Dyno questions

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acotrel said:
About dyno testing bikes which use methanol. In Australia we've only had bike dynos for probably the last 15 years,
Don't be silly, I've got some TwoWheels motorcycle magazines which have dyno charts of road bikes that they tested from the 1980s.
By the Sydney-based ? accounts they published, those folks were very experienced with their dyno even then.

Cook Nielsen in Cycle Magazine (USA) in the 1970s somewhere published a very good series of accounts of dyno testing and developing an XT500,
or TT500 was it?, which they were using in enduro racing ? It details removing the airbox and fitting a larger carbie and different exhausts,
which they ran through a whole series of dyno tests to get maximum torque and a healthy power output. There are a lot of hop-up tricks for the
XT500, and they ran through practically the whole lot of them, one by one. Very strong engine by the time they finished, would have to find the
mag to see what they ended up with...

P.S. I seem to remember they tested a whole series of different carbies in this thing, to see which worked best.
Each one required a little fiddling to get the best from it.
 
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I saw bike dynos here as early as the 80s, however the instrumentation was negligible. I suggest the computerisation is fairly recent. As late as 1990 even PCs were not so common in our laboratories. We had them however they were rudimentary, the decent software is recent - as I said - the last 15 to 20 years. In the mid 80s we were writing our own software for basic chemical analyses, monitoring a dyno and an oxygen sensor with a computer must have happened later than 1990 in Australia. Our bike shops were a lot of duds, I cannot imagine them ever being progressive. I have friends who were racing superbikes in the 80s, I will ask them what they had access to. The state of tune of the bikes wasn't very high back then, many used Yoshimura cams - there was a lot hotter stuff available, but not so easy to find. When did we really start using the web ? I think the bike we raced in 1980 had cams sourced through the Italian consulate in Melbourne.
 
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I'd certainly agree that computers have come a long way in recent years.
However, gas analysers have been around for a fair while - when did pollution equipment come in for vehicles, in the 1970s.
Good equipement then was expensive, its been getting cheaper over the years.

Buying a good dyno setup yourself is still going to cost megabucks, compared to just hiring it as needed ?
And, you get the skill of the operator, who has (hopefully) done it all before.
 
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We have little men running around servicing our gas heaters then testing them with gas analyses for carbon monoxide leaks. The calibration standard is expensive, so many of them don't do that very often. So what do the results mean ? Are you really going to tell me that the average dyno operator is on top of the accuracy and precision of his oxygen sensor ? Or even has an idea of the errors inherent in his equipment ?
 
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hobot said:
Here's some scope on gas analyzers, some DIY. That and a G sensor gizmo might help dial er in at home or nearly so.

https://www.google.com/#bav=on.2,or.r_q ... s+analyzer
I would use a rolling road type Dyno or engine Dyno, (as an engine manufacturer would use) as this is the only method that will put a load on an engine on full throttle, the only safe method of setting up the carburetion is by riding the bike up a slight incline and doing plug chops to get the jets right.
For setting the tick-over (Air/pilot screw, for those non racing carbs that have one) absolutely SPOT-ON a Gunson Colortune Kit is a must, One word of advice use it outside!( away from your neighbours on a deserted road) on a dark night-you’ll see it much better :!: :shock: :D

I have never used an exhaust gas analyser/tester but for £80 this is cheap;

http://www.halfords.com/webapp/wcs/stor ... yId_255216
 
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The only one of those color-tune thingies I've met, if you set up Commando idle as per the manual and then looked at it with a color-tune, it said it was all wrong !!?
 
