Mike Powell's 125 Engine...

As a contast to Snowy's 175 motor here is my 'long in the tooth' 125 motor which has finished
2nd 3rd and 1st in the last three seasons. The cylinder is the one Pete Styles used to win his
three championships in 78,79,80. The motor is a 54x54 bore/stroke.
The cylinder is a D1 and 'had' bridges made inbetween the transfers and also between 2x auxilllary
exhaust ports unfortunatey following a 2001 'blow up' it has been linered and only now features one exhaust.

I don't want to say anymore as I want you to ask any question you may have after seeing the following
pictures...

Evening Mike,
nice images, still capable of winning races i think.
my questions are as follows;
picture 6.
Is there clearance between the cylinder head nuts & the cylinder head cover, if so did this ever give problems.
picture 8.
Witness marks of original stud centres,i am guessing now 60mm ?
picture 10.
Devcon to cylinder transfer entry your theory on this development mod would be interesting.
picture 14
Is there no drain in the L/H crankcase half to let the water out if problems occur ?
thanks Nick

Yes, nice pictures, nice clean engine.
My 1980ish 56 x 54 looks very similar.

Maybe some basic questions:

1. Thinking of turning mine back to thermosiphon, for simplicity and period '60s looks. Is the big tube at the back of the head waterjacket necessary, or I can I continue to use a top central vertical outlet ?
My barrel has two water inlets, the left hand (like yours) is blocked off and the right hand [under the exhaust] is fed by the water pump; looking at Gingers Bultacos, they seem to have a lower pair.

2. Thoughts on piston port Inlet timing ?
LH used 160 in 1980, my first tuner put it up to 176 degrees open, presently 170; with 196 exhaust and 132 on the transfers.

3. Inlet port tract length ?
I guess, depends on carb length too, but it looks as though you have a much thicker spacer before the manifold.

4. Gearbox mainshaft length ?
Is that shortened to bring chain line in closer with 2 bearing crank ?

5. Can I pick up another 5-10bHp (15. with a better modern pipe (on AvGas) ?

cheers

John

Yes Nick quite a few wins this year and won the last bantam race of 2011.

Ref your questions - yes there is a gap between the nuts and the underside of
the water jacket head. I've 3 combustion chamber heads for it with different
cr and head heights and fitted in the water jacket head you can see a ring/collar.
I have 3 of these to suit the cylinder heads. These have never been a problem.

You can see the marks(head) or holes(barrel) of the original 55mm stud centres.
Stud spacing is now 60 left to right, 70 front to back. I don't know why ? Tom?

Well spotted devcon in transfer ducts to make the transfer passages longer and
raise primary cr a bit.

No crankcase drain - at the moment....

John this motor originally ran thermosiphon but has been pumped for the last 30yrs.
I like the look of the big pipe thats why I 've kept it, the good thing is if the pump
stops it thermosiphons.

Port timming are Ex 99(198) Tr 68.5(137) In 100(200) Inlet timing has always been
in the 98 -102 range but bear in mind there is a cutaway in the rear of the piston
skirt so slow opening.

Inlet tract lenght I have played with this season - just trying longer and longer lenghts.
The one fitted is the longest I have at the moment. Also running a 34 Dellorto this season
instead of the Lectron so things are different??

Gearbox mainshaft standard its the clutch that has been modified to allow the chainwheel
to come inboard, to line up with 2 bearing crank. Also my motor has its drive side seal
put in from the inside and butts up aganist a lip, where as Snowy's has a retaining plate
allowing seal changes without splitting the motor.

And your last question ref Avgas - probaly not but may be safer.....

