NOTICE:  This article appeared in Motorcyclist magazine October 1977 issue.  Most of the vendors mentioned are out of business, however all of the concepts remain valid.  Proceed at your own risk.

By Rich Cox

Since we were really pumped on the 750E’s performance we thought we’d take a step farther and check out who's making speed equipment for the Yamaha triples.  Most of the big-time speed suppliers, who build their reputations on racing what they sell, have shied away from the 750, not because the engine can’t be hot rodded or can’t take the punishment, but because the triple has two distinct disadvantages that make it useless for circle or drag-strip racing:  It’s way overweight and it’s got shaft-drive that makes gear changing a bit difficult.  But what about the street rider who doesn’t want to race, but just wants a little more pizaaaaz from his triple?  Powerhouse Products, a small firm in Canoga Park, California, feels there are enough 750 owners out there who want to buy some speed that they’re going to work exclusively on satisfying them.  They’re offering kits in four different stages depending on how much speed you want to buy.  For example:  Stage I is your basic bolt-on performance kit consisting of a set of 34mm manual slide carbs and a three-into-one pipe; Stage II includes an 850cc big-bore kit among other things; Stage III goes a step farther by including a pair of Stage I cams and Stage IV gives you all these goodies, plus a port job on the head.

  Stage I is your basic bolt-on kit consisting of:  34mm Mikuni slide carburetors with cables, K&N air cleaners and a Winning three-into-one   pipe

According to Powerhouse, this Stage II kit gives the largest percentage gain in horsepower per dollar   

You might be interested in what kinds of parts you’ll be getting.  The three-into-one pipe is a Winning Performance pipe; the air cleaners are from K&N; the forged aluminum pistons are made by Arias to Powerhouse spec; the Norris cams and springs are also to Powerhouse specs; and Powerhouse does all its own porting.  They’ve also got a complete machine shop service if you don’t do your own work, and if you have any doubts at all, they prefer you send them your complete engine and let them do it.

Powerhouse happened to have a 750 with a Stage IV kit already installed so we took it riding and here’s what we found.  The 850 kit definitely causes a heavier throbbing under the seat and it does vibrate more than a stock 750, but that’s pretty much expected when you start making holes bigger.  Normally the Stage IV kit comes with 36mm carbs, but you can get it with 34mm as this one had.  The smaller carbs work better for street use but the 36mm jobs pull a little harder on the top-end.  Bottom-end torque didn’t seem to be affected by the racier Stage II cams and it seemed to lope around town as easily as a stock engine. Everything really doesn’t start coming together until about 5500 rpm and from then on you suddenly realize this is no stock 750 engine-it pulls hard on up to redline and past if you let it.

For cruising around town you’ll find the manual slide Mikunis have stiff springs which are a little hard on the throttle hand, and the Winning pipe, that looks and sounds similar to a Kerker pipe, is a nice noise maker if that’s what you’re looking for.  Gas mileage figured out to 33 mpg just driving it easy around town.

Dragstrip times were impressive considering it was an early XS750 with the tall gearing that forces it to trip the lights in fourth gear.  Best time was a 12.04 sec./108.82 mph.  Best speed was a 12.30 sec./111.52 mph.  The hot setup would be to put this kit in the later E model engine and with the lower gearing you’d have yourself a 11-second 750 triple-not too shabby!  For more information contact:  Powerhouse Products, 7801 Alabama St., Unit 13, Dept. MC, Canoga Park, CA 91304, (213) 884-5379.