Cam vs. fuel economy question

M

MotoV

Hero member
I saw some talk of 180 version of the F1 cam and wanted to know what the general wisdom is on the relative fuel economy is versus the A11 cams. My expectation is that the performance would be much better. Based on my RGS MPG of about 45mi/1USGal would a 180 do similar or better with the F1?. I vaguely recall my Mirage getting similar mileage with A11 cams.
With 4C 30-32 mpg was normal although I recall getting close to 40...
 
I can tell you that when I trial installed a set of Megacycle F1 cams in place of 4cs on my '78 (180) Jota, with Mikunis and a Sachse ignition I was getting around 42-45 miles to the US gallon (5.6 - 5.2 L/100km) with the 4cs, but up to 50 mpg (4.7 L/100km) with the F1s, with better "seat of the pants" power and torque across the rev range. I can't say I did a really well-designed study because I was dialling in lobe centres with vernier cam sprockets and didn't run any single cam timing for more than 100km at best. And the whole experiment was put to a sad end when the crankshaft support bearing in the primary case spun its way to the outside again and I realised I'd have to pull the crank out and get it straightened (haven't done it yet; I know I can get it out but not so sure it'll ever go back together).
But the F1s really do seem to work better than 4cs, and still give decent fuel mileage. With worn out Dellortos and 40 year old ignition components/wiring, don't expect the same results.

Ken
 
Ken that is the kind of results I'm looking for. I had a Jota with 4C cams and never got anywhere near 45 mpg. But I never checked cam timing and I get the feeling I need to learn more about doing that. I changed to axtells and never felt a HUGE improvement - seat of the pants said they had better midrange torque.
The F1s have a definite appeal because they seem to be capable of good power and still have good economy. I'll have to go re -re -read Phil Todds cam timing notes...
 
Miss J gets between 44 - 48 mpg, and she is standard '81 Jota except for IIS ignition. (see attached)
and i don't think i'm too slow ??  not as slow as Rocket Rod, eh !
if ya want good economy, ya need to talk to Rocket.   :D

and ,, i'm talking real gallons (imp), and me test level top ups weren't too accurate.
 

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When we went touring in around 2009, "we" were on 3 laverda, Formula 750 CJ, Crispin 120 Jota and myself on my current Triple. The formula was the most economical, followed by my bike and lastly the unrestored 120 jota..
No figures sadly but there was a big difference bewteen all 3 bikes, with roughly the same increments between them . I think I worked it out at the time to be around 45 Imp mpg. The obvious differences were (Less weight although we all had camping gear) and I had 38mm MIkunis correctly jetted,
It's like anything that makes the motor more efficient will improve MPG, ignition, Carbs, exhaust, cams, cam timing,  increased torque etc.
 
The seth african and the 750s both use the same amount of fuel, we are a bit more advanced down here with that metric  blingy stuff, both around 6l/100km, ridden in anger, i think in caveman talk thats around the 45mpg
 
My 3C used  hard with the CV Kehan carbs before dino running lean on 155 mains and hitting 75hp did around 58mpg imperial.After dino on 172 mains and producing 84hp it dropped to 51mpg Imperial.Looking forward to what happens with the F1 cams.
 
Vince said:
My 3C used  hard with the CV Kehan carbs before dino running lean on 155 mains and hitting 75hp did around 58mpg imperial.After dino on 172 mains and producing 84hp it dropped to 51mpg Imperial.Looking forward to what happens with the F1 cams.
Click to expand...
Which cams?
 
I just replaced the 4C cams on my 83 RGS with F1s. Previous mileage was in the mid 40s when riding "normally." I've only just done my first tank on the F1s and mileage was 44, so no change. I'll pay attention and report. I will say that it runs very nicely on the F1s, with what seems an improved idle and better low and mid-range performance. That said, I've been pretty easy on it as it seems I'm getting some clutch slip. Haven't torn down the clutch yet to inspect.
Richard
 
It sounds like there is not a huge difference in mpg between A11 and F1.
I will use the A11 cams to get this bike* running but will keep an eye out for F1s - may check with Wolfgang.

* I'm just starting to bring a US Spec 1981 Jota out of an almost 20 year storage.
Its nice to see an old unmolested bike clean up...things like the ignition pick ups look brand new...in spite of the fact that original stuff may make it more valuable as  original, the fact is the ignition will be the first thing to go..
 
As I said in another thread Metric fuel consumption figure mean nothing to me even with OZ being metric for the last 30 years,but there is an easy confusion between Imperial Gallons and US gallons with MPG figures.To me fuel consumption seems like a good way to check your bike is working to Maxim efficiency.
Anything close to 50miles to an Imperial gal is a great result.
 
I use the metric system all day long for work,but for fuel consumpting and tyre presures,nada.Bar or pascals mean nothing to me in that regard.For engineering cals Kpa do have a meaning for load cals,I live in my own little world.
 
I used A12 cam sprockets for the F1s made by Megacycle, same as A11s. I actually used A12 cams as grind/buildup "blanks" for the F1s. But my sprockets were also vernier drilled for me by Scott Potter (thanks again Scott), and what looked like the original standard hole was not real close to 110o. Not real unusual for Laverdas, though.
But it looks like A11 sprockets are at least a starting point.

Ken
 
any time ken  :D

my mirage with A11's returned 41mpg (us) like clockwork on a 2500 mile trip to barber last year with and without headlamp
(i threw it down the road on the way out and bought a used lamp at the swap meet, hence the need for new paint seen in BOM)
 

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