Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125834
250cc bikes were soon into more trouble than they knew what to do with. The engines developed air leaks, causing seizure and general bad running conditions. Get the air leaks stopped and the pistons failed because compression was too high. Timing specs were wrong. By the time it was figured out that timing should be at 4mm instead of 6mm, you had burned up a couple of pistons. It didn't take lOO long for these riders to figure ou t that they had a one shot engine, and they feU in to a groove that kept the garage lights burning into the wee hours of the night. Trash cans were taking odds on what was going to fUl them the quickest: beer cans, or pistons with funny five port holes right through the top. When you loaded up your bike and headed to the race track, you could be assured of two things: I) Vou would win your class if you didn't fall off and you rode well or 2) your bike would break before the day's racing was done. If it broke you would be back in the garage burning midnight oil while your buddy who rode a CZ or Greeves probably set there on his duff hard-assing you about how your bike broke. He didn't have a chance to win because he was so badly out-horsepowered but he did finish. Montesa won a lot of races back then out of sheer numbers. If over half of the competitors were Montesa, they couldn't possibly all break.. So now Montesa was in big trouble. They had built a 250cc engine with a 175cc bottom end. The cylinder put out more horsepower than what the rest of the bike could stand. After you got the compression down, air leaks stopped, and engine running well, you started burning up bottom end rod bearings. The big end pin was too small and the roller speed was too fast, causing the cage to melt down. Then it was instant one piece crank assembly. Montesa didn't plan on things turning out like they did - not by a long shot. I feel they just didn't get enough testing time on the engine before they let it fall into the hands of the American market. What ever the reason was, the damage was done. The bike had acquired the repu tation of being made out of left over water pipe Left: new Montesa VR ported piston; right: old style piston. and beer cans. The fact that it was fast wasn't enough. The public wanted to ride their bike, not work on it. Making Rickmans La$.t The Montesa factory didn't just sit hack and make excuses. They had a problem and they went right to work on it. During 1968, 1969, 1970 the Montesa engine went through many changes. By 1969, Montesa had their problems sorted out When the Rickman hrothers starled using Montesa engines they were the 4-speed model with right hand shift. These engines had a new design crankshaft big end bearing and a gearbox and clulCh that would shame a diesel truck. Of all lhe 250 Rickmans that I raced then, I never had a gearbox or clu tch failure. For example, lake Andy Ozwell, who has become a very good friend of mine. Andy is Joe Average rider. Well, nol really. Andy's not the Expert racer who goes out and rides a desert race every weekend. That's not enough excitement for him. Andy's weekend begins in the desert on Friday nigh t. Chase bunnies half a day aturday; ride up a couple of mountains just to see what's on thc other side. Take a few sandwashes at full throttle for laughs; it loosens him up for the race Sunday. Or maybe load his bike up and go down to Mexico with friends for a three-day ride. After a year of this kind of treatment, Andy brought in his "fragile" Rickman and J had to bore it. The air filter worked itself loose and it sucked in about 75 miles worth of sand in a Hare and Hound. I t was worn some but nowhere near what one would think. So I bored it, put in a fresh piston and sent him on his way. This bike has not had gear box failures, no clutch problems, nothing has broken in the engine. Andy has since bought another Rickman, a five-speed. His new bike's getting the same treatment as the first - getting the hell beat out of it. r- ,SeO • • • • 11II 11II .... g .... g C(") r-.. O'l ,...., C(") ..... ~ Q) ..0 E Figure 1. Porting the VR cylinder Q) ;> 0 f z .. 1.~50 s, Stock Rickm.... brake shoes were replaced with automobile competition pads that work better longer, even when wet. Making Rickmans Fast The 1972 and 1973 Montesa five-speed engine started a whole new ball game for the tuners. In their stock form, they were a very smooth running engine but a little short on horsepower for the fast boys. However, with an engine that has a sound lower end you don't have to worry too much al>out stacking in some more horsepower. Irv Kanemoto huilt a 250cc Rickman for last years Astrodome Short Track that made most of the boys sit up and take notice. This bike was a real fire-breather. Since we were talking about IT and Short Track with these early five-speeds, maybe you have one and would like to ride some Short Track or Half-Mile. Here are a few points to think about: With the cylinder designed as a third port cylinder for motocross, it became apparent that to get the top end horsepower necessary for Short Track and Half-Mile, it's going to take a completely different top end. Vou have to have an engine that produces 30-plus horsepower to the rear wheel and ['m not talking about claimed horsepower. The real thing that turns over the rear wheel is what counts. Vou can go at it two ways, take the original five-speed cylinder and use it or you can "se a four-speed cylinder. Since you have to weld on it, it doesn't make any difference. First off, you need a new piston (old five type) and new sleeve. These can be ordered through your dealer from B.S.A. Rickman Division, Duarte, California. First step is remove the old liner, and weld up the exhaust and intake track so that it has a width of 1. 700" down the hole. The exhaust bridge and in take bridge are removed. The third port track in the cy Iinder housing is also welded up. After the cylinder is welded up, being very card 01 bore the housing and clean up the welds so that you have an interference fit of .005". This is very importan t for proper cooling. After the cylinder is bored, you're ready to install the sleeve. Now the going gets a little touchy. First step is to put your new sleeve in the freezer and go to bed. Leave it in there all nigh t long. This will put all the heat out of it. Then turn the oven on and put your cylinder in it. Set the oven to 600 degrees F. Now you beller leave the sleeve in there for a couple of hours so you can be sure that it is heated up all the way through. While you're waiting for it to' heat Reed piston Reed cylinder Figure 2. Reed valve modifications The business section of the trick Rickman VR: Bored out Bing, Kal-Gard treated upper end, DH Reed and E.C. pipe. up, set up a couple of bricks about 3-~" apart. This gives you a stand to set the cylinder on so you can install the sleeve. After your cylinder is heated up, you have about 10 to 15 seconds to install your new sleeve before it grabs up. If you don't get it in straight the first time, just reheat the cylinder and, by using a rawhide hammer, you can bump it out and then start all over again. The main thing to remembcr is to have everything ready and don't screw around. Vou don't have aU day. 1 started working on a cylinder for 33 ..