Tight cam chain

Blimey ..... this isn`t going to turn into another " This Bloody Bike " is it ....... ? ........ :oops: .............

Get yourself a copy of the Green Book if you haven`t already ......

It sounds as if you have lifted the head slightly , but you can remove the head completely ( and the barrels ) without having to remove the engine from the frame ..... ( see aforementioned book ) ...... This can be done by removing the head studs .........

Bending one of the studs with a ring spanner to get it out is frowned upon by some , but don`t worry about that ....... I actually had to file a slight flat in the frame tube to get even more clearance , but so what ? .......

Stick with it ... it`ll be ok ....... ( I`ve a feeling I`ve said this somewhere before ....... :unsure: ........... ) ..............



BTW ..... If you`ve bought the correct chain and have attempted to fit it in the correct manner ...... then it really shouldn`t really be a link short ...........

When the previous chain was in place , at least it fitted , even if it did appear to be tight ........ does the new chain have the same number of links and appear to be the same length ?

As I mentioned earlier , these chains can seem to be tight tension - wise when fitted ........ did you give the original chain a good tweak ?
 
Last edited:
Biker bob 16h said:
Thanks how can I check if it’s fitted wrong cheers could well be the problem
Click to expand...
Bob, you mention you’ve only ridden 400 miles on the bike. So I assume it’s new to you? Are there any other clues, like the engine having been rebuilt? And by whom? Has the PO shimmed up the cam blocks to regain valve clearances in the available shim range? My couple of suggestions may sound unlikely but come from experience of being at the receiving end of some of Johnny Jota’s ingenious handiwork over the years.
 
Laverdian said:
Bob, you mention you’ve only ridden 400 miles on the bike. So I assume it’s new to you? Are there any other clues, like the engine having been rebuilt? And by whom? Has the PO shimmed up the cam blocks to regain valve clearances in the available shim range? My couple of suggestions may sound unlikely but come from experience of being at the receiving end of some of Johnny Jota’s ingenious handiwork over the years.
Click to expand...
I was thinking similar. If that comes up, a tight chain is the least of Bobs' problems. :rolleyes:

piet
 
I’m
Laverdian said:
Bob, you mention you’ve only ridden 400 miles on the bike. So I assume it’s new to you? Are there any other clues, like the engine having been rebuilt? And by whom? Has the PO shimmed up the cam blocks to regain valve clearances in the available shim range? My couple of suggestions may sound unlikely but come from experience of being at the receiving end of some of Johnny Jota’s ingenious handiwork over the years.
Click to expand...
yes I am new to laverdas bought the bike was running good till I decided to repair the rocker cover oil leak then opened a can of worms
There are no shims under the cam bearings heli coiled some threads in the head and bearing carriers trying to do a good job but think johnny jota has been before me love my Jota great bike to ride and the sound 😎
 
redax5 said:
IWIS Cam chains are always a tighter fit up then say DID Cam chains
That is my experience after building a couple of hundred triple engines
Click to expand...
Very good point. I had an SF and a new IWIS chain was impossible to join. A DID from Piet went straignt on. I have the same IWIS on both my SF2 but they have had heads/barrels skimmed for compression. Lying on the bench both chains are identical length. Some of the head and base gaskets available now are quite a bit thicker than original and it doesn't take much to make a big difference.
 
Hi Bob
I can think of a couple of possibilities.
There are alternative new billet cam followers, std and extra height. These would be stamped with their add. Height.

Head gaskets come in 1, 1.2 & 1.5mm.
The thicker obviously designed to compensate for Head skimming.

Base gasket is 1mm to my knowledge and should be a single item. You could see this.

Std. Head thickness 94mm

Why not post some photos, it's often easy to spot anomalies.

Rob
 
The bearing blocks seem to be stock, but there are signs of them snagging in their locating slots in the head. Check for alloy slivers in the corners of the slots, these can prevent the bearings to fully bottom, possibly causing the tight chain. Damaged locating slots can make reassembly a pita, the cams never resume their former positioning.

These bearings should always be tightened with all cam lobes off the tappet buckets, carefully seating the bearings before turning a nut...

Timesert or similar for the M6 at #1 inlet camcover fixing?

piet
 
Paul Marx said:
Exhaust cam gear has been changed, likely to conform with 4C specs.
Does the inlet check out okay?
Paul
Click to expand...
Good point!!

Inlet chainwheel needs to be checked, only "A11" wheels had that etching for the timing mark without further designation, factory C4 wheels had clear stampings for both the timing mark and designation.

piet
 
Last edited:
Bob, it would be worth posting photographs of the stampings on the cams and sprockets. The lobes look 4/C but it’s possible that they may be regrinds and pattern sprockets. I had a look at a cam sprocket and the diameter at the root of the teeth looks to be 85mm. Worth checking on your sprockets.
It’s really a process of elimination and the photos may prompt some other suggestions.
 
Cam stamps are factory. What the lobes are is anybodys' guess, but probably stock C4. Measure base circle and lobe height and come back.

In top pic, the marking is at about 8 o'clock, a faint etching. The punch marks have been added by a DPO. As this is most definitely a A11 chainwheel, it needs to be replaced with the correct C4 item or re-drilled and marked to suit. The factory drawings showing the orientation of the different wheels are somewhere in the archives. A A11 wheel can not be correctly timed for a C4 cam without re-drilling the fixing holes.

Can't see any marks on the second from top, but the wheel has 2 sets of bores, so is very probably a re-worked A11 wheel.

Not the cause of your tight cam chain, but should be addressed while you're in there.

piet
 
You must have a thick base or head gasket all the cam wheels are the same diameter and number of teeth, I was going to suggest you may have .4mm offset cam blocks but yours are stock.
Piet might be on the money check the slot the cam blocks sit in, rotate the crank so all three pistons are sitting down from TDC, dont hook the chain up but fit the cams tension them and see if they rotate easily when no valves are loaded.
 
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?
 
You must log in or register to reply here.
Back
Top