That Montjuic of mine

Thanks Mike. Now lockdown restrictions have been lifted I need to visit anyway :D
 
A very minor update today.

I decided to take the pistons off the rods to see what the small ends were like and just give the pistons a bit of a clean because I wanted something to do. The small ends are good but the pistons...

Well it turned out that someone had obviously broken a ring so purchased a set of 72mm rings with the correct thicknesses and just thrown it together because the oil sealing rings were completely different and one side had a stepped top compression ring.

I’ve never seen ones with a coiled spring forcing the seal ring out before so it was a new one for me.
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The pistons cleaned up pretty well after a quick application of some Scotchbrite pads in the Dremel and another oddity was that they’re both AE pistons but one is a B and the other a C. We used to use A, B,C & D pistons in race engines but I’ve never seen them matched to bores for road use before. I’m getting it rebored so it doesn’t matter going forward.

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I’ve degreased the cylinder head and cheated by using fine medium in a small shot blaster to clean the combustion chamber and valve faces while the valves are seated but once they’re out I’ll give it a polish and have a check on the capacity of each port then polish them and match them because I’m stupid like that

I wasted an hour looking for service kits for the brakes and now I’m in a bit of a quandary because I can get fully refurbished calipers for a cost of about £40/side over the cost of new pistons and seals but a) have they just been cleaned and new seals fitted or b) have the bores been honed to remove my scratches and corrosion? I know which I’d expect for £40.
 
I knew I should have left the brakes for another day. The front master cylinder reservoir had a nice layer of black sludge at the bottom and right now it’s showing a definite reluctance to function :blast

If I could get the piston to retract that’d be a start but I might be able to lash something up and use compressed air to force it back. Another day :D
 
A very minor update today.

I decided to take the pistons off the rods to see what the small ends were like and just give the pistons a bit of a clean because I wanted something to do. The small ends are good but the pistons...

Well it turned out that someone had obviously broken a ring so purchased a set of 72mm rings with the correct thicknesses and just thrown it together because the oil sealing rings were completely different and one side had a stepped top compression ring.

I’ve never seen ones with a coiled spring forcing the seal ring out before so it was a new one for me.
f9d6491d4abb16e1ab9d3b306ed6b90e.jpg



The pistons cleaned up pretty well after a quick application of some Scotchbrite pads in the Dremel and another oddity was that they’re both AE pistons but one is a B and the other a C. We used to use A, B,C & D pistons in race engines but I’ve never seen them matched to bores for road use before. I’m getting it rebored so it doesn’t matter going forward.

89b20a07f544886598a65027a01aa521.jpg


I’ve degreased the cylinder head and cheated by using fine medium in a small shot blaster to clean the combustion chamber and valve faces while the valves are seated but once they’re out I’ll give it a polish and have a check on the capacity of each port then polish them and match them because I’m stupid like that

I wasted an hour looking for service kits for the brakes and now I’m in a bit of a quandary because I can get fully refurbished calipers for a cost of about £40/side over the cost of new pistons and seals but a) have they just been cleaned and new seals fitted or b) have the bores been honed to remove my scratches and corrosion? I know which I’d expect for £40.

While it's down will you be weighing the pistons ; or perhaps the rods as well; should help to smooth it out that bit more.
 
I’ll probably be getting the bloke Mike uses to do the rebore and I’d guess he matches each piston to the bore to allow for manufacturing tolerances and will I weight them? Probably yes because at 72mm bore x 61mm stroke it’s short stroke and only produces its real power right at the top of the rev range.

I’ve come to terms with the fact that now it’s in bits I might as well do a proper job then treat it the way it was designed to be treated. I’m scouring the internet to try and find the parts for a close ratio gearbox before everything else is ready because once the engine is back in the frame I don’t want to be taking it out later.

Back to photos...

This was at the bottom of my ultrasonic tank after putting the front master cylinder through it yesterday

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If I can’t get it sorted I’ll order a new one which then raises the question of should I go away from stock spec? Standard piston size is 12mm and I can get a 16mm one if I want to. I’ve messed with master cylinders before and found that going up a size takes away any sponginess but you do have to squeeze a bit harder to get the same end result, they also tend to overheat a bit less with a bigger piston but do I want rock hard brakes on what is essentially a road bike that might go on a track a few times?

