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E: Engine Do Big Bore Cylinder Muffs Need Special Head Studs?

ericg

Well Known and Active Website User
VOC Member
Hi All,
Well, everything is in the title.
There is no way for the standard ET55/2 studs to go through the holes in my Maughan's Big Bore muff and liner kit as they are to small at 10,9mm.
I've made a quick search but I wasn't able to find mentions of special studs in any of the forums here.
Thanks in advance for any info.
 

vibrac

Well Known and Active Website User
VOC Member
These 2 pics may help may help I cant measure it as its now cleaned up and in place its the top hat converter back to standard bore, the engine always had standard studs at a guess there was a 1/16" or so twixt hole and stud dont forget even 2 piece studs are same thread into c-case
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Bill Thomas

Well Known and Active Website User
VOC Member
If it's not much I was wondering if I could File it out !!,
Me being a road side bodger !!.

The last "standard " Barrel I fitted to the L/ning had smaller stud holes in it ,
As was said in another thread.
 

Sten Jensen

Website User
VOC Member
Yes, probably they are all different ;-)
I got this response from Steve at Conways, June 2020 :

Nikasil coated 90mm cylinders complete ? £600 each 8 weeks
Pistons 90mm (8:1 or 9:1) ? (Make ?, Forged / Cast / Low exp. ?) £190 Cast low exp, either 8:1 or 9:1 2-4 weeks
Conventional cast iron cylinder liners in 90mm bore for use with my own bored cylinder muffs ? £150 each 4 weeks
Will I need special cylinder studs for your 90 mm bore cylinders of either type ? No
-----
I ended up buying a set of Terry Princes 600cc Top End Kits with 92mm bore, the dimensions for fitting that can be seen here :
https://www.classicmotorbikes.com.au/tpv-top-end-kit-fitting-instructions/
(I have not fitted it yet).
 
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greg brillus

Well Known and Active Website User
VOC Member
A couple of points to look out for with the new TPV kits.......Check the push rod tube gland nuts spin freely into the head, I have had several of the new kits and found the threads to be undersize, had to use a 1" x 20 TPI tap to open up the threads a bit more.........and yes I tried various different gland nuts, they were all too tight.........Before you assemble the liners into the muffs I strongly recommend you lap the liner top hat into the head recess with fine lapping compound.........It says in the instructions that this is not necessary, but I have found they will leak if the extra attention is not taken. The Harley solenoid decompressors work very well, you need to plumb some banjos' with these and run a line from one to the other, then vent this line down to the rear of the engine........If you simply vent them from the top of each head, if you have an electric start it will sound like a machine gun when cranking over, it can also make a mess as carbon and fuel/oil can be blown out........So this is best vented away and keeps the noise down...........Good luck with it all.
 

ericg

Well Known and Active Website User
VOC Member
Yes, probably they are all different ;-)
I got this response from Steve at Conways, June 2020 :

Nikasil coated 90mm cylinders complete ? £600 each 8 weeks
Pistons 90mm (8:1 or 9:1) ? (Make ?, Forged / Cast / Low exp. ?) £190 Cast low exp, either 8:1 or 9:1 2-4 weeks
Conventional cast iron cylinder liners in 90mm bore for use with my own bored cylinder muffs ? £150 each 4 weeks
Will I need special cylinder studs for your 90 mm bore cylinders of either type ? No
-----
I ended up buying a set of Terry Princes 600cc Top End Kits with 92mm bore, the dimensions for fitting that can be seen here :
https://www.classicmotorbikes.com.au/tpv-top-end-kit-fitting-instructions/
(I have not fitted it yet).
The piston supplied with my kit is an Omega 8:1 (my choice).
There is absolutely no way for the standard studs to go through the 10,9mm holes in the muff I've been supplied with.
The delay was 16 weeks in my case.
My first intention was to go for a TP cylinder and piston as well but unfortunately Terry doesn't wish to sell anything but complete top ends kits so the price wasn't in my range.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Thanks Sten, I think I am just dreaming at the moment, But the Conways standard type barrel
Sounds like a good way to go for me, A lot cheaper,
I can't seem to get started on the welding and boring of my Flywheels for the long stroke,
Fear of messing it up I think, Getting old !, I have had the short Conrod for many years,
If I didn't already have Vincents that I can ride, It would be different I think,
Good Luck with yours, Bill.
 

