Camchain and tensioner seen up close in a cutaway bike engine

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Engine For Nowt

Blog Date - 05 January 2018

Thanks to the Chunky Tread group Sharon and I will be at the Manchester Bike Show once again this year. 

In the past we've taken a couple of the bikes and put up some pictures of our adventures. The thing is the other Chunkies have all been to farther flung places with wilder pictures so we don't really make much of an impression. We want to do something to start conversations with people, to engage them and get them to ask "what ya doing?"

Sam Manicom world traveller at the Manchester Bike Show
Sam's been around the world a few times. I went to Spain once...

Coming soon (with a bit of luck) Sharon will be sharing with the BAT readers what she's been up to with her Keeway 125. Put bluntly she's been all artistic with her petrol tank. The plan for Sharon is to get an old tank which she'll be painting at the show. She's a bit handy at the art stuff and we're hoping it's unusual enough for people to come and ask "what ya doing?"

Of course I don't have an artistic bone in my body - just look at the handguards on the CBF125 and CB500X to understand that the aesthetic aspect of life has passed me by. So what can an uncouth buffoon like myself do? I'll stick with what I know. Spanners.

The handguards on Ren's bike are bodged bits of metal and plastic and very ugly
I don't see the issue myself. Best stick to being a uncouth spanner monkey.

The idea is that I'll get an old knackered 125 engine and strip it down at the show. While the arty farty types what like pretty things talk to Sharon the coarse inelegant grease monkeys can tell me what I'm doing wrong. Hopefully there'll be a few people who might just learn a thing or two about what happens inside their motors if they're interested.

So I need an engine. Ebay offers nothing under £50 that's even remotely complete. So I ask on Facebook's "Shed Built Motorcycles" which is a very active and popular site. I asked...
I'm looking for a small 4 stroke motorcycle engine. It does not need to work as it is for demonstration purposes only! It's not going in a bike it's just going to be stripped. I'll happily pay a little for it and can collect 50 miles around Bolton (UK)

I was surprised at the number of replies! 2 engines for £15, 250 Superdream motor in Blackpool, SR125 engine and so on. Ultimately I plumped for a Chinese motor in Ramsbottom as that was the nearest. That said my heartfelt thanks go out to all the wonderful and generous offers. I'll not name the chap from Ramsbottom, he may not wish to be identified with a muppet such as I. 

So I find myself on a snow-covered road in East Lancashire. My host informs me that he and a couple of friends rent a workshop where they create various motorcycles purely for the sheer pleasure of doing so. 

This engine came their way but the consensus was it wasn't worth the effort of using an unreliable Chinese motor in one of their creations and that's why the motor is coming my way. I duly point out Sharon's cheap Chinese engine has been faultless but I don't push the point, I want the engine. I also get the bucket it is in! This is very handy as it makes an ideal sled to take it down the steep hill to my car.

The 125 engine is in a black rubber bucket on a snow covered footpath
Engine in a bucket. How cool (sic) is that.

So now I have a Chinese CPI motor. A brief look online suggests CPI is not actually Chinese but Taiwanese although they have factories in China and Indonesia as well as Taiwan. 

My next task is to strip it at home then rebuild it. Why? Because I want to ensure I get most of the oil out. I want to loosen any really tight bolts while I have all my tools. I want to know which tools I'll need to take. And - well - I'm curious. If it's a good motor (I have no reason to doubt it's not) I may put it back together and see if I can do anything useful with it.

The engine in the bucket is now in the footwell of Ren's car while the snow is falling
I'm glad I didn't end up with a GPZ900 motor in my little Ka

Hopefully we'll see some of you folks at the Manchester Show - do come along and say hello. Oh and if anyone reading has a spare unwanted petrol tank of any kind do let me know - we need one for Sharon to get all artistic with.

Reader's Comments

Borsuk said :-
Bugger. Working that weekend. Shnashing grashing frashing Dick Dasterdly.

6/1//2018 1:21:34 AM UTC
Ren - The Ed said :-
I'll take lots of pictures Borsuk, just so you know what you're missing.
6/1//2018 8:59:29 AM UTC
Bob said :-
Looks like a CG125 clone.
Have a look at the weird 1/4 speed cam shaft in the top of the cases, just below the barrel.
7/1//2018 10:01:04 PM UTC
Graeme said :-
This looks like your engine. The CPI Astor????? Never heard of it. And what is all the bulk on the left side of the crankshaft????

and here is what it is supposed to do......
8/1//2018 2:10:08 AM UTC
Ren - The Ed said :-
It is an overhead value CG125 clone. Yes it does have the peculiar 1/4 speed single cam with the first set of followers in the side of the barrel.

That bulk on the crankcase wil be the pickup or sensor for the crank position.

Cheers folks! I have started to strip the motor and found the crank to conrod bearing is seized. The oil was very low and rather skanky too. I suspect this engine endured the horrors of being owned by a "yoof".
8/1//2018 7:32:31 AM UTC
Ren - The Ed said :-
Hang on Bob...will it be 1/4 speed? Half speed surely. Camshafts have to run at half speed. The fact there's only one shared cam lobe wouldn't change that.

