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how to make your d1 go as it should have gone
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Anderzander
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August 22, 2016 - 7:53 am
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I just re-read my old thread and I'd written that when I'd fitted the D3 top end it did an indicated 50mph - the speedo has changed since then and I'm now using a bike speedo, but the top speed is now reading 40 on a flat. So either I had an over generous chronometric speedo - or I've lost some speed somehow.

i better have a look before I start tweaking things.

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stubaker58
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August 22, 2016 - 9:24 am
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On the advice of someone on here I purchased a speedo app for my phone, it's very good and presumably satellite based so should be accurate.  Unsurprisingly it's called 'speedometer' and is by Finley miles ... Is that a pun?

D7/14 hybrid (4 speed with D7 crank etc.) on the road, D10 Bushman awaiting rebuilding.

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ferguson
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August 22, 2016 - 12:44 pm
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read a whole article about satellite/gps speeds and not as accurate as some will insist.apparently pretty good if on the flat but anomollies appear decending and ascending.all to do with the angle and the position of the satellite.

talking of mistakes-i just realized i made one in the opening spiel i made-was giving my bantam a service while it waited for its new carb needle and popped the head off to put dial gauge on to set timing/points.my bike one of the annoying ones that has an problem re crank,stator position and cam.result being to set timing i just wind stator to fully advanced and then close points till get to the magic 4mm btdc.points end up at about 10 thou instead of 15.if i put them at that bike runs well but prefers a wee bit more advance[4.5mm] to get the best out of it.at that the points are about 8 thou.-just done it and realized what i had put in the opening 'bit' of this thread.went back to my note book and redeciphered my squiggles.i said advance ignition to 2.8 mm btdc-that's retarding it what i actually wrote in the book was 5.8mm before tdcdoh

in due course will put up some drivel as regards modern petrol and the problems it causes for ancient vehicles-i spend a great deal of time setting up customers vehicles to run 'OK' on modern go go juice.

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mike p5xbx
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August 22, 2016 - 4:49 pm
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ferguson said
read a whole article about satellite/gps speeds and not as accurate as some will insist.apparently pretty good if on the flat but anomollies appear decending and ascending.all to do with the angle and the position of the satellite.
  

most sat-navs use Doppler shift vectoring to work out it you are going up or down hill
and we normally have sufficient number of satellites in view in this country for it not to be a problem.
however the display is not real time so depending on how long it takes the satnav processor to do the calculations they often show a different speed to the vehicle speedo
so you get people saying they were doing 70 and the satnav says 64
if you really want to test the accurately of a satnav try it on a motorway that goes over a hill and count the distance marker posts against the satnav result

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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Anderzander
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August 24, 2016 - 9:34 pm
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Thank you for this Ferguson 🙂

Ive started checking things out - made a little video through the inlet too.. ** Please log in to view **

 

Edited to to fix the link !

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ferguson
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August 24, 2016 - 11:03 pm
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laugh-make sure you just radius all the port edges while you are groveling inside your engine.it helps the gas flow and gives your rings an easier life.pop barrel of and do that-then put barrel back on to mark base of piston that needs removing.more accurate that way round.

some interesting temps we found when tuning d1's.

with squish band the head temp rose by 40 to 50 degree F but the barrel temp dropped by 30 degree's F.

spark plugs.dont be too tempted to put in too higher temp rated plug cos the 'hotter' plugs heat up your engine!going up one grade of plug increased the temp by 10 degree's F.took us a bit to work out why and it seems that its down to the amount of ceramics on the plug.differences between a 5 and a 6 -well they look alike but in fact the 6 has more ceramic than the 5.if you look at an 8 or 9 compared to a 5 then its very obvious.the ceramic is a fantastic heat store-as well as protecting the plug.so only go as  'hot' on the plug as you need.

ferguson

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Anderzander
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August 26, 2016 - 8:34 am
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May I ask a acouple of queries on this that I've been pondering ....

The first is I suppose just an observation ?  With the shape of the chamber being as it is then the squish band must be very narrow ? The ones on my other bikes tend to have been cut at a few degrees above the angle of the piston, and at around 0.8 on the edge, and quite wide  - where's on the D1 it looks like only the skim gives you the chance to cut and then it must only be a few mm wide? Have I got that right ?

