returning to bantam racing

Hi John,

The picture you speak of is still here under "broken gear tooth" topic. But i think alot of posts get missed, better stop at that or Derek will be at me for it being unrelated to his topic!


Eddie

Not on my PC Eddie. I cannot find a title, "Broken gear tooth" -- where should I look??

Just as well I cannot find it, I guess -- because I know my remarks would be considered well out of date... Which, of course, they surely must be. I mean when I was building my 1st Bantam I could buy a Close Ratio Bantam gear set for less than a fiver. That was by popping into MC shops en-route to Leyland and back to London and looking thro´ their "Old Spares" bins. At one place near Lichfield I was GIVEN six gears -- by complete strangers -- and presented with a cup of char whilst I was doing the search.

I wonder if such a thing could happen these days!

While I am on, All the best to your Malcolm & You at Mallory!

Cheers!

JayBee.

John lookm in the English dictionary under Sheep SHagging"

no time so that it till sunday see you all on sunday dont forget we are there most of the day, so dont come early from 11.30 onwards is fine, Nigel you bringing your bike.

Ned "I will answer you, "
but I need three hours" just dont have the time , but come on I mean wake up man - "I posted that in june 2011?????"

Derek

one questioni have is what is the theory on the type of reed valves that should be used, I do seemost of the front guys besides peters and trevors engines arepiston ported.

effectivley i have a yz 125 reed set up from the 1988, what should I be using or looking to use,i have to say i prefer the reed set up easier to get off the line,than my piston ported one that we are in theprocess of converting to a reed valve.

i understand theyare both resonant and one is possibly better topend the other has a stronger in midrange and wider spread.

why is this!

Derek

Me too... I´d like to learn a bit more about the effect of a reed valve. I guess looking under Blair and Qub would do it but I´ve seen very little on here except for Peter saying that the reed valve gave him a better torque curve. I suppose, thinking about it logically, the improvement in crankcase compression must bring about improvement above.

Just seems `Magic´, that those fragile looking reeds can perform the way they do -- hundreds of a flaps per second -- and last.

What is the reliability of reeds like??

just been working it out john a reedvalve openes and actually closes" uptoabout 8000. past it reaches a limit it can notmove any faster so they close down and open up above this, what I think is interesting is at 8000.rpm they do open and close but they change direction more than 133 times "per second" which is about as quickasI rected to miss Mark Carkeek when he dived upthe insideof me and took me onto the grass. !!
"never let sleeping dogs lie" but I do wish my bike was this quick.

Whhen I was refering to the reed we should be using, I was more talking about what is regarded as the correct reed valve /Rad valve /v3 force reed / - material / thickness/ to run on a Bantam,with our rquirement for a wide power band.

Right! let sleeping dogs lie, Derek. From what I´ve learnt on here suggests that I never really got into any REAL WORK on the bike -- including SUSPENSION development -- and left most of the work to my helpers (2 off) that I deserved to have a 12 horsepowered, 8,400 rpm also-ran Bantam. Yet there were fun times and moments of glory. Regards the latter if anyone has results of May 19th, 1973*** -- and photos -- I wish they´d publish them. What a day that was -- after Niffy broke his leg in the Novices race, I mean....

Yaaaawwwnnn! Snore! (sleeping dogs, happy at last!! ....)

***be able to celebrate 40 years next year!!

Cheerrs!

I was asked to provide a 175 and 125cc short stroke cases crank complete Formula bantam engine set up, for a northerner to possibly get involved with building Bantams for a number of friends he racedwith, anyway to complete this little set up, I need two old or used crank bearings, scrap items are ideal the engine will never be run, goodto get others involved with Bantam's I feel.

I had some but threw them away only a few weeks back.

if you can help, last years bearings used or scrap / get them out of the scrap bin for me if they are full of swarf no issues, will do fine, but these need to be the 52x25x15 bearing,

if you could put them in the post to me, - if anyone can help, as I dont want to give away new bearings.

The Forum is quiet,alsowhat happened to my request for information to Mick Potter post did this get deleted. I never seen any replies to it ??
I hope Ihave not upset anyone, with this request.

Mick did you seemy request could you help would you have that type of information or not. ?

regards Derek

Bearings Derek is refering to is 6205 (or a 1205?)

thanks for correcting me Mike on the type of bearing, do you have some old un's. ?

what is a 1205 ? clearly it must be the same size bearing, ! is it the fiber cage type

and what advantage does this have over normal bearing, les friction and can you feel the difference between bearings on power/revs at all.

