Reed Valve 125s

Hi thought i'd start this instead of putting in 'Heavy crank'.

Trevor your motor has 1.4:1 ccr where as Ian and mine are 1.38:1 but yours is a reed
and Ian's and mine are piston ported. Mine and Ian's ccr don't inclued any inlet tract but
your reed does!

Also you have 360inlet timing and I was wondering if you have achieved
this by putting a hole in the rear of the piston? large piston cutaway? deep inlet floor?
connecting passageways between inlet and transfers?

or a combination of the above..

Your answer may give new starters an insight into what you did...

Regards Mike

Hi all

Trevor may I add a question to the items Mike has asked. Why have you picked a reed valve over a piston ported ?

Two for Mick Scutt - if you where advising a fresh starter what class would you advice to start first build a 125cc short stroke, or a 186cc Bantam if you chose a 125cc to start with would you go piston port or reed valve, and why

regards Derek

Derek wrote - if you where advising a fresh starter what class would you advice to start first build a 125cc short stroke, or a 186cc Bantam if you chose a 125cc to start with would you go piston port or reed valve, and why. >>>>

I'm sure the easiest way to start is with a 175.
The formula is designed to make building a 175 relatively cheap and easy. You don't need so much engineering expertise or facilities to build one and when it is built it will probably go faster than a 125 built by the same person simply because of the extra cc's. Add to that the fact that it will be easier to ride because it will pull out of corners better then to my mind there's no contest.

Reedvalve or piston inlet ? For a newcomer - indeed for most people I would suggest using a piston port inlet.

Reasons ? Putting a simple flange on the back of the barrel is more straight forward than a reed-valve housing, You avoid the decisions which reed to use, which petals to use, what to do with the back of the piston and of course don't need to buy one! Personally I think a piston port is easier to tune and carburate but you don't have to look far to see some very good reed motors in the paddock. Perhaps some of their owners would chip in here ?

Mick

Goody goody -- I am learing a bit more -- now you are onto Reeds....

Since I am on (really strange that -- no problem!!??) I´ll answer Derek´s query he put on the Topic (Heavy Flywheels) that should not be used since it was was given the Last Post yonks ago!

That was referringto the "....`Ideal´ compression-pressure curve" and I said it was a compromise -- and I meant by that -- a compromise to reliability if on a low octane fuel like C7H16 (or H14 or whatever it is for Super-Premium crud or whatever...) and if considering the FULL P-V DIAGRAM the IDEAL for that is that the ideal is a pure-air compression at high -- above 19:1 compression-ratio -- accompanied by a diesel type of high-pressure expansion giving fat (slug-like fat...) diagram where the otto-petrol style diagram is thin (worm like). Since it is the area inside the diagram which is work (to eventually become power ) the combination of Otto-petrol and diesel type of FAT, P-V diagram gives a massive amount more power ... which comes back to the Walsh way of making a Bantam sing in powerful manner. i.e. 16:1 compression ratio using methanol as fuel...

I realize again, gabbling on like this is like speaking without hands -- A DIAGRAM -- a P-V DIAGRAM IS NEEDED!!!! HELP!!

If you haven´t seen the film, "The Workld`s Fastest Indian" then you have missed a funny motorbike film based on fact. Bert Munro (played by Anthony Hopkins) as he
prepares to sprint the much-mofified 1915 Indian on the famous American Salt Flats pops a pill into the petrol tank. My heart condition pill, he tells spectators,
just for luck. In fact it was a tablet containing nitro-glycerine which might well have been capable of doing what the tetra-ethyl lead does -- or in all probability it myight have beenTEL in solid form...?

Gone Five `0´clock here -- I´m back to bed -- gotta go fitness training inthe morning -- sod it -- retirement??? who´s kiddiing??

Hi all,
Trials engines need clean , crisp throttle responce , it be instantly available, and delicately stable with no assistence from a resonant exhaust.
Motocross engines need many of these atributes but with a much higher power output and rely on a resonant pipe to assist in acheiveing that
performance level . Race engines need higher specific power but far less demand for low speed , low rpm running . All these types of engines
share one thing in common , reed valve induction ! Should a Bantam engine be the exception ?
I don`t know what inlet timing is currently favoured by the piston port runners , but it`s unlikely to be more than 200* , remains the same
irrespective of rpm and is symetrical about top and bottom dead center .
On my engine at 6500 rpm the total inlet period is about 250* of rotation , move on to 10500 rpm this extends to 290* by means of a shorter
dwell at bdc and also a higher reed lift after exhaust closure . Move again to 11000 rpm , the reed closed period remains about the same but
reed lift is higher again and the fully open period is longer and closes far slower , giving ample time for a long , deep induction draw .
Add to this the gas dynamic action of the pipe opening the reeds at a point where piston port is still closed , gaining more advantage, the case
for reed valve induction becomes pretty compelling , top end performance might just be comparable but else where the reed will excell .
Then again , i might alone and out on a limb in thinking this way !