Second pondering ...  I presume that skimming the head at an angle must be at a very slight angle, with their not being much depth to go at, and also to stop the front edge of the fins touching the barrel ?  Unless I've misunderstood then - it seems surprising that yields best results when the angle is so slight and presumably that (without further machining) will mean the CR is increased less than a flat skim ?

Last one !  With mine being a D3 top end I was thinking about machining a D1 head to fit - cutting the smaller bore out from 52 to 57 after the head is skimmed should give more metal to go at in getting a better squish band ... What do you think ? 

Any thoughts welcome !

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ferguson
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August 26, 2016 - 9:52 pm
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firstly the squish band is narrow.go for 0.8 to 1mm deep.depending on the original casting it normally works out at 2 to 3 mm wide.we used to leave them flat 'cos were so small -just radiused the inner edge so not a sharp edge.if tilting the head the compression is lower but the squish band much more effective.we used to go for the max possible by machining off the fins till a reasonable gap.it is a slight angle but you can easily double the squish band size at the front..if doing the d1 head on the d3 barrel check for thickness to play with and taper the squish band gently to make a taper to push fuel/air mix into centre of head.

seeing as how you are going for it i will translate some mild porting pictures into words for you[but not tonight as knackered].

ferguson

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Anderzander
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August 26, 2016 - 10:02 pm
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That sounds fantastic - thank you. One other quick question - did you run with a head gasket?

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ferguson
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August 26, 2016 - 10:21 pm
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what's a head gasket?laugh.no never use them on bantam's.my current d1 is minus its head gasket.

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ferguson
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August 27, 2016 - 12:00 pm
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ok -here goes.

basic principles.port timing is everything on a 2t.the height of the ports controls timing -but the width controls how much go go juice enters the engine.so be very careful on the heights but also dont get carried away on the widths as too wide gives your rings a hard time.one area to concentrate on is the corners of your newly enlarged ports.they must be well radiused to help the rings.the verticals and horizontals need a wee radius but the corners need doing well.

easiest way is to strip engine down-put crank,rod piston etc in one crankcase and fit barrel on.on exposed end of crank fit a timing dial with suitable pointer set up and have a fine pointed sharpie[felt tip pen] to hand.

remember not all bantam's engines the same and compromizes might/will have to be made on piston positions compared to ports.

exhaust port.point of opening of exhaust port needs to be 80 to 85 degrees before bdc.aim for 80 and by time edges radiused nicely in the zone.make it 32mm wide max.easiest way to get height is to measure rather than do it in degrees so total height[before radiusing] should be 19mm.however check where piston crown  is at bdc-should be level with bottom of port.if a touch high just ease edge of piston in area covered by port if too low-like mine- take of that meat first from port then mark up at 85 bbdc and check height before attacking the barrel ports.

the transfer ports should also be level with the piston at bdc.they should be opened up to 22mm wide.they should be opening at 60 to 64 degrees bbdc.again aim for 60 then radius edges.not going to give a height for these.bottom edge set by piston and just aim to open top edge up to 60 degrees-are incredibly variable in their position and expect to have to compromize!

inlet port-opening 75 to 80 degrees before tdc.again aim for 32mm wide.most of meat will need to come of bottom of port [normally] where there is likely to be a small v in the port shape.normally this all disappears.needs to be 22 mm tall.

dont make top edge of port lie below the lower edges of the exhaust and transfer ports or power like an on/off switch and right up the rev range.

will explain crank cut outs and transfer port internals later when my brain recovered -pictures would be so much easier.

ferguson

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ferguson
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August 27, 2016 - 12:21 pm
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should add-once inlet port done check masking by piston.me personally used to just take 2.5mm of whole of the piston skirt.on most models of piston there is a little step on inside of bottom of piston-just take it up to that step.-but just taking visible 'bit 'through port quite acceptable.

 

nearly forgot.piston cutouts at bottom of the piston.not always do they line up with the  ports and the edges can mask the ports.gently ease back the edges till line of sight clear of piston bits.

by now you might have realized just how variably 'well made' d1 bantam engines can be -or rather not!

