1. Husqvarna Motorcycles Made In Sweden - About 1988 and older

'73 Cr125 (long)

Discussion in 'Vintage Restoration Projects' started by Parh 474, Nov 25, 2010.

  1. Parh 474 Husqvarna
    AA Class

    Location:
    Newbury Park, CA
    Husqvarna Motorcycle:
    '73 Cr125, '06 Cr125/144
    Other Motorcycles:
    Ossa, Bultaco, Puch, Maico, AJS, Yam
    A long time ago, I raced motocross. I had a 1973 CR125 Honda, but one of the guys I raced against had a Husky 125. He and/or it weren’t very competitive, but I really liked the look of it. Fast forward about 25 years, and my wife sticks her head in the garage and says, “Are any of these bikes race-bikes?”
    “No why? I sold the Bultaco to my brother in Australia, after our first kid was born”, I say.
    “I was just thinking that the kids should be able to see you race.”

    Yessssss. I knew I married the right girl.
    So I immediately placed an ad in the Husky Club on-line classifieds (that’s how long ago this was) for a ‘73/’74 125 Husky. The thought process was that I would be safer and more competitive on a slow Classic 125, and the AHRMA rules allowed the later ’74 in the ’72 and earlier class because it was essentially the same as the ’72.
    I ended up with a bike and a half, all in pieces. It showed up on my front porch in a couple of rounded cardboard boxes. I called the feller later and he said he realized it might be a problem when he saw the UPS man rolling the boxes to his truck. But all the major components were there and amazingly not too beat. Whoever had this bike rode it a lot, because the pegs were hanging down, and the paint was worn, but the stock bars and levers were there and straight. In my spare moments at work I compiled lists of the things I would need to make a trick classic 125 racer. I got my brother to send me a Mikuni carb, some forks he found in the dump, along with an alloy tank, and some really nifty alloy Betor handlebar clamps to replace those dopey U bolts that Husky put on the original. I impatiently bought a bunch of stuff from Matt Hilgenberg of Speed n’ Sport, and parked it in the new cabinets I built in the garage just to do this project right. I tore the carcass apart and started cleaning parts, I bought service manuals and, and, … then it all just sat there. I had a dozen excuses, I couldn’t recall which street the sandblaster for the frame was on, I misplaced the Husky Club newsletter with the frame color info, the clutch hub was not perfect, none of them real reasons. I think maybe I was nervous about going into sacred Torsten Hallman territory. I’ve had his signed Mr. Motocross book since it was new and knew it front to back. I used to have the attitude that anything European was better- drank Beck’s beer, drove a VW, listened to Kraftwerk and PFM; but this was the real thing, a Husqvarna. Even if it was a 125.
    I bought some more parts, notably an ’80 lower end with the idea of sticking the later clutch in the early 125. It might have worked, but would have meant finding odd size bearings and grinding away a bunch of the clutch cover. The one part I don’t have a spare for. I also bought a Dremel tool with the right angle attachment so I could port it to Nils Arne Nillson’s specs in the 1974 Popular Cycling Hop Up article. Even with some modifying of the right angle attachment it didn’t fit in a 125 barrel. So it sat some more.
    So I did what any reasonable vintage bike guy would do, I bought another bike. My wife said it was OK. I think it was my Father’s Day present or maybe Valentine’s Day. So I got all obsessed with an Ossa Phantom for a good long while, and started racing that and doing pretty good, and decided I needed a 125 racer.
    At this point I declared to myself that it’s a race bike and not a sacred site, and slapped it together to see if it would start. It didn’t. Up to that point I had thought of myself as a pretty good mechanic. I was a VW tech for awhile, I could replace a Honda Cr125 trans after school and still go riding before dark, and here this thing wouldn’t start. It was virtually new- new piston, new bore, new PVL ignition, rebuilt carb with new jets. It had spark, gas, OK compression- kind of weak, but it was a 125 with a new bore and ring. After swapping complete top ends, and ignitions, and carbs around without success, I started measuring things. I realized the piston was not coming up to the top of the barrel. With the stock base gasket it was .230” short of the head, the little paper in the Wiseco box said it should be .030”. The stroke, or something, was practically a quarter of an inch short! I used to get .020” milled off the head of a 125 and could feel the difference, and this was ten times more than that. All I can figure is that the crank bore is south, and the base gasket surface of the cases is north. Very odd.
    So I did what any reasonable vintage bike guy would do, I sent it to a pro. In my trolling the internet sites, I came to the conclusion that J.P.Morgen of San Francisco is the Husky 125 man. After telling him my bike’s story, he didn’t have an explanation, but it didn’t matter, because it was going to get a new longer rod, and a new 1979 Honda piston with a spacer under the cylinder. The stock rod is a weak point in this bike. Three of the four motors I had, had blown lower ends, the fourth had the magneto nut twisted off the wrong way, so a new crank was in the plan anyway. J.P. Morgen was saying that with the longer rod the piston gets a little more hang time as it passes over center at the top and at the bottom of the stoke, so it has more burn time at the top, and more fill time at the bottom. He was saying this rod is 78mm long (I think) and the new KTM 125 is over 100mm long. Also, in the Nils Arne Nillson article they were modifying the exhaust port by welding in a little ramp to compensate for a big step in the port. This was to help eliminate turbulence that kept the expansion chamber from doing its job of keeping the fuel charge from slipping out the exhaust before the piston seals it off. Husky recommends it in a technical bulletin. J.P Morgen did a much nicer job than the article and also narrowed down the exhaust spigot itself. He said even a two cylinder TZ250 exhaust port isn’t that big. Strangely Husky did the same thing a few years later with the 125 GPs. He then ported it to the specs in the article, more or less.
    I got the crank and top end back in reasonable time, and stuck it all back together with the carb as close to the cylinder as the mounting would allow. I had to cut some fins and find a pull choke arrangement to replace the lever. The choke came off of some weird oval bore Mikuni that Gil the parts guy had in a box. Then I had to adapt the Mikuni to the Husky air cleaner. I ended up with a hose from a boat supply place that I modified to fit over the carb and into the air cleaner bell.
    Its fun going around to all these places trying to explain what you’re trying to do, and hoping they’re willing to help out. Some people are like, ”Yeah, whatever.” And others really get into it, and want to start brainstorming with you. And still others look at you like you just landed from another planet- usually the younger or foreign guys. “You got what? And you want to do what? With that? And you want what?” They make me feel like I’ve got some kind of habit I shouldn’t be discussing in public. Maybe I do, and maybe I shouldn’t be.
    Anyway, next step was a pipe. Based on dimensions from the same magazine article I had ordered some cones and pipes from Aircone in Nevada to make my own pipe. This was back when the rules said only two cones- one ascending cone and one descending cone. Just like the bad old days when Bassani was the trick unit. But my plans had two ascending cones, so I got the engineering whiz at work to calculate the volume of the two cones and translate that to one cone, and that’s what I ordered. The whiz at work had Pro Engineer software but he did it with Microsoft Excel. After I got my cones back, AHRMA changed the rules to allow two ascending cones on Classic 125s. Apparently a Husky guy convinced them that they were outlawing the stock Husky pipe, so they made an exception. So I cut up what I had and made a pipe. The first ascending cone is a curved tube with long triangles welded in. See photo. It tucks in well enough that it doesn’t need a heat guard. Although I do have to be careful on the starting line when I’m straddling the bike with my feet down and pushing the bike around. I got an YZ 80 silencer off of ebay. I had to swap the end caps around to get the mount in the right place. Otherwise it miraculously fit right on.

