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ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 8:46 pm
by stew79
1979 ccm 500 q3 4va very good bike. (apart from the frame breaking at the head stock)

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 9:39 pm
by chucksy
very interesting,keep posting,lovely to see the old girls being brought back to top condition.They are the Spitfires of scrambling.

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 9:54 pm
by Andy Chaos
Great description Chucksy does that mean a 75 is a Hurricane.
I like the brake skimming plate Stew.

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 10:02 pm
by chucksy
you could say that,its a toss up ,tween the two really, 50 50. I like my 79,s, but I loved my 75,wish I still had her.

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 10:14 pm
by Malcolms Lad
Amazing what a beast these things are, love the organised caos we all seem to live in!

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 10:59 pm
by stew79
some more ccm pics

Re: ccm in bits to fit new cam

Posted: Sun Feb 14, 2016 11:33 pm
by minetymenace
Tell us more about your ignition and those ring down curves.....
Andy Chaos wrote:does that mean a 75 is a Hurricane
.....nope, a 73 Hurricane is a Hurricane. :cool:

Re: ccm in bits to fit new cam

Posted: Mon Feb 15, 2016 10:27 am
by Mark Cook
Wow, a serious amount of work reinventing a wheel. You will have problems, but I can see that given time you will get there.
I just wish I had the spare time that you've put into that.
Well done.

Re: ccm in bits to fit new cam

Posted: Mon Feb 15, 2016 1:03 pm
by stew79
ignition ring down curves are obtained on the scope using some clever techniques from an Australian boffin called hugo holden. he has been very helpful in sorting out the ignition, and coil. unfortunately electrons is too big a subject for me to even scratch the surface of, (bikes, mx, engineering, tuning, anything that i can see working is my limit) so i can only say that coil "a" is more efficient than coil "b". i have a methodical mind to copy and improve on something that is in front of me. one day i might even invent the wheel ! (self employed, not down the pub very often, kids grown up and moved out, can mean spare time to sort out the important stuff)

Re: ccm in bits to fit new cam

Posted: Mon Feb 15, 2016 8:44 pm
by beat
wheels can be very different, and each has some good sides and some bad sides.
so, - why not reinventing a other one for a particular use :?: :?: :?:
at least myself, - I had to learn this.
<212

how ever, very good and interesting stuff.

keep going stew :!:

:thumb :thumb
beat

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 4:12 pm
by hwan
STU - are you using a washing machine motor for the electrical test unit .... what are you using for speed control - a light dimmer, or is it DC ?

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 7:22 pm
by beat
stew79 wrote:good coil (experimental)
stew79 wrote:made in china patter coil (very inefficient but still works fine)
if I am right, you go from the lenght of time of the primary bouncing to decide the sparks energy ore duration ??

beat <201

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 8:07 pm
by stew79
hi hwan, yes its a washing machine motor (universal type) with an 8 amp variac . (£40 of ebay, bargin !) speed is 0 to 12000 rpm. (i have a digital hand held rev counter.) with over voltage it might do 15000 but never tried it.

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 8:33 pm
by midgie
just looking at your new kickstart quadrant, the nose looks like its a b25 or b44 type and not the short nose b50 type, I could be wrong but worth checking.

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 8:45 pm
by stew79
hi beat, as i understand it, the voltage peaks (- and + ) can be used to calculate the average current, then the energy (for the first few oscillations ?) this is with a 100 ohm resistor in parallel with a 0.1uf cap between earth and the outside (earth) of a spark plug. (set with a 1mm gap) the duration is across the screen in what ever time scale you are using. the boffin hugo in australia could come up with all sorts of equations and maths to explane all the joules of this that and the other divided by so many milliseconds, but i dont need to know that. using the scope like this for me is to compare one cdi coil against another at a specific speed, or over a range of speeds. with a more efficient coil (home wound) you can have the same spark energy and time factor with a much smaller main capacitor. (cdi stuff only) this means less stress on the rest of the ignition components. it is also the only way of seeing if your spark polarity is correct. (sparks negative first) the next thing is to fit a points plate, cam etc on the rig and look at some mdi ignition sparks on the scope. (6 and 12 volt supply) to see how my collection of normal coils compare to each other.
stew

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 9:00 pm
by stew79
hi midgie, i dont know ? i copied the old one except for the length of the end with the roller bearing in it. its approx 0.050"longer to reduce the end float on the lay shaft. (cant remember back, but i think float is about 0.005") should have made the spline 19mm dia and used the standard xt kick start arm in the first place, but i thought the ccm arm was savable. (theres another part you cant buy)
stew

Re: ccm in bits to fit new cam

Posted: Tue Feb 16, 2016 9:41 pm
by minetymenace
stew79, not quite sure of your circuit for the ring down, but if you can draw it, I'll let beat know the equations.....

