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Author Topic: Banquo's Mighty Falcone top end rebuild  (Read 961 times)

banquo

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Banquo's Mighty Falcone top end rebuild
« on: March 27, 2018, 12:27:44 am »
It's taken a very long time, but I finally put the Mighty Falcone back together today. I don't have any heating in the garage, and I'm far too old for working in sub-zero conditions these days...

Here's a summary of what was done:

The valve gear was very noisy, not so much at tickover, but at mid engine speed it sounded like a battalion of dwarfs hammering on steel anvils. The bike ran well enough, and didn't use any oil.
When I took the rocker box off, I discovered a large flat on the rocker - valve face.

inrocker2 by bancquo, on Flickr

As we all probably know, lubrication to this face is poor, and relies on oil spraying up from a slot in the rocker end face. According to the Paul Friday archives, oil is supposed to be delivered via a slot in the rocker spindle.
However, mine didn't have any slot, and instead, the bushing inside the rocker had a groove to deliver oil to the slot.

slot align by bancquo, on Flickr

arm slot by bancquo, on Flickr

This is probably an improvement, as you don't need to worry about aligning the spindle slot with the slot in the rocker. However, it clearly didn't work. I had foolishly decided that as I do very small mileages on the Mighty Falcone, I didn't need to bother with an oil feed. The bike has only done 21,000 km since I got it in 2002, and it was some surprise to see so much wear with such low use.
The standard fix is to add a second oil feed to the banjo fitting on the right side of the head. However, I have always thought this very ugly, and devised a new system where the spindle is drilled from the left side, so only a short copper pipe is required. See post:

http://nuovofalcone.createaforum.com/engine-and-transmission/alternative-inlet-rocker-oil-line/

Of course I broke an exhaust stud, and there was no way it wanted to come out, even after soaking for a week in Plus Gas...

plus gas by bancquo, on Flickr

The valves were in good shape with hardly any wear or burnt faces. A serious decoke was required though, and it's clearly running quite rich...

combustion chamber by bancquo, on Flickr

crown2 by bancquo, on Flickr

My troubles didn't end there.

On stripping the head, I discovered significant wear in the valve guides (and I believe that this is a precursor to stuck valves and catastrophic failure, as we never hear of dropped valves on new or recently rebuilt engines). I could have simply replaced the guides, but decided to have the head professionally rebuilt with smaller valve stems (8mm and 9mm), oil seals on the guides, and lighter springs. The smaller stems are supposed to be better, but dropped valves have occurred also with them, so they're not bulletproof (according to Huub, who has experience of that). However, the lighter springs reduce loading on the camshaft and cam followers, so it seemed to be the way to go. I was fortunate to have a good friend, who organised having the head rebuilt.

This was the end result - better than new!

head top by bancquo, on Flickr

Ports were polished

exhaust port by bancquo, on Flickr

inlet tract by bancquo, on Flickr

The new valves are a little shorter, so caps are supplied to extend them to the correct length:

stem caps by bancquo, on Flickr

You can just about see the oil seal in this photo, and the lighter springs:

double 2 by bancquo, on Flickr

The mating face was skimmed flat:

face detail by bancquo, on Flickr

New exhaust studs and flange plate:

exhaust stub by bancquo, on Flickr

I did consider twin-plugging the head, but was advised this was pointless unless the engine was tuned for performance, and I have no interest in that.

IMG_0858 by bancquo, on Flickr

With the head off, I discovered the cause of an oil leak since I first got the bike. Whoever assembled it had fitted the pushrod tunnel oil seal incorrectly, so it had been squashed over the top of the head gasket, damaging both seal and head gasket:

macro by bancquo, on Flickr

removed by bancquo, on Flickr

I also removed the cam followers, and found pitting on the faces that bear on the camshaft:

Inlet left Ex rt by bancquo, on Flickr

I bought a pair of NOS followers to replace these.

lifters by bancquo, on Flickr

I didn't want to pull the camshaft, but was able to inspect through the cam follower tunnels:
Not much sign of wear on the peaks:

cam2 by bancquo, on Flickr

cam4 by bancquo, on Flickr

For the bore, it was obvious that the barrel was rusted on the base, and had probably been lying in a pool of water since 1972, until I bought it 30 years later...

