Author Topic: Through bolting head/barrels  (Read 2883 times)

Offline muskrat

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Through bolting head/barrels
« on: 14.10. 2009 12:30 »
G'day all,
            something for the racers and rev heads to think about. I lifted 3 top ends off due to high comp (13:1) and revs (8000) but have seen the same with 9:1. The barrels break around the flange, thats why the thick flange came about. Through bolting will give added strength. I will let the pics do most of the talking. I only use 1 finger to type. I don't race anymore so can share the mod.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline a10gf

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Re: Through bolting head/barrels
« Reply #1 on: 26.10. 2009 00:30 »
This is nice work indeed.

A10 GF '53 My A10 website
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Offline beezalex

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Re: Through bolting head/barrels
« Reply #2 on: 26.10. 2009 13:04 »
Thanks for the pics.  Those should come in handy when I get around to building my A7 racer.
Alex

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Offline alanp

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Re: Through bolting head/barrels
« Reply #3 on: 26.10. 2009 15:16 »
Agreed, thanks for the pics. I can also see your oil pressure connection near the pressure relief valve, if I'm not mistaken. *yeah*
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Offline muskrat

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Re: Through bolting head/barrels
« Reply #4 on: 27.10. 2009 08:43 »
G'day alanp, sorry for not posting the pic of the oil preasure fitting. Having NERDBOX probs at moment, won't get pics from camera or print or scan. Wish it went as well as the cafe. Took it out for a shake down spin of 35 miles yesterday. Was real hard turning back. lots of grunt up to 3K due to the long inlet then starts to hit the cam at 4K. I had to resist going further. Think it might be a weapon. 60 MPH at 3250rpm, should see 7500 easy when run in, say another 35 miles LOL. The longest run in this bike has seen since 1990..
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Online chaterlea25

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Re: Through bolting head/barrels
« Reply #5 on: 27.10. 2009 13:54 »
Hi Muskrat,
I would love to see some pics of the completed bike
sounds to have about the same gearing as my SR
23 tooth engine sprocket? and starts to go like f**k at 4000
I dont think I am brave enough to rev to 7500, I think I would fit new rods before I revved it that hard!!!! *eek*
Cheers
John O R
1961 Super Rocket
1963 RGS (ongoing)

Online RichardL

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Re: Through bolting head/barrels
« Reply #6 on: 27.10. 2009 14:37 »
Hi Muskrat,

It's not like I'm going to do this, but, just so I can stop being confused (again!), could you explain something to me? Am I correct that the idea is to get four more studs threaded into aluminum to hold down the barrels in addition to the nine already at work? Next question: is there any reason that a recreational rider (not racing "recreation") would do this?

Richard L.
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Offline tombeau

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Re: Through bolting head/barrels
« Reply #7 on: 27.10. 2009 18:37 »
A friend was told by an old boy who raced, that he always used thin flange barrels because they were easier to get hold of. He would wedge a bit of teak in against the top of the frame to hold the barrels down.
Could be a tall story, but gave us a laugh anyway.
Cheers,
Iain

Offline A10Boy

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Re: Through bolting head/barrels
« Reply #8 on: 27.10. 2009 19:00 »
Quote
is there any reason that a recreational rider (not racing "recreation") would do this?

No, not if you have any respect your 50+ year old BSA.
Regards

Andy

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Plus
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Offline muskrat

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Re: Through bolting head/barrels
« Reply #9 on: 27.10. 2009 20:08 »
G'day all,
John O R, primary ratio is 1.88 : 1 belt with diaphram clutch. 7500 rpm if balanced & lightened right.
Richard L, for racing or very hard riding only, 9 studs + 4 through studs 5/16 at cases to 3/8 at head.
Iain, also have a 9/16 nut attached to bottom of frame rail with a bolt that screws down onto 1/2 plate over rocker box.
A10Boy, No BS here.
Cheers
PS still can't fix nerdbox to do pics.
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline Rocket Racer

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Re: Through bolting head/barrels
« Reply #10 on: 29.10. 2009 04:27 »
Muskrat,
are the through bolts running through the original holes in the head or are they realigned?
While I can appreciate that some think only factory original and genuine bikes are worthy of note, the bike I'm building is a collection of swap meet parts and will be a very pretty race bike.  The reality is we love our beesa's! I'm proud I'll be racing an A10 
I love what you've done with your A7.*respect*
A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Offline muskrat

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Re: Through bolting head/barrels
« Reply #11 on: 29.10. 2009 05:59 »
G'day RR, the stud holes are about 1/2 a hole further out than the original holes.
I plug the head holes with alloy and the barrels with studs I made out of cast iron so the drill would not run off. First I drill the cases with 1/8" at marks ( see pic ), place 3/16 ball on holes, place cyl block on base studs & tap to mark the flange. set up cyl block on marking table and transfer marks to top (head ) surface. Now drill 1/8" and do same to mark the head. The cases can now be drilled & tapped 5/16" BSW. The flange 5/16", the rest 3/8". Start with 1/8" and go up in sizes, make sure everything stays square. Studs are 5/16" BSW one end tapered up to 3/8" BSF at top (same thread as bolts). You will need to make new head gasket.
Copy an original, all but the outside holes and give a bit more material there. place between the head & barrels then drill down through the holes. Advise to find an old rooted set to practice on first.
Jeez that took a while with 1 finger typing.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline The General

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Re: Through bolting head/barrels
« Reply #12 on: 17.11. 2009 20:42 »
That's a bit more than I would want to attempt and I own a machine shop!
I began thinking about what tombeau said about wedging against the frame.
So I came up with this bolt on goody.
Maybe it's just a feel good device, placebo effect ya know?
Like tombeau said you can get a good laugh out of it.
Might even work for us non-racers.
1962 Super Rocket

Offline muskrat

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Re: Through bolting head/barrels
« Reply #13 on: 18.11. 2009 06:58 »
Good one TG, can't quite see if you retain the original braces back to the frame for fore and aft movement.
Looks a lot prettier than my set up.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline The General

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Re: Through bolting head/barrels
« Reply #14 on: 18.11. 2009 09:52 »
Yes, the side braces back to the frame are still there.
They don't show up well in the picture, they are on the inside of the rocker top brackets.
I didn't put much pressure on the bolt, maybe another 1/4 to 1/2 turn after it touched.
I have thick flange barrel.
1962 Super Rocket