Regards Mike

Pic 1. Sounds too simplistic to ask -- what is the flywheel on the timing side -- is that some sort of old-fashioned flywheel mag ignition system? Would add to the flywheel effect on lesser acceleration -- of course? The life story was of flywheel diameter change -- I´d really like to tie that up with theory somehow?
Pic 2. Another Simple Simon -- the pipe from the chaincase -- a Breather? or are you cooling the chaincase oil -- somehow? You were changing nthe oil there at Cadwell -- weren´t you? Why?
Pic 4. Using only 6 clutch springs -- at Cadwell?? Lot of people are using 9 springs?? The old Club Curcuit at Cadwell was a horror story of clutch
problems for the heavier riders -- what weight are you -- fully race clad -- these days? Or were at Cadwell??
Pic 5. Layshaft plain bush? -- you won the last race at Cadwell with that engine -- didn´t you? Does it suggest that ball bearings on the layshaft are not necessary after all?
I am wondering why the combustion chamber (in the head) looks cleaner than the top of the piston? and the reason for the strange burn pattern on piston crown?

There´s obviously something ´makiing this engine different and although the layhsaft is in plain-bearings ( at least at one end) surely it cannot be lower mechanical losses... Then it has to be induction -- perhaps, mayxbe?? Better suction like??

Good pics Mike!
go well and keep well!

PS -- after a second look -- I take that back about layshaft bearings ... Looks a bit like something different -- ball bearing on one side and needle rollers the other?? or...?

John - Flywheel is a Honda RS125 1988 CDI ignition Rotor etc,

Pipe from chaincase a 'breather' you'll also notice I put one the same
on Snowy's(Jimmy's).

Yes only 6 springs (used to have 9 as you can see on spring carrier plate
also 3 screw hole for holding the cover plate, no longer used) I've posted
before on the subject and use different plates and holes9and springs) -
6-7-8and 9. I'm 79kg in race kit and 11st 7lbs in real life

Yes it's ball bearing on drive side layshaft and a needle roller on output
side. Well spotted! I believe Tom is now fitting plain bushes again.

Head chamber... what strange burn pattern .. you mean its not meant
to look like that?? Carbon sticks piston as piston is hot, doesn't stick(much)
to head as too cold? I think...

Thanks for yours questions people - there is a lot more to come out of
those pictures if you look closely ...

Regards Mike

Thanks Mike! What I was wondering was this: is the head being overcooled? The piston looks warm and OK but the chamber looks cold. It might be a debateable point -- on here -- with my saying the head should be kept hot whilst the piston be kept as cool as possible ....
The burn pattern has me feeling that there is a lot of turbulence going on during heat release into expansion which might well be why the engine is performing so well

PS -- just like my riding of a road race motorcycle -- I lost control again and didn´t finish ---

-- this b....y computer -- took over....

-- what I wanted to finish with with was that a lot of people water-cool the barrel and have the head air-cooled.

Does your cool water go to the head first and then to the barrel -- I think the cooled water should go to the barrel first and that warmed-up water then circulate thro´ the head.

What do others say??

mjpowell wrote:

- yes there is a gap between the nuts and the underside of
the water jacket head.

That's a good mod that's been made since I rode that bike and like most things with the benefit of hind-site so simple and obvious.
The original w/c engines had a spacer between the head and the jacket. At one meeting I retired from each race due to water leaking from the head and it wasn't until after the last race that it dawned on Tom what the problem was. He had skimmed the head before the meeting but had forgotten to skim the spacers to suite, consequently they weren't allowing the head jacket to pull down tight enough on the barrel.

Notice Viton O ring in cylinder head, good idea; slightly narrow ?modern squish band an shallow combustion chamber ?
In comparison
just apart, needs good clean !

https://2img.net/h/i1182.photobucket.com/albums/x450/johnSbantam/c81dd6f3.jpg

Good morning John,
Great to see your pictures, what i am enjoying in this thread is we are able to study these images
in detail ,while in the paddock we only get the odd glimpse of the bikes.
It would be nice to see more of your water-cooled and maybe a bit of blurb, as per Mick on the Snowy/Tom 175 motor.

all the best Nick

P.s. who was it who said a picture paints a thousand words? some stupid song i think?

