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A70 rebuild on youtube #791253 11/25/19 11:20 am
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gavin eisler Online Content OP
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see here.
https://www.youtube.com/watch?v=omDPExaO-lo

I recently came across this interesting rebuild series. The author is generally meticuluous but is clearly not very familiar with the OIF A65 details. I cannot access my google account so am unable to comment at the you tube site.
I offer the following observations here, hopefully this will be taken as constructive criticism.

primary side rebuild,
no mention of primary chain alignment, particularly engine sprocket shimming.

Sets primary chain tension without finding the tight spot.
Chain tensioner adjuster top button is missing,ie the plastic disc between adjuster bolt and adjuster shoe.

Timing side,
kick start spring retainer fitted hook out, this will foul the outer case, should be hook in.
Use of impact driver to tighten case screws (I winced). Impact drivers are handy for removing stubborn screws, should be left in the tool box for fitting.
Screws tightened in wrong order rather than working from centre out radially, worked from front and then round in sequence then centre last, this will buckle the case. Also appeared to miss the two lower timing case fasteners on the exterior face beneath the kickstarter area.

I havent watched all the vids in the series,


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
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Re: A70 rebuild on youtube [Re: gavin eisler] #791261 11/25/19 1:52 pm
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Allan Gill Offline
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ouch!


beerchug
Re: A70 rebuild on youtube [Re: gavin eisler] #791281 11/25/19 7:05 pm
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Manx Offline
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I was waiting for one of the heads to sheer. Good luck trying to remove those with knackered heads, even with an impact driver.....

I normally dont comment on youtube vids but I think your points are very valid Gavin and I will post as many as I dare without trying to upset the chap.


1966 Rickman Metisse (a65)
1957 B33
1959 lambretta li 150
1960 lambretta li150
Re: A70 rebuild on youtube [Re: gavin eisler] #791287 11/25/19 8:11 pm
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Shane in Oz Online Content
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Angus is a long-time Triples Online contributor who has managed to track down some extremely rare late model BSAs and Triumphs (A75V, A70L, E35, T35).
Let's just say that his way of working on said machines, at least in the Youtube clips, is rather "different", and leave it at that.

Re: A70 rebuild on youtube [Re: gavin eisler] #791292 11/25/19 8:46 pm
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gavin eisler Online Content OP
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I dont like the idea of folks using these as guides for assembly, does he ride his bikes?


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A70 rebuild on youtube [Re: gavin eisler] #791298 11/25/19 9:42 pm
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Shane in Oz Online Content
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Originally Posted by gavin eisler
does he ride his bikes?
Most definitely

Re: A70 rebuild on youtube [Re: gavin eisler] #791322 11/26/19 2:14 am
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He has some interesting bikes. Good thing no one has video of me hammering things together frown I don't actually use an impact driver, allen head screws and rattle gun get them tight enough.

I wonder if he will dyno the A70 when it's done? It would be interesting to see if the head was machined better, like seems the case with some Spitfires. Are there specs on the A70 for advertising with hp and stuff? I imagine they would have been higher compression.


mark
Re: A70 rebuild on youtube [Re: gavin eisler] #791336 11/26/19 4:51 am
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I don't like to see cases open with no sheet/rag over the top of 'em.
He obviously doesn't get mud wasps there.

Re: A70 rebuild on youtube [Re: gavin eisler] #791339 11/26/19 5:37 am
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I once dropped a 12mm nut down the reed valve on a lambretta engine... I suppose that's how you learn.

He has replied to the comments and seams to take it as advice but I don't think we should push it.

These days I think that blue loctite is a better option than an impact driver, if you are worried about stuff rattling open.


1966 Rickman Metisse (a65)
1957 B33
1959 lambretta li 150
1960 lambretta li150
Re: A70 rebuild on youtube [Re: gavin eisler] #791355 11/26/19 11:21 am
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Interesting to see the A70 crank flywheel is not full circle, my 71 A65 crank must be a good bit heavier, are all A70s like that?


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A70 rebuild on youtube [Re: gavin eisler] #791356 11/26/19 11:31 am
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gavin eisler Online Content OP
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I dont know if Angus will read this, if he does.
A wee note on airbox side panel fitting.
Maybe its just my bike , I found that it was impossible to fit the side panel so that the top lips remained clear of the coil bracket and batt carrier rubber mount bracket, my thoughts are that the model was rushed into production and some finer points which should have been tweaked out didnt happen. Later years Ts with the same set up had generous scallops cut into the top of the panels to provide clearance, a bit of judicious filing and it all fits without interference.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A70 rebuild on youtube [Re: gavin eisler] #791369 11/26/19 1:32 pm
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Originally Posted by gavin eisler
Interesting to see the A70 crank flywheel is not full circle, my 71 A65 crank must be a good bit heavier, are all A70s like that?


Not only do all A70s have scalloped flywheels, the very late A65s were like that as well, see pic. A65 on the left has a 40mm flywheel width at big ends and the A70 on the right is somewhat narrower. (35mm?)
It would be interesting to know what effect this had on the balance factor. (Probably due to the introduction of the steel capped conrods?)

There are several area's of Angus's videos that had me cringing. I was shouting at the screen at one point for him to remove the gearchange quadrant from the inner timing cover before he starting hammering it on with a mallet. It's much easier fitting the quadrant first before fitting the cover. I don't think rotating the gear shift shaft with a pair of molegrips did the spines much good as he was hammering either.

[Linked Image from i.postimg.cc]

Last edited by Servodyne; 11/26/19 1:46 pm.

