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[Wheaters]

I’m intrigued to read the the compression pressures are only 120 psi with 10 to 1 pistons fitted. How are you measuring this? Do you hold the throttle open when spinning the engine over?

My kickstart only 350 is fitted with a standard piston and the pressure is +/- 130 psi.

[Steve]

Never thought to measure the resistance on the spark plugs. The New Champions had 27-41 Ohms resistance, New NGK had 0-2 to 0.3 Ohms. Set the gap to 0.018 and she fired off quickly with the electric start.

As for the compression, the cylinders are in sad shape and thus not a great seal. The measured compression of 120 PSI was with "as is" cylinders. A sip of oil and a couple of kick overs and the compression is much improved.

The "Covid Bunny" brought me nice 0.040" overbore, 10:1 pistons from Ross Racing Pistons and the cylinders will be bored for those. Should keep me sequestered for the cold Minnesota winter.

Thanks to everyone for the comments and suggestions. I still am curious if anyone would measure the resistance to ground on the kill switch post on their SR2 or SR1 magneto.

Steve

[vince]

Hi, as a matter of interest what records does the bike hold? Vince

[Steve]

American Motorcycle Association (AMA)
750cc Production - Production Vintage (750 P-PV)

2013 - 79.415 mph
2014 - Rain out
2015 - Rain out
2016 - 83.691 mph
2017 - 87.938 mph
2018 - 95.318 mph
2019 - No Record
2020 - Covid cancel

Our goal is to crack a ton before we kick the bucket!

[vince]

Hi, sorry for the ignorance , what type of competition is that?

[Steve]

Vince,
It is Land Speed racing at the Bonneville Salt Flats in Utah. There are many, many different classes for motorcycles, from stock 50cc machines to streamlined high horsepower machines capable of 400+ mph!

The Salt flats are an ancient dry lakebed with an equivalent altitude of ~6200 feet.

In my class you have one mile to accelerate, you are timed over one mile, and you have one mile for deceleration. To set a record you average two runs in opposite directions on the same day. My class requires the machine was made prior to 1956 and to be externally exactly as it left the factory. Internal modifications within the rules are allowed.

If you have not seen it, rent the movie “Worlds Fastest Indian” staring Anthony Hopkins.

Steve

[vince]

Thanks for that, yes well known, I was originally assuming you meant drag racing. Vince

[Adrian]

Do your racing rules specify that you have to retain the original ignition?

A.

[Steve]

Adrian,

Yes, for the Production Vintage classes you must have original ignition, carb, exhaust, muffler, tank, fenders, etc. Handlebars, gearing can change. Unseen, internal modifications are ok. Overbore up to .050” allowed as long as you stay under (750cc in my case) the limit for your class.

Hitchcocks has been outstanding as a source of needed parts!

Steve

[Adrian]

So no fancy digital aftermarket electronic ignitions with Petronix Flame Thrower coils, then! It really is the case of getting the best possible compromise of plugs for starting and high speed runs, and some racing HT lead if it's not already fitted. Platinum points were fitted to BTH racing magnetos, but I don't know if they were ever made for the Lucas SR range. Maybe the points off a later Lucas racing mag might fit? Complete guess, there!

The original ignition requirement would also rule out a Lucas K2FC or a BTH KC2 of some description, presumably.

A.