Author Topic: Long stroke A7 Pitfalls  (Read 1362 times)

Offline fastharry

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Long stroke A7 Pitfalls
« on: 03.02. 2018 09:43 »
Before i agree to my friends request to build his 1947 Longstroke A7 engine from a box of parts acquired from different sources, are there any pitfalls i should be looking for, any idiosyncrasies (took me 6 go's to spell that right) particular to that engine? SRM refuse to touch them. I have possibly 10 good years left in me so i do not want to get bound up in this one for to long!!

Offline duTch

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Re: Long stroke A7 Pitfalls
« Reply #1 on: 03.02. 2018 10:14 »

 
Quote
.....any idiosyncrasies (took me 6 go's to spell that right)....

 It still didn't look right, but I realize I see the plural version even less often; bluffing it through nicely *smile*

 I've had nothing to do with longstrokes, so'll stay out of it, except to say if you have ten good years, save them for later and in the meantime use the crap years you have to do the 'stroker *smile*...then you'll enjoy the good years even more  :!
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online muskrat

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Re: Long stroke A7 Pitfalls
« Reply #2 on: 03.02. 2018 19:21 »
G'day Harry.
The only things I know about are cam/follower wear and different marks on the timing gears.
Have a good look through the topics in this section.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline trevinoz

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Re: Long stroke A7 Pitfalls
« Reply #3 on: 03.02. 2018 20:03 »
Rods can be a bit bent but easily straightened.

Online chaterlea25

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Re: Long stroke A7 Pitfalls
« Reply #4 on: 03.02. 2018 21:13 »
Hi Fastharry,

Quote
a box of parts acquired from different sources,

That is the biggest pitfall *pull hair out*

It is very time consuming sorting out all the parts  *ex*
Mostly you will find out why they were thrown into a box by the seller /donor  *sad2*

Do not take this job on at a fixed price  *warn* and try and get the owner to do the legwork sourcing the parts

I have built lots of engines for customers, the ones that arrive in boxes are THE WORST  *ex*

John

1961 Super Rocket
1963 RGS (ongoing)

Offline fastharry

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Re: Long stroke A7 Pitfalls
« Reply #5 on: 04.02. 2018 09:40 »
All good points guys thank you . You are quite correct John. It would be impossible to give a fixed price on most engines in my experience, Numbering and sourcing parts has to be the worst part of the job, The biggest problem i find is that customers will nearly always go for the cheapest option, something we all no will more than likely lead to problems further down the line. If i take it on, i have decided it will be my last one for other people, I have around ten valuable bikes i need to get done before i keel over.

Online chaterlea25

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Re: Long stroke A7 Pitfalls
« Reply #6 on: 04.02. 2018 16:05 »
Hi fastharry,
Quote
I have around ten valuable bikes i need to get done before i keel over.

10 *ex*  *????*     Is that all  *????*  =  *work*

I know how you feel and swore not to do another complete bike for others after the last A10  *pull hair out*
I am concentrating on engines/gearboxes now
Currently I'm rebuilding a 23 HD model F that's to do the upcoming USA Cannonball run

I really need to get some of my own projects worked on  *problem*

John
1961 Super Rocket
1963 RGS (ongoing)

Online RichardL

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Re: Long stroke A7 Pitfalls
« Reply #7 on: 04.02. 2018 16:12 »
John,

Are you coming over for the Canonball Run? It has a stop pretty close to where I live (outside of Chicago) and would love to meetup.

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020. This year it's a solo or pillion ride in dapper attire. Watch website at https://www.gentlemansride.com for details.


Online chaterlea25

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Re: Long stroke A7 Pitfalls
« Reply #8 on: 04.02. 2018 18:30 »
Hi Richard,
Quote
Are you coming over for the Canonball Run?

That is the plan at this stage, Lets hope it all comes together

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Craig

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Re: Long stroke A7 Pitfalls
« Reply #9 on: 06.02. 2018 09:28 »
Hi

From my experience:

New parts for the LS motors are hard to source.

CAMSHAFT - can re-condition (just done mine but yet to install). I was lucky enough to find second hand one in reasonable shape (took me 3 years of searching). 
CAM Followers - almost impossible but old ones can be redone.
Big end shell bearings. Depending on the size (or oversize) can be hard to find from time to time. I had to wait ages to get mine
Conrods - only second hand on the market from time to time. Quality variable and most need to be machined to fit correctly (bushes etc)
Cranks - hard to find second hand ones. Check how far the wear on the big end is now and if re-grind is even possible. Seen a couple of second hand ones that could not be reground.
Conrod Bolts - cannot find any. Had to use old ones with new castle nuts (loctite)
Head bolts / rocker bolts : Classed as impossible - never seen any new or otherwise. Make sure you have them - old ones totally useable.