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ferguson
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August 27, 2016 - 3:13 pm
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brain recharged-firstly if you remove 2.5mm off bottom of piston it makes it racier-pushes max bhp up the revs a bit but engines love it cos you get a dwell period where everything[gas flows] can catch up with each other.will explain more if anyone so desires but quicker bike if done-but a bit peakier on revs.

inlet tract.in most peoples eyes bigger must be better but for a road bike definitely not.again its down to where the power delivered. big holes mean power higher up the rev range and flat as a pancake low down -fine for racing but not for the road.max i would drill out the inlet tract is 22 mm to still keep a usable engine.easiest to just drill out but better if done by hand and start at 22 at carb end and taper it gently in until 25mm away from the port itself.just a little taper to give a pinch point at 25mm from the cylinder wall.this speeds up gas flow and makes engine more tractable. from the pinch point just flare it out to flow into the port shape.the exhaust tracts are normally pretty good but a pinch point 19mm in from thebarrel wall again helps with the gas flow-again just worked to flow into the port .

so now you have a barrel that can boogie but the crankcase breathing will cripple itdohcrankcases first flaw is the little shoulder found[normally] on them-just as the gases reach the barrel-remove it then enlarge them by 2 to 2.5 mm on all 3 sides.normal rules apply so make it flow nicely down into the cases.coat with engineers blue or use a base gasket as a template and transfer shape to barrel.the internals of the transfer passages are notoriously difficult to reach unless got a dentist type drill machine so taper them in as far as you can get.one area to be careful of is where the gases exit the ports.you will notice that they come out basically at 90 degrees to the piston-try very hard to preserve that angle as the gases flowing out over the top of the piston cool it.years ago the trend was to open up the angle to the gases went upwards by 10-15 degrees.this does work on a gas flow basis but was found to be detrimental to piston life.we used to reckon at a 5 degree upwards angle to be the absolute max.

now put it all back together and boogie timelaugh

where the little hole is for the main bearings get their oil-just dish out the top slightly -helps collect essential oily fluid for the mains.if taking it out to 22mm on the inlet tract then definitely time to retire the 361 amal and i like the dellorto's.if only drilling out to about 20mm then the 361 will do the job but will require drilling out.think it will go to about 19mm before the slide will just fall out.if you dont have the proper gear safest way of doing it is very slowly with an adjustable reamer.

ferguson

do ask questions if my descriptions not good enoughget-me-coat 

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ferguson
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August 27, 2016 - 8:23 pm
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should point out all of the above is pure plagarism.my father gave me a 2t tuning book at an early age.me and my friend paul ploughed through it and just got confused so instead just read up on what everyone else was doing and with lotsa trial and error came up with quite a quick bike.if you do all the above it is definitely time to rethink your brakes!

my son phoned tonight-he claimed to have found a d1 carb[complete] in a flea market in holland.when he is back he will post it up to me so if any good i might bore it out to 19ish mm and see how it goes on a standard bike.i actually dont believe him-he has the mechanical aptitude of a dead gnat but his wife is a different story.lovely girl but comes from hull and probably hot wired her first car aged 3-i'll bet she spotted the carb-not my son.jets would be a problem normally but luckily i own a jet reamer kit.comes from russia where aftermarket jets kinda scarce.when russia makes a vehicle you get what the state gives you and the jet WILL be the right one so the inhabitants get round rejetting by reaming out jets to the size they require.

ferguson

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Mags 1
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August 28, 2016 - 1:18 am
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Thanks ferguson for writing down some very interesting stuff about our engines and how to improve them.

I realize that the first steps are only to make the engine more efficient and maybe even run cooler, who knows.

What I'd like to know is, although more efficient, will a first stage modified engine use any or much more fuel?

I think we mostly all know that you don't get anything for nothing in this life, but inefficient engines also use more fuel sometimes.

Have you done any research/projects for economy on Bantams too?

Yes, I know you can't usually have both!

Four now on the road and at least several in bits.

