Cycle News - Archive Issues - 1970's

what to do for cams, but the Sifton "A" cams with the same timing marks as used on the aluminum racers work just fine. I'm sure that the minus-minus grind could be had wi th these timing marks by special order. All the cylinders will he available with or without fins so they can be run on the street. The only exception will be the 3 S/8" bore which would have clearance problems and will probably have to be run with exposed pushrods and modified tappet guides. CN: Any problems getting the engine into the frame? The engine looks huge. Scott: Using the Goldstar heads increases the height of the engine by about an inch. Our frame is at another shop having the top tube moved. We had to fabricate a rather odd looking oil tank since the carburetor for the rear cylinder is where the oil tank used to be. Incidentally, if at all possible, one should come up with one of the electric start type frames. Those are the ones with the rear down tubes kicked back. The extra space is very helpful for getting the thing in and out of the frame- and .for routine main tenance. We've had the engine in the frame already, but we thoughfwe'd take the time now to raise ita Ii ttle more so that the engine over there will fit in when it's complete. CN: We hadn't noticed that before; what is it? Scott: That's stage two. Bore is 3 S/8", stroke is S", about 103 cubic inches. Goldstar head Is on left. Note stralght·in porting and tapered valve guide. cylinder and piston. The Goldstar head available in that bore size. Later we're bolts on from underneath, like the coming up to 80 or 90 cubic inches, but Seventy-four. We had considered we want to get the bugs out in a small using studs! coming up from the motor first. crankcase through the head to eliminate We want to see what happens if we cylinder stretch and to allow us to use make a motor we can spin up to 7SOO the Goldstar aluminum cylinder. RPM. At that engine speed our cams, CN: Why didn't you do that? heads and tuning all start working Scott: The mounting holes are so far together. The valves in the Goldstar are apart on the Goldstar that it would have slightly smaller than the valves in the been impractical. In some cases the stud iron Sportster. They are closer to the would have to be in thelsame place a~ size valves in the aluminum racing the tappets. It just wouldn't have' heads. The smaller valves allow us to worked. In the end the simplest keep the gas velocity high. approach worked the best. We modified The stock stroke allows us to take a Seventy-four cylinder by moving the advantage of an almost theoretically holes in the base to fit a Sportster and perfect 2.0:1 ratio between the stroke bYlmoving the ilOies in tile base'to fit the and the rod length, the result being Goldstar. greater power and much increased We sleeved the cylinder to fit the component longevity compared to a stroker, assuming the displacements are _ Goldstar pistons and' opened up the crankcases to accept the larger the same. We feel that we can gain more Seventy-four spigot. We had to turn the by boring than by strOking since we can spigot down a little so as to nave enough spin the motor faster without raising meat on the cases for a gasket. In the piston speed. future we plan to have cylinders especially cast and machined if the demand warrants it. CN: You plan to sell the cylinders? Scott:. Sure. What we'd like to do is market a kit containing all the nonstock parts, like pushrods, cylinders, pistons, brackets, nuts, bolts, etc., everything that is not either a stock Harley or CN: What kind of horsepower are you Goldstar part. The customer will supply getting? his own Goldstar heads and Scott: That's hard to say since we rockerboxes, etc. . don't have access to a suitable CN: How much will it cost? ' dynomometer. I'm very skeptical of Scott: We're not sure yet but we won't pronouncements based on calculation offer it if it doesn't compare with other without some sort of empirical products in terms of dollars per evidence. Like someone said, "The dyno horsepower gained. has no friends to reward, no enemies to CN: What about the pistons? punish." Scott: You noticed that the heads are CN: jCpuld you make an educated not both facing the same way. Since the estimate? Goldstar was designed as a single there Scott: We'd sort of hesitate to do that was no reason not to