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New 750 a65 barrels
#795074 01/07/20 3:12 pm
Joined: Jun 2015
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Hi all , a few questions here !
Ok I’ve had these john hill barrels for about 18 month and finally getting round to fitting !!!!
I’ve got a 69 lightning and have machined the crankcases to accept the spigots , tapped the mouth stud holes out from 5/16 to 3/8 unc
It’s all ready for assembly so...
do I use a base gasket or just rtv ?
Cylinder head tightening sequence and torque ?
Base nut torque ?
Timing ?
Any other thoughts ?
I didn’t want to ask John as he’s had to deal with some personal issues and I wanted to respect that .


1969 BSA A65 Lightning
1994 moto guzzi California
Triumph sprint GT
1971 BSA B50 Victor special
1968 BSA B44 SS
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Re: New 750 a65 barrels
richiedan40 #795076 01/07/20 3:49 pm
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First dry fit the barrels no gasket or pistons to be sure everything is kosher, I found two of the rear stud holes needed a touch with a round file .

Essential tool, a thinned bi hex ring spanner to gain access, this will probably need thinning round the rim and top / bottom faces.
Std barrels have two spigoted studs , replace these with two regular .
i use a std , trimmed for larger spigots base gasket with a smear of Wellseal. torque similar to head pattern, start in the middle between the cylinders and work diagonally front to back about 5 ft lb at a time to around 20 ft lb. The barrels will settle once running, retorque after a few heat cycles then again at 500 and 1,000 miles. my old iron barrels were similar.
time to std strobe marks, then retard a degree or so if pinking is noted on steep hills.

If you want higher compression omit the base gasket.
With stock B44 pistons , 2 mm head gasket, cylinder base gasket, and relatively unskimmed head, I got around 9.5:1. pistons are smoothed on top , v/v cut outs radiused. John also offers a 1mm gasket which will take the comp to over 10:1
With std valves and cam i had no fitting issues, plenty clearance.
Rings were gapped , top around 0.015", 2nd ring and oil ring around 0.012" , the wider gapped top ring was deliberate, google ring gaps, its supposed to improve ring seal at the 2nd ring . Seems to work..

First time around I re used the old base studs. Second time around one of the studs sheared when torqued up, new studs are a good idea.

I used the dryish ring assembly technique, fitted the pistons with inner circlips fitted to the bores,fitted the base gasket then lowered the barrels onto pipe foam packers and inserted the gudgeon pins , fitted outer circlips then lowered the barrels.Alloy barrels are a lot easier to handle than the iron barrels.
Head was torqued to 25 lb ft and rechecked after a few heat cycles then again at 500.Use the pattern in the manual, essentially centre to outer diagonally. I fit O rings to the head gasket drain holes ,not critical for size so long as they are squished a wee bit and dont block the holes, got them in a Lidls selection box..

Dont start the bike and leave it running for ages, then repeat while you video it for youtube. You only get a small window to seat the rings .

Do use airfilters, the Nickasil lining is not good with dirt in the air, I got away with a few hundred miles with no filters, but its not a good idea, it will fail if run long term no air filtration, google nickasil / air filtration/bore wear.

On start up , my bike was ready to ride, so was I, first run out up to temp for around 5 miles and a quick raz in 2nd to 5k on a grade to seat the rings, after that ran it in at sub 4 K for 500 miles, 5 K till 1000 miles, then business as normal. oil consumption (Morris Golden film 20/50 W) is around 1/2 pint every 1,000 miles after 10 k miles.

Last edited by gavin eisler; 01/07/20 4:06 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: New 750 a65 barrels
richiedan40 #795085 01/07/20 7:11 pm
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Thanks for that gavin . I think I’ll fit the base gasget , I’m all for lower compression makes it more rideable .
What difference in running did you notice with the 750 barrels?


1969 BSA A65 Lightning
1994 moto guzzi California
Triumph sprint GT
1971 BSA B50 Victor special
1968 BSA B44 SS
Re: New 750 a65 barrels
richiedan40 #795094 01/07/20 8:08 pm
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My bike originally had devimead 750 iron barrels when I got it in 1982, before that i had a 650 tbolt.
An end fed 750 is smoother and has a good bit more midrange grunt than the std 650.
The biggest difference with the alloy barrels is weight saving, followed by tighter running clearances, and better cooling. I nearly went for the thinner high comp gasket, last year with bad sciatica i couldnt get my leg to the top of the kick swing, I was very glad of the easy starting on 9 ish to one. If racing or max HP is your thing then yeah Hi Comp is better. Mine runs fine on pump fuel here , either super or normal, super gives a few more mpgs.
I have kept the stock 30 mm carbs, this makes life easy, it might go a bit better with bigger carbs but the low down /middrange is so good i am reluctant to change. Its most fun from 3.5 - 5 .5 K , revving harder in lower gears doesnt make a huge difference in acceleration apart from wearing quicker.