The decay of the ring down is proportional to the resistance in the (HT) circuit, (bigger resistance = faster decay)
The frequency of the ring down is the resonant frequency of the L (coil + other inductance in the circuit) & C (100nF).
The energy (for comparison anyway) is proportional(ish) to the peak voltage (kind of, the bigger the first ring the more energy)

In reality (in the engine and running) the secondary will not "ring" as in the above traces, but as the Boffin of Oz seems to imply, its not a bad way investigate getting the most out of your nishers.....

Re: ccm in bits to fit new cam

Posted: Wed Feb 17, 2016 11:09 am
by stew79
hi minetymenace, both the scope pictures were taken using an experimental cdi for a S*zuki, at 3000 rpm, 1uf main cap.the firs pic is a home wound experimental coil, (0.1mm wire on secondary, center tapped, but 0.15mm seams more durable, easier to solder) the second pic is from the pattern coil thats fixed on the test board and is the same on the ccm. the ht lead goes to a new plug (from a car) with a 1mm gap.the plug is screwed in a tufnol plate with the earth going to the 100 ohm resistor then to actual earth. the 0.1uf cap is across the res, with the scope probe going to the plug thread and the ground lead to earth. the voltage drop across the resistor is only there when a spark is happening. the probe is 1;1 so the readings in the 2 pictures are what was going on. (you can see what ranges it was on, the y center is slightly up of center to keep the reading within the screen) i had my only one and only small disagreement with hugo over the spark gap. apparently it is usually taken that an ignition system is tested at 1000 volts using a string of zeners (2 strings with cdi) instead of an actual spark gap. i argued that testing at a low voltage dose give accurate figures for comparison purposes, but a second test should also be made at a higher voltage as well. (5000v) as in an engine at high speed 1000 volts wouldnt do much good. he says not to worry as the maths say it is ok.
stew
ps dose the maths really mater as long as the bike runs well ?

Re: ccm in bits to fit new cam

Posted: Wed Feb 17, 2016 8:39 pm
by hwan
VRIAC .. you're controlling rpm on voltage, does it give a reasonably linear rpm range? ....... have you ever tried using a Dimmer/SCR type device ?

Re: ccm in bits to fit new cam

Posted: Wed Feb 17, 2016 8:47 pm
by beat
stew79 wrote:dose the maths really mater as long as the bike runs well ?
at the end, the ignition should be to serve the engine - and not the bike ( ore the mats ) the ignition!

beat :grin:

Re: ccm in bits to fit new cam

Posted: Wed Feb 17, 2016 10:28 pm
by stew79
hi hwan, the variac works very smooth and progressively. the motor will idol at 50 rpm ( 60 volts) and is so controllable that you would think it was designed just for this purpose! i thought about a dimmer switch to start with but the motor load is very reactive so that could fry the switch, also it might not handle the power. up to about 3 hp.(i test alternators etc on it, so it can draw a high current)
stew

Re: ccm in bits to fit new cam

Posted: Thu Feb 18, 2016 12:13 pm
by hwan
Stew, thanks for this info - as ever the simplest solution is best (KISS principle).

i've used a dimmer in the past, and yes it failed 'interestingly' when i loaded up the w/machine motor ........ and i guess it was inductive loads as they are not known for operating strip-lights for long.

I'm tinkering with my flow-bench - primarily to see what valve lift air flow drops off in a standard b25 head - and was looking at alternative idea's other than switching on/off various fan units or (very non linear) orifices.

Question answered. :grin:

Re: ccm in bits to fit new cam

Posted: Thu Feb 18, 2016 6:06 pm
by stew79
hi hwan,i have often thought about the merits of flow benches, and if they could really help. as i see it an engine runs on a wide variety of pulses of air fuel mix with nothing smooth and steady that a flow bench has?. resonance, port length and diameter, the blank spot caused by the diameter of the valve etc all come together to form an insolvable problem. in the past with tuning small hondas i have considered running the complete engine with a powerful motor (no ignition system or petrol in the carb) to see how changes to port size etc effect how much air it can draw in at a certain speed and throttle opening. as the more air it can draw the more power it could make when actually run as an engine. but far too technical for me, i like looking at ports, valves, valve seats, (thats the place were you can make a difference) squish bands, etc. to try and improve performance. but put all that to one side, carb jetting is probably more important anyway. (assuming the ports arnt tiny, and you have a good spark) the size of the fuel droplets is where extra power can come from. i have had help here from white bross racing usa, who wrote me a letter in the 80s (before internet stuff) with some good advice on using modified 2 stroke carb parts in a high performance 4 stroke. i have never looked back.
stew

Re: ccm in bits to fit new cam

Posted: Thu Feb 18, 2016 7:20 pm
by hwan
As with all these things, they seldom tell you answers, but point you into a hopefully meaningful direction.