Just for a little variety, and if some others are interested this is Tom miller 2008 revised version of the Colin Halls engine design, campainged by me this season ,proved very reliable. Great fun









cheers Nick

John B yes the head is to cool ? How do suggest i get it to run hotter? Its water 'in' at base of barrel
'out' top of water jacket not other way round.

John S and Nick repost your motor pic's as a new title... ie Nick Bramley's/Colin Hall motor and
John Sendall/Lionel Howell motor...etc I've got questions but don't want to confuse people between
different motors..

John S got any other shots .....

Regards Mike

The cold water should go in at the top of the barrel circulate around the barrel and be made to go to the lower regions of the cylinder barrel to then go to the head and out... Indications are that the cold water comes in and immediately rises to one side of the head -- cools it too much (burn marks on one side of squish band area) and by the pump pressure gets the water shoved -- indiscriminately(direction wise) -- around before going out ....
I feel sure it would suffer piston seizure if it were a thermosyphon system -- a steam pocket would form and the the hot water would not flow...??

Just guessing, of course! the above suggests there are no flow-deflectors -- or flow directors, if you like -- and that is what is needed. I should think it difficult to do but maybe it is possible ...??
What is possible is to put a restrictor-plate in the head on the side where the burn marks show and just making ONLY that ONE change take the plot out for a test session and see what the pattern looks like after giving it a hard time for a short period.
I´d suggest investing in a simple thermometer to install somewhere -- or maybe that plug washer temp indicator would be more simple -- so that you can stop before it is too late -- and I don´t then get blamed for a wrecked motor??

I´ve got another Q for your pics but the above is enough for now -- ey?

A neat engine stand -- 9 marks out of 10...

... 9marks out of ten for the engine stand Mike, but you must stand in the corner for being a Bad Boy!

That CDI ignition rotor is a flywheel and you NEVER mentioned it when you started that ruckus about
Rossi mentioning his Ducati flywheels ...

Now, what dia is that rotor and how much does it weigh?... and please confirm the flywheels dia and weight as shown here?

Cheers!

John.. which do you think is front and rear on the cylinder head pic?

I'll weight ignition rotor and measure diameter, why did you assume it didn't have
an ignition rotor? in your 'Heavy crankshaft' posts ??

Whats your next question?

Hi Mike

1) Timing side bearing what type is it? a/c
a) The cage appears to have over heated?
b) Is it a fibre cage type? I think I can see inner /outer supports.
c) I have never seen one like this only rollers look similar

2)Inner transfer walls please explain! The shape and/or reason ? “what difference” does it make? and do you alter the shape at all while experimenting., “I noticed you said dev-con” they look like cast Iron.

3)Have you identified each shot with a number to show you are showing us something or is this to be able answer questions on each one, or are you pointing that we should be looking for something on each photo,? I think there are so many aspects on each shot I will send you a PM with some other questions.

4)Please explain the gearbox ratio’s on top gear ? I have counted these several times, I even asked another to do so who like me could not believe this, does this actually work ? I just could not believe it, at first, but it is 22/24. ? so I’m very interested to put this through (John Senddle) – gears ratio /calc table on this forum a while back, to see what ratio it gives between the gears, but it would be so much easier if you just told us why? And the reasoning behind this, Mike but more importantly what difference it makes when changing between 1st 2nd and Top obviously this will be different for others but , my give a clue?

5)There are so many other questions, and gems I have spotted, but I can not ask all the questions, I’m sure others would like to have a go, at spotting the other more critical gems in these photo’s “some very interesting aspects, I have never seen inside this engine before. Amazing I can see no braze too on this cylinder.?

6)All we need now is for "Trevor Amos "to strip and photo his engine in the same way and post it too.

“I feel the engine stand, Is a step forwards for us “just got to get one of those”.

Derek

I assumed it didn´t have an ignition rotor because we had a contact breaker there and on some race bikes I´d seen the Hall Effect sender, gapped wheel -- or holed wheel with battery and coil ignition , of course.

Another question relative that snapshot -- the rotor has 6 circular things in a plate on the outside that look more like clutch spring covers than anything else I can think of...?