Catch you all again later , regards Trevor

Hi Mick

Trevor makes a preity compelling case for a reed, that is clearly more complex with respect to tuning resonant waves and detail in setting it up, one question on this how does one know this information, ie where the reed is at 6500 and 10500 and 11000.0 are you taking pictures, ir is it a known thinkness or material of reed to achieve this?.

if you do have to measure it I would like to know or see how, I check this in my shed, if I'm can check this then maybe we could tune the pipe accordingly, or are there some fundermental telltail signs like carburatuion or other things, "well hopfully it will give me a much better understanding of what is required from my current reed motor a new pipe!".

we have an issue with our MOTAS IW software, loaded to my laptop the original disc and dongle, but it keeps giving me a 38 error will not load, anyone know what this issue is. ! do I have a file missing.?

regards Derek.

Trevor - I see you are not prepared to answer my question then?

The forum and information is for the good of all - so everyone becomes a winner!!

Regards Mike

Mike,
Not prepared, or, haven`t yet ?
Information on the forum , i recon i give more than i get , however , that could just change !

Just for reference on on the reed v piston ported debate, here's a bit of history :-

Dim and distant past to 1983 all championship winners - piston ported

Recent(?) history

1984,85 P.Tibbits Reed
86 M.Powell Piston
87 M.Powell Reed
88 P.Tibbits Reed
89 C.Hall Piston
90 P.Tibbits Reed
91 M.Carkeek Piston
92,93 B White Reed??
94,95 M. Carkeek Piston
96 M.Powell Reed
97,98 M.Powell Piston
99 P.Tibbits Reed
01 M.Powell Piston
02,3,4,5,6,7 M.Powell Reed
08 I.Scutt Piston
09 M.Powell Piston
10 P.Tibbits Reed
11 I.Scutt Piston

So thats about 15 Reed to 11 Piston ported ?? I'd better dust my Reed valver down !!

Trev - yes lets hope that changes. With respect what you give I and the rest of the laymen don't understand anyway

Keep it simple , out there !!

Mike

Well -- yer...? I am asking how you measure the efficiency of a reed valve´s function?

Of course, I should shut-up, I don´t need it ---

-- ey oop! If I win the Lotto I shall buy a W/Shop-Machine Shop and start producing Bantam engines and Bantam bits and sell `em at such a low price would-be Bantam racers will think the clock turned back to when Icarus-1 was built for 80quid....

Yaaaaaawwwwwnnnn!

Derek

if the error is generated by Windows rather than your software, have a look at this page -

http://support.microsoft.com/kb/310123

Mick

thank you Mick - but still no go the same - it use to work fine dad bought it many years ago,

the error is shown in a small box like this.

- error 38 - HARDLOCK API error code 38

regards Derek

oh by the way Mick love the picture of your Avertar, as I first remeber I recon about 1969/1971 cadwell

regards Derek

[quote="john bass"]a compromise to reliability if on a low octane fuel like C7H16 (or H14 or whatever it is for Super-Premium crud or whatever...)

C8H14 - I'm sure john - But I would understand it better if you said "compression reaction to octain".


regards Derek

Hi Derek

sounds like a driver problem try looking here -

http://www.hasp.com/support/hardlock/downloads.aspx

Have you switched from XP to Vista?

Is yours a 32bit version of Windows?

Mick

Night time is for sleeping Mick!!

Derek you asked, -- "... compression ratio reaction to octane..." (I think that´s what you said because part of your message was chopped off before its end which I couldn´t get..."

The Octane number refers to a fuel´s resitance to detonate at rapid acceleration and high temperature -- sometimes called "Knocking resistance" and is determined by what is called the "RON" -- `research´ method and "Mon" the "motor method" adopted by International Standards organisations where Ron is an acceleration test for `Knocking´ (silent detonation shown by transducer...) and Mon the test for detonation at HIGH Speed.
By this ridiculous standard `Premium´ petrol is 95 by Ron and 85 by Mon & "Super Plus" is 98Ron & 88Mon....

So in daft manner you have a difference of 10octane for two standards of determing a fuel´s octane level?????

SO FORGET ALL THAT and concentrate on your question -- by considering the following:-

"Iso-octanes" are fuels at >100Ron octane rating with less-than 0.013grammes per litre of tetre-ethyl lead. One such is C8H18 -- the only one I know!!!!!
This fuel with 1% to 2% tetre-ethyl lead added becomes the popular aviation fuel
(probably Avgas mentioned on here!) whose octane number can reach 153Ron...!

I have already said that with the higher compression ratios a petrol of lower than 100octane -- say Premium with 98Ron -- will detonate either as `pinking´or inaudible detonation on ACCELERATION UNDER LOAD load which produces spikes of high pressure -- BEFORE TOP DEAD CENTRE.

