Reed valve or not

Just thinking of engines and remembering that I'm actually using my spare (slow) engine and have been since my fast piston ported engine blew up 'big time' at Lydden in 2001. The remnants of that engine plus an old 6 transfered Peter Styles cylinder now lives in Aiden's SMS-002 rolling chassis. Now is it rose tinted specticles? - but I'm still sure that not reed engine was faster and easier to ride!

Points of interest :-

First reed valved bantam champion - Peter Tibbitts- 1984
Last not reed champion - Me - 2000
Out of interest - 1987 - champion - Me on Aiden's SMS-002 with original engine, the one that now lives in Micks SMS-004....

I'm off work at the moment, recovering from an operation so have more time to think, waffle and leave messsages on the forum - sorry
Regards Mike

Hi Mike
The debate on witch type of induction (Piston ported, read or disc valve) is best, has yet to be finalised. If it was every bike in the 125 & 250 world championships would use the same induction method.
I have allways been of the opinion that the read valve gives the lowest maximum bhp compaired to the outhers. But if you compair the average bhp from max torque (whear the power band begins) to the point of power tail off (whear the power band ends) the read valve has the advantage. If you have 6 gears there is not mutch in it, but we only have 3

Hi Mike, Mick & Peter and you other Bantam Ravers!
Glad you got off the wobbly wheel waffling -- I was losing my way in among the vast variations of factors affecting handling at high speed, particularly when you think of the rear wheel being also connected to the front -- albeit wobbly like...!
The 175 formula is almost keeping to the true traditions of BANTAM with its piston-porting etc... etc.... Remove fairings from the 175 formula and I reckon the cheating, of the `true-to-Bantam´ authenticity, almost ends...
OK! So the reason given -- way back in the dark days -- was that "Racing Bantams" did not look the part without fairings... Particularly in the Island.
No fairing makes the 175 a less expensive racer to build which ought to be considered in view of that lower-cost attraction to a beginning-or Old Timer returining -- newcomer.
I´d even think about coming out of retirement if that happened: I hated fairings.
I hope you have recovered from the op Mike -- was it a problem with those 180° rotation muscles in your neck?
And Mick: Even though there are so few Bantam Racers out there I still think the finishing points award a good idea.
And Peter -- how´s your weight?
All of you -- Go Well & Keep Well in `08...
(Perhaps I´ll keep quiet for a while...)
JayBee.

John it is very rude to enquire of a gentleman's weight, but since you ask, it is too great.

Effectively we have the top half of a six speed gearbox, so a wide torque curve suits most circuits.

I would suggest reed is better than piston port for our purposes. Dont know what disc would give us, when combined with sloped ignition, ie all the top end of a disc, with the low down grunt from ignition advance.

As disc is difficult to implement on Formula 125 (may even be illegal), our best bet must be reed with sloped ignition.

My reed block is modest - 1984 Yamaha YZ125, just upgraded with carbon fibre reeds. Hmm...

Hiya
Pete, its true you can't disc valve a bantam under the rules which i think is a good thing coz theres a lot of engineering complications and we are meant to be keeping bantams simple!

Mick, interestingly my old piston-ported motor had more power 23.8 and more torque and a remarkable spread of power!! I don't know why either? it just did! and it used the exhaust that my reed motor used..

John, My neck is repairing just fine, i've had the lock stops moved to allow 187 degree rotation - a procedure called a Parodectimey (not sure on spelling)

Mike

Just weighed myself in work clothes on the Fleet Workshop scales. 191 lbs
whereas last season I was hovering around 187 lbs with the same set up. Where's that alloy barrel?

Pete,
You need to cut some bits off the body parts and wear a mag alloy helmet! that should should shift a spare 8 ounce or so.....
Alternative is we change the rules and allow the "all plastic bantam"? Careful design work will let you flex round corners without the need for lean.
Fun Eh?
Alan

OK! Sod the formulae*** -- I am working on a sleeve-valve motor***...
Have it ready for `09.
Peter! Nothing in the mags (Professional Engineer -- in particular...) I haven´t heard anything lately on ceramic-coated combustion chambers (to keep the heat in...) that were all the rage a decade back. Fill me in please?
I know you´d like to...
John-Boy(special tablets an´all that!).
*** He who controls the past, controls the present...