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youtube Colortune to see what it should and should not look like but mostly just idle setting tool so not that useful otherwise. I will attempt to dial in Peel's crude Lake Injector with and w/o boost going by the way air craft users do it, very tedious part throttle adjusting till WOT and flow measuring then needle scratching in stages. There's a 1/2 m long straight steep 10 miles from my office with a truck brake check pull over at base, so about perfect place to nail it up to top, kill and coast back to check plugs and review data logger clues for how hard I can actually load engine on real road loads. I have practice climbing loose steeps keeping tire spinning so expect similar on testing Peel up this hwy steep, so don't know how that'd translate to strapping down on drum dyno. I know she'll be well over 100 mph by 1/4 m mark with a sharp turn at top so hope the slope allows slowing up in time to matter. i just ordered a car cam with GPS and G-force sensors so it data logs in case i'm too occuplied controlling the tire spin crashing practice. On the loose steeps it turns into a slight flat tracker style of going up in a crabbed skewed angle to not slide off slope of crown. Fun-weird steady state condition that's throwing rocks back off front and rear but not hard to hold balanced- as long as can keep the acceleration up, soon as front loads down though I never know if i can control it on the Snot like uneven surface. Good throttle control practice not to spin right down yet not bog down either.

I do know that a potentially wonderful engine can be a dang dog till everything just right then suddenly wakes up like crazy on very last little thing done in desparation depression of boggy soggy power prior.

I had talk with the fella who sold me pre-Peel. He does the garden tractor pulls with flat head side valve twins. Says he gets over 100 hp/9500 rpm on 1100 cc with big valves, .6+" valve lifts and 52 mm carb. Can ya even imagine being beaten by a lawn mower clunker : ( Ugh I can as I've seen em pull loads that'd tear a Norton apart, ugh.
 
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I would have thought the setting the idle mixture is a matter of leaning it off until the motor misses then backing offslightly so the it just beings to run smoothly, how can you get it wrong ?
 
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Amal idle scews controls the AIR SUPPLY.
So you set it accordingly, in conjunction with the throttle stop screws, to give best slow idle...
 
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I think the idle screws on some amal carbs adjust the petrol supply. If you screw it in and the engine starts spitting back through the carbs, what does that mean , Rohan ?
 
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acotrel said:
I think the idle screws on some amal carbs adjust the petrol supply.
I've never met an Amal that works like that.
(And can't comment how Amal Mk2's work...)

acotrel said:
If you screw it in and the engine starts spitting back through the carbs, what does that mean
Don't know, never been in that situation. !
(And read the comment above).

Any of the Amals I've met, it would be time for a beer at that point.
 
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Rohan, If your carburation is correct, you should always get spitting back through the carburetor whenever you cold start the bike without using the chokes. It is a sign that the carburation is lean. When you set the idle on your bike, you should do it with the motor hot, and lean the carburation off until the motor spits back, then richen the mixture slightly until the motor idles smoothly ? I believe the idle screw on Amal GPs and TTs adjusts the petrol. It doesn't really matter, as soon as you start turning the screw , it becomes obvious. If you screw it in and the motor spits back through the carb, it controls the petrol. I don't even remember what the idle screws do on my Mk2s, if I adjust them it doesn't present a problem. I know instantly if it is running rich or lean as soon as I turn the screws.
 
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Anyone who adjusts the idle mixture while the motor is cold doesn't know what they are doing ?
 
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This has been one of the most entertaining and knowledge building threads that I have read lately. That’s why I like this forum. Great stuff.
Cheers,
Thomas
CNN
 
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When I was a lad we were told that it's a waste of time setting idle on a cold motor. Further to that, part of the same instruction was that if your engine did not require choke when cold it was set too rich, possibly as a result of setting idle when cold!!
I forget the details now, after all it was 40 years ago, but the last time I set up a pair of Amals, it took about ten minutes to get them in the ballpark, having previously satisfied myself that the jets, slides etc were i.a.w. the book. Then I went out and found a quiet long straight road with a bit of an incline, so the thing was pulling in top, had a few minor fiddles. It was all done in an afternoon. It idled nicely, cold started with choke, hot started without choke, clean pick up, clean all the way through the rev range, good economy. Mind you that was with the instructions from Amal and what would they know?
cheers
wakeup
 

texasSlick

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Back in the old days when auto engines had carburetors, I adjusted the idle screws until I obtained maximum manifold vacuum. This gave the most economical idle (tickover). Above idle in these carb. equipped engines, fuel mixture is controlled by the main jets, so obsessing with the idle screws which control the idle jets is of little or no consequence.