And that can be the sort of disaster I experienced with Andy Boyle´s 250 ABS at Snetterton on the OLD Norwich Straight with the ABS passing everthing ... there was a sudden "Eek" -- no pinking! -- and the piston seized at the same time as a hole came in the piston crown. That, when a full day practice at Brands (4 days before) -- with the Gardner rep checking my plug chops -- showed no sign of detonation. We were, of course, on Premium petrol of that `70s´ era....!


Cheers!

Derek,
Email Ian Williams direct, quoting your serial no from the Mota registration form , you may need a revised dongle ,or just advice .
He has always answered my questions in the past , so i`m sure he will know the problem at first hand .

Trevor

John,
Avgas 100LL contains .56g/ltr of tel , and is required , by formal legislation , to be no less than 99.5 octane and no more than 102 max.
I have seen it suggested that this lead content is to be reduced soon , and , that 100LL as we know it is to be superceeded by a "greener "
alternative ! But then you can never be certain of anything when the rumour mill gets grinding ! Strange thing is i cant seem to find the
chemical makeup published anywhere , It must be out there , but i did find out how to make a pipe bomb !?

Must catch up on some sleep now . Trevor

Aw Trevor! I thought you´d know the cXhY of all of them -- all the Xs & Ys --?

What Mackerle (Air Cooled Automotive Engies) says is that iso-octane without TEL has 100 octane whether running lean or rich and similarly with 1.03cm³ TEL added per litre ups the rating and it will be 153octane lean or rich.

Seems the ideal fuel: C8H18 with a heart-attack pill dropped in....??

The smell of over-rich methanol was wafting about on the air at Cadwell (25th Sept...) so strong made my eyes water and brought on a spell of grass-track nostalgia and a 500cc JAP engine in an RE Bullet frame -- 100mph at High Wycombe on grass....!!!
I wonder the Do-Gooders don´t get at the users of methanol...??

I wonder where one can buy nitro-glycerine? without prescription??

Cheers!

I have to aggree with Trevor & James.

The choise between piston ported or reed valve is a no brainer from my experiance. The outright BHP from a piston ported engine can be higher than that from a reed valve engine, but the peak power is verry short lived. A read valve engine usualy has a slighly lower max BHP, but the power peak graph is much flatter and the average BHP in the power band is higher than a piston ported engine.

Every GP racing 2 stoke that I can remember has been reed valve or disc valve. Do we know something they dont?

Mick.

Never played with a reed valve nor for that matter read owt about it/them so I am trying to see in my mind how it works when Piston Ported?

I assume:- As the piston travels upwards from BDC the petals are sealing the crankcase compressed air-fuel mixture that has already moved up the transfer ports hence reducing the pressure. The plugging pressure wave from the exhaust -- if correctly tuned -- then pushes the fresh air-fuel charge (that was heading to escape thro`the exhaust port) back in, thus keeping the pressure high & virtually supercharging the air-fuel charge during the loop-scavenge process and keeping the petals closed --but as soon as the transfer ports close, suction begins underneath the piston -- by the piston´s upwards movement -- which then causes the petals to lift and the air-fuel mixture to begin entry into the crankcase to open fully as the piston approaches TDC -- seems a bit muddly -- or rather exceedingly & cunningly clever -- I mean in getting the system to work at all,
much less efficiently...

Then I am faced witha "Piston-Port" which is new to me. So when is the piston-port open during the cycle?
... and is that the HOLE which has been referred to on Mike´s drawing juts below the piston rings....?

As I see it the timings of each activity must be critical to good efficiency because the cycle is taking 1/167th of a second at 10,000 rpm, which is a lot of petal fluttering which also makes me wonder how the spring strenth of the petals is determined? and reliable the reed valve system is??

I have only seen diagrams -- never the real thing!!?

Hi Mick potter I liked your write up on frames Mick it was great, just been talking to Ed, he thinks the same as me we "feel" you should leave the debate on tuning specifically "piston V reed valve" debate to those who can add proper scienticfic reasons Other than well he jumped in the river "so I will too". !!!!

hope your well

best regards Derek

Please accept humble apologies Mike for me asking such a stupid question. I looked at Andy Boyle´s ABS piston because of Sticky Mick´s pic showing detonation damage and saw the port (on Andy´s piston) just a short way down from the piston rings, on the thrust-side of the piston -- quite a small hole compared with the one you show in your drawing.

And 65.5mm dia piston -- hmmm, just thinking -- 250 with 65.5mm bore -- quite a Long-Stroke motor. The ABS had 5 gears -- FIVE...!! and with an obvious good torque curve was so much easier to drive than a 3-speed Bantam -- far less clutch-slipping!!!! My gear change leg used to ache after Llandow ....

Some readers here must be saying things -- like this bloke never knew what he was racing???

Could be right!! Too busy at other things ....