Hi!
I told myself to leave it be... Let the lads get on with their bike prep, it`s far more important than this continual prattling on and on... but that bit about getting 23.8bhp with a wide spread of power wouldn´t let me rest -- Mike? You are talking about the engine giving 12 - 15% more than seems reasonable, even if we try bringing experimental error, correction-factors, subjective feel and other twaddle into it... And with `... a wide spread...´
But then -- ? It could happen. Just recently I was looking at the comments made by Bill Lomas on the Walsh Bantam which repeatedly beat many good 250s Down Under ... There was nothing fantastic about this machine -- it looked a right heap! Really rough. It was, of course, running a high compression ratio*** on a dope fuel and had one 16 thou piston-ring which was repeatedly changed during practice and races... No rev counter -- just a speedo! When Bill Lomas tried it he was told to rev it until it peaks! Oh wow! Now that does not obey physical laws as most Science Profs know them. High CR usually means lower peak revs and high torqe...
So, what might the phenomena be? Maybe I am wrong. Maybe in the process of that one ring wearing itself out the sealing and gas exchange worked at its optimum -- with almost perfect sealing everywhere -- which could have been happening with your 23.8 hp motor.
*** There´s often confusion over compression ratio in the sense that
a measured static C.R. might not be what the combustion chamber actually sees...
e.g. A well ported engine with say, a static CR of 9:1 can have a much higher CR at high revs (because of the `cramming´ effects and the resonant exhaust pipe ...) whereas a badly ported engine might start of with 12:1 and be around 6:1 at peak revs because of poor gas exchange.
...
Yet (in the picture I saw) the Walsh Bantam did not have a resonant exhaust pipe.
Last word (I promise!). The Walsh Bantam Compression Ratio was high to start with because of using an alcohol fuel. If the above hypothesis is right, at peak revs the dynamic CR could be something like 16.1 (ideal for methanol) which on the Air Standard efficiency curve shows an increase of 15% in thermal efficiency over that of say, 6:1 through bad porting.
Pick holes in that!
Go well & keep well,
Aye! JayBee.

I for one believe piston ported is best on a bantam, because at the end of the day a reed valve is a restrictor in the inlet tract and any restrictor is going to impede gas flow. However because no factories have played with P-Ported motors for 30? years there is no up to date info to copy. My last P-Ported motor was in the early stages of re-developement when it cried its last and suffered terminal pistn then engine failure.

Don't rule out piston ported motors yet ...........?

Quite by accident went thro´some old Classic MC Legends mags and came across an article by Bill Lomas mentioning how he played with ports on an RE 125 and made it perform better. More torquee too. Another was where Bill tried the Walsh Bantam in Oz... Seems he had a soft spot for Bantams. I was wondering if it is possible to get the man again interested in Bantam doings and give some advice? How to get round corners and not fall off like -- as well as port tuning.
He also mentioned the Chief Engineer of Royal Enfield, Tony Wilson-Jones, who wrote a paper in 1948 -- or thereabouts -- on `Handling´ and used MOMENTS for his argument. Tony Wilson-Jones was a big bloke and when cornering on a tiny RE 125 wouldn´t need to lean the bike at all just move his bottom in towards the centre of the curve...
Peter doesn´t want to reply to my challenge on them... Moments, I mean. Perhaps he thinks they are something to do with our Bantam RC committee meetings where this young lady in a wide-belt type of mini-skirt said, "They keep calling me `Hotpants´-- I wonder why?"
First time I really saw the effectiveness of `climbing-off´ was frightening. It was at an Assen GP where, in a right hander, Randy Mamola´s left boot was level with the tank top -- he was that far over, hanging off ... (Maybe that should be `just about hanging on´...?)
I´m all for banning (in Bantam formula) reed-valves, fairings and riders who don`t keep both feet on the footrests for the whole of the race.
Yeah I know, its time I shut up. Yesterday my loving wife said, "I´d smash your teeth down your throat -- if it weren´t for the fact they cost so much".
Stay cool!

Reed valves or piston ported? was the question i asked a while back and out of interest, our one race at Donington Park produced a winner on a piston ported bike and so was the runner up! The reed valvers being in 3rd 4th and 5th !! Well Done to Ian for moving up to Lincoln and therefore having a lot move sucess... and posting the outright bantam lap record!
Also it was weird to have myself and Mick Potter out on 175's where you would normally expect to see us out on 125's. Thanks to Jimmy for lending me his bike.... Roll on Three Sisters...