Cyclemaster Performance

Hi Gordon,
 
I am genuinely interested in the feedback from forum members on this one. Most of my recent riding has been on larger capacity Cyclemasters with engines modified in some way...
 
I did however spend a full year "touring" a standard 25cc Cyclemaster round a 10.7 mile circuit from my home (by touring I mean lying prone in shorts and trying to get round the lap in shorter and shorter times - ahem!). My best lap was at 22.1mph with a maximum speed of 33mph on the downy-bits and a minimum of 12mph on the uppy-bits
 
Wind and hills make a big difference to top speeds of course, and maximums well into the 30's mph are possible on a standard machine if so assisted. However, at those sort of speeds on standard gearing, the time-area of the exhaust port is about half of what it needs to be to produce peak power, the engine is adding little or nothing to forward progress and so little fuel charge is being pumped by the engine that the plain little ends become vulnerable.
 
Cyclemaster were of course very sensible in designing the engine to produce good(ish) low-down power, achieved in part by closing the disc valve just 33 degrees after TDC and by keeping the exhaust duration (130 Degrees) and transfer duration (110 Degrees) conservative by comparison with geared bikes.
 
In my experience, on the dead flat in totally windless conditions, a really good 25cc Cyclemaster will hit about 25mph with a prone rider in the saddle. Tales of 35mph "blueprinted" standard 25cc Cyclemasters are I'm afraid "bar talk"
 
Interestingly, the time-area of a 32cc Cyclemaster exhaust port is even more conservative than that of a 25cc barrel. Cyclemaster clearly opted for much better climbing characteristics than for power higher up the range that may have resulted in the marques good reputation for reliability being dented...
 
Cyclemaster claimed 20-25mph for the 25cc machine, whereas the 32cc bikes were clocked at a sustained 23mph in period road tests...
 
If you have two 25cc engines fitted to your bicycle Gordon, I reckon you might add a few mph to the quoted 25mph, but the engines will still run flat at higher revs as the blowdown period will be insufficient to promote good scavenging. If you want more speed, higher gearing and /or porting will be required, but that will knock your bottom-end performance of course...

Now here's some interesting info. from the 'other' camp! That is the BSA Winged wheel.

After a good run on this year's C2C, and having run with some of the Cyclemasters, some comments;

• The Cyclemasters seem to be lower geared than the BSA, and climb further and easier, if slightly slower. I had to start pedalling at a higher speed to keep the little BSA motor interested in life.
• On the other hand, when running on the flat without a strong headwind, the BSA would probably run along marginally faster than the Cyclemaster. The 25cc bikes ran amazingly well, and surprised me with their climbing ability and how they would keep fighting at low revs.
• The BSA had odd periods of four stroking, and would occasionally flood the carb. -Fixed by riding for a few hundred yards with the petrol tap 'off'.
• Thinking today about various things including ignition and carb. flooding. Some may know that I have temporarily given up on the original magneto and indeed two other magnetos that I simply cannot get to run acceptably and currently use an old chainsaw ignition! Purely out of curiosity I tried today opening up the plug gap from the 18thou I have been using. I expected trouble at a 25 thou gap, but it started fine and ran fine. Perhaps even smoother than before! So, I thought I would push my luck and go for 32 thou. Amazingly, it still starts fine, runs better at lower revs, and pulls very cleanly when under load. 
•  Amazing really for an ignition with no points and no condenser, and which I pulled out from the garden shed at the bottom of the garden where it had lain neglected since it conked with a seizure about ten years ago. Moral - don't throw anything out!!

J.

Interesting replies guys.

My 25cc motors seem to be a little 'flat' at the moment, one at a time they give 18mph using a hand held GPS for speed, that is on the flat, bolt upright, no wind.  Both together give 22mph + although 'front' engine is reluctant to rev properly under load, its probably 4 stroking beyond this.

I have just swapped exhausts from front to back - main reason is so I can fit right angle bend on front exhaust to deflect fumes from feet,  One exhaust is 'odd' in that there is an un-boltable section in the 'silencer' with no baffle, it will be interesting to see if there is a difference in 'go' with them swapped over.

Now both motors a bedded in I will recheck timing and try to set mixture better..

My 32cc bike will reach 25mph plus on flat but I tend to back off on slopes and 'cruise' at 18 - 22mph.  On a steep downhill I pull in clutch and either let engine idle or stop then restart when speed gets sensible.  I have one of Pete Stratfords pointless ignitions on this bike, brilliant spark but runs best with a new old stock 'KLG cyclemaster plug'.

Gordon

Maybe I need to give Pete Stratford a call!

Best,

J.

Hi Gordon,

Absolutely echo your riding technique. Since I knocked-out two little ends in succession mercilessly flogging a Cyclemaster down a long steep hill near my home about 5 years ago, mechanical sympathy has prevailed and whipping-in the clutch around the 28-30 mark and coasting until the speed drops-back to the mid twenties is now my preferred technique too...