There is some colleration between a flow increases and a power increases - however a 5% flow increase will seldom translate into anything near 5% more power.
Sadly an inlet port modified to flow air into the cylinder will tend to flow better in the wrong direction !
Flow-benchs have come up with some interesting counter intuitive techniques which have shown useful low rpm torque increases.

As ever any mods need to tested on the track/salt .... even a dyno will tell you lies.

Re: ccm in bits to fit new cam

Posted: Thu Feb 18, 2016 9:17 pm
by beat
hwan wrote:There is some colleration between a flow increases and a power increases - however a 5% flow increase will seldom translate into anything near 5% more power.
stew79 wrote:carb jetting is probably more important anyway.
stew79 wrote:the size of the fuel droplets is where extra power can come from.
gents, - I put my hands in to the fire for this :!:

totale agree :thumb

beat

Re: ccm in bits to fit new cam

Posted: Fri Feb 19, 2016 6:26 pm
by hwan
Re Jetting - the jetting depends on where the air is flowing in the cylinder - lots and lots of technical papers written on this subject - also connected with fuel droplet size (centrifuging out onto the manifold/port/cylinder walls).

Lean burn engines rely on well mixed fuel/air - i.e. lots of controlled swirl/tumble and fine fuel droplets - hence direct injection, etc. as opposed to single point injection.

It is well known that some car engines prefer (produce better torque curves) Delloto's over Webers ... surprising since the Dellortos's are basically a Weber copy - the slant 2.3 vauxhall engines always produced more power on Dellorto's - yet the 4 valve Lotus headed HSR version preferred Webers (despite being supplied with Dell's from the factor)
Droplet size has been confirmed as the difference.

You simply cannot say 'big' droplets are better for power.

As for how important jetting is ..... get it on a dyno and you find that you can go surprisingly rich before power drops off .... as long as the ignition is up to scratch and the ignition curve is right.
A lean setting can be 'hidden' by slight over advance (lean mixtures burn more slowly).

An endlessly fascinating and frustrating subject.

Re: ccm in bits to fit new cam

Posted: Fri Feb 19, 2016 8:10 pm
by stew79
hi hwan, its always nice to read stuff about this endless subject but......... i dont feel car stuff can be compared to bike stuff. i did only say that bigger droplet size "can" lead to more power, as you know thats not just my opinion. back to the bike stuff please,(far more exiting) tradition says bleed type spray tubes (with lots of holes for air) with a tapered needle in the middle, are for 4 strokes. this gives you a very fine mix (tiny droplets) with a cv carb it works well, economical, smooth, can be quite lean with not much ignition advance,good mpg, no good for max power or hard sudden acceleration. (like your average car) tradition says primary type spray tubes (no mixing holes just a single air inlet) with a tapered needle in the middle, are for 2 strokes. this gives you a very coarse mix (big droplets) to help the mix get through the reads, round the crank, ports, etc and up to the combustion chamber. with the right jets this type of coarse mix is excellent for a 4 stroke, the richer the better.!! advance the timing till it pinks, then increase the fuel till it just splutters, then try a bit more advance.!!! (if the squish clearance is small enough, and the spark is strong enough, you will make more power) the hardest part is to balance the pilot side with the needle to clean up the slower running part, but it is possible. the end result is almost like having an accelerator pump on the carb, it will respond to sudden quick openings, and pull from low revs as well. i have used these techniques on 20+ bikes of all makes and it really works (thanks whit bross racing usa) in bike world i find that week mixtures dont like much advance, which is the other way round to car world ?
stew

Re: ccm in bits to fit new cam

Posted: Mon Feb 22, 2016 1:23 pm
by hwan
So the air/fuel in a car engine is different than a bike engine?

As for 'tradition' ....................... i think i would simply like something that works - hence using a Kehein flat-slide - intended for a two-stroke (KDX200) on my B25 MX'er ... but then again i was masking an ignition curve problem.

