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New D14 or B175 crank
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Ringting
Newport Pagnell
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April 28, 2019 - 11:09 pm
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Hi folks, just taken my D14 engine to bits to rectify a knock and vibrations. It has a B175 crank fitted. To cut a long story short, does anyone know where I can buy a complete brand new crank?

It needs a new big end and rod and a new right side main shaft as someone has damaged the tapered spigot where the points cam fits. It has 3 cracks running down it. And the left side flywheel oil seal face has deep corrosion pits in it. Then the flywheel side plates need to come off to clean inside properly and be remade and fitted somehow. 

Overall I'd rather just replace the whole thing if possible and the price isn't prohibitive.

Any thoughts gratefully received.

Alan.

D1, D14/4, Guzzi LeMans, Triumph Trident 900, Maserati 160 t4. Mk1 Mini Traveller, Berkeley T60.

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Sponge
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April 29, 2019 - 9:01 am
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Hi Alan, 

Original BSA Crankshafts are getting rare nowadays - I am hoping that somebody will start making them again soon - but they are unlikely to be cheap. 

Just some thoughts:

Bantam John may have an original NOS D14/4 crankshaft in his stock. If he has - it will be one of the last ever and will not come cheap.  If money is plentiful then suggest you ring him.  

I noticed an advert that Rex Caunt is making newly manufactured Trials Crankshafts for Bantams - I am not sure how a trials crankshaft differs from a road crankshaft but also worth speaking to Rex to see what is what.  If Rex has made it then it will be top notch. 

It might be possible to make up a crankshaft by using D7 flywheels and D14/4 mainshafts.  With a Rex Caunt big end assembly and careful machining/balancing I see no reason why it wont be as good, or better, than a NOS item.  But - who can do the job - there will be somebody out there who can.  

Advertise for a good useable D14 crankshaft and have it reconditioned (cleaned and repaired etc, new big end and rod etc)  by one of the Bantam specialists.  

Take your existing crankshaft to an engineering specialist and see what can be done. It may be possible to recondition and repair it. You might be pleasantly surprised. 

Regards

 

Sponge

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Mags 1
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April 29, 2019 - 12:46 pm
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Alpha Bearings at Dudley still repair Bantam cranks I think?

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

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SpacedMarine
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April 29, 2019 - 5:19 pm
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I second rex caunt.Thing is they aren't cheap at £600 a pop but they are cnc machined with new shafts,rod,bearings etc.Apparently made by TT racer Mick Grant.I feel your pain.There are many d7 and earlier cranks on Ebay however d14/b175 cranks are rare indeed and a replacement motor is north of £600 and again they are rare.

Also the idea of d7 flywheels and shafts from a d14 would probably work and its something I've been thinking about myself.

I've got myself a lathe to build my own in the future once I get my garage sorted out not sure how it'll go but I'm intending on making my own shafts and big ends aswell.Im sure they wont be anywhere near the quality of rex's but if they work I'll be happy.Just speak to Rex he's a lovely chap and always has time to talk about bantams and impart his wealth of knowledge.

What's 7/16 in mm again?

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Ringting
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May 1, 2019 - 9:34 pm
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Thanks for the replies chaps. I'm now waiting for a reply to my email from Rex who I understand has a medical issue that's being sorted so slowing things down. 

Have rung Bantam John but not got a reply yet. I'll keep trying. I think If I could get a right side main shaft from him Rex could sort the other issues. Then..... Do I refit the flywheel side plates or not.... Dum de dum....

Plan to do a bit of mild tuning as well. Just port polishing and alignment to make the best of its potential.

D1, D14/4, Guzzi LeMans, Triumph Trident 900, Maserati 160 t4. Mk1 Mini Traveller, Berkeley T60.

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cocorico
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May 2, 2019 - 7:37 am
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Ringting said
...Plan to do a bit of mild tuning as well. Just port polishing and alignment to make the best of its potential.  

Have a look at ** Please log in to view **, it's on the D1, but applies to any Bantam.

The Bantam Club Forum - all the answers are in there. If not, Google may.

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Ringting
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May 14, 2019 - 4:54 pm
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That's interesting reading Cocorico. The ports are rough as old boots and alignment with the crankcase is poor so I think there's potential to re-gain some (if any) performance loss from leaving off the crank plates. 

I wonder if BSA lost the plot in their quest to keep the plates in place. Cutting access holes in them for the crank pin rather defeats the object. The amount of rusty oily abrasive gunge that was behind the plates when I took them off was quite shocking. What that was doing for engine balance goodness knows and I certainly don't want that circulating around my nice new bearings.Img_2085small.jpg

It's a pretty complicated business when you read into it. For example, Increasing the crankcase compression by fitting the plates or packing the crankcases will increase pumping loss on the piston down stroke. It will also increase blow back through the inlet port at low revs. So is it better to have less crankcase pressure so it can use longer inlet port timing? Who Knows! What we are trying to achieve is getting the mixture up through the transfer ports either by pushing it harder or making it flow better (or both). It would seem that making it flow through the ports easier with less push must be a win win. Can't do any harm.

As for parts, I've had an offer of a rebuild-able crank from someone on here so I'll take that up. And I spoke to Bantam John this morning. Very down to earth. He basically said that he'll have anything I want so I read him a list, he gave me the prices, reasonable I thought, And I've ordered a load of stuff from him, including a new right side main shaft so I can have a spare crank in stock. Can't wait to see what turns up.

Watch this space!

