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A65 valves hitting piston #735324
05/14/18 11:59 pm
05/14/18 11:59 pm
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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Frogeye1000  Offline OP
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East yorks
Hi, first post

New to forum and British bikes

I've got an a65 lightning who's inlet valves are clipping the pistos. Took head off and was going to dremmel away part of the crown, but wanted to ask how much does the timing need to be out for the valves to hit, and would it run that far out.

Or indeed does the timing need to be out for the valves to hit.

Cheers

Richard.

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Re: A65 valves hitting piston [Re: Frogeye1000] #735326
05/15/18 12:07 am
05/15/18 12:07 am
Joined: Jan 2014
Posts: 4,016
Aus
N
NickL Offline
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Aus
Either the valve timing is out a fair way or the barrel has been skimmed more than 40 thou.

I suspect the valve timing is a couple of teeth advanced. It's timing cover off i'm afraid.............

This assumes the motor is in standard trim?

Last edited by NickL; 05/15/18 12:08 am.

No-one expects the Spanish Inquisition................
Bring in the 'Comfy Chair'
Re: A65 valves hitting piston [Re: Frogeye1000] #735352
05/15/18 7:06 am
05/15/18 7:06 am
Joined: May 2004
Posts: 3,859
Sydney Australia
B
BSA_WM20 Offline
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Sydney Australia
A65's have a land ( raised area ) above the top fin
It is not uncommon to find the barrels machined down to be level or partially into the top fin.
Same story with the head .
Back in the day 10's and 11's were all the go for us who thought we were substantially better engineers ( and riders ) than we really were.
In any ase you will need 30 to 40 thou clearance measured satic between the piston crown & the valves when running or it won't run for very long.

So what is the history of this engine ?


Bike Beesa
Trevor
Re: A65 valves hitting piston [Re: Frogeye1000] #735404
05/15/18 3:29 pm
05/15/18 3:29 pm
Joined: Feb 2014
Posts: 1,204
Lancaster, California
C.B.S Online content

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Lancaster, California
There are a couple things to check and to go over:


#1 - stock cams will not allow a valve to hit a stock piston

#2 - make your sure your valves are the stock length

#3 - make sure ALL your pushrods are the same length

#4 - make sure your cylinder head has not been milled

#5 - take your inner timing / gear box cover off and make sure your cam is installed and lined up properly. BSA is a "unicam" set-up, timed and ground accordingly from the factory

#6 - you can always put a degree wheel on the engine to check cam timing

#7 - if all check outs fine I would be inclined to see if your head has been skimmed

Good luck!

Re: A65 valves hitting piston [Re: Frogeye1000] #735411
05/15/18 4:30 pm
05/15/18 4:30 pm
Joined: Jan 2004
Posts: 3,843
ca, us
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DMadigan Offline
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ca, us
CBS, I think you mean
#1 - no interference with the cam timing correct
#3 - exhaust pair and intake pair are equal (valve screws take out small variations)

Re: A65 valves hitting piston [Re: Frogeye1000] #735435
05/15/18 7:10 pm
05/15/18 7:10 pm
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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East yorks
And I thought having a brit bike would be simple😟

Thanks for replays.

I bought the bike from someone who passed away and I didn't know so I have no idea of its history.

I don't like to speak ill of the dead, but I seem to spending a lot of time brining things up my standard, which isn't that high☺

I know the Bush the crank goes through was replaced and the engine has been rebuilt, but as I said, to what standard I don't know.

Barrel and head still have a chunkable size land/ridge/raised area before fins. So my plan of action is to relieve the piston crowns a bit and refit head and see how it runs. It did start and run relatively easy before but with quite a loud tapped noise. Now I know why.

If I think it's down on power I can investigate cam timing with head on.


Cheers

Richard.