Pistons - easy to get - I have got +40.
Rocker spindles - easy to get
Oil Pump - easy to get
Bronze Bushes - easy to get (timing, idle pinion /
Shims - easy to get
Crank bearings - easy to get
Valves / Valve Guides / Valve springs easy to get
Sludge trap hex head bolt - easy to get


As other guys say - getting parts just takes time. Need to shop around and keep looking. And good machine shop helps

I have done everything except the crank and camshaft (split the cases). I have everything on hand now for when the rain starts here and will get that done.

Happy to help with more info if you need.

Personally enjoy the LS engine - just did 100km on my "49 on weekend. Done over 1000km since engine work with no issues.

Craig

Offline stev60

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Re: Long stroke A7 Pitfalls
« Reply #10 on: 14.02. 2018 17:51 »
Head  and rocker  bolts are easily made, Heads  bolts are 3/8th BSF. They can still be purchased  just a case of grinding the flats down a bit.

Offline vinver

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Re: Long stroke A7 Pitfalls
« Reply #11 on: 13.04. 2018 03:39 »
Early XA7 engines (up to about serial number 600, so only about 500 units)  had a built-up crankshaft with unique rods and construction. The whole crank/rods assembly can be replaced with the one that followed but that is even hard to find.  As mentioned, cams are the Achilles heel of the longstrokes- would be the first thing to look at if you are planning a rebuild. Searching for a cam can take a long time and money.
1948 A7- the perpetual 25 year restoration.  1954 A10 , 1957 Ariel Huntmaster

Offline cardoso1

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Re: Long stroke A7 Pitfalls
« Reply #12 on: 21.05. 2021 14:52 »
sorry for the delay!

we've found 2 points of pitfalls, both are about lubrication.

1. the lubrication of the rockers from the oil pressure release is done just on the inlet side. We've sorted this by extending the release pipe to the exhaust side as well.

2. the lubrication of the cylinders, specially of the left one, the pressure (around 50 psi) is just not enough for the oil to get past the crankshaft holes and lubricate the cylinder/piston, because there's no clear path, the conrods are on the way. We've sorted this by making a very small drill/hole on the conrods (as later BSA 50's models have).

3. Make sure you have low compression pistons as per the books say (coming harder to find good ones!) and the correct clearances on the piston/rings to the cylinder!

Apart from these, (sourcing parts would be the most difficult!), everything else is pretty standard if you are used to restore engines and follow the documentation available (sheets+manual)! I'm a newbie! Never knew what a BSA was until i was the owner of one!
Learnt all the above the worst way possible! But all now worth it!

Would love to exchange pictures with a 47 owner!

Regards,

Offline Swarfcut

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Re: Long stroke A7 Pitfalls
« Reply #13 on: 22.05. 2021 09:24 »
Just read back thro' Jojo's previous posts. This bike is one with the early drop down spring loaded pogo stick stand.

   Early A7 Longstroke had a single oilfeed to one rocker spindle, the exhaust.. Later variants do have the familiar two  banjo feed, as always fed from the return line to the tank. Nothing to do with Oil Pressure relief or release. The PRV vents into the oil pump cavity, no feed to the cam as on later designs.

  I've never considered bore lubrication to be a problem on these engines. The crankcase does not have the later trough to hold oil, so any oil from the inlet rocker box is immediately flung from the camshaft, hence the high rate of wear to the cam and followers but plenty of oil  droplets and mist circulating within the crankcase.  With a feed to the exhaust rockers, oil will drain down directly onto the flywheel to be flung up the bores as well.

  For those looking for a new cam, the good news about the Camshaft is that they are readily available, as Forum members have found when ordering A7 cams for the later engine only to have a Longstroke cam arrive instead. Word on the Forum was that these were actually UK source, from David Newman Camshafts in Orpington, Kent,  and marketed by Wassell under their Hepolite Brand.  Feked show them, made of precious metal.......

 Adding that oil hole as on later engines is certainly pushing the boundaries of our knowledge and will be interesting to follow up. The timing bush running clearance and a nice clean sludge trap/oilway are the keys to  good consistent big end lubrication. Regular oil changes are a must for long life.

 Looks like this project is progressing, so well done.

 Swarfy

Offline fido

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Re: Long stroke A7 Pitfalls
« Reply #14 on: 18.06. 2021 07:30 »
My observations are the opposite of those stated! My 1959 A7SS which I restored in the early '80s had bad cam and follower wear but my 1948 longstroke that I bought in 1995 and ran for years without looking inside has very good cam and followers, despite the followers having a much smaller contact area than the later type. The only damage on mine is some scuffing on one piston due to a stiff little end and both pistons with oil rings seized in their grooves.