750 sf primary chain

S

squalomediterraneo

New member
Location
italy
hello, I am continuing the restoration work of my 750 sf of '71.
Unplugged the carter I found this controller on the primary chain that does not look like the original one.
I have to replace it because it's consumed, do you know which model it is, and where can I find it?
thank you

https://flic.kr/p/ZEZBUi
 
The pictured tensioner is the earlier version, later replaced with the slipper tensioner.

I can supply a reproduction roller for the tensioner, as well as triplex primary chains.

PM me if interested.

piet
 
Leave it as is, the new roller would wear to the same in a short while.

As it is now the chain is better supported on its rollers.

Andy
 
andychain said:
Leave it as is, the new roller would wear to the same in a short while.

As it is now the chain is better supported on its rollers.

Andy
Click to expand...

That one looks virtually new Andy. I have a new one kicking around somewhere and it's ridged that way. Wear occurs when the chain rollers bite into the nylon and teeth appear on the tensionner wheel.

Paul
 
Yes, the tensioner rollers are ridged so only the chain rollers are in contact.

The problem with the material that Laverda used in this application isn't wear in the usual sense.  The plastic becomes brittle with time and little bits of plastic are smashed out of the surface upon contact with the chain.  While the roller may look to be in excellent condition, it is however well over 40 years old and has been subjected to oil and heat, not a healthy environment for plastics...  Same applies to cam chain damper and tensioner wheels.

Repro rollers are made from a polyamide grade that withstands both oil and heat, seem to last quite OK.

piet
 
sfcpiet said:
Yes, the tensioner rollers are ridged so only the chain rollers are in contact.

The problem with the material that Laverda used in this application isn't wear in the usual sense.  The plastic becomes brittle with time and little bits of plastic are smashed out of the surface upon contact with the chain.  While the roller may look to be in excellent condition, it is however well over 40 years old and has been subjected to oil and heat, not a healthy environment for plastics...  Same applies to cam chain damper and tensioner wheels.

Repro rollers are made from a polyamide grade that withstands both oil and heat, seem to last quite OK.

piet
Click to expand...

We'll see in 40 years time  :D

Paul
 
Laverda SF said:
The last thing you want is for them Teflon Chips fouling the top end - It will wreck your day.
Click to expand...
Spot on Ron. I've found shards of the roller plastic sitting nicely over the oil holes from rockers to cams. ugly and expensive ... and the mesh filter won't pick them up. An easy replacement at reasonable but regular intervals is the go.
 
  I make my own rollers (both cam and primary) from a more "modern" material I also fit the needle roller conversion as per the SFC 750 - have done it on the cam chain tensioner wheel too. When i checked the "Croatian Cracker" i found it to have a bronze sort of material used as the cam chain tensioner roller. It was showing no signs of being chewed up and bike had been used successfully over quite a few years. - Regards - Phil
 
phil37 said:
  I make my own rollers (both cam and primary) from a more "modern" material I also fit the needle roller conversion as per the SFC 750 - have done it on the cam chain tensioner wheel too. When i checked the "Croatian Cracker" i found it to have a bronze sort of material used as the cam chain tensioner roller. It was showing no signs of being chewed up and bike had been used successfully over quite a few years. - Regards - Phil
Click to expand...
Acetal C?

I have few acetal C rods in stock on my humble machine shop. Haven't thought earlier what is a good material for these chain rollers inside engine. Earlier I have made secondary drive rollers from Nylon.

Edit: Didn't noticed polyamide was also confirmed to work well.
 
phil37 said:
  I make my own rollers (both cam and primary) from a more "modern" material I also fit the needle roller conversion as per the SFC 750 - have done it on the cam chain tensioner wheel too. When i checked the "Croatian Cracker" i found it to have a bronze sort of material used as the cam chain tensioner roller. It was showing no signs of being chewed up and bike had been used successfully over quite a few years. - Regards - Phil
Click to expand...
You use rollers on the primary chain tensioner, Phil? So that's in place of the slipper type? Any advantages? As for brassy stuff? Wouldn't it eventually leave fine deposits?
 
Piranha Brother 2 said:
You use rollers on the primary chain tensioner, Phil? So that's in place of the slipper type? Any advantages? As for brassy stuff? Wouldn't it eventually leave fine deposits?
Click to expand...
  yes Quentin - My 270? Sf has an early motor and  had the early type roller adjuster fitted - on looking at it I decided that there was nothing wrong with it and it may well give less friction and better wear to the chain - can't really say for sure. On the Croatian cracker i was astounded to find the bronze type wheel - but it was showing no signs of scuffing up , so, as the motor had been raced very successfully for quite a few years, i decided to leave it - of course - i can't say exactly how long It'd been fitted - but there were very slight indentations from wear on it rather than removal of the material. - regards - Phil
 
am I right in thinking that the primary chain for 750 twins and 1000/1200 triples is one and the same (when talking about triplex) and ditto when talking about lengthwise for Merc Duplex or a pair of simplex?

Or is my brain now too old for this sort of thing?
CLEM
 
More so you don't want them chains to rattle or wine spewing plastic through the oil system.

Adjust them - LISTEN.
 
And if necessary, on your judgement, you can clean them up using a fine file to get a few more thousands miles outta them tensioners before replacing them.
 
We have used a littlebit different system to adjust the primary chain on a couple of Breganzie twins and triples.

Here it is:
1. Engine must be carefully warmed up (needs riding of course)
2. Adjustment is carefully adjusted to zero clearance
3. Half turns out
4. 1/12 turns in (half nut corner)

This gives a very small clearance, is fast and those "spoons" will work longer than with the original adjustment for triples.
 
its the "zero" clearance that's the problem, because the slipper tensioner is pliable, "zero" is place that is not easy to find.

It might be different with the original roller type, that looks to be a harder material, and with Phil's manufactured type different again,

I like the idea of Andy Wagners viewing window bolted onto the primary case, so that you can see inside, but have never done it (ugly, non original, spoils a good case) but a better idea would be a removable "door" so that the chain(s) can be felt with a finger, (even worse)

What I have works, and I will leave well alone (another job I don't have to get done), and as a result, I probably run the chain too slack.  In Spain earlier this month with much slow mountain work (hairpins etc) I was aware of a lot of "slack" between drive and driven, but the rear chain was just right, so that's not it.

CLEM
 
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