Derek

google it Derek ....

THATS COMPLETLY UNSUITABLE FOR A CRANK MIKE i dont follow you.????

Derek

Unsuitable ??

what happened tomy pictures

cadwell park was an interesting event for us.

i have recently recieved some technical information on squish bands this has been sent to all the midlands boys,

out of interest when I modified my squish with the same compression it gave a wopping great increase in torque and power on the dyno with my old pipe.

we had two new pipes made as we have run our of gas and all frame building is at a stand still untill we can resolve this., anyway the one pipe is a very kind gesture from Trevor Amos that work straight away on the dyno giving me another two HP with any adjustments, after some carb tuning this increased further but my goodness what a difference in the btm end. off the line I feel with the right adjustment on the clutch the bike was a match for most this was very pleasing.
Our second pipe gives a little more power but no overe rev staht now appears so important, as it curtailed my top speed.

the Bike was pulling very well, 15x51 sat and 15x49 on the second day, we are peaking at about 8500 to 9,400 so some mods required to get it to rev, I do not want to shorten the pipe as my pipe is already about 4 inches shorter than Nicks Pipe, I seen quite a few have thier exhausts rapped, we did try this many years ago, with bad results of servier overheatng,

so I think we will try this again, i believe it increases the gas temp so the sonic waves travells faster returning a quicker puls.


I hope everyone had a great race and I was not too much of a mobile chicane, my private notes read of how smooth ,Mick potter and mick scutt were through the Goose-neck, my failed front brake in the last race, running on saturday with a partly seized rear wheel bearing, how it pulled another 1000 rpm once it over heated and freed itsself. (i was very lucky).
out of interest what are the numbers for a std Bantam rear wheel bearing,?

nothing else to report only thanks to Trevor for the head squish drawing that I machined both heads to and the exhaust pipe, it certainly was a big improvement over what I had.

Mick Abbey made both pipes i was using at Cadwell.


my mods for Snetterton are.
1) stick with the diet to lose some more weight another 2 KG is hopped for.
2) modify the tail pipe diameter down to 23mm of the one pipe,
3) order some new rear shocks
4) pre load the front fork springs and sort out the correct level of oil in them.
5) sort out some softer /new front brake linings.
6) finish of the fairing ducts, the current /new nose mods appear to be working very nicley.
7) repair petrol leeking from the tank weld.
change the clutch oil and wash out, Gear box ready to start.


'O' yes" I was running rich on the saturday it appears my pilot system adjusting screw, is very very sensitive, only the width of a screw driver blade in turn on the pilot screw and the whole systme goes exsesivly rich, I was wonder if the pilot system seat is damabged possibly through over tighten ing

regards Derek

Hi Derek! Trevor did mention earlier on that the exhaust gas temperature has an effect on the speed of sound in the pipe but I thought it was not that critical unless a methanol fuel was used when the difference in temperature is quite large -- somthing of the order of 200°c - less - I think!!??

Cheers!

Derek are you able to share the details of the difference in old and new squish bands ?

Hi john john and john

yes absolutely but I got the information on squish bands from Trevor, he did not say to me why it was like this but was very helpful on the reasons to promote turbulence, My bike has gone from an also ran to one that is clearly very quick with some minor adjustments to porting crankcase volume, and the work on the transfers that dad has been doing has all helped but there is no way I would have achieved thesis in this short time without the work on the DYNO, Trevor has been posting me a few items I will have to ask him if he wishes them to be known I have to respect that if so sure no problem will post it for you. and the pipe dimensions if he,s ok with it.

Trevor sent me two drawings, I have shared these with the midlands lot except Mick potter I don't have his email,drawing with others but not on line I sure Trevor will not mind but I will just ask first if thats ok his pipe is very nice and instantly gave a big improvement.

On the squish what I have been playing with is very minor details but my goodness they have really sharpened up the Power line and flattened out the torque curve bringing it up at both ends.

