Update:

Well, it has been a year since I put my new 120-inch Merch motor in our dresser. Those of you who know me personally know I was pretty happy with my turbo motor. I have somewhat of a reputation among Harley riders that I have rode with for the past 30 years... I always had cars which were faster than the "norm" and I have always had bikes which were "faster than yours!"

The common quote of "If I have to explain it...you would not understand" applies to more than just Harleys. Those of us who have the Horsepower Bug have a sickness. It is incurable. It is addictive. And guess what? - I don't want to be cured. I have a 454 El Camino, a 1970 Olds W-30 with a Mondello 455, and my 120-inch Merch Harley. I started this trip in 1968 with my first car - a 421 Tri-Duece Poncho - and I have never looked back. Many cars and many bikes later, I am still on my journey to Horsepower Nirvana.

Which brings me to date - I have been doing some R&D work for Merch for the last year. I have tried different pipes and ignition systems and documented the results. I rode the bike for a year in stock form as their low-compression, low-output motor. It produced 106 horsepower and 125 ft-lbs of torque (see original article below).

I have just returned from the Merch USA Headquarters in suburban St. Louis. We decided to tear down my motor and see just what it looked like after a year of "normal" driving (as if life with me is normal). I have probably had over 100 different people ride my bike to experience the fun of the big motor. I am not known to spend excessive time warming the motor before leaving, and the different combinations of pipes and ignitions have resulted in repeated cycles of rich/lean and advanced/retarded timing.

We were more than pleasantly surprised at the condition of the motor parts! I have always had a slight noise in the motor... We had several opinions based on past experiences, but the noise turned out to be caused by a misalignment of my primary chain.

We started tearing the motor out of my bike at 7:30a.m. and we split the crank apart at 9:30a.m. Six hours later, the motor was back in the bike, ready to fire. We used my old crank pin, but we did hone and resize the rods. We put in the new forged flywheels, the Stage 3 Merch heads, a Bob Woods F-grind cam, a Mikuni 48mm carb, and an M-6 chain tensioner.

We spun the motor for 15 seconds with no spark plugs, then put them in and the bike fired with less than 1 turn of the starter. To those of you who have heard or rode my bike, you ain't seen nothin' yet! This baby BARKS. I ran the bike through 3 heat sink cycles in St. Louis and brought it home. I have spent two days of more heat sink cycling (run the bike to operating temperature, shut it off and let it cool) and am now ready for a few hundred miles of easy break-in.

Oh yeah - special thanks to the entire Merch crew in St. Louis: Don Sekora for his labor in pulling and reinstalling the motor, John for his help with all those little nagging machine tool brackets, spacers, etc., Don and Bo for their care with my heads and manifold, Jim Sekora for his generosity with miscellaneous parts and shop labor, and all the rest who helped. Thanks!

- The Dynoguy

Original article:

There are a lot of big motor choices out there: 96 inch, 113 inch, etc. Several of the bike builders use these engines, and yes they run harder than the stock 80 inch motors. But - as most of you know - stroker motors shake, rattle, and vibrate your teeth out and generally leave something to be desired. So how do you cure the problem?

You build a "square motor." That is, you make the bore and stroke the same, then everything smoothes out. The Merch 120 inch motor is my choice; they have a 4.25 inch stroke and a 4.25 inch bore. These cylinders look like they belong in a locomotive! Make a fist; it drops right through... Smooth performance and impressive power.

I have the low-compression, low-output engine. It "only" produces 106 horsepower, but - and this is a big but - it produces 125 ft-lbs of torque at 3000 rpm. Can you say "effortless wheelies?" On a dresser, no less... Just roll along in low gear, snap the throttle only, and the front end of my dresser climbs like the Space Shuttle until you let off the throttle (usually at about two feet in the air). Dressers don't belong in the air...

Then let off the gas, shift to 2nd and snap the throttle open again - and boy oh boy - here we go again! All you can do is try real hard to make sure the front end is straight when it comes down. Shift to third - snap the throttle open and...yeah, you know. I figure that I will put on 8 or 9 rear tires to every front I replace...

Two-up on a dresser, doing wheelies, passing sport bikes off the light with the front end in the air; it really ticks them off! They just don't understand...

Okay, to be fair, lets talk about parts. Ever hear of the "weak link syndrome?" My 11mm primary belt turned into spaghetti (two of them, actually) within 1000 miles. So I went back to a chain primary. I know from my turbo experience that if I ever "stick" my rear tire - as in a launch at a drag strip - that I will spit my rear belt out the back. Been there, done that... And yeah, I will need a stronger battery, and a stronger starter would be nice, but so what?

I know -it's a sickness- so I guess that I'll take two asprins and call my parts man in the morning...

I'll keep you posted, but for now,tell me - is my tail light working???

- The Dynoguy

Speaking of Merch big-inch motors, here are a few dyno runs showing what they are capable of: