Added reply in a thread It's a Cinco! (Jumping 5 in a row) 3/31/2021 5:33 PM

Call it a nickel, like a nickel defense in American football.

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 2/21/2021 9:35 PM

That tank is another great piece, really vibes first-gen Japanese dirtbike, plus is comfortable for your knees. Today I grabbed a picture that I think is Brad Lackey winning his class on a 250 Eagle in 1969:

Added reply in a thread Webb pitboard "red plate" 2/6/2021 11:05 AM

The U. S. peak may have been when Marty Tripes used to struggle with his weight and Bob Hannah's mechanic laid a big submarine sandwich on Tripes's front fender just as the 30 second board went up at a supercross. By the next race, the AMA had added ... more »

Added reply in a thread Fastest pre75 250 Engine 2/4/2021 12:28 PM

You're welcome, Mugen racer--one of the most interesting old article scans I've seen surface via Facebook, and one of those cases where it feels a little weird to think I possibly saw Bob Grossi ride one of the resulting team bikes at Rio Bravo with ... more »

Added reply in a thread Fastest pre75 250 Engine 2/3/2021 12:59 PM

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Added reply in a thread Fastest pre75 250 Engine 2/3/2021 12:52 PM

I had to dig around my desktop to find the files for the 1972 magazine article on Eyevind Boyesen's modified Husqvarna 250, but here it is. I remembered wrong about the use of injector ports/Boyesen ports to feed the main transfers directly; this engine

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Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 1/21/2021 2:52 PM

I would challenge the notion that there was no fork technology in 1968; true, it was either leading link or simple damper-rod tech, but damper rods done right were far better than poor ones. Ceriani, Betor and Marzocchi were producing some decent stuff--the ... more »

Liked a bike check 1980 Husqvarna 390 OR 1/20/2021 1:44 PM
1980 Husqvarna 390 OR
Added reply in a thread MX Front Drum Brakes 1/20/2021 2:01 AM

Worth trying once and worth trying again, @Bret--if the self-energizing effect causes grabbiness, it still ought to be the rider's personal standard for what constitutes "grabby," not a one-size-fits-all decision by the manufacturer. A big, skilled rider ... more »

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 1/19/2021 3:15 PM

Well, ca. 1972, shocks were often the big expenditure on a race bike, so you're being authentically old school. Seeing how simple inside those Boges are, it's a mystery to me why China doesn't clone something as simple as that; I guess the cruiser market ... more »

Added reply in a thread Houston 1 Supercross - Night Show Bench Racing 1/16/2021 10:19 PM

Didn't Jaroslav Falta win the 1974 Superbowl on a CZ with their air shocks?

Added reply in a thread Fastest pre75 250 Engine 1/11/2021 8:48 PM

Isn't that what Puch did on the 250 that won the 1975 world championship? Another bike I thought of was Eyevind Boyesen's 250 Husqvarna project in1971 IIRC, which pioneered the reed valve + bypass passages to the transfers that he patented. Supposedly ... more »

Added reply in a thread Fastest pre75 250 Engine 1/10/2021 3:41 PM

I was gonna vote for the Rotax. Too bad Can-Am didn't sell more of them, but IIRC, a magazine put a Skyway pipe on a 1975 model and it made almost 35hp on a dyno that showed other 1975 models around 27-29.

Added reply in a thread MX Front Drum Brakes 1/7/2021 8:08 AM

Wondering about the physics of it: isn't the leading shoe actually pulled into the drum surface by the drum's rotation, creating more braking force? Much more force than our hands alone can supply--that is why DLS front brakes let you roll backwards ... more »

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 1/4/2021 11:25 PM

Speaking of spring rate, Moto-X Fox had a worthwhile formula as shown below:

It is biased towards fast riders a bit; note their examples below, as Fox elsewhere recommended 60lbs. for Elsinore 125s, 70 lbs. for experts, and the Husky example ... more »
Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 1/4/2021 10:25 PM

The Japanese really struggled with off-road shocks prior to the 1973 Elsinore 250. They seemed to favor spring rates suited to two US-size people riding two-up, with rebound damping that probably wasn't enough for the spring rate for a single small Japanese ... more »

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 1/3/2021 6:14 PM

I meant to suggest a formula attributed to the late Gil Vaillancourt, who founded Works Performance and built many, many shocks for vintage bikes of different eras. He said that anti-squat characteristics were best if you line up the countershaft center, ... more »

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 12/29/2020 6:08 PM

Rick Siemen had a piece on used bikes to seek or avoid, since some earlier bikes were still competitive and reliable enough to be a potential bargain way of getting into racing if you found an example that wasn't worn out. Bikes like sidepipe CZs or ... more »

Added reply in a thread 1969 kawasaki F21m green streak -style vintage mx AHRMA low budget build 12/29/2020 2:35 PM

Fabulous work, and it's great to watch a genuine bike BUILD from the frame up. I am curious about the 238, as I am pretty sure the first MX bike I ever saw was an American Eagle 238, and it seems like a very underrated engine for the time frame. Not ... more »

Added reply in a thread Why Honda triple clamps from the 80's are black 12/29/2020 2:14 PM

Anti-glare measure? I thought that was why the 73-75 Elsinores had the painted panel on the top of the tank. You can debate whether it mattered enough to be a genuine problem, given how many bikes were out there with natural/ polished clamps, but Honda's ... more »