have the exhaust since undoubtedly some of your readers pipe come almost straight out the front will want to try the conversion and will of the head. Unfortunately if we tried be disappointed if they do not achieve that on the Sportster, the rear exhaust the same power they are expecting. would feed right into the front intake OK, let's make a kind of off the wall port. Great for reducing emissions and guess. In the late sixties a number of beautiful for mileage, but pure hell on people claimed that they were getting power. about eighty crankshaft horsepower out The front head was rotated slightly of an 883cc XLR motor. Considering anticlockwise and the rear head was drive train losses, that probably meant rotated a little more clockwise, so as t(') around fifty-five horse at the rear wheel. have room for the rear exhaust pipe. We've hard chromed all the mating Doing all the moving wi th the heads steel pieces in the engine and caused another problem: What to do transmission. Gears, sprockets, shafts, about valve pockets? We started out carns, tappets, everything. We expect all using stock 8.S: 1 Goldstar pistons. this to gain us in the neighborhood of 20% power at the wheel. Since the pistons were relatively low Since the old XLR used a single prome and were fairly thick on top, we carburetor it gained no advantage from just cut a little pocket in the intake tuning. We hope that all our appropriate place with a mill. The work will give us a 20% increase for piston would up stronger than the stock tuning, another 30% for the greatly 883 piston. The front and rear pistons improved flow of the Goldstar head, are different and must be installed including the better volumetric correctly. We mark ours just in case. One of the west coast piston efficiency and thermal efficiency. manufacturing firms that has been Various minor improvements such as making hotrod stuff for cars has the reduction in valve train weight, recently entered the motorcycle field. resulting in more accurate cam They have been considering machining following will get maybe another 1Q%. The increase in displacement from 900 up some pistons for us on a mass to 1100cc's might be good for another production basis. 20%. . This will make it so the stock CN: That's a total of a 100% increase. Sportster rod and small end bushing can That means about 160 horsepower! be used, along with either a Sportster or 'That's unreal, ' Seventy-four piston pin, depending on Scott: See why you don't make bore size. Right now, we have been using a Goldstar pin, which is slightly estimates? ,CN: What do you think someone could smaller than the Harley pin. Rather than expect out of a machine that was street weaken the piston by boring the pin driveable and dependable? boss out to fit the Harley pin, we Scott: Assuming that you weren't installed a smaller bush in the small end going road racing and maybe only an of the rod. occasional stoplight contest on a cool Interestingly enough, the deck day, I think that 120 horsepower would heights of the twolPistons are virtually be more realistic. the same. No problems with the piston CN: That's still a fantastic amount for hitting the head. The Seventy-four and a street machine. the Sportster have the same length Scott: It would be quite peppy. cylinders, about S 3/8" from deck to CN: 1 guess so. Can you describe the deck. Lots of things just sort of fell into problems you have had to overcome? place. Scott: The biggest problem was the We were worried for awhile about •••about 160 horsepowerl Engine Is no wider than stock. Front exhaust pipe exits between frame tubes. r ... § GREEVES - OSSA HODAKA ~ CARABELA - STEEN ,~ I I ,....",......" ......" ...... NICK NIC'1,O!'tOtMOTORS lii': 11573 VANOWIEN STREET ~ NO. HOLLYWOOD. CA. (2131 764-8674 !i § lIl1 ,~ ._- , '~ .... ··MONTESA ~ WARREN t WILSON 9000 SEPULVEDA BLVD. • South of lIiordoff in Sepulveda, Calif. MOTORS ,- Motorcycle .(21~) ~~4-9218 ...... - Sale. Serylce i .. , MONARCH PLASTIC FENDERS _Ask your dealer for One Year Guarantee Black White Grey Red Orange Yellow No. No. No. No. 101 4" 102 4" 105 5" 106 6" Front 15" & 16" Wheel Front 17" to 21" Wheel Rear (for small bikes) Rear (fOT large bikes} .$3.95 .$4.95 .$5.95 .$6.95 MONARCH PRODUCTS CO. P.O. Box 466, Wilmington, Ca. 90744 (714) 539-1980 (213) 835-8938 Distributor inquiries invited , ~ ~ Z ~ w Z W ...J U >U

• Cover