Lemans and a GRiSO

Went for a ride in Southern New Mexico Sacramento Mountains. Great time, both bikes ran like champions. Lemans all original down to still having points and got 63 mpg vs my 42 on the GRiSO. Fun times, rode almost 300 miles[You must be registered and logged in to see this image.]

That Lemans sure is pretty.
Thanks for the pictures

am I reading this right?

The Le Mans got 63 mpg = 26.78 km/l?

That's even better than what my Breva 750 gets out in the country. How could this be?

barry.b wrote:

am I reading this right?

The Le Mans got 63 mpg = 26.78 km/l?

That's even better than what my Breva 750 gets out in the country. How could this be?

Remember, even though the MkIII is a big block it is only 100cc's bigger than the Breva. Yes, it's heavier, but it revs slower at any given road speed, has a very small frontal area, (It was the last of the 'Low Head' Tonti 'Sports' models.) and very importantly it had the, what I call, 'Lean Burn' PHF 36 carbs.

With the advent of the Mk III Guzzi used a version of the PHF that have a shroud around the atmospheric side of the atomiser orifice. Like a 2 Stroke carb this is there to increase the depression around the annulus between needle and atomiser so more fuel is pushed up from the float bowl. The combination of this with AB268 atomisers and K18 needles made the bike extraordinarily crisp and also very economical.

Sadly the general view at the time, (And one that persists to this day with most people, including those who should know better!) was that the seemingly lean jetting, (The MkIII used 118 mains rather than the 130/132's of the earlier roundfin LeMans.) was there because the evil gubmint was trying to stop people having fun. Shops used to sell 'Hot Up' kits to get around this that included 265 atomisers and K5 or 6 needles and 132 or even 135 mains to slip into the carbs. Problem was that with the shrouded carbs all this did is make the poor things run hellishly rich, foul plugs and not be able to pull the skin off a rice pudding! When I first started Motomoda I had a seemingly endless stream of Mk III's with worn out top ends and lousy performance and fuel economy. The really sad thing is that a lot of their owners would pay for a new top end, I'd correct the jetting and they'd come back a few months later and I'd find they'd put the old, wrong, jetting back in! Either because their mate had told them I didn't know what I was talking about or they simply didn't believe me! Sometimes they even said it ran better with *My* jetting but they couldn't see how it made that much difference and, because they had always fitted pod filters they *Needed* more fuel. Even though the plugs and pipe told them it was running pig-rich!

When their rings wore out in six months and they started drinking oil again it was, of course, all my fault. One look in the carbs? Warranty declined........ There are no Purple Hearts for self inflicted wounds. Idiots.

Ah Pete, you remind me of back when I was trying to get the carbs right on my old SOHC Honda. I had 836 cc pistons, mildly hotter cam, mild porting, and a Hooker header. Stock carbs and pods. In the end, I enclosed the pods to create dead air space, (stock airbox was warped), and spent a day fiddling with jets and needles. That bike runs like stink and gets 50-60 mpg if obeying traffic laws. BTW, I'm running much smaller jets than the "experts" recommended.

In my experience fuel consumption that good on a LeMans also indicates that the ignition timing, valve clearances and throttle synchronisation are pin sharp.
Get it right and they sail along on a breath of throttle
Congratulations on a job well done!