I,m absolutely convinced there is at least 20% more torque to be had if you not running this mod,

out of interest for your ref these are approximate figures and will vary from Dyno to Dyno I have now 17.8 HP and 9.5 FTLBS or torque, Its taken me a while to get the dyne set up right having the correct knowledge is the difference.

we are back on tail pipe diameters for now but I really do need to try and finish Eds Bike off he is clearly not going to do it and Im getting a hard time from her in doors to also get on with it,

what I have found out since getting this top secret squishband information is just how open and helpful Trevor Amos still is and what a wealth of knowledge he has,

back on with the squish = \
is that it promotes additional turbulence ! from Trevor@ but more importantly I have researched that it actually helps reduce deternation or helps stop it developing, when it otherwise would do, for the same volume \temp gas



my temp probe dropped 25 degrees with the same volume head the shape I found a better performing head than the conventional hemispherical however I was not running it at Cadwell but will be at Snett, head, adding to this I am running a Bindy cylinder head, this is far more effective at cooling than a std bantam, BTW, or Ned head, ref Johns Jib at radii the flat at the root has a very big effect over the ability iof the head to transfer heat to passing air?

the other thing to comment on is how slow things are to search out if they work, I ,m really starting to see why software can be a big help,
things are slow but we have another half horse power since Cad-well, and I hope to try the other head again, I do hope my reliability continues, but with such a low revving engine I can not see why it should not, I am marginal on the big end as it was changed but a lot of play in the rod that dad lapped, this will be an issue to move forwards.

I intend to log all my experiments, and adjustments with the pipe drawings from Trevor as long as he is ok with this, on here, i think anyone building a pipe need look no further than this as a starting point.

if anyone wishes to comment @please do so@ any advice would be very welcome.

regards Derek

I expect I have to be careful saying this -- I have assumed the quoted values of horsepower and torque from dyno testing I see frequently on here are automatically corrected for ambient temperature and pressure in the software of the dyno computer.

I mention this because with the weather changes we have had recently the comparisons from engine development changes might not be exactly comparable. High humidity, particularly, is known to improve an engine output ... OK! so by only a small amount -- prehaps -- but gaining 2 horsepower more by some small change might not be the change at all but just the effect of ambient temperature, pressure & humidity change. There are five Standards -- or Norms -- to my knowledge in general professional*** use and Slick (my son in the IoM) uses SAE j 1349 which is slightly more optimistic than the German DIN 70 020 but that makes no odds as long as the same one is used all the time...

In business, the professionals must quote the Std or Norm used in quoting power output from an engine but, of course, in the Bantamites case that is not necessary but it is important in making small changes in development with hope to being correct in what is done.

Cheers!

will comment on this later under pressure going out John

Dyno testing can be frustrating -- you make a small change and the engine goes much better and you think you´ve mastered the art of engine development. then you make another change -- that everybody´s been raving about -- and your engine doesn´t respond.

Sickly nostalgia again. I was up at Leyland Motors when they went public on two new engines and then changed the drawing dimensions on the 0700 (the larger of the two )to S.I. Metric from British Imperial. In the changing of dimensions by a few thou here and there the larger engine LOST 40 horsepower on the dyno. We, at Simms Motor Units, never found out why it happened and believed Leyland never did because their supremo bosses decided the 0500, smaller engine, would replace the larger motor and squashed the 0700. These engines were known as "The Headless Wonders" because Block and head were cast as one and the machines for shaping the combustion chamber and cutting valve seats etc... etc,.. were very special. Made only in Germany, of course!! -- Plus Leyland had a complete new factory built for the production of these two new engines. Whole thing was a disaster and one of the helping reasons for Leyland to sell out to DAF....

Cheers!

i agree John, in many ways we have had a steep learning curve what we do is start each session by re cheecking the last setup modifying the carburation then making the changes or parts required for our experimenting.

derek

Quid Pro Quo , Derek , or that could mean , Persona Non Grata !

An informative PM would indicate a little gratitude and help fill my results and developement note books ?


Trevor

... Trevor, I think he said, on a posting of his on here somewhere that he was grateful to you.

You´ve gone quiet lately -- something peculiar going on in the West Country???

Cheers!

Trevor Amos wrote:

Quid Pro Quo , Derek , or that could mean , Persona Non Grata !

An informative PM would indicate a little gratitude and help fill my results and developement note books ?


Trevor

Hi trevor you need to check you PM box mate its must be full of comments and requests for permission to load the details you sent to me, that has been really really helpfull in my quest for more power.

so for your reference from my meeting at cadwell park last year I was a full 20 seconds per lap faster, I think I really raised a few eye brows especially those watching me over the mounting in the second race on the saturday cadwell meeting, in practice I have no problems.

actually not sure what update your looking for so will start with the dyno gone from a 12 hp and 6ft lbs to a 17 BHP in fact almost 18 BHP

torque has in the past runs moved from 5.5 to 9.6 lbs of torque, about 2 more than the very quickest 80cc racers.

