SF3 top end rattle

M

macavity99

Full member
Location
Bedfordshire, UK
I'll soon be taking off the head to replace valve stem oil seals and piston rings.

I've read advice on the forum that shims can be used to eliminate rocker end float on the spindles. Can anyone advise what shims to use and where to get them?

Any other camshaft tips while the head is off?

Thanks

mac99
 
Just out of curiosity Mac, how many fins does your cylinder head have? (seriously!) 

Trying to ascertain when the 16-fin heads were introduced.  Must have been the last of the line as indicated by the part#.

Another method of reducing rocker rattle is to machine the axles a little.  A lot easier than fiddling around with shims.  These do need to be the hardened type.  Soft ones, commonly available from bearing factors,  will wear away in no time at all.

piet
 
There is nothing to stop the studs from blocking the oilflow to the rocker spindles and cam. From my experience SFs can suffer excessive cam-wear as a result. I always use the simple solution in the pics to remove any doubt. I also polish the cam-lobes and the flats on the rocker arms to remove any scoring that may be present. The extremities from the oil-pump also receive the least oil, and that is the benefit of the larger oil-pumps you can now get (from e.g Lav Paradies). Other things you can do if you are really keen is fit flat ball type valve adjuster screws (I have used them from a Rotax motor), it takes a little modification, but prevents the problem of the tappet adjuster screws burying themselves in the valve tip.
Check your spindles/rocker bushes for wear. It is easy to shim up for end-float using any hardened shims from whatever source. They weren?t fitted standard and end float doesn?t always cause rattling.
Have your bores and pistons properly measured with a micrometer for wear. You can fit just rings but if the bores are fairly worn it is a short term fix. You are naturally getting your valves/seats tidied up and ensuring that the guides themselves are good, aren?t you? Use the best place you can find to do the work on the head because any mistakes are not easy to reverse.
If you can be bothered, measure the cc volume of your combustion chamber before you remove the head. I?ve seen std SF1-3 with about 8.5 to 1 compression. They respond very well with their specified comp.
Good luck
Ciao
Lee
 

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macavity99 said:
Sixteen fins plus one formed by rocker cover.

Machine the axles? How?
Click to expand...

Thanks Mac.

Engine #?

The portion on which the rocker bears can be shortened.  Best to stuff it all together, measure where the excess clearance is and how much and turn off a sliver from the axle so that it goes into the head a bit further, so taking up unnecessary play.  Give the rockers at least 0.10-0.15mm clearance.

piet
 
I'm away from home until weekend, will get engine no. then.

Thanks to all for the advice.

Replacing rings, pistons, valves, springs, bearings etc can cost up to ?1000. That's a lot and frankly I'd rather put that much money towards the cost of a more modern bike. Hoping that I won't find so much wear as to require a big spend. Won't know until I get it apart...

mac99
 
Update

Engine number is 18674.

Have just done a compression test -- 170 psi both cylinders. So I guess the rings are good.

So why is the right cylinder smoking? It is blue smoke so definitely oil.

Could bad inlet valve oil seals cause this? Or is it the classic Laverda problem of an air leak at the cylinder head exhaust port?

mac99
 
macavity99 said:
Update

Engine number is 18674.

Have just done a compression test -- 170 psi both cylinders. So I guess the rings are good.

So why is the right cylinder smoking? It is blue smoke so definitely oil.

Could bad inlet valve oil seals cause this? Or is it the classic Laverda problem of an air leak at the cylinder head exhaust port?
Click to expand...

You'll find out once you tackle the rattle... head needs to come off, gives you a chance to tend to all other ailments.

Thanks for the number.

piet
 
I once counted fins on lots of 750 engines, but lost the data. If I remember correctly, the switching to 16 fin heads happened with the SF2 in 1974 (end 73), but I have seen (probably early) SF2s with 17 fins.

Marnix
 
Marnix,

How many fins on the Eletronica heads?  Don't have one here at the moment... :D

According to the part #s, these were concieved/made before the 16-fin items.  As they are totally different internally, I  can imagine the factory to have used the outer models/moulds of the Eletronica and inserted the skulls for the cooking models.  Another tell-tale is the inside cast boss for the rocker axles.  IIrc, this is bored centrally in the SFC heads, whereas the SF3 head has it bored quite a bit off-centre to accomodate the "normal" valve angle.  The 17-fin heads have the boss bored centrally, but it is positioned differently.

Only noticed these details lately when replacing a totally knackered/butchered head on a wannabe SFC engine with a NOS item.

piet
 
      Hello Piet,
                my no. is 19007, it has 17 fins, its blowing a mist of oil from the right side cam cover, but l dont hear

        any strange noises, just the usual clatter when hot. Cause for concern?
                          tia  eric
 
eric said:
       Hello Piet,
                 my no. is 19007, it has 17 fins, its blowing a mist of oil from the right side cam cover, but l dont hear

        any strange noises, just the usual clatter when hot. Cause for concern?
                          tia  eric
Click to expand...

Eric, if it is actually "blowing" oil mist from there you may have a leaking head gasket pumping pressure into the cases. I have seen a head gasket leaking to a stud and venting via a camcover. Neither of my SFs rattle when hot.
Cheers
Lee
 
eric said:
       Hello Piet,
                 my no. is 19007, it has 17 fins, its blowing a mist of oil from the right side cam cover, but l dont hear

        any strange noises, just the usual clatter when hot. Cause for concern?
                          tia  eric
Click to expand...

Do you mean the cam end cover?
They often leak from there. Check the bearing isn't proud of the head casting.
Ciao
Paul
 
The SF1 motor I have here has 17 fins, I also have a SF3 head that has 16 fins and as Marnix said my disc brake SFC has 16.
Apart form the number of fins, whats the diff??
 
motoddrob said:
The SF1 motor I have here has 17 fins, I also have a SF3 head that has 16 fins and as Marnix said my disc brake SFC has 16.
Apart form the number of fins, whats the diff??
Click to expand...

Nothing really, Rob.

Just wondering what coaxed the factory into making a completely different head.  Just for the sake of it?  Was Massimo bored and wanted something to do?  The cam covers need to match, and afaIk, there's also cylinders with differing fin count, ie, 14 and 15.

The 16-fin head takes the different rocker axle location for the Eletronica heads into account.  Up till there, the SFC had the normal "skull" heads fitted with 7mm stem valves.  It would have been far easier and cheaper just to move the rocker axle boss to suit the Eletronica layout than to make new models and moulds for completely new castings.

puzzled piet ???
 
Well fuck me Piet, never new that the barrels had different number of fins :o Just counted, the SF1 motor has 14 and the SF3 and SFC have 13 Are you sure thay came with 15??? Learn something new every day eh?
 
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