Short timing chain?

michipons

michipons

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Palma de Mallorca
Hi guys!

Don't be angry at me... I have already used the search function but didn't find a direct answer...

I am now installing the new timing chain (never did before). When I try to join both ends, there is a complete sprocket "valley" between them :'( I have tried everything, checked that all is in place. I even have compared both chains, old and new, they have the same number of steps, but apparently the new one is 1 or even 2 mm shorter when I pull them. The old one is super easy to install, it just falls into the last valley easely.

Finally connecting the old to the new chain, if pulling hard from the old chain, I manage to put the new chain in its place, but is SUPER tense, and when I release a bit of tension, it springs back, so no chance to put the link, at least by myself, or without the use of an special tool (is there one?)

I have fixed the head with one stud to the barrel, to avoid being lifted when moving the crank... maybe I should put all of them and give them a good torque using a long bush up to the thread?c Maybe I would gain a gold mm?

The chain was provided by Wolfang, so my guess is that the chain is correct and I am doing something wrong, but can't say exactly what ::)

Help please!
Miguel
 
Hi,
I am talking about a 750sf3, chain was provided by Wolfang, no idea who is the manufacture, it says ?japan?
I saw in older topics that people are using a chain puller, that might be the way, I have ordered one per ebay, lets see if it works🤷🏼‍♂️
Miguel
 
Common issue for SF regulars, Miguel. You're almost there ... yes, fit spacers to the four inner studs (ensuring no damage to the top gasket surface of the head) and tighten to a medium torque - that should shorten the total height and allow you to join the chain. Once the head is fully tightened, even though you can't see it, the cam chain should be at a sensible tension. Goes without saying you DON'T have the cam chain tensioner fitted when trying to fit the cam chain??!!  :o

ONCE THE HEAED IS TENSIONED, have a feel of the chain through the tensioner opening and there should be some give. Push and lock the adjuster plunger as far back into the tensioner housing as you can. You MUST make sure that the tensioner isn't putting excessive tension on the cam chain when you fit it, ie, when you fit it, you don't want to be using the four bolts to be pushing so hard on the chain that you have to force it to close onto the mating surface - a small amount of tension is OK. I think there's a trick to prevent this (maybe shortening the tensioner spring to allow the plunger to recess sufficiently??? But don't quote me - I've never had to do it on many, many SF motors). Once the housing is in place and you release the plunger retaining bolt, if the plunger moves even a tiny amount you know you're OK.

Hope this helps. Good luck with the first startup! PS, if it doesn't fire straight away, you may need to swap the wires from the points across - sometimes the cam can be timed 360 degrees out from the points. Old trick.
 
Another old trick is to slowly roll the motor over by hand before you try starting it.
If you?re having trouble joining the chain it?s easy to forget to keep looking at the timing marks!
 
The chain is DID, they fit quite well when the head is pulled down with the spacer trick.

Always a good idea to fit a new damper rubber to the tensioner lever, the soft rubber allows a little more leeway against the old, hardened one.

piet
 
and wash the chain thoroughly in a petrol bath and dry it with an air line before you install it, but be sure it is well oiled before you run the motor, no matter which way you choose to do that.

CLEM
 
CLEMTOG said:
and wash the chain thoroughly in a petrol bath and dry it with an air line before you install it, but be sure it is well oiled before you run the motor, no matter which way you choose to do that.

CLEM
Click to expand...

Unless Wolfgang drags them through a sand pit before dispatch, the chains are clean as a whistle and are not oiled, they have only a thin coating of anti-corrosion stuff when they come from DID.  No need to clean it.  Install and throw a bucketful of oil over it before you close the lid.

piet
 
sfcpiet said:
Unless Wolfgang drags them through a sand pit before dispatch, the chains are clean as a whistle and are not oiled, they have only a thin coating of anti-corrosion stuff when they come from DID.  No need to clean it.  Install and throw a bucketful of oil over it before you close the lid.

piet
Click to expand...
I think CLEM meant degrease new chain to make it as long as possible not that they are dirty.Jason
 
Before you install a cam chain ensure you pull out the cam chain tensioner and pull the plugs = no compression. Wrap the cam chain to the top of the cam sprocket from the front and wire hold the rest of the chain from falling into the sump pump, pull it up as you rotate the engine and place it in the next tooth and when on top install the gear link with the the keeper facing counter rotational.

Ensure your Crank to Cam timing is right on.
 
Dellortoman: He could be slack at TDC with a tooth out - You never know ?

If you never done it before, it took me 2 or 3 attempts before I figured it out with an 750 SF.
 
Care definitely needed to ensure the marks line up - seen many a foul-running SF with one tooth out on the cam. Hopefully the distractions of trying to get a tight chain fitted doesn't result in missing the marks!
 
Hi,

Thanks Laverda SF, as I am reassembling the engine, I have still no plugs installed. I also thought about missing one tooth or may be that the chain was jumping one step in the crankshaft sprocket... I disassembled all several times to have very clear that it was the chain?s problem beeing a bit to short/tense.

Regarding the marks, yes, I will properly align them, of course. But as I didn?t manage yet to close the chain (waiting for my neighbour to help me to have a second lair of hands), I still didn?t see the problematic you mention, but definitively I will have a look at it, thank you.

I ordered the puller that Grant said in another topic to hold both ends together, so I will avoid the link falling down.

So I understand that the close end of the link has to face the exhaust part?

Regards
Miguel
 
The pic from Ernesto depicts how it can be done without any hassle. I have used M12 nuts to substitute the spacers, 4 on the inner studs, 2 on the outer studs. Then placed the dome nuts on the threads and torqued up to 30 Nm in cross over pattern. 12 hours later the new gaskets have set and the chain ends meet up nicely, without disturbing the TDC setting on the cam wheel. Rags stuffed around the cam wheel and timing chain keep everything in situ and the master link slips in. Check TDC by rotating the crank a few times.

HTH
Gerald
 
"While you're at it", check if the timing mark on the case is in
the correct position to align with the freewheel mark at TDC.
Sometimes it's not. Deviation will always be on the case mark, not
on the freewheel mark.

Ernesto
 

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Provisionally button down the head with a couple of spacers, 2 spacers placed diagonally across the chain tunnel normally suffice.

Line up the cam and crank marks, pull the chain to one side of the cam sprocket and jam a thin-nosed pair of pliers down the chain tunnel, these will hold the chain onto the sprocket nicely.  Then pull up the other end of the chain and repeat with another pair of pliers.  The pliers allow you to lever the chain onto the teeth you want, insert connecting link and clip, check markings... easy as, done in 5 minutes.  Throw a good dowsing of oil over the chain once the tensioner has been fitted, torque down the lid, finished.

Alternatively, you could make a pair of wedges from hard wood, aluminium alloy or plastic (that would give your 3D printer a good workout!).

piet
 
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