I still need to get the pistons out of the brake callipers and if the callipers are snotted then I’ll do the whole lot with higher spec parts
 
I’ll probably be getting the bloke Mike uses to do the rebore and I’d guess he matches each piston to the bore to allow for manufacturing tolerances and will I weight them? Probably yes because at 72mm bore x 61mm stroke it’s short stroke and only produces its real power right at the top of the rev range.

I’ve come to terms with the fact that now it’s in bits I might as well do a proper job then treat it the way it was designed to be treated. I’m scouring the internet to try and find the parts for a close ratio gearbox before everything else is ready because once the engine is back in the frame I don’t want to be taking it out later.

Back to photos...

This was at the bottom of my ultrasonic tank after putting the front master cylinder through it yesterday

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If I can’t get it sorted I’ll order a new one which then raises the question of should I go away from stock spec? Standard piston size is 12mm and I can get a 16mm one if I want to. I’ve messed with master cylinders before and found that going up a size takes away any sponginess but you do have to squeeze a bit harder to get the same end result, they also tend to overheat a bit less with a bigger piston but do I want rock hard brakes on what is essentially a road bike that might go on a track a few times?

I still need to get the pistons out of the brake callipers and if the callipers are snotted then I’ll do the whole lot with higher spec parts

Nova might be worth a look for the gearbox; kerchink; do the later 650 gearbox internal's fit; could be worth a look.
 
The gearbox isn’t really needed so I’ll not be going to all the trouble of getting gears made up but if a complete one is available at a realistic price I’d buy it.

I’ve been fucking about with brakes today and the front master cylinder simply isn’t having it. It seems that the piston is seized so rather than buy a kit, force it apart and find the cylinder is fucked I’ll buy a new one.

I’ve given up completely when it comes to counting the cost now I’m into the brakes as well as the engine so an electric start for the Norton can wait.

The calipers are another odd one. I’ve got 2 with identical code markings and one that looks the same but has a different code. So where are they on the bike? Mixed at the front :blast

The back one seems to be functioning so I’ll strip everything apart and give it a look over then probably end up buying 3 new calipers rather than fuck about. The rear master cylinder can come apart and if it’s ok in the bore I’ll just change the seals a matter of course and stick with it. I rarely use the back brake so as long as it passes an mot test I don’t really care :D

I’ll order new hydraulic brake light switches rather than bleed the brakes and get them working only to find the switches don’t work. They’re available easily enough at about £25 each advertised as Laverda parts on eBay or about £5 each after a 2 minute search on the internet. Guess which I’ll go for?
 
Holy fuck Batman, that was a bit expensive!

I’ve just ordered the engine parts (minus valve springs and collets which they don’t have) and rebuilding Monty engines isn’t bargain basement.

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I’ve also ordered all new brake pistons and seals plus a new front master cylinder. The rear one is working perfectly with the piston returning like a rocket so I’m happy with that.

With a bit of luck the brake parts will be here by Friday/Saturday and I might even have the wheels back in the next few days.

I’ve got a few days of tidying things up which will involve removing, blasting and painting a couple of bits and pieces then removing and polishing the outer covers.

The valve guides definitely need replacing because top limit is +0.03mm and mine range from +0.07 to +0.25 so it’s no wonder oil was getting down them and burning off on the exhaust valves :blast

It’ll only be worth the effort if it leaves my wifes 350LC for dead :green gri
 
Have you considered guide liners? http://cylinderheadshop.com/k-line-guide-liners/

I wouldn't hold out too much on bettering an LC, I saw one a couple of years ago at a CRMC meeting at Cadwell, he was well behind a MZ 250 (which I'm sure still had indicators on!). I hope it was a reflection of rider ability and commitment.
 
I’ve got a set of guides ready and waiting.

I’ve got more than just a suspicion that a previous owner did a top end rebuild but previously guides and seals were rather than rocking horse shit so the old ones stayed in.

I’ve had the guides for a few years and even when I bought them you couldn’t get seals but now nearly everything is on the shelf.

The only real test of it against her LC is someone else riding both on a track, I can lap her inside 8 laps on most circuits, less on longer ones like Silverstone GP and putting me on both in quick succession would be stupid 😀
 
It’s a bloody money pit!

I’ve just paid for a new front master cylinder, pistons and seal kits for all 3 calipers, new pressure switches for brake lights, new bleed nipples (do people use old ones?) and a new front brake lever because the old one wobbled on the pin.