Re: A65 valves hitting piston [Re: DMadigan] #735436
05/15/18 7:16 pm
05/15/18 7:16 pm
Joined: Feb 2014
Posts: 1,204
Lancaster, California
C.B.S Online content

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C.B.S  Online Content

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Joined: Feb 2014
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Lancaster, California
Originally Posted by DMadigan
CBS, I think you mean
#1 - no interference with the cam timing correct
#3 - exhaust pair and intake pair are equal (valve screws take out small variations)



ok so we are talking about an A65....... My mind is Triumph 650 programmed

Re: A65 valves hitting piston [Re: Frogeye1000] #735441
05/15/18 8:16 pm
05/15/18 8:16 pm
Joined: Oct 2009
Posts: 496
new jersey usa
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pushrod tom Offline
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new jersey usa
Check cam timing first. Not that big of a deal. In standard form there is lots of room. PRT

Re: A65 valves hitting piston [Re: Frogeye1000] #735446
05/15/18 8:49 pm
05/15/18 8:49 pm
Joined: Oct 2007
Posts: 1,542
Auckland NZ
Ignoramus Offline
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Auckland NZ
some times it can turn out to be a real thin cylinder base gasket or head gasket so of the new head gaskets are real thin compared to the old ones...............what the above have said about plaining too much odd barrels/head is right as well

if its not the timing try a thicker cylinder base gasket and let us know how thick the copper head casket is


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
Re: A65 valves hitting piston [Re: Frogeye1000] #735447
05/15/18 8:50 pm
05/15/18 8:50 pm
Joined: Mar 2005
Posts: 10,220
Boston, Massachusetts
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John Healy Offline
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Boston, Massachusetts
Exactly where is the valve "hitting" the piston. a. on the face of the valve pocket. b. on the side of the valve pocket where it is cut into the top of the piston???

Which valve is hitting the piston: a. the intake b. the exhaust?

Is either valve oversize Stock valve sizes:
1962-1965 intake 1.470" exhaust 1.410"
1966-1971 intake 1.598" exhaust 1.410"

If any of the valves are of a commercially available oversize the dimensions above would be plus .060"
for example a 1972 intake would be 1.598" + .060" = 1.658"

In some case the diameter of the valve pocket in the piston MIGHT have to be increased to accommodate the oversize valve. This is done without removing any material from the face of the valve pocket. This is where some PlayDough (kids play clay). Put some between the valve and the piston. Turn the engine over once and measure the clay.

Removing material from the face of the valve pocket must only be done knowing that the piston area under the face MUST be at least .125" thick.
Before removing any material from the face of the piston's valve pocket I strongly recommend that the thickness of the piston in this area be measured. You will need at least .040" clearance between the face of the valve and the piston (.060" is even better) and have the thickness of the piston under the valve pocket at least .125".

Once you check that the valves are standard you must then determine if the cam timing is correct (this get a bit fussy when you do not know if you have other than a stock cam - where all you have to do is align the dots) and neither the head or cylinder has been cut. If it is a accessory cam then you can take opening and closing figures and lift and see if you can match it up with known cams. Also you can time the cam so the intake and exhaust lobe centers are around 102° to 104°. The cam might work to its full potential, but few people could tell the difference.


Re: A65 valves hitting piston [Re: Frogeye1000] #735448
05/15/18 8:53 pm
05/15/18 8:53 pm
Joined: Apr 2015
Posts: 49
Florida
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BillD47 Offline
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Florida
I had a similar experience with my A65 after the pistons were replaced. Since you don't know your bike's history, yours may have been replaced as well. My problem was that the intake valves were catching the raised valve clearance portion of the piston as it was moving down and making a "clicking" sound. Increasing the radius of the cutout slightly (.020") using a Dremel solved the problem. You should see the light scrape marks of the valve on the inner raised section of the piston valve cutout if this is the case. If your head is still off, this will be a quick check.

Re: A65 valves hitting piston [Re: Frogeye1000] #735451
05/15/18 9:13 pm
05/15/18 9:13 pm
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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Cheers guys.