bore by bancquo, on Flickr

I now think I could have rebuilt without changing anything; the engine wasn't burning oil, and I think the rust was secure in the pits, and forming a good seal. However, I made the decision to give it a light hone (on advice from the Engineer) but this made the situation worse, lifting the rust out of the holes, and opening up the pits. A rebore was required then, but I couldn't buy a piston until I knew how much needed to be removed to clear the pits. I had the work done at Engine Resource in Dundee (the owner is a member of our classic bike club, the SCMC) and we ended up with 88.4mm. This was good, as although NOS pistons are available in all four oversizes, not all of the rings are available. 88.4mm is available as a pattern piston from Gandini, and it comes complete with gudgeon pin, circlips and all rings, reducing the number of order lines.

domed by bancquo, on Flickr

piston by bancquo, on Flickr

I've often wondered if gapping rings is really important, but this photo of the oil scraper ring shows why it is; jammed solid in the bore, with no gap at all. I used a diamond file to adjust. The compression rings didn't need adjustment, and actually the top ring gap was over spec.

scraper gap by bancquo, on Flickr

I decided to fit the piston on the bench as being easier than fitting it after the piston was fitted to the con-rod:

barrel-piston by bancquo, on Flickr

piston fitted2 by bancquo, on Flickr

Then align the piston so the larger valve cutout for the inlet valve is at the top:

valve cutouts by bancquo, on Flickr

Then fitted the barrel to the cylinder studs, warmed the piston with a hot air gun, fitted gudgeon pin and circlips:

base gasket by bancquo, on Flickr

gudgeon pin by bancquo, on Flickr

Circlips are conventional type; not the wire ones as fitted to the original Mondial piston

circlip1a by bancquo, on Flickr

3 by bancquo, on Flickr

That was it for the day:

barrel fitted2 by bancquo, on Flickr

New gasket and pushrod tunnel seal:

head gasket by bancquo, on Flickr

Torque head to 45 N-m

torque by bancquo, on Flickr

Fitted pushrods (inlet is nearest the crankshaft and exhaust nearest timing side:

pushrod alignment by bancquo, on Flickr

head fitted by bancquo, on Flickr

Fitted the valve caps with grease to hold them in, then fitted rocker box:

valve caps by bancquo, on Flickr
Good view of oil seal on this one:
oil seal by bancquo, on Flickr
Bit of a fiddle locating pushrods into rockers:
pushrod-rockers by bancquo, on Flickr

Added the new oil feed:

oil feed by bancquo, on Flickr

After that, it was just fitting exhaust, carburettor, spark plug etc. and set the valve clearances (I use 0.1 and 0.2mm)
I kicked over the bike a few times to get some fresh oil through the system, and was pleased to see oil being delivered from the new feed to the inlet rocker: note position of end float spring on inlet rocker shaft to left of engine; exhaust is on the right side:

oilfeed proof by bancquo, on Flickr

And that's pretty much it. I'm not a confident engine builder  :-[ so I won't be happy until I've done a few hundred miles on it, but on the plus side, it did start second kick. A bit smoky at first, as all the assembly oil burned off, but that soon cleared. Fingers crossed that I haven't screwed up on anything, and that we have a few thousand miles before the next time...

« Last Edit: March 27, 2018, 04:53:52 pm by banquo »

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guest107

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #1 on: March 28, 2018, 07:38:44 am »
beau travail félicitations , c'est reparti pour quelques décennies

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #2 on: March 28, 2018, 06:25:50 pm »
J'espère que si mono; Merci pour vos commentaires

JamesNFalconaut

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #3 on: March 29, 2018, 01:51:09 am »
Great photos and documentation Banquo.
Will be very useful when I do my head (in) with new valves

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #4 on: March 29, 2018, 12:13:38 pm »
Hope it goes well for you; I would have had mine assembled earlier, but this winter has been six months of cold, snow and more cold....

olebmw

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #5 on: March 29, 2018, 08:35:56 pm »
Where did you get your light weight valve kit?