Cyborg

Well Known and Active Website User
VOC Member
Good point Bill
Could happen with either intake spindle. First photo is the front intake. Notice the little shards of thread left where the spindle bore intersects the stud hole. These are ancient NOS cases with current new spindles (presumably from Maughan) installed. The threads suggest the spindle hole was bored first and then the stud holes were tapped. When I go to install the studs, I’ll clean up the threads first and then after the stud is installed, check to make sure there isn’t any swarf hiding at the bottom of the stud hole waiting to fall into the sump..... or get pushed through the oil hole in the liner and get dragged around by the piston skirt.
Hard to get decent photos with an iPhone, but if you look closely you can see the end of the rocker spindles are “very” close to the threads. The part of the spindles that are closest to the threads are hiding in the shadows and hard to see. The spindle holes are offset to the rear of the stud holes so it’s just a corner of the spindle that might protrude.

B573FD03-82FA-4A5C-8634-4FB67DE4400C.jpeg931F95B4-643C-44AB-9E56-C211FEAFC208.jpeg
 
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oexing

Well Known and Active Website User
VOC Member
To be open, I never liked the original design of bolting down the lot to the engine case. Even less the B-Rapides two part bolts. All components should be a good fit as they are parts of the chassis , no frame here on the bike. The not so great way of positioning is the long fit of bolts in the through holes so you have to pull the lot all along the bolts for disassembly and same when mounting all. It is common practice since a long time to have hollow dowels like in engine cases for cylinders and heads as well. Just 1/4 " depth bores - or 5-6 mm - for short bushes , 2 thou max slop , and all components will fit nicely, from top to bottom.
Certainly this is a job for the mill and DRO fitted but later you just have simple 10 mm studs , I had 10 x 1.5 mm standard thread in alu adapters in the case and 10x1 mm fine thread on head brackets. All stainless bolts, do my own tread rolling in seconds, without having easy machining stainless. No eight nuts per head for mounting head plus bracket, questionable practice in my eyes,so a no-no for me.

Vic
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oexing

Well Known and Active Website User
VOC Member
Wow, extremely fast thread rolling - but this would not come really handy for a private workshop. I got, with some luck, two sizes of rolling heads and several rollers for pitches and diameters. The procedure is much like spokes threading but pitch dia. is adjustable for more thread sizes with one head and rollers. You can set thread length and a stop will disengage the rollers by opening via eccentric pivots inside. Once you have tried diameters for turning bolts and did a few threads for pich dia. you get perfect thread fits to your liking at perfect surface finish too, no troubles with blunt dies and chips. So I had a number of M 8 titanium bolts for engine case through bolts - because I can . But yes, for one or two threads it is too much hassle to set this up when you have no preset head ready.

Vic
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oexing

Well Known and Active Website User
VOC Member
Yes, adapters imperial/metric , 7075 plus Loctite 222 extra mild. For sealing I had grub screws loctited down in the bottom through holes so no oil should creep up there as well. I take mild Loctites in many places, no troubles undoing bolts or nuts , just like nylocs in strength.

Vic
 

greg brillus

Well Known and Active Website User
VOC Member
I had 2 sets of new cases from that knuckle head Harry Cowley an ex pom living in Germany now who makes new cases and other parts that are total crap........ I have no problem shooting him down as the guy is a total crook and deserves to be shot at best........anyway after much re-machining of many defects on his cases, about 55 plus on the timing side alone.......The last straw was the threads for the cylinder hold down studs were all crooked...........when you wound the studs in they were all out by about 4 or 5 mm at the top and all pointing inward.........To fix this we had to screw in a full set of studs, cut them off level with the case deck, then re-center the lot and drill/tap the steel inserts to 7/16" UNF then we had to make new studs with the same matching threads to suit.......... Vic I just hope your inserts are strong enough........Cheers........ Greg.
 

oexing

Well Known and Active Website User
VOC Member
Greg, I spent hours thinking about matters but I am quite confident to be safe. The case threads are standard imperial, 9/16 something dia. and the very strong 7075 inserts tapped M 10 x1,5 mm standard, same like on 1000 cc BMWs for decades. They had M 10 since prewar I think, but only 750cc max then. Yes, there is an extra load on Vincent studs from acting as frame parts but I´d think less than a ton load from this so no real factor. The 460 Horex single got only M 8 studs but is allright with it, even with easy machine stainless steel studs from own fabrication. My guess cylinder studs are getting torqued way too high commonly for no good, just stretching threads and distortion. You have to see that heat growth adds extra strain to steel studs in alu engines too. Stainless steel is a little better here with higher coefficient.

Vic
IMG00016.JPG
 

greg brillus

Well Known and Active Website User
VOC Member
Hmmmm, Love your work Vic, But you have got me worried........I hope you and your bike don't end up in an untidy mess in the middle of the road with the heads and barrels hanging like figs off the upper frame.........Personally I would have made the inserts from steel..........Anyway, you know what your doing....... Cheers.
 

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