Stubborn 750 cam chain fitment

TeddyG

TeddyG

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Location
Portland Oregon
I own a 74 750 SF2 that had work done to the cylinders and head, and in re-fitting the original cam chain, I'm having problems getting it to fit back properly for the new master link. No matter what I try, the chain doesn't meet up and is shy of one link. The motor has been tilted to remove the cylinders and head, and I've tried tilting the motor back. Only the old master link was removed, so the chain is the original length. From looking at the removed sump cover, the chain appears to be properly engaged on the lower sprockets. I've tried lowering the chain and giggling it, but still no results.
Any suggestions?
 
Yes, cam chain adjuster is removed and original cam chain in place as noted above. Only the original master link was removed- nothing else has changed. Chain had to be re- inserted after it fell into the case. Pulling on the chain ends doesn’t bring the chain together enough for the master link- it remains 2 links apart.
 
As Ernesto has said, it has to be tightened down, especially if fitting new gaskets. Rock the motor a tooth or so backwards and forwards while pulling on the chain both sides. It also helps to have the head surface horizontal, by blocking up the front of the crankcase.
If the chain is very tight after you get it joined then the tensioner may not want to fit properly, in which case use more gaskets.
 
Have you torqued down the head properly or just nipped it up? Mine was tight with original chain without the tensionor fitted.
You have to torque down head to compress gasket- use spacer tubes on top of head ( without finned top cover) to get the play you need.
 
Diffrent sizes of the gaskets ?
Had a big problem with my 750GT and changed the cyl base gasket then it worked it was almost 1mm diffrens between the gaskets.
 
laverdaparts.se said:
Diffrent sizes of the gaskets ?
Had a big problem with my 750GT and changed the cyl base gasket then it worked it was almost 1mm diffrens between the gaskets.
Click to expand...
The base and head gaskets shouldn't be much thicker than 1mm total. 1mm TOO thick? That's not right - unless they're made for heads that have been shaved too many times.

As mentioned, putting some even torque on to head with spacers and washers will compress the new gaskets sufficiently to get the ends to seat into the top sprocket. As Tippie says, don't force the cam chain tensioner in using its 4 bolts ... if it's that tight, space it out.
 
Some gaskets sold today are thicker than the original factory items, I have seen half a mm thicker, but if using the chain that was on it before dismantling you will definitely fit it with the head tightened down as explained.
 
TWO WHOLE teeth short of joining??????? the chain just has to be missing the crank sprocket, I second the "use stud spacers" comment, but save the last 5ft/lbs of torque for when you fully assemble.
AAAAAAAND take the motor out, get it on the bench, its only two more bolts.
CLEM
 
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Thanks guys,

I've been wondering if the new gaskets from Wolfgang are thicker, but after comparing to the old ones, they look the same. I've used spacers to snug everything up, and also tried lifting the motor back to horizontal. And yes, the tensioner is off. Peering thru the open sump cover shows the chain is engaged on the crank sprockets, and manually rotating the crank back and forth while holding the chain ends shows that the chain is rotating without binding, so it must be the chain is not fully seating into the crank sprockets. I'll temporarily join the chain w wire and fit the cam cover and torque it down to 20 lbs, but I don't think the marginal compression will have any impact. As it is, the chain is completely taunt when I try joining it up at the center of the cam sprocket, but there should be some slack for the tensioner to do it's job.
 
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Well, I've tried everything suggested, and there's still a gap of 2 links. A friend and myself have checked everything and looking w/ a boroscope w the sump cover removed shows the chain is engaging w the crank sprockets, and pulls freely when grabbed at both ends while advancing the motor back and forth- there's no kinked links. I've removed the chain and count 88 rollers, which I understand is correct. The plates just have "Regina Extra" stamped on them and I'm assuming it's original. I read on Breganze that these can sometime fit tight and they recommend an IWIS G67WZ chain that supposedly fits looser. They claim Regina C121HCS should be avoided.
Thoughts please?
 
i have a std regina Extra cam chain in my motor and std aftermarket gaskets. The chain goes straight on once the stud spacer system is employed. I do need to apply a slight pressure to the chain to get it to mesh byt using a large flat blade screwdriver as a wedge.

Something very odd going on with yours ... if it came out of the motor it MUST fit. Can you post a pic of just how wide the gap is? It almost sounds like there's something fouling the crank sprocket that isn't visible through the sump hole. With the motor vertical and wire through each side you should be able to drop and move the chain and move it into different positions when it engages with the crank sprocket.

As a thought (and without being bothered going into the shed to look at my spare cases) there's no way the steel 'blade' that retains the gap between the outer races of the inner main bearings can be between the chain and the sprocket is there? From my ageing memory it's on the upper side of the sprocket.

Bearing separator - No.48.png
 
Thank you again Pirhana,
This motor has been previously touched by another mechanic of dubious reputation, and I don't see item #62 or 52 (hard to see the blurred type on the diagram)- is that the stud spacer? One thing I've noticed is that with the chain ends slack, the chain won't pull up freely, and has to be giggled alot before the chain is freed and pulls upward. I've removed everything from the engine including the chain, but when it's together, the chain stays 2 links apart on the cam sprocket. From looking thru the sump cover opening, it appears that the chain is engaging, but I could be wrong. I see a separate sprocket but its off to the side and the chain can't fit over it.
 
CLEMTOG said:
AAAAAAAND take the motor out, get it on the bench, its only two more bolts
Click to expand...
I'm with Clem. And support the front end, so that the cylinder is in the vertical position.
It really makes a difference.
What you see next to a central bearing isn't another sprocket. I think it has to do with
the manufacturing process.

Ernesto
 
There is also the nylon roller that bolts on the top of the barrels. If the motor has done miles it'll likely be chewed out abit. Make sure the chain is sitting on that properly. Trying to do it with motor in frame with front end in the way makes it difficult. For the sake of 2 bolts just remove it and set it up on a workbench.
The stud spacer isn't part of the motor. It's to clamp down the head barrels replacing the top plate so you have access to the cam chain.
Once the cam chain is linked piss them off and fit the top plate
 
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OK, thanks. I,ll try one more time w the engine back to vertical position- the last attempt like that resulted in no change. I,m also soaking the chain in gas to clean any dirt or grease buildup. The main roller isn,t worn much but I noticed that the one mount flange was drilled off center, and the other side flange was drilled correctly, so the roller is slightly crooked. I may end up removing the motor but it’s a heavy lump as you all know.
 
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