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grubsie
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August 28, 2016 - 2:47 am
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Very interesting reading. I sure wish someone could put this in formal documentation or pictures. I read some documentation online somewhere about racing mods for these bikes but can't remember where I saw it.

I have my bottom end rebuilt and finally got my cylinder back with a fresh re-bore for the new piston-rings and would love to make the proper modifications discussed here for top performance before buttoning everything up. Problem is, the more more info I read on this thread, the more confused I get.

Maybe I need to print everything out and study it a little more before attempting the mods needed. I have done mods like this before with some Japanese motocross bikes in the past but had detailed documentation to work with. The difference was like night and day. With the size of the cranks on these D1's vs the bore and stroke, 35-40 miles per hour should be the worst performance due to low compression and/or a badly tuned engine. A fresh top end along with proper tuning should have far better performance.

I would be willing to bet that it was luck of the draw back in the day as to how well these bikes performed when new. Your buddy could have bought one the same day/same time you did and his would have blown yours away or vice-versa.

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BonesCDI
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August 28, 2016 - 7:29 am
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Mags 1 said
Thanks ferguson for writing down some very interesting stuff about our engines and how to improve them.

I realize that the first steps are only to make the engine more efficient and maybe even run cooler, who knows.

What I'd like to know is, although more efficient, will a first stage modified engine use any or much more fuel?

I think we mostly all know that you don't get anything for nothing in this life, but inefficient engines also use more fuel sometimes.

Have you done any research/projects for economy on Bantams too?

Yes, I know you can't usually have both!  

Hi Mags,

My D3 has basically all the mods Ferguson has said nearly verbatim, and I get about 170-180 km out of a tank. This is obviously dependent on how you ride it, but if I am on a rally that is my estimated range before refuel.

Bones 

Running and project bikes from 1912 -2005..........She hasn't said stop yet.........

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ferguson
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August 28, 2016 - 10:53 am
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mpg-if you just tidy up the engine,that is up the compression and make sure all correct internally-as in the first bit of this spiel then 120mpg normal unless you ride it like you stole it.if you attack the ports like just mentioned,with an expansion chamber fitted and ride it like you stole it then 70 to 80 mpg likely,possibly even a bit less but would be collecting speeding tickets like they were going out of fashion.you can take the porting further than advised above but definitely for the race track only and that would eat fuel.

ferguson

p.s. to reiterate a point mentioned by bones and myself-if going to play do get your crank sorted first.just aligning the absolute minimum-which you can do yourself with a couple of v blocks and a dial gauge[and a lot of patience and a heavy rubber hammer].if feeling flush give it to a 2t expert and get him to balance it-true balance on a single actually basically impossible but it can be improved with judicious adding or removing of metal in the right places.

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ferguson
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August 28, 2016 - 3:28 pm
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harping on about the crank again-when we were building silly bantams we bought a 1953 plunger-only because it was very quick for a standard bike.was duly tweaked and it turned out to be the quickest one we ever made.paul stripped it back down to see if we had done anything different but not the case.it was rebuilt with a different barrel and was still 5mph quicker than anything else we made.we concluded that it must be down to an exceptionally well balanced crank when it came out of the factory.paul still has that bike but it now sports a disc front brake and honda forks.it has a 7/8's amal tt carb on it and an expansion chamber and used to be good for nearly 80mph[the tt carb probably worth about 1/2 the value of the bike nowadays]

ferguson

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Anderzander
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August 29, 2016 - 8:13 am
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Loads to go at there Ferguson - thanks for sharing your notes.

On my D3 top end the i.d. of the carb and inlet stub are pretty much a perfect match - so as tempting as it is to open the carb and inlet up, I think I'm going to do things incrementally.

So, I'll start with assuring all the ports aren't covered: from memory with a base gasket fitted the bottom of the transfers and exhaust just cleared the top of the piston at bdc - I remember checking.  I obviously forgot to check the inlet though! So I will sort that out.

i will also do the head - so will be reporting back on that as I go along. If I can find a spare barrel I will do more to that and the spare carb body I have - whilst keeping the bike running in the mean time.

Oh last thing - I've ordered a carb refurb kit from Amal to get that on the proper baseline.

Looking forward to it!

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