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D1, D14/4, Guzzi LeMans, Triumph Trident 900, Maserati 160 t4. Mk1 Mini Traveller, Berkeley T60.

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Maico490
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May 15, 2019 - 10:20 pm
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Must have caught him on a good day!

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Mags 1
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May 15, 2019 - 11:06 pm
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Surely there's hundreds of old worn out cranks knocking about, in all the different guises of Bantam manufacture, all they need is new crank pins and bearings which are sold by many Bantam specialists? Yes, the con. rods too are often worn right out as an extra headache.

Can't think why anyone would want to actually make new crank webs on a lathe, they are cast steel, not mild steel or cast iron?

I must have twenty scrap big end assemblies myself, it's just the cost of having them repaired that prevents me from having the lot refurbished, at maybe £150 - £200 each? 

It's still an interesting subject for posting though, maybe someone who understands it all can put a post on and explain it simply for us from start to finish and not leaving anything out, often folk who work on such things take a lot for granted when assuming that ordinary biking folk fully understand the nitty gritty facts about cranks. (And why they're so expensive?)

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

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SpacedMarine
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May 16, 2019 - 3:31 pm
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Hi mags.I believe they were actually forged then machined in the factory.I thought they were cast myself until Rex Caunt told me otherwise!

As for making new ones at least you'd know they were accurate depends on your circumstances I suppose.

Theres also the thing with the plates as illustrated above.You buy an intact crank then have to remove the plates to clean out all the gunk behind them and depending on which model crank you have you're back at square one.Yes you can run them without plates and yes they may not make much difference but if they are the riveted type you have to drill them out and are pretty much left with a crank that needs some kind of re-engineering anyway so why not just build a new one?That's kind of where I am at the moment.Just working out the best way of going about it.

As for crankcase pressure my theory is that with the advent of expansion chambers the high crankcase pressure wasn't necessary as the pipe acted like a pump once it was working sucking the mixture through rather than having to "push" it through with crankcase pressure.Kind of like a pulse jet engine???

I read an anecdotal piece about the aprillia gp team testing an rs125 without pipes and it made about 10 hp!whereas the same engine with pipes made over 40!So there you go.As for the validity of the story who knows???

What's 7/16 in mm again?

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mike p5xbx
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May 16, 2019 - 4:59 pm
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Nice animation of a 2Stroke and Expansion pipe exhaust
and why its a bad idea to use a Paper pancake filter directly on the carb

expanshion-pipe.gif

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

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SpacedMarine
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May 16, 2019 - 6:56 pm
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I guess that's why an airbox is a good idea!

What's 7/16 in mm again?

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not henpecked
Near J 11 of M42
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May 17, 2019 - 9:02 am
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A question for Mags 1

I understand that the flywheels are forged so they are not cast iron but, if they are not mild steel what metal are they made from? I'm guessing a mild with a few bits added i.e. an EN someting or other to make them tougher like high tensile bolts of 8.8 grade. I'm intrigued.

B175, being updated & now much closer to completion. Honda XBR 500, and ....... Suzuki Burgman 200 scoot! Nicknamed "The hair dryer" - by me I hasted to add; & great storage under the seat when you get to your destination.

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SpacedMarine
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May 17, 2019 - 9:59 am
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not henpecked said
A question for Mags 1

I understand that the flywheels are forged so they are not cast iron but, if they are not mild steel what metal are they made from? I'm guessing a mild with a few bits added i.e. an EN someting or other to make them tougher like high tensile bolts of 8.8 grade. I'm intrigued.  

En15 so mild steel 

What's 7/16 in mm again?

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not henpecked
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May 17, 2019 - 6:38 pm
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Hi Again

Thanks for the answer SpacedMarine.

From what I understand En 15 is a low carbon steel with some maganese and other undiserable elements minimised to make it tougher.

And (I was told never start a sentence with "And" - but who cares...?) whilst on the thoughts of cranks, when I last went to Rex Caunts he showed me some new cranks for the as he said "The trials Boys". They had been made fron solid lumps and the wheels were smooth so no problems with gas flow.

B175, being updated & now much closer to completion. Honda XBR 500, and ....... Suzuki Burgman 200 scoot! Nicknamed "The hair dryer" - by me I hasted to add; & great storage under the seat when you get to your destination.

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SpacedMarine
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May 17, 2019 - 8:08 pm
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not henpecked said
Hi Again

Thanks for the answer SpacedMarine.

From what I understand En 15 is a low carbon steel with some maganese and other undiserable elements minimised to make it tougher.

And (I was told never start a sentence with "And" - but who cares...?) whilst on the thoughts of cranks, when I last went to Rex Caunts he showed me some new cranks for the as he said "The trials Boys". They had been made fron solid lumps and the wheels were smooth so no problems with gas flow.  

Yes I was very tempted myself.I think they're also heavier than standard.The original was a solid lump just squashed with a big hammer 😉

What's 7/16 in mm again?

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Ringting
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May 19, 2019 - 10:02 pm
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Hi folks. Received the parcel from Bantam John. Got everything I asked for except the right side crank main shaft which he says he can't locate at the moment. Mostly small stuff, lock tabs, washers, nut and bolts, but also the 22 tooth main shaft sliding gear which I thought might be a problem. I'm hoping I'll get a call from him to say he's found them.

In the meantime I have a complete crank on its way to me that I can get rebuilt and I've bought a die grinder and burrs to get stuck into the blue printing. 

D1, D14/4, Guzzi LeMans, Triumph Trident 900, Maserati 160 t4. Mk1 Mini Traveller, Berkeley T60.

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