I'll take some photos and try uploading them tomorrow

RichaRd.

Re: A65 valves hitting piston [Re: Frogeye1000] #735477
05/16/18 12:09 am
05/16/18 12:09 am
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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East yorks

Re: A65 valves hitting piston [Re: Frogeye1000] #735508
05/16/18 7:16 am
05/16/18 7:16 am
Joined: May 2013
Posts: 4,997
Rotherham - S. Yorkshire
Allan Gill Offline

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Rotherham - S. Yorkshire
Shouldn’t have a problem wth your pistons, valves, cylinder or head..

Those are some nasty impressions there and would benefit from being smoothed out to stop any pinging. First thing I would do is check your push rod lengths, maybe you have some A50 exhaust rods used as inlets (inlets are shorter than exhaust) with a stock cam you can advance/retard the cam by more than a tooth, I was supplied with an A10 crank pinion when I first built mine, pulled well... but some years later when I dialled the cam in properly I found I was 20 degrees advanced at the cam (that’s over one tooth) I could still turn the engine over if I advanced it further or regarded it a tooth past where it needed to be. It’s still worth checking you have the correct components in there.

But what I’ve found will effect it is too big a cam positioned wrong or using the wrong followers or push rods the wrong length.


beerchug
Re: A65 valves hitting piston [Re: Frogeye1000] #735517
05/16/18 9:41 am
05/16/18 9:41 am
Joined: Aug 2001
Posts: 4,103
argyll. scotland, uk
gavin eisler Online content
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argyll. scotland, uk
In the first pic it looks to me like the pistons are fitted the wrong way round , the big cut out in the pic is on the exhaust side. The big cut out should face the other way.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 valves hitting piston [Re: Frogeye1000] #735549
05/16/18 3:40 pm
05/16/18 3:40 pm
Joined: Mar 2005
Posts: 10,220
Boston, Massachusetts
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John Healy Offline
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Boston, Massachusetts
Who said a picture is worth a million words.


Re: A65 valves hitting piston [Re: Frogeye1000] #735554
05/16/18 4:03 pm
05/16/18 4:03 pm
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Central Virginia
That's good news and bad news ... Good news is you may have found the present problem.

Bad news is that if the same guy that didn't do things to proper standards (as you've noticed) AND put the pistons in backward, also installed the lower end of the engine including the timing side bushing, then it might need to come all the way down. Installing that bushing is a specialist job - someone who's an expert on Sportsters, Triumphs, and small-block Chevy cranks can screw up a BSA bottom end something fierce if he doesn't understand about end-float, bushing clearance, and line-boring ....

When you take the cylinder off to reinstall the pistons, at least check the end-float of the crank to see if it's in spec ....

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
Re: A65 valves hitting piston [Re: Frogeye1000] #735571
05/16/18 8:15 pm
05/16/18 8:15 pm
Joined: Aug 2001
Posts: 4,103
argyll. scotland, uk
gavin eisler Online content
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I put my specs on this time, I see the writing on the piston is the right way up, my eyes might have been fooled by the cut outs,, possibly cam timing is advanced by a couple of teeth, pull timing case to check. Better check the inlet valves still seal, I would be surprised if they are not bent. Doesnt bode well.

Last edited by gavin eisler; 05/16/18 8:17 pm.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: A65 valves hitting piston [Re: Frogeye1000] #735577
05/16/18 8:57 pm
05/16/18 8:57 pm
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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East yorks
Cheers

The piston cut outs look identical inlet to exhaust to me.

On this basis one is right way round one isn't because the writing is one way on one and t'other way on t'other


Richard.

Re: A65 valves hitting piston [Re: Frogeye1000] #735580
05/16/18 9:16 pm
05/16/18 9:16 pm
Joined: Apr 2002
Posts: 94
cleveland,ohio
smitty Offline
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cleveland,ohio
I noticed during disassembly the odd way the timing gears are marked for timing,offset which according to my manual is correct,any one know why they did this and not just mark the gears like most do with a mark where they are in complete contact?