I could feel this as the bike lap after lap was lifting the front wheel with eas over the mountain. so progres has been great.

what Ihave done for this increase applied the simple rules and explanations you have sent me, the squish mod gave me an extra 2 hp and lifted the torque curve line either side of ppeak power to a form a horizontal line from about 6500 to 9500 It just pulls like a train, but is not to say Ihad a trouble free day as after the second race when it was just so fast the rear wheel bearing seized then freed off on the last two laps it run dry, was binding so badly after i could hadly push the thing, so there is a lot more to come, I was very relaxed about the gearing, but on the dyno it excellerated so quickly I had to double check the sprockets to make sure I had not forgotten that Imay have changed them. which I had not.

anyway all these changes elevated me from a winging also ran to mid field position with a nike that is so capable of so much more it was ambarrising at times it was so quick. i'm really looking forwards to snetterton, but MY little D1 cast barrel lost another two fins its holding pressure ok but will need a new Barrel we had satrted a new barrel but loads of work to do on it before its finished too much for this season.

although I do have another pipe that works slightly better than the pipe dimensions you sent me Yours has a much wiider rev range and revs on better so top speed was better.

I was pulling 15x51 on saturday moving to 15 x 49 it made no appreciable difference to btm end, just slightly over the mountain so I think I will go higher for snetterton possibly one ofn the front, the seized wheel bearing will be sorted this must be having an effect and Ilost my front brake in the last race, round Cadwell its very difficult without a front brake that works, !

also Ihave a few carburation issues Ithink the eother the pilot system of chke system is causing issues with the carburation making it drift richer as Im going along not sure why this is yet.

Many thanks to you for your assistance I was hopping to share the information with others on here, but obviously would not do this without your permission I think your pipe would make a fantastic Formula pipe for a startee at it works very well and straight away.

while I understand John has critisised my work on a dyno there is no doubt Iam going in the right direction and can not wait to get some more time to sort out the other options on head shape that proved sos succesfull in my earlier runs before I started the exhaust development.

I am not running any special advance or retard but hope to try this at some stage and to run with a better Handling bike Iwas clearly out riding the capabilities of the chassis, so having had both Mick Potter and Nick take a look I have a nice new set of shocks being made and intend to increase the spring pre load to stiffen the front fork springs and reduce the oil viscosity to increase the travel as it was btming so chattering very badly both round Barn, chriss the goose neck and through the right hander over the hill, you know Ihad to brake at the top of the hill before turning right ? to go round charlies and back onto the straight, never had a bike Ihad to do this with only my little Honda.

I hope this gives you an idea of what some simple help can do to get you a little push along the path that always has many directions to travel, you have certainly pointed me down what appears to be a down hill path of development to such a rate not sure what to try next as I have lower revs higher power and higher torque. I would really like to lift the revs up to 11,000 what would you suggest to do, my exhaust timing is about 94ABDC or 188 total open transfers are 62 or 124 total open I have a third transfer fed from a little window high on the skirt. Im running dykes rings to that really help with the starting. carbuation seems to have a lot of difference on what it pulls with the carb doing fully things not sure what the bike is really doing on the dyno or track, but we can see its very safe and rich, when it cleans up its certainly does make a difference. I hope not to change too many things but now I know what Im doing ? I think I can easily duplicate this on another engine Ihave made scruplilus notes, your welcome to read them any time, my goodness the transfers forgot but Ihave sent you a lot by PM by this larady so lets keep em guessing and not give it all away just yet, also another unberleavable effect was how I lost 1 ftlbs and 1 hp by cleaning the squish band surface finish, Ithink Imay have modified the edge of the chamber when doing this but only with hemery paper, the surface finish, so the squish finish makes considerable effect to the torque, did you know this in fact its like rinding a different bike one less pulling thant the other thats really strong.

hope this is enough for you to make those notes sorry my spelling grammer so poor its my lack of a proper "education" but look at the time of work in 2.5 hrs not gone to bed yet!.

hope you enjoy reading this as much as i did building making experimenting and riding a bike that now seems to have so much potential to go very quickly.

kind regards Derek