Cycle News - Archive Issues - 1970's

• .• • • • ENGINE HORSEPOWER CURVE Customer Tom Gille Bike RickN.R. Displacement 25Oc:c Date Various a.m./p.m. - . I e 1011 ...--. c<') O"l -_ .... - I c<') ;---1'"" ... S ~ ,. :> 0 _.- -- .. . , - I . : -,, - , - '. , -- - i .. -_0- _i I , _ ; I i : 1 ...,- -- , 17-. .WI' ,. 'I ~ --rA. 1 i W ! i U)a:: _.L.-"- I I I ~ I~, i ' ~ ~ /0 ;. I I . -I--r: I I ., >-- - :5~ I 1 LL- L 'I : I I ,; ~ : I J...I I fl I I I i , , : I , I , , I .L. ' I ! "';"--+0-- , , I I I , , I - H-, - I I I , r I I I I I I I ; I I I I !. I ! I I : . I , I I I I , I , I i i .-...- I ! I , I 'I, , I , I I - j 'I '/1 ; I .. . '/1 !I 1/ I I I , : ! ----~-I-- 'I ' , , , I I I -~ - " '. • -STOCK Steve PoneJeit six months ago. Steve is still in a cast and in no hurry for it, good thing for me. I've wasted three sleeves, built a truckload of pipes, used every carb I could lay my hands on and, so far, I haven't reached the goal I'm looking for, but I'm close. I want a SOoplus HP engine out of this one. If you grind your new dream cylinder to the indicated specs (Fig. 1) and make a manifold for a S6mm Bing carb, you will be close to that SO HP figure. This cylinder on a motocross bike just won't handle it. It's way too hard to ride. Larry Watkins rides a 250 Rickman for Triumph-BSA·Norton-whatever. I did everything in the book to this bike to try and get top end horsepower with adequate torque on the bottom end. Everything I did resulted in a big fat zero. In final desperation, I decided to build the engine with a reed-valve. This was the magic touch. I dido't want this engine to have a reed-valve because of the hassle. You have to keep a closer watch on a reed engine than you do a piston port engine. The reed petals are like spark plugs. When you go to race, you change them so they won't break up. I use D.H. reed assemblies on all of my reed engines. Dale uses a fiber phenolic material for his reeds and if they break up, they won't hurt a thing in the engine. I feel they are much better than steel reed petals for this reason. For your reed valve 250 Rickman engine, I advise that you use a five port piston instead of the piston that is in it. -... I ! i i j -: 9i at i IT! 1/ -l---~ I I 1 I I! -, - 4 - - . ill I i i I I -----. 'I +-_.LL __Lj ~ --, 1 ] ~ ; I _lI I ~_. 1~il _LL~ _ L--<._ .r .. .- I TTl , I\. , _-"_-if - .- I ~~ II . I I I I I I ; , I ~~-- ~o;-a:: I _ .•.•_._ -: , -L.._ __ . Z -+ I I I t -. I _.1 __ •. --_ ... _- ~ .0 j J -. , . I r--. • 34 rear are: Gear 1st 2nd 3rd 4th Primary 13 15 17 19 Secondary 24 22 20 18 Ratio 1.846 1.466 1.176 0.947 5th 20 16 0.800 These gears are spaced just about as perfectly as you can ask for. Tom Culp had the problem of spinning a f1ywhed key on the V.R. he tested and the V.R. Rickman we tested did the same thing. Tom's cure was take a gentle five-pound hammer and pop it a few times to set the flywheel (Well, maybe not a five-pounder. He is not quite_that "batchet. ") But for sure you will have key problems if you're not cool. So torque that flywheel nut down to 72.5 ft.-Ibs. and you won't have a problem. Cylinder base nuts at 11 to' 15 ft.-lbs. Cylinder head nuts 22 to 25.5 ft.-Ibs., and the clutch plate nut 14.5 to 18.0 ft..lbs. for the rest of the engine screws and nuts, just use common sense. The factory says to set the timing at Smm B.T.D.C., but we have found, with our better grade of fuel, through dyno testing that S.S to 3.5 B.T.D.C. will produce the beat horsepower output. The dry weight of the Rickman 250 is 212 Ibs. These two bikes that are built into trick bikes weigh 195 Ibs. with a quarter tank of gas. They have been put on a very strict diet plan. As you can see by the dyno chart, the V.R. engine produces 26 horsepower at 7,250 with peak horsepower 26.5 at 7,850. The stock engine has a very wide flat powerband. Now dynos are all like women: some good, some bad. My dyno is a water brake pump and reads horsepower off the rear'sproc ket, or what is better known as "rear wheel" horsepower. It has been checked for accuracy and tells it like it is. I've dynoed many 250cc bikes that just barely make it over the 20 horsepower mark. A SO horsepower 250cc bike on my pump is almost impOSSlble to achieve. So what does this all mean? It means that to improve over the stock Montesa engine is very hard to do and it should not be messed with unless you really know what you are doing. So ride it. With this kind of horsepower curve, you can win with it stock. The Trick 250 Em.-ges '1)j 100 8(jDO 104 100 RPM '" - REED This piston doesn't have the third port in the back of it. I feel the horsepower is probably better with this piston than the original, but I've never had time to back it up with any dyno proof. When I dyno-ed Larry's bilte, I just didn't have time to try the original piston in the reed engine. The biggest problem building your engine with a reed valve is the hassle. You have to do some pretty trick machining to the back of the cylinder to get it mounted. The Montesa Motor Today V.R. stands for Vehkonen Replica, I think, but to me it is "Viva Racer." Montesa has fmally put it all together. With the new V.R. enginer in the Rickman 250, we have a bilte that is race ready righ t out of the box. Larry Watkins rode it box stock and it demonstrated it had what it takes. The Montesa V.R. engine is a complete new design. The cases are thinner and engine weight is lighter than the Cappra engine. A new shiting mechanism that lets you shift on the left side makes it a lot nicer. (Especially if you just got rid of your Japanese "fits·all" bike, deciding that if you keep on racing it, you are on borrowed time). If you buy a Rickman 250 at least you won't be scaring hell out of yourself the first time out by trying to use the gear shift lever for a brake. What is the V.R. engine like inside? Well, it, has a bore of 70mm and a stroke 'of 64mm, compression ratio from the factory is 12 to 1. Gear box ratios with an I I tooth counter and 56 But if you must have The Secret Weapon, read on: Tom Gille of St. Clair Shores, Michigan called me one afternoon and said "E.C. I want you to build me the trickest 250cc bike that can be had." Well, we talked for a while about all the 250cc bikes that were available at that time and fmally decided to do it with a V.R.