Oh you got me thinking now!!
8/1//2018 7:52:01 AM UTC
Bob said :-
Pretty certain he's 1/4 speed. One complete revolution every 4 strokes of the engine. Normal camshafts are 1/2 speed because you've got separate lobes for exhaust and inlet valves, but when there's one lobe to do both jobs it must me 1/4 speed (I think) - have a look when the barrel's off and let us know.
8/1//2018 9:59:22 AM UTC
Alistair said :-
What you came to Rammy and didnt drop in for a brew? Thats you off the Christmas card list lol
8/1//2018 11:03:59 AM UTC
Ian Soady said :-
I can't understand this 1/4 speed thing. If we consider just the inlet cam it needs to rotate at 1/2 engine speed so it opens and closes at the correct times. 1/4 speed would mean it only opened once every 4 engine revolutions.....

A little while age I posted a picture of an Ariel single cam setup. It worked by having lever followers fitted either side of the cam. And the cam definitely rotated at half engine speed. Can't find that one but here is the whole bottom end.

8/1//2018 12:22:01 PM UTC
Ian Soady said :-
41 is the crankshaft pinion; 40 the half-time pinion and cam; 46 the followers.
8/1//2018 12:23:20 PM UTC
Ren - The Ed said :-
Alistair - I'm far too polite to turn up unannounced! Anyhow on that day I don't think I could have driven up your street.

Bob - think about what you said. "One complete revolution every 4 strokes of the engine!" One stroke is HALF a turn, 2 strokes 1 turn, so 4 strokes is 2 turns of the crank. Yes - I too confused myself thinking the cam is shared so only needs to travel half the pace - but no. It's just that one cam does the task of the two cams.

It confused me but thinking about it yes the cam will rotate at half crank pace as any other cam does. DOH!
8/1//2018 2:25:47 PM UTC
Bob said :-
Of course, it's the difference between strokes (4 of them) and revolutions (2 of them) - never sat down to think properly about it until now!
Live and learn.
On't subject of strokes I'm liking the atkinson cycle engine. I believe Toyota are rolling one out. It allows more power to be extracted by having a longer power stroke, but avoids having too high compression by having a shorter compression stroke.
9/1//2018 1:47:21 PM UTC
Ren - The Ed said :-
We are but humans Bob. I too am liking the idea of the Atkinson cycle engine, I have some concerns that it could be complex to implement. From the scant details I've seen they're talking of variable valve timing to allow for standard 4 stroke and various levels of "Atkinson-ness". I just hope it doesn't get ridiculously complex.

It'll all be a mute point anyway *IF* the electric powered vehicles come to the fore.
9/1//2018 2:12:21 PM UTC
Ian Soady said :-
Never come across the Atkinson engine before - many thanks for this Bob.

From what I read on Wikipedia it seems mainly to hinge around keeping the inlet valve open longer (as long as the more complex linkage designs are avoided). I'm not sure in real life how much more efficient they are although I was surprised to see how common they seem to be.
9/1//2018 2:50:25 PM UTC
Bob said :-
It's supposed to be quite easy to implement, it's just a matter of getting the cam timing right. I think Toyota added their VVT to it also, but you don't need VVT to make it work.

Electric cars, where to start..
There isn't enough Lithium on planet earth to make enough batteries, Lithium is hideous stuff to mine process and dispose of, there aren't enough power stations to charge the cars, are we to build 20 new nuclear plants to charge them up? If not, coal?. It's just a flash in the pan brought on by short sighted government policy (see the rise and fall of diesel cars).

Hyrdrogen fuel cell is the only viable option. Mitsibushi have just launched another fuel cell MPV, Honda have filed patents for a fuel cell motorcycle.
The Hydrogen can be generated from sea water using renewable energy(yes I know you need to use twice as much energy to get the Hydrogen as you get back by burning it but that no longer matters because the energy can now be renewable).
"Burning" the Hydrogen produces just water.
Endless sustainable ecologically neutral transport, the only reason we're not doing it already is the vested interests of Trillions of $ & £ in the oil industry. When it becomes no longer economically viable to dig up the oil then the Hyrdogen will be rolled out.
The future is bright, don't waste your money on ridiculous rechargeble short lived, coal fired power station charged, heavy metal pollution generating electric white elephants.
Rant rant......
9/1//2018 2:52:35 PM UTC
Ren - The Ed said :-
...and breathe Bob.

I can certainly see the benefits of the hydrogen system. My concern is the transportation, storage and "filling" of a gas under enormous pressure. That said we already transport highly explosive petrol between our legs so what are we worried about.

I don't know which method will win out. There may be a whole new option come to the fore soon enough too. Meanwhile it will be interesting to see if the Atkinson powered Toyota is a success.
10/1//2018 10:59:37 AM UTC
Ian Soady said :-
The wikipedia page has a very long list of car engines allegedly using the Atkinson principle but I suggest they just have a delayed inlet valve closure point.
10/1//2018 3:12:55 PM UTC
Ren - The Ed said :-
In a nutshell...that's what the Atkinson cycle is innit?
11/1//2018 1:54:25 PM UTC
Ian Soady said :-
That seems to be a simplified form but if you look at the wikipedia page the full monte includes a complex linkage arrangement for the crankshaft.
11/1//2018 3:01:08 PM UTC
Ren - The Ed said :-
Yeah - I guess if Wiki's take is to be used it's the "Modern Atkinson-cycle engines" section we're referring to.
11/1//2018 3:15:24 PM UTC

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