    Almost all of the hardware is stainless. I asked the guy at the industrial hardware store if they sponsored vintage motocross racers, and he just laughed and said, “Why? You buy all this stuff.” Well, yeah, but that’s not the point.
    I made pegs using the stock base and welding on peg wideners. They bent first time out. I didn’t even fall off. It’s now got later stock Husky pegs off of ebay again. I had to cut the grippy teeth back to allow them to fold up. I can see that if I were to crash hard enough on the right side the peg could actually break the side case by smacking the shifter pivot. Someone pointed that out on a website discussion board. Useful thing that internet is.
    On another discussion board I got into a conversation with Dirk in the Northwest. He was adding foam to the seat in an effort to get weight forward to make a Husky turn. Seemed to make sense so I added half an inch to mine when recovering the seat. If it turned any better, it still wasn’t very good. I was racing it and would find that my feet were bouncing around on the pegs because I couldn’t get my weight on them. That made the front end feel vague and hard to place. The front end actually washed out curving onto a fast straight and dropped me on my head, blurring my vision and scratching my new Arai. So much for safer Classic 125s. I started making measurements of my Ossa, which handles great, and comparing them to my Husky. The tank and seat turned out to be farther away from the handlebars due to the big single tube backbone frame. So I moved the tank forward an inch and a half and bolted the front tank mounts straight into the steering head by using threaded inserts. I cut a chunk out of the front of the seat base and moved the rear mounts back as far as they would go. I added a one inch piece of closed cell foam under the stock foam and recovered it. Now it feels more normal in a turn and I can weight the pegs. The front end will stick better in the corners and both ends will break loose at the same time.
    I also got a later swingarm off of ebay, and cut the front pivots with the needle bearings off and welded them onto the stock arm along with an extra inch and a quarter- kind of a jury-rigged MAG swingarm. Now the wheelbase is 54” and a bit, instead of the stock 53”. It’s got the 2 rib 7” travel Husky forks that actually don’t work very well. I found some 30 wt. fork oil for a Harley to replace the 20 wt that’s in there. I also put an early 250 front wheel on that has a larger diameter than the stock Leleu. I got the brakes relined with a woven material and when I first tried it, it barely worked at all. What a disappointment. I arced the shoes to the drum by using chalk and a file, on the recommendation of Ossa/Husky friend. Worked a little bit better. I then lengthened the brake arm on the hub, and it’s now barely acceptable. The answer is to send it to Vintage Brake and get it relined and arced to the hub. But that’s time and money. I did that for my Ossa, and it is a big improvement. The Vintage Brake guy claims it will rival early disc brake performance. I think that just isn’t saying much for early discs. It is getting better as it beds in. I skidded the front wheel down a hill at the races. That scared me into going faster through the corner at the bottom of the hill.
    So I painted the blue alloy tank I got on ebay the stock Lion Yellow with stickers from Eurodirt in CO, and went to the AHRMA National in Arizona. My Chinese friend from work helped drive out from Los Angeles, and we camped out the night before. We met a cool CZ guy from Tucson around his campfire, and he got all interested in my friend because he’s from China. I learned new things about the guy I had worked with for five years. The next day I lined up on a grid of over a dozen Classic 125s. Almost all Huskies and CZs. I don’t recall them being so popular in 1972. My theory is that they’re the only bikes with transmissions that have held up. The gate dropped and I holeshot my first moto and led for a lap or so until some fast guy went shooting by on another Husky. Apparently the motor work is a success. I finished third overall for the day. I’ve also been racing the SVRG series and took the Classic 125 Int championship against no competition, so it’s not really anything to brag about. They gang all the odd classes together in the first race of the day so I get to race 50 yr olds on BSAs and oval barrel Maicos, Hodakas, 14 year old girls on Cr85s, and 15 year old hotshots on Rm125s. If they make the kids gate separately I can usually beat them all to the finish.
    Along the way I felt that the motor wasn’t making good power on the top end. I was at the Carnegie and Tulare Nationals and I met a guy with an AT-1 like I had as a kid. I started chatting and he turned out to be a motor builder/road racer moonlighting as a motocrosser. Scott Clough sounded like he knew what he was talking about and more important than saying the right things, he didn’t say anything that sounded wrong or wacky. Sometimes a person can sound like they know what they’re talking about if they read enough magazines, but will give away their inexperience by saying something off the wall. So I sent him a diagram of my ports. He called back and said that I must have measured something wrong. No I said, that’s what it is. He said my transfer ports were way too high and that I could go bigger on the exhaust. He said we could use epoxy to lower the transfer ports, just tape up the port on the bore side and slither some goop down there then using the porting tool get it to where it should be. And if it didn’t work, burn it out with a torch. Well, OK. After that, and straightening out the intake port and raising and squaring up the exhaust port and a fresh bore, I took it out and it worked. It was faster all though the powerband, more middle and a top end that kept going. I also started to start in first gear, where I was starting in second before. I had been hesitant to just drop the clutch for fear of bogging so I was slipping the clutch and not getting the advantage of starting in second. Starting in first solved that.
    With motor and starts sorted out I started winning AHRMA Nationals in the Intermediate class. I went to the minimum number of Nationals I could get points for and ended up meeting a great bunch of people.At the finish line of the last moto at Tulare my kids and my friends shared with me winning a National Championship.
  2. dumbdotdog Husqvarna
    AA Class