I agree with Rohan, the Idle screws on my Amal monoblocs control the air supply (they are throttle stops). I obsess with getting each cylinder contributing equally to the tick over, rather than being concerned over mixture ratio, which I can't control except by adjusting the needles, main jets, or slide cutaways.
 
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Tex, the main jets usually only operate at above 3/4 throttle, and it is possible to get the situation where the carburation never comes onto the main jets.
It depends a bit on which fuel you are using, however in bigger Amal and Mikuni carburetors which meter methanol (usually in speedway bikes) it is common to use X and Y type needles which come down very quickly to a very sharp point, and an oversize needle jet is used. If you try to jet a two stroke with that combination, it becomes impossible. In our H1 and H2 Kawasaki triples, the required main jet is the same size as the needle jet. To stop the system metering on the tip of the needle at full throttle, we recess the needle jet so that the tip of the needle is still captured at full throttle, and the metering occurs at a slightly lower level. The other thing is that we use needles with a petrol taper, and get the mixture as lean as possible right down the needle for the full range of throttle openings. I've used methanol in a T250 Suzuki road racer, and the danger is that on a long fast straightaway, when you shut the throttle you can get a seizure. It is critical on road racer bikes that you get the metering at 3/4 throttle right. Setting the idle mixture is the least of your worries on a four stroke, however on a two stroke, the motor can even refuse to start if it is set slightly wrong, and the motor might even refuse to transition from the idle circuit to running on the needle jet. None of this is difficult stuff, but you have to be clear in your mind which jets are working at various throttle openings. Personally on my Seeley 850 , my main jets are rich, but it is very lean right over the full range covered by the needles and needle jets, the idle is set lean enough to need the chokes to start when the motor is cold and doesn't miss when warmed up. I will say one thing for the 850 commando engine - it is great on methanol. However I've never used petrol for road racing except in two strokes. I wouldn't even attempt to race a Kawasaki triple on methanol on a road race circuit, it would be extremely expensive and hazardous.
Are you permitted to use methanol fuel in AHRMA racing ?
 

texasSlick

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To Acotrel:

I think we are talking about two different situations: you are obviously into racing carbs, my post regarded street set-ups. I know nothing of racing carbs. I have had my monoblocs and auto carbs completely dissassembled, and once knew and understood aircraft carbs. These fit my post.
 
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'the Idle screws on my Amal monoblocs control the air supply (they are throttle stops). I obsess with getting each cylinder contributing equally to the tick over, rather than being concerned over mixture ratio, which I can't control except by adjusting the needles, main jets, or slide cutaways.'

There are usually two things - throttle stops and the screws which adjust either the petrol or air for the idle mixture. I usually wind the throttles wide open and check that the slides are at the same height . Some carbs have no stops, and rely on the cables to hold the slides up when the bike is idling. I believe my old Amal TT carbs were like that, and also the Amal GP. Whenever I've set the idle on my Seeley 850, I've usually done it without thinking about it. I don't believe I've changed the stops on many occasions.
A few months ago I had my bike at Winton Raceway, and it refused to start. One of my more helpful friends (a local expert) decided the problem must have been the idle setting, so readjusted the screws to the correct number of turns out from fully closed. I watched him do it with a bit of amusement, and after I'd found a plug spanner and replaced the plugs and started the motor, I told my other mate to wind the screws back in (after the other guy had walked away to ride his own bike). I've never previously had a problem starting the 850 motor, however this time the bike had been sitting for many months with plugs still in, with carbon on them - when I tried to start it, it coughed once and refused to go. I still can't remember whether the idle screws adjust fuel or air. I simply wind one in and watch what happens, then go from there.
I really love my Seeley 850, it is such a fun bike. I think you guys need to relax more.
 
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