Board index Flathead Power-Technical Questions, Answers, and Suggestions Big Twin Flatties BONNEVILLE Speed Week 2008

BONNEVILLE Speed Week 2008

Moderators: Curt!, Pa

Post Thu Oct 16, 2008 5:32 pm

BTW: against my better judgment, I'm still slowwwwly constructing a special frame, blown, fuel, 1,350cc flathead, but won't waste any more time and effort attempting to anticipate what hissy-fits the "tech committee" may produce along with their excrement rendering anything I build illegal for AVBG-1000 class, so it will have EFI (MicroSquirt, single 60mm TB on the Eaton M45 inlet).
No, I won't fare well against crew-served Hayabusas, but I don't care.
The engine is already 71 years old, and I intend it to have a Viking funeral.

Post Thu Oct 16, 2008 5:36 pm
Pa Site Admin

Posts: 5547
Location: Ohio USA

Sounds like a suicide attempt Panic. :mrgreen: But MAN !!! Would I love to see it run once!!! or twice, or three times, if it stays together that log. :wink: All joking aside....sounds like POWER !!! :D Pa

Post Thu Oct 16, 2008 5:53 pm

Posts: 766
Location: CA USA
I share your frustration. I was building a nice 650 cc WL/R [WL cases machined to WR specs] motor before the rule change. I think it would have been competitive with hot 350 cc OHV bikes. I set it up with S & S WR flywheels and Carillo rods. The top end is made of the WL repop jugs sleeved to reduce the bore, the intake ports enlarged to take the UL nipples and oversize valves. A specially crafted 4 bolt manifold holds a rebuilt M53. I had special pistons made to my specs. Francis Clifford had ground some cams for me before he passed. I was just starting to work on the pop up relief in the heads when I learned that I had been wasting my time. Now I have a ton of time and $ into a motor that I can't use. I've been so discouraged that I've just left most of the stuff on the shelf and went on to other projects. I suppose I'll remove the sleeves to make the jugs useable and make those expensive pistons into pencil holders. I can reuse the bottom end parts, so I'm OK there.
I'm sure that I'll probably start another salt project, but right now there is still a bitter taste in my mouth.

Post Wed Oct 22, 2008 12:21 am

Posts: 530
Location: Ogden, Utah, USA
Panic and Beach Dog: I am beginning to understand the drive to the original "outlaw" riders. They had the AMA and you are up against the current sanctioning body. Perhaps the "industry" should start to support the riders and let the little guy try. Or not. Anyway I for one would love to see if not hear either of the projects. I would wish you all the best and hope the bikes will come together for the sake of the thought and work involved. Worked hard to make a better flat tracker in my time. It was fun and work as well. But I never found a better way to learn something new. Some things worked and some did not, and some things blew up with much enthuasim. There is no way to explain the feeling you get from a rod thru the cylinder locking up the wheel at 100 miles an hour. And there is no way to explain passing that guy you chased all season long on the back straight away to take a chekered flag. But both will teach you something. :D Steve
Steve H

Post Wed Oct 22, 2008 10:32 am

Re: "I was building a nice 650 cc WL/R [WL cases machined to WR specs] motor before the rule change. I think it would have been competitive with hot 350 cc OHV bikes."

I had the same thought, never went any farther due to being near the end of the "to do" list.
The existing record (as of August 2002) was 89.834 mph, held by Dale Martin on a Triumph 350. I was going to shorten the stroke:
Engine displacement for class is allowed to deduct .050" of bore size:
2.745” std. + .050” overbore - .050” allowed for class = 2.745” × 3-5/16” stroke = 39.36"or 643cc (the actual displacement is 40.65" or 666cc). I didn't go any smaller (sleeved down to 2.59" × 3.00" stroke is 498cc; ran against 250 OHV under the old rules, against 350 under current rules) because Truett can't move the pin down any more, and because getting compression with a smaller engine will be really tough.
The shorter stroke gives about the same inertial load (107,000 f/s/s max accel) at 7,600 as the original stroke does at 7,000. The rod ratio also goes up, which should help the small intake ports.
As a guess, 35 hp looks good.
I could still build the engine, but I don't have a suitable chassis...

Post Wed Oct 22, 2008 10:50 am

A 650cc 45 unfortunately must now run against the GMA All American Scout, Tatro KR and other serious bikes in 500 OHV.
The current rule only allows 525cc SV for 350 OHV class.
For a 525cc motor I would start with a 741 instead, shrinking a 45 motor down that far doesn't look good.

Just a thought: the record for 500 OHV blown doesn't look too tough at 86.276 mph.
A 45 needs much less mods to go from N/A to blown than an OHV, probably just new pipes and wider lobe centers would do well.
Current record: MPS-VBG; Goldwing Lyon Corn; Triumph (pre-1956 T100 B Range pre-unit twin); 8/08.

This is the reason I decided to use methanol/Eaton for my 1350 SV - I don't see a record for the 1000cc vintage blower bikes at all (VBG or VBF, any chassis), although they must be out there - Clem Johnson, Alf Hagon etc. all set the design 40 years ago with JAPs & Vincents. ... _bikes.htm

Post Sat Oct 25, 2008 1:49 pm

Posts: 766
Location: CA USA
I've looked at those classes. Very interested. I don't know anything about turbos or superchargers, but I'm willing to learn. I have the chassis and the bottom end all sorted out. Easy enough to add partial streamlining. Just need to look into what would be best top end stuff for forced induction. Any advice? Would WR jugs work best or would the smaller ports of the WLD provide better velocity.


Return to Big Twin Flatties