    Location:
    Reno, NV
    Husqvarna Motorcycle:
    70 360 74 125SC 74 250MAG 81 250CR
    As you allready learned, 74cr used a long rod, 72-73 and 74sc used a short rod, pistons were not interchangable, 74cr cyl had larger ports with updated exhaust port, Pic of my motor with 74cr cyl. and internal motoplat. [IMG] [IMG]
  3. Parh 474 Husqvarna
    AA Class

    Location:
    Newbury Park, CA
    Husqvarna Motorcycle:
    '73 Cr125, '06 Cr125/144
    Other Motorcycles:
    Ossa, Bultaco, Puch, Maico, AJS, Yam
    Nice! You've got the best of everything.
    Attached is a picture of my exhaust port modded by J.P. Morgen
    [IMG]

    Uploaded with ImageShack.us

    [IMG]

    Uploaded with ImageShack.us
  4. dumbdotdog Husqvarna
    AA Class

    Location:
    Reno, NV
    Husqvarna Motorcycle:
    70 360 74 125SC 74 250MAG 81 250CR
    That exhaust flange is a work of art, your port is similar to the 74 cr, probably larger. The thing in common is that they both delete the drop-down step at the bottom of the port.
  5. Parh 474 Husqvarna
    AA Class

    Location:
    Newbury Park, CA
    Husqvarna Motorcycle:
    '73 Cr125, '06 Cr125/144
    Other Motorcycles:
    Ossa, Bultaco, Puch, Maico, AJS, Yam
    The port in the cylinder is really big, but the spigot is smaller

    [IMG]

    Uploaded with ImageShack.us

    Chord means straight across port- not wrapping around the cylinder wall.
  6. Parh 474 Husqvarna
    AA Class

    Location:
    Newbury Park, CA
    Husqvarna Motorcycle:
    '73 Cr125, '06 Cr125/144
    Other Motorcycles:
    Ossa, Bultaco, Puch, Maico, AJS, Yam
    Pipe dims based on a 1974 Popular Cycling article covering Nils Arne Nillsons' GP winning bike.

    [IMG]

    Uploaded with ImageShack.us

    All measurements are I.D.