Re: ccm in bits to fit new cam

Posted: Mon Feb 22, 2016 3:27 pm
by stew79
hi hawn, i have played about with many old cars with webbers. they as you no have an emulsion tube or two with lots of little holes (no needles though) but with out an accelerator pump to help acceleration, it would be un derivable. its the old problem of a steady engine speed with not too many emissions, against quick response and maximum performance. (also in car world there is usually more cylinders than carb chokes, and inefficient manifolds etc) su carb are ok for most gentle driving, but imagine it being on a single cylinder bike ! throttle response would be terrible. the slide will only rise as the engine speed increases, even with the butterfly wide open.(to keep the mixture within certain limits) to make the slide open quicker (quite simple) would lead to a week mix and a stumble. i have spent all my bike life involved with racing stuff for road, track , mx, beach, anything but cruising along. the requirements for both worlds are TOTALLY different. inside your kdx carb is probably a "primary" type needle jet (spray tube thing) this is the supposedly "only for two strokes" part. these are the parts (sometimes needing additional machining) that can make all the difference to a 4 stroke.
stew

Re: ccm in bits to fit new cam

Posted: Mon Feb 22, 2016 6:15 pm
by hwan
I actually deleted a long ramble about various carbs and their designs and uses, about how many cars, boats, motorcycles, scooters and one airplane i've modified, tuned, raced, rally'ed and drag-raced since 1969.

I wont mention the 20 years working on unsteady fluid flow in rotating equipment (including 3 years working with Cambridge Uni), the work i did on my PhD on rotational flow inside Cylinders at Liverpool (granted i left before finishing the work) or the various bits published in scientific mag's.

Because after reading what you wrote about the Keihen carb, i realise you are absolutely right i know f**k all about the subject.

Re: ccm in bits to fit new cam

Posted: Mon Feb 22, 2016 7:07 pm
by Andy Chaos
hwan wrote:I wont mention the 20 years working on unsteady fluid flow in rotating equipment (including 3 years working with Cambridge Uni), the work i did on my PhD on rotational flow inside Cylinders at Liverpool (granted i left before finishing the work) or the various bits published in scientific mag's.
.
But you just did :?: :roll:

Re: ccm in bits to fit new cam

Posted: Mon Feb 22, 2016 8:13 pm
by stew79
hi hawn, i dint mean to offend you in any way. i have never studied anything this technical, or ever had anything published. (about anything) i was just replying to your question.
stew
ps i like mikuni better than keihen anyway.

Re: ccm in bits to fit new cam

Posted: Tue Feb 23, 2016 2:25 pm
by Mark Cook
It's a shame there is not the room on most B50's. In another life running 920 Nortons for sidecar cross. The best carb we found was the DCOE weber. The manifold was an interesting thing to make with limited tools though. Never measured for power, it out pulled any other outfit. Inspired at the time by work I was doing on cosworth based rally cars. Car engine research has had more money spent on it than any motorcycle.

Re: ccm in bits to fit new cam

Posted: Tue Feb 23, 2016 2:47 pm
by hwan
Mark .... time/money spent on cars Vs bikes ... agreed

Part of my deleted ramble included Webers on bikes (and Amals on cars), my NRE went well on them, just too damn big so reverted to Amals - i did think of split Webers on the BMW but found the CV Bings performed ok, so they were left on.

Stew - I will agree with MiKuni Vs Keihens - the K's are incredibly well designed - to a price & spares are relatively expensive.
The oval bore 30mm Kehien ended up on the B25 as it was the only arrangement i could get working despite trying Amal mk2/concentric/Mikuni ... as i say, it turn out to be an ignition curve problem.
The Mikuni's are easier to tune with infinite needle & n/jet combinations available (for many people, too many and they disappear up own a***e).

Re: ccm in bits to fit new cam

Posted: Tue Feb 23, 2016 3:16 pm
by stew79
hwan, theres the problem....i have never owned a race car of any sort. i have been comparing race bikes to run of the mill car stuff. (no good) and i have never owned a flat slide carb (or even oval) its been the old vm mik, usually second hand. in defense of keihens i must praise the std 1979 xr500 carb, its very good (event though it has the conventional bleed type needle jet)
stew

Re: ccm in bits to fit new cam

Posted: Thu Mar 31, 2016 7:58 pm
by stew79
hi all, not really anything to do with cams but.............. having re built so many cranks, i must just make a comment about the b50 / ccm ones. i think there is lots of possibility for these to be assembled together wrongly. to try and pull the pin in to the fly wheels with just the nuts, is never going to be very secure , and will probably loosen when its trued up. the overall width may also be too wide if the tappers arnt seated. i have successfully built them up before on a press, timing side first, then clamp 2 thick parallels across the outer diameter, and pressed the drive side on. it takes over 5 tones to seat the tappers up against the shoulders, then fit the 2 nuts and torque them up. this method will usually give you a very true crank with hardly any further tweaking. it will also be the correct width.
stew

Re: ccm in bits to fit new cam

Posted: Thu Mar 31, 2016 8:33 pm
by beat
stew79 wrote:this method will usually give you a very true crank
:thumb

myself, - I give this job to others, ... Mark Cook in this case.

beat :cool:

Re: ccm in bits to fit new cam

Posted: Wed May 17, 2017 1:37 pm
by stew79
10 new 4 valve cams copied from my factory special. just got to make some good followers to go with them.
stew