumpsteer kits, longer front a arms, handlebars etc.. Thats a long time back. The hard part to learn was to calculate the flow of that same degree of taper of that same straight cone when you have to turn it say 180 degrees. The volume must be the same. The degree of taper must change to do this. Whew, lots of math the hard way, manually. Now they got programs for this. I did my cones from the old school projection layout technique 2 dimentional drawing to a 3 dimension layout as in a frustum cone layout.

Propably the only other 2 stroke pipe I will ever make in my lifetime will be for my Maico rebuild. Thats it. To much like work and I am going blind from too many years of this stuff. I get my fill at work. I don't do much moonlighting any more. Getting to old and busy on the weekends with my Rental properties. Which will be my retirement fund someday or sooner if I get pissed off and "Drag Up" from my Govt job. I get to be a fulltime Slumlord when I grow up.

 

[troy deck]

dang i was gona try to talk you into making me a YZ50 pipe lol i kinda need one ..quad dynamics ?? didnt they blueprint rotax trannies and build crazy rotary valve can-am/atk's do you know Daryll Smith of daryll smith race cars he left AZ about 2 years ago

 

[Tinken]

we might already have one, Ty was Mr Yamaha for awhile

 

[Big Timmy]

fran...k,
No problem bro. I like your ideas and thoughts. it's all good! Theres alot we can share. I don't mean to get you all excited or pissed off. I come from a long line of Educators. Sorry if you were offended. I myself being an actual person who has worked in the industry for 40 years doing this kind of stuff silently under a hood you learn a lot but I find it difficult to put into words what I am trying to say for a person who doesn't work in the industry. Thats all. You are not one of those people who doesn't maybe follow what we may both understand. Most people outside of the welding industry don't understand the proper Nomenclature as an example. Must of been something I should have reread and changed my wording. But thats the definition as I remember it. Again I find it hard to put into words. Didn't I say that? I tend to over explain things because I don't feel that I am a good communocator of such things. I just try too hard to let others understand the stuff thats why I have such long posts and try to be so thorough. This stuff takes time. I'm not going to mention details without explaining the details, after all isn't that what the forums all about ? Sharing information and Learning, not selling.

My Dad taught shop to junior high school (7th,8th and 9th grade) students for 38 years. I wasn't one of his students in a class room. Just all the rest of the time when I was around him. We have of course different interests. I started out with a certification for stainless steel at 15 and got a job building electron magnets for Alpha Scientific. I didn't even have a drivers license, my Mom had to drive me to work and back 4 hours later while I was still going to school. I learned how to build saddles and do custom leather work from my Dad when I was about 12 years old as he did this as a profession himself before he became a teacher and I did that full time during and straight out of high school for about 4 years and was welding at the same time until I did saddles full time for a few years... but I had muscle cars and dirt bikes and dirty hands and grease didn't mix well with leather work and I didn't make as much money, so I went back to welding full time and never looked back. My Dad made me what I am though. I could never have done what he did though having a new set of students every 4 1/2 months. First of all I cuss to much and don't have the patience he has. I might have offended someone also because of that alone. Probably do it more often than I even know.

Timmy

 

[Big Timmy]

dang i was gona try to talk you into making me a YZ50 pipe lol i kinda need one ..quad dynamics ?? didnt they blueprint rotax trannies and build crazy rotary valve can-am/atk's do you know Daryll Smith of daryll smith race cars he left AZ about 2 years ago

No telling what John Cowgill did back then. After I left Ca. in late 91'. Quad Dynamics rented space from "Jorgy's" Cycle in Stockton Ca. Thats who gave Chris Carr his first Sponsorship, "Jorgy's". Chris's Dad was the Official Starter At the Lodi Cycle Bowl.
John Cowgill last time I checked was a Real Estate Agent in the Stockton area and still is. He was a former sprint car racer and applied that technology to Flatracking and TT Racing Quads back then. He had his little shop and sponsored myself and his other riders, "Team Dogstyle"

I never met Daryll Smith but I have heard of him.