It doesn't suprise me that the twin-wheeler is down a bit on speed when driven by just one wheel because the bike still has to drive the chain and clutchshaft of the silent engine and drag another 30 lbs in weight along. Mind you, low twenties under one engine sounds nearer the mark.

As you will appreciate, with Cyclemasters, small improvements add-up.

My first 25cc machine would only do about 20mph when I first got it running. Over several months I made many changes, each adding a little to the performance:

* Bicycle chain too tight, loading the freewheel sprocket - loosened the chain
* Ignition too retarded - set to 23 degrees (eventually to 28 degrees by slotting the mag backplate)
* Mudguard kissing the tyre - sorted the mudguard stays
* Brake blocks kissing the rim - trued the wheel
* Tyre pressures too low - inflated to 50+ psi
* Mixture strenght too rich - dropped needle 1 groove and then shimmed-up the needle by the equivalent of half a groove with gasket material under the clip
* Top end slightly coked - full decoke of ports and ring grooves.
* Rings not fully seating in the bore - lightly honed bore and lapped-in the piston and rings
* Transmission noisy and "hunting" - replaced the final drive chain
* Etc. etc.

Of course, several changes made things worse, but striving to get every last bit of performance from the standard engine was a great learning experience.

By the time I'd finished, the little bike would lap my circuit without pedalling at any point and would average almost 6mph more than before whilst consuming considerably less fuel.

It took a full year to get this result however and fettling two engine wheels will I think take some time!

Incidentally, I was lucky in having a turbine smooth base engine to start working with. For this you need to have:

* A good crank, true to within 2 thou TIR.
* Good main bearings.
* A good magneto rotor with no looseness at the centre.

If not, at higher speeds, the motor will start to vibrate and this clips-off power a little...

interesting comments to a cyclemaster virgin, like me...incidentally, on the norman nippy carburettor, the needle clip is dished, so that , by inverting it, you can move the needle in half step increments...whether it would be possible to "adjust" the cyclemaster clip to give this effect I don't know...mine is the 32 cc version....where can I get the drive chain from?, also the tension adjuster?  I read that there isn't space for a split link on the chain, is that the case?

Continuous chain is best, but I have seen many Cyclemasters working perfectly well with a split link chain fitted. Just make sure that the retaining clip faces away from the hub (i.e. faces the back of the petrol tank) Also, be sure that the chain can not rub on the inside of the hub, even when you lightly press down on the magneto cover. If it does, you may need to:
 
* Fit new engine mounting rubbers or tighten the mounting bolt.
* Adjust the wheel cones (on coaster hubs) to take up excess play
* Space the engine towards the magneto side on the mounting bracket bolt by using an additional (thick) mounting bracket washer between the engine and the bracket.
 
I have got a spare chain adjuster if you'd like it KJ and a bit of chain. I'll send you an email shortly...

many thanks, Peter.....forgive my ignorance, but I can't help wondering why you have to have two carburettors...surely one carb would be enough, as the induction period is going to be effectively alternating between cylinders, and the imbalance would be self regulating, being dependant on the individual cylinders  sucking requirements...the only proviso I see is that the fuel feed is sufficient to supply the increased consumption rate, which on single cylinders is only a dribble at most.....in my youth I well remember the pain of trying to balance S U carbs, so that the crankshaft didn't break in half, due to imbalanced carburation!

Just tell me which chainsaw they came off as for my next project I want two. Grumpy

Back in 1985 about this time, a young man  age 17 called Jon Shanks left me a Cosworth Formula One piston. He had entered the Shell Mileage Marathon with a car using three bicycle wheels with a Aircraft camera pod as chassis.   He made for it, in my works and foundry a small engine with Aspin type sleeve valves and and we all helped this inivative and industrious boy.. It just about worked.I persuaded him to take a Honda 50 engine with him to Silverstone as back up, I was certain the Aspin wouldnt do what he wanted. The Honda engine did I believe do about 1300 MPG. easily beaten by several others. He was however presented with the inovation award by Cosworths MD for his Aspin type engine. He left school and went to work as invited to Cosworths. It is not unfortunately a happy ending as the piston inscribed by him ( which I treasure) was found in his flat, after his death in a motorcycle accident on his way to work. His aim was to search for the best not just in speed but also in economy. Engine and rolling tune go hand in hand wether its for speed or frugallity but most importantly perseverance and constant search for little improvements are the key. I think next year I might organise a," how far can you get run" on a measured fuel load. I would not be surprised if a 50 cc  wins.   Grumpy

Hi Phil,

Sorry to disappoint, but having re-visited my garden shed, I find that it was the strimmer and not the chainsaw I had robbed of it's ignition!

So here we go, the strimmer was a 'Flymo Maxitrim 430'. I expect that any of the small Flymo' motors would have similar ignition systems. I guess that it is approx. 32cc, and it would date from about 1990.

The Winged Wheel certainly runs sweeter on a larger plug gap. I would expect that as the revs. drop to a slow tickover, sooner or later the spark will snuff out as there is no spark when the flywheel is flicked round by hand. It does however start regularly first time when I engage the clutch, lift the back wheel off the ground, and just push the pedal round with my left leg, so the spark is good enough at that cranking speed. The flywheel mass is much less than the original Miller item, so the BSA will not tick over slowly, I presume partly because of that. It will drop down smoothly to a fast walking speed, and accelerate away from that OK.

