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I wonder if anyone has fitted a Maney stage one head to an engine with a standard cam
750 engine tune.
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I wonder if anyone has fitted a Maney stage one head to an engine with a standard cam
Yes, you do need performance for that in town 20-30 mph stuff- around zook 80 or Honda 90 performance lev. They go across town in heavy traffic just as quickly as a Hayabusa.
With any of the 650 and up roadbikes I use here the throttle barely is used in this traffic.
So as long as the bike idles reliably and makes enough power to ride off without stalling it works fine.
What does one do with massive stump pulling low end?
The only use I can see for that might be a heavily laden bike or one pulling a trailer.
I agree that stockish tune is best for a roadbike, but if the perked up bike works fine when using light throttle and low rpm, accelerates moderately hard from 3 k to to 4500, then rockets to 7 k, wheres the problem in that ? Sounds like fun to me.
Glen
With any of the 650 and up roadbikes I use here the throttle barely is used in this traffic.
So as long as the bike idles reliably and makes enough power to ride off without stalling it works fine.
What does one do with massive stump pulling low end?
The only use I can see for that might be a heavily laden bike or one pulling a trailer.
I agree that stockish tune is best for a roadbike, but if the perked up bike works fine when using light throttle and low rpm, accelerates moderately hard from 3 k to to 4500, then rockets to 7 k, wheres the problem in that ? Sounds like fun to me.
Glen
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If you take a stock rm1 head and open the ports up to 34 mm then yes agreed, the effect willbe to lower air velocity-but that is not a Maney head which has 3mm oversize inlet valves.
In fact I have an RM1head which i ported out to 32mm as per the Dunstall tuning guide, sometimes I regret and may well sleeve it back and experiment . However my Maney stage 2 head is a work of art and will do fine as it is .
built into a race motor.
IMO this engine owner has attempted to tune the engine for "top end" performance, expecting to keep the bottom end power. We all wish to have an engine like that. In real life, you have to accept a compromise, you can have a highly tuned engine with the bottom end performance missing, or an engine with slighty better than normal bottom end power, but with lower than top end power than above, but not both. I have ridden a stage 3 tuned grand prix racing bike, it had no pilot jets in the carb circuits, no power until you hit the sweet spot "when it came on the cam" if you want and expect both, well you also want to live in cloud cuckoo land ( wouldn't we all?) 
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I asked a couple people I know had FA heads, and theres only a "half-spoken for" 850 head.
There are a bunch of 750 heads on ePray - https://www.ebay.co.uk/sch/i.html?_from=R40&_nkw=norton+commando+750+cylinder+head&_sacat=0&_sop=3
Matchless
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Thanks for looking Gortnipper. If I fit another head I would prefer a Fullauto but if one doesn't turn up may well have to fit an original type. Later this week I will be having a play with the bike & trying a few of the ideas mentioned here.
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you havent saidwhat the gearing is ... go for 19 or 18 .and hang on.
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Mentioned earlier, but drowned out with all the compression and top end posts. has the timing been checked.
Advancing timing and increasing CR does create a detonation issue. But that's your tradeoff, a tuned beast that drinks hot sauce, or gentleman that sips tea
Advancing timing and increasing CR does create a detonation issue. But that's your tradeoff, a tuned beast that drinks hot sauce, or gentleman that sips tea
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In my 20's I opted for the hot sauce but over the years learned that a "gentleman who drinks tea" is a much better ride for any use other than the race track or bragging rights. 
Matchless
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Just been out for a short ride with the inlet valve clearances set at 0.025", 0.008 before as per Maney ally barrel/cam. It has made a slight improvement to low down pulling but only around 10%. The problem was keeping it from stalling once it had warmed up. The next thing to try will be temporary eccentric sleeves in the inlet ports. Watch this space as they say, whoever they are.
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you can advance or retardthecamtiming by 5degrees at a time. Means taking riming cover off and playing about with the timing gears
have you tried raising the needles a notch ?
Matchless
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I finally got around to turning up a pair of inlet port reducing tubes & went for a test run today. It is about 20% better up to 3000rpm now & they don't seem to have affected performance above this. The next item on the agenda is the cam timing which as Oldmikew points out can be moved + or - 5 degrees. Watch this space.
baz
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That's interesting
Thanks for sharing
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Make sure your cam is not retarded. It should be advanced (about 2 degrees) for better lower end. If your intake and exhaust lobes have the same lift and duration then you should check the lift of each at top dead center (measured at valve spring retainer). Your intake should have about .015" more lift than exhaust at TDC.
motorson
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I read most of these posts. My 750 has a conglomeration of incorrect parts which work together for a rather pleasing result. I have a Combat head which has been slightly ported. 8.9 compression Ratio. 22 tooth front sprocket. I'm using the 312a cam Web Cam advanced 5 degrees. I have 932 Amals. Set up like this it makes 42 rear wheel horse power at 5500 rpm. The power falls off after that. In this shape it will go about 105 mph in 3rd gear but will only hold about 95 mph in 4th at around 5000 rpm. With this set up it pulls pretty good from 2500 rpm and comes on very strong at 3000 to 6000.
I could improve it by going to a smaller port head and 930 carbs. Also, the compression could be bumped up a bit. I do cruise at 2500 rpm in 4th gear on twisty roads, which is 50 mph on the speedo. It will hold and even accelerate on a mild hill at that rpm but a down shift helps. At 50 mph and low throttle setting I don't feel like the engine is laboring but it does feel that way if you open up the throttle. It gets great gas mileage too.
I have a fire breather in the works but for now this one is a very pleasing Commando!
Dan.
I could improve it by going to a smaller port head and 930 carbs. Also, the compression could be bumped up a bit. I do cruise at 2500 rpm in 4th gear on twisty roads, which is 50 mph on the speedo. It will hold and even accelerate on a mild hill at that rpm but a down shift helps. At 50 mph and low throttle setting I don't feel like the engine is laboring but it does feel that way if you open up the throttle. It gets great gas mileage too.
I have a fire breather in the works but for now this one is a very pleasing Commando!
Dan.
Fast Eddie
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When people say they “advanced the cam 5 degrees” it actually doesn’t mean anything unless you know what the timing was before advancing it and what the ‘correct’ timing is meant to be.
You only ‘advance‘ a cam by advancing it compared to its correct timing figure. If you advance a cam that is retarded, you are simply ‘correcting‘ it...
Not all cams come off of the grinder 100% correct. Same for cam sprockets. I believe that a lot of people who “advanced” their cam x degrees have actually just put the cam timing to where it should be.
I recently fitted a cam from a known good vendor, I had to alter it by 5 degrees simply to get it to his suggested figures.
But, FWIW, he also suggested that such a small change would probably not make any detectable difference !
You only ‘advance‘ a cam by advancing it compared to its correct timing figure. If you advance a cam that is retarded, you are simply ‘correcting‘ it...
Not all cams come off of the grinder 100% correct. Same for cam sprockets. I believe that a lot of people who “advanced” their cam x degrees have actually just put the cam timing to where it should be.
I recently fitted a cam from a known good vendor, I had to alter it by 5 degrees simply to get it to his suggested figures.
But, FWIW, he also suggested that such a small change would probably not make any detectable difference !
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