I’ll get the calipers in the post tomorrow so Lo-IQ can Cerakote them then go to visit Mikeyboy and swap Laverda parts for Ducati parts :D

I suspect the Ducati will be put in the roof of the garage until I get this Monty on the road because I can’t fit another bike in the workshop right now but the longer I’m off work the sooner the Monty will be moving.
 
It’s been a quiet day due to waiting for parts to arrive so I took the barrel, cylinder head and valve guides up to Mikes workshop so he can vapour blast parts before the new piston set arrives and he gets his mate to rebore it and if he feels charitable fit the new guides to save me cooking it in the oven at home.

After that I put the brake calipers in the post to Low-IQ so he can Cerakote them into a state of satin black loveliness before I fit new seals and pistons.

At that point the rot set in so I took the fork legs out to make it easier to fit new steering head bearings and decided to give one leg one hour of my time with a polishing mop. The results are promising but the trouble is any remaining marks look shit! That’s my weekend sorted.

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I’ll need to order some more Scotchbrite pads for the Dremel and just keep going at them.

Of course this means that I’ll start looking at giving them a full service and then worry about the 2 or 3 rust marks on the sliders and end up getting them re-chromed.

Never mind, nobody died and it’s only money.
 
Well I stripped one leg, cleaned all the parts and had a quick appraisal of what needs replacing.

Strangely enough I could probably get away with just re-chroming the stanchions, replace the seals and dust covers and bung them back together. I haven’t checked the bores in the bushes yet because the back of my van is full of Ducati parts so I can’t get at micrometers but they look ok. The seals are cheap so it’s stupid not to replace them, the seals in the damper units are scuffed and the steel bush at the bottom has very light scuffing but nothing that wouldn’t polish out with the inevitable Scotchbrite. The main springs are within spec, the damper springs are a bit of an unknown because I can’t find tolerances for them and the fork tops need replacing because the bleed valves are chewed up and can’t be shifted.

My gut feeling is that the main springs have been replaced along with the seals because 40 years and 25k miles would normally see them going out of spec and they’re bang on size. Damper parts are harder to get which would explain why they look a bit worse for the wear and the bottom line is that they’re 40 year old Marzocchi units that were top spec in their day but now the only way to adjust them is to drill more holes in the damper tube and change the weight of the oil.

I’ve sent an email to Maxton asking for a price to supply a set of emulators made to suit my spindly little frame and road surfaces rather than race tracks. I’m also going to get a price for a set of Race Tech emulators then put progressive springs in as a one time upgrade. Either of the companies supplying emulators will do fork springs to match the Ikon units on the back so it doesn’t transfer weight too dramatically and once I’ve fitted new swinging arm bushes and steering head bearings then fitted modern tyres it should handle better than new :thumb2
 
Great thread Andy,thankyou for taking the trouble to posting.As for a Laverda,loved the Jota's and also the Montjuics,but never got round to getting one.Good luck with sorting it.

Kimbo
 
Another couple of hours blown away stripping the second fork leg and generally inspecting parts with no real surprises found but I’ve got time on my hands at the moment so that’s no big deal.

Maxton got back to me with a surprisingly realistic price to basically convert the forks to full on classic race spec including the ability to hide the compression and rebound adjustment and sneak past scrutineering :D

https://www.maxtonsuspension.co.uk/files/sd20.html

The cost would be about £700 including vat if they have to do any machining to the fork bottoms but that includes cartridges, springs, seals and rebuilding the forks. All done to suit my weight and the Ikon shocks fitted to the bike. Add another £200 to re-chrome and grind the existing sliders round it up out of sheer malice and it’s a grand :blast

I reckon I could fit new seals to my existing damper units then sell the fork internals for at least £250 because the dampers and springs are hard to find and my springs are in spec with no signs of damage. Another way to view it is it’ll cost me about £400 to put them back to standard so would I pay anything up to £600 for a Maxton front end on the bike? Fuck yeah, of course I would :okay

The downside to all this work is that I’ll feel almost obligated to race it on road circuits which probably won’t end well.
 
Olivers Mount Scarborough.....Ready and waiting.....:thumb

You’ll be waiting a long time. If I decide to race it then it’ll be in Europe where I can get a weekend licence without all the hassle of having to start off on the ACU licence trail again with the added complication of a bike that would get bumped for being too noisy at every circuit in the UK.

They don’t care quite as much in Belgium :D
 
If you're lashing out on full race forks wouldn't you be better off with linear springs?
 


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