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #6 on: March 31, 2018, 01:28:25 pm »
I had the work done for me by Fischer in Volkach in Germany.
I believe the valve conversion is the same as the ones supplied by Pirner

Sigean

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #7 on: July 12, 2018, 05:54:56 pm »
Hi,

Great article about the Falcone's renovation.  I particularly liked the new oil feel design - very neat!

I don't think I have input to this forum since my return from France a couple of summers ago on my Falcone, when its engine dropped an exhaust valve.  A sad end to a 5000 mile trip through France, Italy and Austria......  I have left the bike in the shed whilst pondering its fate, and during the intervening time have bought a couple of modern bikes, a Honda XR400 and a CCM 404E.  The Honda has provided a significant distraction, not least from its fantastic performance and great fuel consumption and is with me in southern France right now, but it seems to burn oil like a two-stroke, and after only 10k miles(!) - must look at that after my return to the UK.  The CCM is still in the workshop, its charms yet to be revealed.

But your article has me thinking that an engine overhaul might be the best way forward for the Falcone, and a power upgrade by having the head welded as I have seen in some other parts of this forum.  Much food for thought, and I hope you will not mind if I am in touch through these pages for specific points to be cleared up as they arise.

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #8 on: July 12, 2018, 09:02:15 pm »
Hi Sigean, you're more than welcome, although I have to say that I don't know much more than I've posted already! Ken's ex Paul Friday NF is the one with the squish head, and he's very happy with the performance. I chose to keep things as stock as possible, rightly or wrongly, although Ken's doesn't seem to have suffered at all from the extra power.
« Last Edit: July 09, 2019, 03:16:43 pm by banquo »

Dunders

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #9 on: October 19, 2018, 09:13:48 pm »
Very clear write-up: thanks Jake!  I hope I won't have to do that for a while, but at 20kKm it seems likely soon.  The POs had documented much work and maintenance, so I'm hoping it's been cosseted.  You never know.  One of the POs did fit the (ugly) oil mod, but then removed it because of smoking.  I'm intending to replace it this winter, possibly with an external oil filter.  There's a Cali to sort out first, though!
Paul

Lost in the Irish Sea....

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #10 on: October 19, 2018, 11:04:34 pm »
Mine doesn't smoke or use oil, but then it also has new valve guides and oil seals on them too....

Dunders

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #11 on: October 20, 2018, 03:43:35 pm »
I'm only going to do that when I *have* to.  Or this winter, if I run out of other things to do.  Not likely.... SWMBO can always find me things to do:-(
Paul

Lost in the Irish Sea....
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JamesNFalconaut

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #12 on: March 10, 2019, 09:56:00 am »
It bares repeating Banquo, your write-up and pics are proving very useful.
Thanks!

banquo

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #13 on: March 10, 2019, 11:26:32 am »
It bares repeating Banquo, your write-up and pics are proving very useful.
Thanks!

Glad it's been useful; makes it all worthwhile, and the whole point of this is that we all help each other out  8)

cloggy

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Re: Banquo's Mighty Falcone top end rebuild
« Reply #14 on: March 15, 2019, 10:08:32 pm »
"I discovered significant wear in the valve guides (and I believe that this is a precursor to stuck valves and catastrophic failure, as we never hear of dropped valves on new or recently rebuilt engines)"

Not sure why you've said this banquo since you were in on another conversation in which a forum member  replaced his valves with thin stemmed examples and promptly had the brand new plot drop another valve. Or perhaps you've forgotten? He came to the conclusion that tappets gaps or rather lack of were the cause. One size of  the volkswagon flat four Beetle engine was also known to do this in the very late 60s early 70s,  To rid themselves of the problem Volkswagon changed valve clearances from .004mm to .006mm. NLM used to set their valves to no gap whch seems ok as long as the engines aren't worked hard, but continental advice has always been that the valves are fine as long as the valve clearances are correct. Since these engines have very heavy valve gear and the engine unshrouded by the fuel tank, the tendancy is to run them tight to quieten the valve gear, Big mistake, standard these engines should always sound very tappety, somewhere between an industrial sewng machine and a concrete mixer..... with gaps set at .010 and .0.20mm respectively for inlet and exhaust cold engine I think. Perhaps you can advise?
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