Tight cam chain

Schurminater said:
So thinking outside the box,if the bike was running okay with no issues and nothing seemingly disastrously untoward with the cams and sprockets,is it feasible to get a cam chain with 1 extra link added to just overcome the seemingly overtight chain?

Would thicker gaskets determine the need for this?
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One extra link would be insanely long!! Even adding a half-link (even if it were possible, even more insane) would be miles too long ... we're talking fractions of a mm in distance from crank to cam here ... like a 0.5mm thinner base gasket would probably cover it.
 
Interesting,and thinking about it afterwards would this play a part in creating timing issues?
Its good to learn from these problems as we all may face a similar situation in the future.
 
Yes the bike was running fine 450 miles easy starting ticking over fine no knocks or rattles pulled like a train one more link would have solved all my problems
 
Are you sure it's actually on the bottom sprocket properly? I had to refit mine last week when I was building the engine because it hadn't sat correctly when I fed it around the crank sprocket.
 
As I understand it , the original chain was in place , but seemed far too tight ..... ( impossible to move up or down at all , not even by a couple of mm ) ........

The replacement chain is impossible to fit as it seems to be too short ........


Was the original chain tested at other points apart from the recommended TDC position ......... It would be interesting to know if there was some slack with the crank and cams in varying positions ....... or was it tight wherever it was positioned ?

Will the new chain fit with the rear tensioner blade removed ........ and with the blade fitted , has the tensioner adjuster bolt been undone as far as possible so there is no contact with the blade at all ?

Probably not of much help ...... just things I`m imagining I would try , or experiment with , if it were me ........



If I remember correctly ........ and it`s beginning to be a long time ago ........ whenever I fitted a new chain ( always Regina ) , tension when checked would always have been virtually zero ......... even with the tensioner fully wound out , as I mentioned earlier ........

What I mean is , the movement up and down would be almost zero , maybe just a couple of mm ......... certainly a fair bit short of the recommended 5 mm up or down from centre ......... It would depend on how hard I would be prepared to tweak the chain ........

Push really hard and you might get another 1 mm ............ adopting an imaginative state of mind would give you another one or two mm ................

So there you have it ..... 5 mm ...........just as it says in the book .....................


Sorry , doesn`t really help with the new chain being too short though .............
 
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Running "fine" and running properly can be 2 totally different things, especially if you don't have another example with which you could compare it to. Even the tiredest old dog of a triple can make a big impression on an uninitiated.

1mm head gasket would be standard thickness. A new DID chain will tolerate a +.5mm head or base gasket without issues. I have never needed to alter a triple timing chain to get it to fit.

Pat, if the chain runs next to the crank cog, it will be far too loose... basically impossible to position it to have the links riding on the sprocket teeth, in that case the ends wouldn't come near enough to close the chain. Apparently the chain was already tight when the engine was running.

I'd simply try another chain.

piet
 
I’ve fitted a few IWIS cam chains and to be honest never had any issues. To have both Regina and WIS chains feeling on the short side is long odds but not impossible.
Bob when you fitted the new chain did you visually confirm it was engaged on the crank sprocket? I usually take a photo to confirm this for peace of mind.
Again, it would be worth confirming this, if only to rule in or out another possibility.
 

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As an aside ....... I`m just imagining how Nino Caretta and co would have dealt with a triple top end rebuild and cam chain issues half way through a 24 hour race .........

Chain won`t fit ? .... throw the tensioners away if necessary and make it fit .........

Tension too tight ? ...... who gives a stuff about the tension ...... Just get it all back together again and back in the race before we lose any more laps ........


Probably not the best approach for a road bike though ..............
 
I have removed the rear chain adjuster completely and the rear slipper which is new with no wear marks on it at all even after doing 400 miles also the front slipper is and can’t see any marks on that either but haven’t managed to remove it yet have double checked that the chain is correctly fitted on the crank sprocket am thinking the bottom of the bearing carriers are to thick hence raising the cam shaft I’ve worked on a lot of engines bsa triumph Norton I think I must be missing something simple the chain was literally coming straight up the tunnel no where near the rear slipper and straight down the front tunnel not touching the front slipper
I’m very grateful for all the comments trying to fix this problem
 
Bearing carriers look stock though?.....did they all look correctly seated on the head before you removed them?....were the cam locating half moons correctly located in the centre blocks?

Just thinking out loud trying to figure it out too.
 
Cut out photos showing partial cam chain run Bob and lower sprocket pedestal,cam chain has no option but to run near past tensioners when correctly fitted.
 

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Another thought?.....there has been some issues with the fitting of new cam chain tensioner blades,something about needing to pre bend them before fitting otherwise they can put too much tension on the chain even before the adjuster bolt comes into play?????

Piet am I right in thinking that?
 
The front guide can only be removed without damage once the cylinder block is lifted at least 5mm from the crankcase.

piet
 
I just know how to fix the cam chain at the 120 deg engines. The chain is always very tight and to close it with the lock you have to turn both cams against each other with two spanners by the fixing screws of the cam sprockets and as well a third hand ( my wife) with a pliers to bring both ends close together and put the lock in. Having closed the chain there is no slack at the chain at all but you can move it up and down 5 mm with some strong pressure of the thump.
Maybe it is different at the 180 deg engines and when no cam is under spring pressure you have some slack, but if it is similar as with the 120 deg engines, there might be no slack but you can move it vertically with some pressure.
Andre
 
Thanks for that by why is the chain not touching the rear adjuster blade when I took the rear adjuster off the adjuster was not wound in at all perhaps I’m making it harder for myself maybe I should have just wound the adjuster in to touch the blade I did manage to link the new chain together
 
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