1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando
1961 Norton 99
Re: A70 rebuild on youtube [Re: gavin eisler] #791387 11/26/19 4:19 pm
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The weight taken off the A70 crank is far more than required for the steel rod caps. I had Dan Macias lighten my '71 flywheel and it was done the same way. He said some people lighten the flywheel by skimming the diameter which is wrong because it weakens it faster than side cutting.
A70s were intended for dirt track racing so acceleration was more important than smooth low speed running.

Re: A70 rebuild on youtube [Re: gavin eisler] #791410 11/26/19 10:25 pm
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Originally Posted by gavin eisler
Interesting to see the A70 crank flywheel is not full circle, my 71 A65 crank must be a good bit heavier, are all A70s like that?


The late a65's and the a70 had scalloped flywheels whether steel capped rods were fitted or not.
The a65 flywheels were not that much lighter in comparison. Light flywheels are not always such a good thing, certainly on a bike that gets ridden on the street.
The normally imagined faster acceleration given by lighter flywheels is countered by snatching, vibration and easily stalling motors.

Re: A70 rebuild on youtube [Re: gavin eisler] #791422 11/26/19 11:50 pm
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Offset cranks can be lighter. My 90 degree Norton crank is 20lb 12oz, stock A65 crank 21lb 3oz, 90 degree 74mm A65 17lb 13oz, the latter by far the smoothest. When we swapped a 90degree 74mm stroke crank into my brother's A65 he would not believe it had the same gearbox sprocket without lying under it and counting the teeth. It's obviously more than just the weight reduction, but a noticeable increase in response, part weight, part configuration. An interesting experiment would be to dyno identical motors with the different cranks, in theory they should be the same but they are not, and the different dynamic needs to be factored in.

When I fitted an A10 crank to an A65 the flywheel was too big for the case, requiring me to fit an A65 flywheel, after chamfering an area to get it on.


mark
Re: A70 rebuild on youtube [Re: Mark Parker] #791424 11/26/19 11:53 pm
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Originally Posted by Mark Parker


When I fitted an A10 crank to an A65 the flywheel was too big for the case, requiring me to fit an A65 flywheel, after chamfering an area to get it on.


Now there’s something I didn’t know. I’ve never compared ODs or seen this commented elsewhere.


beerchug
Re: A70 rebuild on youtube [Re: gavin eisler] #791448 11/27/19 6:03 am
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It's all in the game Alan, nothing is ever that easy eh?
The other thing with using an a10 crank is that you must use steel capped rods or aftermarket types.
If you don't, the cases need hogging out a fair bit.

An offset motor is like a vee, you can't really compare that to a 360 deg twin or a single.
I tried various weights of flywheel on my offsets, but for my use in a sidecar outfit a heavier one
was my preference. I never used one on the road or in a solo so i can't comment on how that would be.

Re: A70 rebuild on youtube [Re: gavin eisler] #791615 11/29/19 3:13 pm
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Originally Posted by gavin eisler
I dont know if Angus will read this, if he does.
A wee note on airbox side panel fitting.
Maybe its just my bike , I found that it was impossible to fit the side panel so that the top lips remained clear of the coil bracket and batt carrier rubber mount bracket, my thoughts are that the model was rushed into production and some finer points which should have been tweaked out didnt happen. Later years Ts with the same set up had generous scallops cut into the top of the panels to provide clearance, a bit of judicious filing and it all fits without interference.


Hi Gavin yes I do now I'm registered. Thanks for the heads up - mine seem to fit fine but will check.
Rgds, Angus

Re: A70 rebuild on youtube [Re: Manx] #791616 11/29/19 3:20 pm
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Originally Posted by Manx
I was waiting for one of the heads to sheer. Good luck trying to remove those with knackered heads, even with an impact driver.....

I normally dont comment on youtube vids but I think your points are very valid Gavin and I will post as many as I dare without trying to upset the chap.


Hi Manx,

I'm too long in the tooth to get upset over a little constructive critique - nobody's perfect. I only tapped the impact driver to tighten a little more securely than by hand so these were never going to sheer. Certainly not as forceful as an impact gun on allen heads which Meriden used to use.

Thanks everyone for any interest in the channel though, and I do have a few items to correct this weekend, e.g. kickstart return spring plate and stator mounting. It was 44 years ago when I last had an A65!

Rgds,
Angus

Re: A70 rebuild on youtube [Re: gavin eisler] #791617 11/29/19 3:31 pm
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Welcome aboard Angus, keep us updated on the beesa rebuild. Theres a wealth of knowledge among the members here.
Re Fitting kickstart spring.
Find a jubilee clip that fits round the kickstarter shaft, fit the retaining washer over the two flats then hold it in position with the jubilee clip, thread a length of stout wire round the spring end hook, use the wire to tension the spring and hook over the tang. Carefully remove the jubilee clip, kickstart spring fits with no swearing, mole grips or loss of blood this way.

Last edited by gavin eisler; 11/29/19 3:37 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A70 rebuild on youtube [Re: gavin eisler] #791674 11/30/19 8:12 am
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Originally Posted by gavin eisler
Welcome aboard Angus, keep us updated on the beesa rebuild. Theres a wealth of knowledge among the members here.
Re Fitting kickstart spring.
Find a jubilee clip that fits round the kickstarter shaft, fit the retaining washer over the two flats then hold it in position with the jubilee clip, thread a length of stout wire round the spring end hook, use the wire to tension the spring and hook over the tang. Carefully remove the jubilee clip, kickstart spring fits with no swearing, mole grips or loss of blood this way.


Thanks Gavin - will sort that this weekend.


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