-<:ngined Rickman. The first step was to break the bilte in. After servicing, I sent it to the desert for a week.end of play riding to get everything bedded in. When the bilte came back, we went to work. Next step was to get a dyno figure to work from. You can't make it better if you don't have a baseline figure to work from. As I said before, with a stock horsepower curve such as the V.R. engine has, I knew my work was cut out for me. Next step was to put the bike on a diet. Fork. tubes were pulled off and turned down to get rid of unneeded weight. Also, the top of the fork sliders were machined, too. They got two fork seals per slider to eliminate leaking. Stock fork seals just won't handle the job. Andre bars and Boge unbreakable levers handled the bar weight problem. Total weight trimed off the front of the bike was six pounds. AlI stock fiberglass was replaced with Rahm Plastics. Rahm Engineering of Long Beach. Calif. has made molds to duplicate the Rickman glass with unbreakable American plastic. The plastic is much Iigh ter than fiberglass and can be had in many different colors. This got rid of anotber five pounds of weight. Rickmans have never been famous for their stopping when the brake shoes get wet, so I had the shoes relined with a special web brake lining used on race car brakes. We use these brake shoes now on all our racers and they have proven to be well worth it. (These brake shoes can be had from Precision Cycle on an exchange basis or purchased in sets.) Now Came the harq .par~: ..~~e it faster. Tom wanted an engine with lots of bottom end torque because their tracks are tigh t and sometimes very muddy in Michigan. With the past experience we have with reed engines, I decided to build this engine with a reed valve. First step is that you have to machine the back of the cylinder off to get enough clearance for the reed unit. The 34mm Bing carb that comes on the Back of Monteaa cylinder must be milled off to accept the reed val... bike is perfect. All you need to do is machine the spigot so it will fit into the Suzuki carb flange. Porting to 'the engine is as per Fig. 2 The head was milled .020" to get the proper compression. The final step was to "KaJ·Gard" the cylinder, head and piston to reduce heat and friction. The engine was reassembled and 'the bilte was put back on the dyno to see what we had come up with. Three weeks of sweat and tears was poured into this bilte and now was the time for the moment of truth. The bilte was fired and warmed up: pump readings were charted. Next, into the office with a slipstick to see what the horsepower was. Bitchin" Just what I was afraid of. 1 spent three weeks and built an engine that was worse than stock. The only thing that it had going for it was three more horsepower on the top end but it had to wind another 500 RPM to produce the same horsepower that the stock engine did until the new curve crossed the stock curve at 6,500 RPM. AlI was not lost since the runs had been made with a stock V.R. pipe. one week and a big pile of "reed" pipes later, we finally got the curve that we wanted. The Pro Machine My service manager has bought a V.R.-<:ngined Rickman and has Jim MacDonald pilot it for him. Here at So. California tracks with a good bike and good rider you can make money. When you're the owner of a "Pro" bilte, and the money to keep it going is coming out of your pocket, you think long and hard before you buy. The bike as you see it is set up with the trick things that make it into a Tast class Pro bilte: forks were turned down, all bolts have .250" holes drilled through them; the new D.1.D. 4O-hole rims with 8-gauge stainless rear spokes and 9-gauge stainless up front. South Bay Motorcycles makes an alloy brake lever for the CZ and we have made a kit so they can be adapted to the Rickman The biggest reason we wen t to this brake lever wasn't because it was lighter but because it goes over the top of the peg instead of under it. This makes it a lot less apt to hang up in the ground if you do get off. The engine has been ported and the Bing carb machined out to 36mm. No reed on this one because with a good pro rider like Mac you can steal some bottom end torque. The need of the better experts is for more top end horsepower. All Rickman tanks are made out of steel, which is heavy, so I've contacted Alex Steel wbo is making aluminum alloy tanks now for the Rickmans. With the aluminum tank and gas, the bike will weigh in at 190 pounds race·ready, I think. Is a Rickman 25U for you? Well, only you can answer that question. But two things to remember: box stock it will win for you, and if you want to trick it out, it's got room for the personal touch. Before you spend those hard-earned bucks. look at all of them and weigh what each bike has to offer you. The stock bike you buy is what you start with and you can't make chicken salad out of turkey meat. •

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