... you sure you haven´t got a KERS (Kinetic Energy Recovery System) on there that you clutch-in
during the race when the time is ripe???????

CDI -- I take it means capacitor-discharge-ignition -- `scuse me for being a simplrton!

Cheers!

Interesting engine internals being exposed , could be brave or foolhardy , depends upon what the competition seize on or eliminate !
One thing i have noticed which is common to all the engines shown , bronze bushes in the sleeve gears ! Am i the only one to install
needle rollers here or are there others doing this ? I did this in Nov 97 and, incredibly, the originals are still in place , a real fit and
forget mod .

Cheers for now , Trevor

-Pic #8 -- re front & rear ? of cyl head in pic 8 -- is difficut to be sure because of the head´s symmetry but if pic 8 and pic 9 are related then it is the left side which does not show much `burn´ as does the piston crown on what is the exhaust (left) side. Where the four circular patches show as clean there are indications -- I think?? -- of the head, momentarilly lifting clear, letting some combusted gas thro´there, then sealing properly later -- when properly WARMED UP!!???

So, just another GUESS on the Mike P... 125 -- there´s a slight leakage there on start-up which obviously goes away once the head has warmed up*** -- yet I still think it is running too cold under full load conditions.... .

***otherwise there´d be more carbon and the leak would worsen until disaster took over!

Cheers!

Fantastic amount of clever work on this engine. Lots of aluminium welding on the crankcases -- -- and the padding?? Mike? -- what is the crankcase compression-ratio??

The clutch looks different. The centre bit looks "worked-on" -- something to do with the push-rod bearing??

Re the flywheel dia and weight -- I have, I think, already included it in the treatise Peter has -- but ALL rotating parts of the engine must be included in calculations and the clutch and any other rotating parts are effectivly acting as the engine´s Flywheel.

So the question is how heavy is that clutch?

Its all a bit of guesswork anyway and my interest is the question, that won´t go away -- why the `big´ flywheels on the 175?
I thought the conclusion I came to was satifactory but doubt has crept in and I´d like to get to the bottom of this one.

We all know why the flywheel is needed. It is as Trevor once said, on here, during one revolution to provide energy to overcome the resistance to rotation***. Which means that from TDC -- during expansion of the power stroke -- the speed of rotation is faster than when the piston is travelling from BDC on compression stroke towards TDC. Long long ago I made a single-acting steam engine model which, without a flywheel, would only run at 1 to 2 revs per second and its exposed crank could be seen to move rapidly from TDC to then slow to hardly moving as the piston moved from BDC to TDC again... The indication was that the friction losses during that period were more than the inertia of the crank assembly could provide to keep it moving fast.

So, for the Bantam 125//175 difference -- I concluded -- perhaps wrongly -- that friction losses of increased piston dia were the reason...!!

***not his exact words but having same meaning. Trevor quoted the amount of ' Cyclic Velocity Variation´ at a given speed and I forget what that was.

If someone knows WHY -- then I´d appreciate being put out of my misery before it is too late!!!

Cheers!

Sorry JB haven't done rotor measurements yet - forgot (work gets in the way you see)

Trevor, true enough, just thought I'd let some secrets out as I can't expect the class to
thrive if new starters/old hands haven't thought about other ways of doing things. Hopefully
people after viewing other 'engines' and will improve there lot and performance, I do it for the
good of the class.

Derek I will answer your points but not tonight as about to go out. I'll answer all messages on
open forum not private pm..

Regards Mike

We (me and my father) dont normally go in for an opinion but felt it was time,


Apologies if it is in the wrong post/Topic,


Without a doubt we think it is great with all the engine pictures and show's what is and can be done, but also surely a good rider compliments a good bike?

This is an open forum and so may the better person win as im sure everyone gets the gremlins!. Without help from the experienced riders and builders then how are newcomers meant to progress with a build as complete race bikes come up very very rarely.


Kind Regards


Edward & Malcolm