If this type of system could be used on the 'twin', I think the small flywheel mass will not be so critical due to the two power strokes per revolution. All you would need would be one flywheel, and two ignition coil units. A simple, adjustable back-plate fixed to the original backplate mountings, with the coils 180 degrees apart should be foolproof??!! You will have to cut a new taper and keyway for the flywheel to fit the Cyclemaster crank, but hey, you would do that in your sleep, right! In addition to the clamping screws for the backplate, I drilled and tapped the crankcase and backplate to lock it into position once timing had been set. Timing will be fixed, and not variable with revs. as modern electronic systems may be.

Oooooooooh, sounds like a great project that shouldn't keep you out of mischief for very long!  Good luck with the hunt for Flymo bits.

Best,

John.

Hi Phil.

A quick search on Google suggests that new ignition units are available at about £30 apiece, and the flywheel is about £32, all no doubt plus vat and postage/packing.

It goes against the grain using new stuff, but at least it should eliminate the problems you could inherit with secondhand stuff.

Try: www.shop.flymo.co.uk

Best,

J.

Thanks Potty P  The project is not to fit it to the 65cc Twin but for another where the engine goes closer coupled on the other end as a write up sent to me by Colin K. Originally this way was considered for my twin and was used in a 50 cc racer. but would have had to be out in the frame and I did want it as per cyclemaster in a wheel.. So you know who its for dont you? If any one has a mag flywheel for a twin I am in the market.It should with a few gears reach 50MPH but we shall see.  Grumpy

Its interesting to note the difference between plug types, and makes, and plug gaps. As mainly a four stroke man, the main criterian was plug reach unless much higher performance and therefore temperatures are involved. My old Norton had a plug you could strip and clean the electrode and I think I never bought another plug for it. My power pak synchro, which has fired, wont spark on some even new plugs but will on a scabby old one. Peter is very specific on plug type and gap for Cyclemasters and swears that this does change performance where I swear when it is something else.My main problem is that since most components have, on my bikes, been modified I am unable to refer back to the original designers who sweat blood to arrive at the best compromise.That is why one of my cyclemasters is bog standard ( at least in its engine) and has the original design to refer back to. Talk of hot plugs, gaps, exotic electrodes can be a bit premature on a silent motor!!!!    Grumpy

Has anyone else tried this ignition system? 

OI have one fitted to my 32cc cyclemaster and the spark / starting is brilliant.

http://www.greenmachinery.co.uk/product/-/MPMD724/-/sid/EQ8H-TtQw-zm2A-aVD9-IjkR-8A

The MECO SIG-01 ignition module is a metal-encased solid state unit suitable for most small single cylinder petrol engines. It is fully sealed against oil, dirt, moisture etc. & is maintenance free. Fitted to many chainsaw, lawnmower & brushcutter engines it replaces mechanical contact breakers and condensers and improves starting. Timing is fully automatic and is permanently set, so fuel economy is maintained. Each unit is supplied with a full set of fitting instructions and wiring diagram

Hi Gordon,

Could you tell us more please? Any photos, how does it work, how does it fit, do you need an external coil etc. etc.

Thanks,

John.

Looks really interesting Gordon.

My guess is that it will rely on an external power source and an ignition coil to function?

I'm dying to know more...

It works using the coil and flywheel of standard mag.  You just replace the points and condenser, dont ask me how it works but I think it is the 'impulse' or magnetisim in the mag that does it.  How the 'electrickery' in it works I do not know.

I bought one from Pete Stratford a few years ago for my 32cc Cyclemaster, the bike stars as soon as wheel turns now.

I was hoping someone else had used one

My 32cc cyclemaster has at any time most of the faults mentioned above including 

Buckled wheel kissing the brake blocks
Mudguard stay rubbing 
Tyre rubbing on the frame 
Cycle chain is too tight, I have it stretched to give the tyre clearance...
Drive chain is slack and rubs on hub, at least there are newish looking scratches, adjustment is at max...

It manages 24mph. It went from 4 stroking at 21 mph to not four stoking and 24 mph by half of a turn of the mixture screw (thanks Peter). Incidently 25 mph using super unleaded perhaps not worth the extra cost. 

Perhaps if I give it more attention will it challenge or even beat a honda novio (second slowest on our runs out)? 

If someone can point me to a source of 1.75" section tyres (once inflated) three of those things can be corrected and the race could be on. My current tyre measures 1.85 inches across though the letters state 1.75. no point doing anything until I can get a tyre as I will leave alone rather than mess the the frame about. A 1.75 section or perhaps better a 1.50" would make life easier.

I attempted to true a bike wheel once, I made it worse then broke a spoke. I am reluctant to try on my cyclemaster. Do you need a jig?

Will new bushes take some of the slack out of the drive chain? 

Thanks,

Woka.