pistons and valves contact

[rgh0]

Thanks very much for all your replies, I've had a good examine of the followers and they are lightly scratched all the way round. When they are in the head you can push them round with your fingers, I have smeared them with Graphogen and you need a rubber suction to remove them. I've managed to get the ex. cam to rotate round and round on its own, but fixed up with the inlet cam/timing chain after a turn on the crank spanner it jams.
I have ordered a new set of followers, I don't have a digital measurer

John

If the cams can be turned when installed individually in the head and with all the pistons at mid stroke and the crank can be turned with both the cams removed then the issue is with the timing of the cams with the crank when installing the timing chain. this process is well described in the workshop manual and in previous posts but if it is not clear to you I am happy to clarify any issues or questions.

You say you cant post pictures but dont explain why. Any mobile phone can take suitable picture but they may need to be reduced in size to post here. This is easily done by emailing them to your pc at reduced resolution.

If doing you own work on a twincam I would highly recommend you at least get yourself a cheap set of digital calipers. Even new followers may not match the followers you have currently fitted to your engine causing problems.

cheers
Rohan

[englishmaninwales]

Are you using an after market front timing chest cover? I had a situation where the casting was inaccurate around the cooling passage to pump (Burton supplied). This resulted in the timing chain fouling when tensioned and the engine would not turn over.

[checkrail]

Hi Rohan, I have ordered a set of digital calipers on ebay, the followers should come today from Piper Cams.
My computer skills are very basic and I only have an ancient mobile for emergences, but I have a small digital camera which is useful for reference photos i.e. rotor arm position for TDC ( I have an electronic dizzy)
I should be setting the timing right as I have plenty of reference -- Workshop Manual, Miles W. B.Buckland . I have a standard front cover.

John

[rgh0]

if you have reference photos on your camera then it is relatively simple to up load them to the computer and from there add them to a post.

When you get the calipers measure all the followers diameters at top middle and bottom and let me know the results. Compare those results with the new followers.

Also measure the thickness of the pad in the middle of the inside of the follower that the shim rests against for both existing and new followrs. With calipers you need to do this by measuring from the bottom of the follower to the pad using the depth rod and then meausring the overall follower length and subtracting the difference to get the pad thickness.

Also measure the overall length of the followers for both existing and new.

All these dimensions can vary depending and supplier and modifications done to the engine during previous rebuilds and while I dont believe the followers are your probable problem they are worth checking.

As I said previously if the cams turn and the crank turns individually but not when all three are installed and connected by the timing chain then the problem is likely with something in setting up the timing. Have you inspected the timing chain tensioner sprocket to confirm it is turn freely and is not worn so that it tilts and maybe jams when load is applied when the chain is tensioned (which must be done before turning over the engine after setting the timing)

cheers
Rohan

[checkrail]

Fitted the new followers with plenty of oil, no problems, the cams rotated easily all the way round.
Connected the chain, had to move the inlet sprocket one tooth, the timing marks line up.
Started to rotate the crank and heard a metallic noise which seemed to come from the timing chain slipper and it jammed. Thinking back I'm sure that I've heard that noise when its jammed before.
I've looked down with my inspection light but cannot see anything obvious

John

[rgh0]

Hi John

How are you adjusting the timing chain tensioner, do you have the spring and piston proper in place and when the adjuster is tightened is there still thread showing above the locknut. Does the tensioner sprocket on it rotate freely and is it not sloppy on its shaft.

If the tensioner is not adjusted or fauklty and there is slack in chain you can get the chain jamming where it runs off the crank sprocket as you turn the engine making the metallic noise you hear.

cheers
Rohan

[checkrail]

Hi Rohan, Yes is plenty of thread showing, as there has always been previously, I will have another look at the tensioner sprocket, I know that it revolves freely, but maybe too sloppy?

Cheers John

[checkrail]

Have ordered a new pivot bolt, there is a bit of play on mine

John

[rgh0]

The play may come from wear on the bolt, wear on the brass pivot arm bolt hole , or wear on the sprocket bearing bolt or sprocket. The pivot arm can also be twisted

I would remove and inspect each compoent to see what is worn. The pivot arm and sprocket assembly can be removed with the head in place

cheers
Rohan

[Craven]

Have had the chain not engaging correctly with the crankshaft sprocket, getting jammed to the side

[rgh0]

Have had the chain not engaging correctly with the crankshaft sprocket, getting jammed to the side

Yes that can also be a problem but usually you cant then turn the cams at all. That is why I always put the sump on last as it is much easier to make sure the chain is properly engage on the crank sprocket. Plus if you drop anything down the chain cover when fitting the cams you can easitly retrieve it

cheers
Rohan

[2cams70]

Note for when you get it running - if you have changed the followers you should bed the cam in after the first start. Be careful to use some assembly lube on the followers and cam lobes. I prefer to use assembly lubes with a high concentration of Molybdenum Disulphide on these parts only - that ugly messy dark grey stuff!

[checkrail]

Fitted the new pivot bolt, turned the crank from TDC with a wooden dowel in no.1 plug hole, it then jammed with the dowel at the bottom of the stroke. There wasn't any noise this time, the chain is aligned on the sprockets but of course I couldn't check the timing marks.

John

[rgh0]

Fitted the new pivot bolt, turned the crank from TDC with a wooden dowel in no.1 plug hole, it then jammed with the dowel at the bottom of the stroke. There wasn't any noise this time, the chain is aligned on the sprockets but of course I couldn't check the timing marks.

John

I presume the cams turned smoothly as you turned the crank. If it jammed with No1 at bottom of stroke then No2 and No3 are at top of stroke and potentially hitting the valves. It still sounds like the timing is off for some reason.

Are the locating dowels present still in the cams to locate the sprockets. One of the sprockets should be marked "EX" and this be on the exhaust cam

cheers
Rohan

[checkrail]

Yes Rohan the cams turned smoothly, the dowels are stil there in the cams. The teeth on the inlet sprocket looked a bit worn so I replaced it, The sprocket is marked for either EX or IN according to how you fit it, I am sure that I am fitting it correctly because it lines up with the dowel.
I will try the old sprocket

Cheers John