Motor out, head strip with new valve spring compressor

[Spyder31]

After a few weeks of trying to figure out why the 3C was sick after a winter layover I found cylinder 2 & 3 with low compression's.
Pulled the motor out of the left side with a crane (tight fit and not looking forward to putting it back in) and pulled the head off.
Old school valve leak test (fuel in the combustion chambers) didn't provide conclusive results but I removed the valves and they all look like they would benefit from de-carbonizing and re-seating.
While I was able to find many past posts helping me with the engine removal I never managed to find a good tip for a valve spring compressor.
I ended out getting a Lazer 5272 motorcycle specific compressor and its works brilliantly and at 46 quid decent value.
Meanwhile inspection of the bores shows some scoring so Im going to measure the bore and order new oversized pistons.
Any replacement piston advice would be appreciated?

 

[Rusty Spokes]

I like the ROSS pistons in my 3c. 77mm HC. Be careful with having the valve seats done. A machine shop will need to realize you do not have much room to go cutting away at the valve seats..you will lose your clearances with available shims. Use one of the Laverda specialist near you.

And that "O" ring on the head stud? Looks collapsed? That will impair the oil flow to the cylinder head.

 

[Spyder31]

I like the ROSS pistons in my 3c. 77mm HC. Be careful with having the valve seats done. A machine shop will need to realize you do not have much room to go cutting away at the valve seats..you will lose your clearances with available shims. Use one of the Laverda specialist near you.

And that "O" ring on the head stud? Looks collapsed? That will impair the oil flow to the cylinder head.

I hope not to cut new valve seats, the first pair of valves have lapped in nicely.
The o-ring having collapsed could have caused oil starvation to the head (past tense)? cam journals look ok so dont think it caused an issue in the past and with new o rings there should be no future problem?

 

[AndyB_11]

I?ve got the same valve spring compressor and it works a treat but I did find that when refitting the collets it was easier to drop them on top of the top plate then compress everything, give them a jab with a scriber to make sure they were down and back the compressor off and they all seated perfectly.

I?m a bit old school and I?ve got a brass drift with a 10mm hole in the end which I use to ?bump? each valve after assembly to make sure they collets have seated properly.

 

[Rusty Spokes]

past and with new o rings there should be no future problem?

New "O" rings and there are some that are Viton and a British size that work well. I need to go back and look or other may know without research.

You need to check head warp and the steel cylinders for the steel barrel surface to aluminium. There should be a slight recess. Do a search on the technical pages.

 

[chrisk]

I?m no mechanic, but those little scores may clean up with a hone. Spank me if I?m wrong...... please

 

[Spyder31]

I thought the same but I need to take the barrels to be measured as Im running out of space for tools that I use once every ten years 

 

[CLEMTOG]

the low compression may have been down to zero or close to zero valve clearance, did you check the gaps before dismantling?
CLEM

 

[Spyder31]

Hi Clem, I checked the clearances and while they were a little tight at 0.15 there was enough of a gap to get a seal.
It is still a bit puzzling as it was running reasonably well before the winter.

 

[piranha-bro2]

The motor will still run fine even when it's down a bit on compression. I couldn't believe that my SF1 had even been running, after I pulled the head and barrels off and found the top rings in about 15 pieces and ridges so deep it had to go straight to 2nd OS. Too many km in Australia's far north with no air cleaners!! And that included thousands of km of dirt (bulldust) roads. But it ran and idled and seemed OK ... until after the rebore and head revitalise and i realised just what a slug it had become  8)

I'll never run my bikes without air cleaners again.

 

[CLEMTOG]

get them barrels of Spider31, but remember to stuff the crankcase throats with cloth, that in itself is nearly impossible.
CLEM

 

[Spyder31]

get them barrels of Spider31, but remember to stuff the crankcase throats with cloth, that in itself is nearly impossible.
CLEM

Off and stuffed, decided on a set of Ross forged pistons

While cleaning the head I found some unusual pitting on number 3 inlet port, Ill get it pressure tested but interested to hear if anyone came across this before?

 

[T.C]

Looks like white ants, if you have disturbed them they may have all gone, they dont like light.

 

[Rusty Spokes]

That inlet port is likely fine. You can check it with kerosene/gasoline once you have the intake valve correctly lapped in and installed. Fill the port and see if it leaks out.  Laverda had/has a reputation for porous castings, for some reason. My 3c has them too.

You may want to consider new valve springs, if yours are the originals. Wolfgang has some excellent German made replacements available.

 

[Spyder31]

That inlet port is likely fine. You can check it with kerosene/gasoline once you have the intake valve correctly lapped in and installed. Fill the port and see if it leaks out.  Laverda had/has a reputation for porous castings, for some reason. My 3c has them too.

You may want to consider new valve springs, if yours are the originals. Wolfgang has some excellent German made replacements available.

Good advice, based on the historical documents/invoices it had a replacement head back in 1990 but no listing of new valve springs.
The pistons are from Wolfgang so Ill add the springs to the order.