68 BSA 650 streefighter
71 honda CT70H
72 triumph T25T (sold)
71 Ossa MAR (waiting for engine donor)
71(?) BritCHonda 230


if this was easy everyone would do it
Re: A65 valves hitting piston [Re: Frogeye1000] #735618
05/17/18 5:51 am
05/17/18 5:51 am
Joined: Jan 2014
Posts: 4,016
Aus
N
NickL Offline
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Aus
You do have to rotate the engine a few degrees to line up the idler/cam pinion marks then back to make sure the crank/idler is correct.
For the valves to hit the pistons it would be at least 2 teeth out with a standard cam and pistons. Your pistons look like standard 9-1 ones to me.
The valves also look to be standard.


No-one expects the Spanish Inquisition................
Bring in the 'Comfy Chair'
Re: A65 valves hitting piston [Re: Frogeye1000] #735619
05/17/18 5:55 am
05/17/18 5:55 am
Joined: Aug 2014
Posts: 313
Bowral NSW Australia
John Goodwin Offline
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Bowral NSW Australia
Two head gaskets is a quick fix! How thick was the last head gasket, was it one of the solid copper one's or one of the composite gaskets? How thick was the used gasket?


Current: 2 x 1966 A65S, 1 x 1967 A65SA, 1 x 69/70? A65LA space Y, 1 X D14/4 & 1 x B175
Past: 4 x 1976 T160V, 1 74/5 T150V, 83 model GSX 750 ESD, Z650, Katana 1100(Bathurst Model), 79 T140V, 70's TR6, 2 x 1971 BSA 250 Gold Stars, 50's 350 Goldie, A65 Spitfire semi basket case, 1965/6? A65 LC, Tiger 21 350 & a D14/4 Bantam, 175 Bridgestone Twin with Zimmerman discs!
Re: A65 valves hitting piston [Re: Frogeye1000] #735622
05/17/18 6:37 am
05/17/18 6:37 am
Joined: May 2018
Posts: 11
East yorks
F
Frogeye1000 Offline OP
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Frogeye1000  Offline OP
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East yorks
The head gasket is about 1mm thick solid copper.

Looks like the side casing is going to have to come off.


If thiat wasn't enough, my daughter's car has just threw its timing chain and my other half has informed me that this is more important than a stupid old bike. 😞


Cheers

Richard

Re: A65 valves hitting piston [Re: Frogeye1000] #735658
05/17/18 2:05 pm
05/17/18 2:05 pm
Joined: Mar 2006
Posts: 1,358
Magnolia, TX
htown Offline
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Magnolia, TX
I'd carefully measure the cutouts in the pistons with a pair of calipers. Intake valves are always bigger than exhausts.


1978 Bonneville T140E
1974 Trident
1970 BSA Thunderbolt
1971 Norton Commando
1972 Norton Commando
1973 Norton Commando
1974 Norton Commando
2004 XL 1200R Sportster

Everything will be alright in the end. If its not alright, its not the end.
Re: A65 valves hitting piston [Re: Frogeye1000] #735661
05/17/18 2:44 pm
05/17/18 2:44 pm
Joined: Jul 2001
Posts: 12,962
Central Virginia
Lannis Offline

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Central Virginia
Originally Posted by Frogeye1000
The head gasket is about 1mm thick solid copper.


If thiat wasn't enough, my daughter's car has just threw its timing chain and my other half has informed me that this is more important than a stupid old bike. 😞


Cheers

Richard


If that's what she told you, you'd best pay attention! help Although if it's an "interference" engine, you'll be looking for either a new engine or another car!

Sorry about the bad luck, seems to be the way it happens ...

Lannis


I stopped believing for a little while this morning. Journey is really going to be upset.
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