The other big changes in my motor are , clutch 7 plate conversion, highly recommended, the stock clutch is past its best with the extra grunt and will slip with the slightest wear, also a bearing outrigger plate replaces the seal plate behind the clutch, this was fiddly to fit, seems my bike isnt the same exactly as most others, i needed a slightly oversized spigot to get a good fit.( thank john). and rocking horse dropping 5 speed cluster, wonderful, PES have the bits, John did the fiddly stuff making it work. Boyer ignition, stock 6 volt coils, NGK B8 Es plugs.
Latterly I have been experimenting with the inlet ports, slavishly copying Mark Parkers good work, the stock ports are not that great, search for Mark's inputs here, in essence the port floor is filled and the lower entry to the valve seat radius is increased so that gas is not making sharp turns as it flows down into the cylinder.There is a little more to it, material is removed either side of the valve guide to give a sort of cobras head effect. An evening looking a Jim Schmidts( Sp) norton head work on you tube is good background. The result of this port change was big drops in main Jet sizes , and needle jet, suggesting much higher gas speed, its possible now that I may be a little under carbed, watch this space, 32 mm OKO knockoffs are in the pipeline once I figure out an air box connection.. I have no dyno numbers, maybe 50 HP, but a very fat torque curve.

Something to check before you put the head on, this tip from Nickl years ago, the head bolt seats get distorted, last time mine was off I had the seats spot faced at a local guys shop , the centre mount was badly out of whack and the inner 4 cleaned up a bit, getting to the outer 4 under the fins was not attempted, needing different tooling.
John supplies special washers with the head bolts which help a bit, also check head bolt straightness , even if new,
mount in soft alloy tube in lathe and clock near head, you will be surprised! ( the clock is overkill) they tweak straight fairly easily.

Last edited by gavin eisler; 01/07/20 8:17 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: New 750 a65 barrels
richiedan40 #795237 01/09/20 3:27 pm
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Thanks very much gavin.
Very interesting stuff
I also had concave bolt seats so I machined them flat and I’ve bought thick washers and cleaned up the threads I’m going to use a bit of mild loktite on the studs
Previously it always blew at the back of the ports towards the carbs so John said he torqued his bolts up to 30 lbs
I’ll copy that , 25 then 30
See how it goes 👍


1969 BSA A65 Lightning
1994 moto guzzi California
Triumph sprint GT
1971 BSA B50 Victor special
1968 BSA B44 SS
Re: New 750 a65 barrels
richiedan40 #795238 01/09/20 3:28 pm
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Not ports , cylinders .


1969 BSA A65 Lightning
1994 moto guzzi California
Triumph sprint GT
1971 BSA B50 Victor special
1968 BSA B44 SS
Re: New 750 a65 barrels
richiedan40 #795252 01/09/20 7:41 pm
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i used to get a leak around the back of the head, turned out it was a lack of fibre washers on the centre rocker cover studs, easy to miss out . I have had difficulties in the past sealing the head, one thing that helps is Coppercoat applied to both sides of a freshly annealed gasket , easy to apply , V difficult to get off, but a good seal none the less.
i think most of the issues were cleared up with a 3 thou head skim and flattening the bolt mounts.
But I still used the Coppercoat, its a Loctite product , not easy to find locally for me, the Internet will find it. Comes as a brush on goo, or aerosol, the goo lasts a lot longer on the shelf.
Have fun, these are very nice motors , mine easily pulls a 21 tooth gearbox sprocket 47 tooth rear, 18" rear wheel.

my bike ran as a 750 for years without the main shaft outrigger bearing, its a bit of belt and braces now, but if you are in deep its not too hard to fit, PES have these for B50s, IIRC they need modified to fit an A65, different bearing I think, will chat to JH, I am shaky on the details about this. John has fitted them to a few bikes, turns out mine was not to std spec for the spigot to be a tight fit.
HTH


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: New 750 a65 barrels
richiedan40 #795427 01/12/20 7:22 am
Joined: Apr 2005
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I made a tool to machine the head outer nut faces using a tap seat cutter screwed onto a bolt with spring, so you put the spring on the bolt which has a sleeve on it to fit the hole, push it up through the hole and screw on the cutter and a lock nut and drive it gently with a R/gun the direction that the cutter works and it does a nice job.

I don't use base gaskets, and generally the 750 big bore can use more compression than the 650. And it can be a big difference, 650s can ping on 9-1 and require retarding a little, 750s can be ok at 11 or 12-1 which requires less timing anyway.

I've never used air cleaners on mine, it probably depends how much dirt road you ride on. Alloy cylinders certainly makes a lot of sense. The nicasil gives an excellent ring seal.


mark
Re: New 750 a65 barrels
richiedan40 #795514 01/13/20 11:57 am
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Cheers everyone 👍


1969 BSA A65 Lightning
1994 moto guzzi California
Triumph sprint GT
1971 BSA B50 Victor special
1968 BSA B44 SS

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