J motor Cam Chain Tension

[Pigford]

Having degreed in the cams on the Lawson.... an interesting point has cropped up

Does the cam cover tensioner press down on the cam chain

I think it is only a GUIDE so stops a loose chain hitting the cover direct, and making a hideous noise

If it does (I don't think so) this will effect the inlet cam timing

How do I get round this without cutting a hole in me cover

[Al]

Hello Mark good news on the cam timing etc.
The guide in the cam cover does deflect the cam chain down considerably and does alter the cam timing of the inlet when you so carefully set it without the cover on and now its out!!

You can verify this for yourself by putting the cover on temp and taking it straight back off again. You will see that it has dropped the cam chain down by about a quarter of an inch along the top run.

Also if you look at the top guide it has a curved profile. Looking at the wear marks you will see that they extend all the way to the ends.

Just done mine so i set the exhaust cam timing first and rather than abide by the pre-stamped timing mark on the inlet cam wheel i set the timing with a drooooop in the chain. Its about two teeth out from having the chain flat across the top.

Manual says do it with the chain flat on top so i guess they have figured in an allowance for the downward deflection that you get from the top guide. Which suposes that the inlet index mark is already set two teeth out on the circumference.
In reality the 'actual' innacuracy afforded the inlet cam timing by the deflection created by the guide blade; i measured at about one tooth plus or minus half a tooth!

I'm going to guess that you found the cam timing one tooth out previously and now you have corrected it it runs as you think it ought but is still giving symptoms like before?

As a possible alternative. Do you have a spare old top roller guide from an early engine which you could mock up on the top of the head to hold the hyvo down and set the inlet timing exactly?

Hope this makes sense


AL

[kano]

has anyone here cut a cover up so you could adjust timing perfectly.?
i saw one on ebay a while ago but i have forgotten what it looked
like after being cut.

[Al]

Kano a man of you demonstrable abilities could fabricate one in under an hour if you set to it.
Bit of flat bar curved on top and two arms extending down to form a top hat section. Two holes into the two central cover mounting screw locations. No need for spare guide blades just a simple measurement of the bottom of the level of the guide blade from top face of the head/ lower face of cam cover.


AL

[Ginger Bear]

Piggy, I might have a slightly modified cover from one of me Jeepsters, the one that had been turboed had an oil return mod if I remember rightly. I think they are the same It's yours to chop up if you want it.

[Pigford]

Cheers GB....... are you going to the Sunday Lunch on Sunday

[Ginger Bear]

Yes I am, might have to take the Harley if it's rainin'!! Shall I bring it with me

[Al]

Took a little while to get round to it but managed to get in the garage today and make this.


Its made from one of those guides you get with a jigsaw that no one seems to use.


It does not have to fit inside the cover because the cover is left off.





The curved part is identical to the top guide blade.



The measurement is taken from the inside of the cam cover with the blade fitted inside it.
Its 41mm to the bottom of the blade from the top surface of the head.
41mm also includes an allowance for a gasket as this will space the guide blade slightly higher and further away from thecam chain.


I have all the other dimensions if anyone wants them.




Several more pictures here if needed.
http://s254.photobucket.com/albums/hh86 ... 20dialler/



AL

[kano]

very cool ill buy one lol.

[Al]

Kano it saves cutting up a usable cover.
Sketch for dimensions is a little crap it was only a guide as i was originally going to cut it out of flat sheet 3mm mild. However a rummage in the scraps bin turned up the guide blades as, if i used a jigsaw i wouldnt have enough fingers to type this with.
Probably took no more than an hour all told.



AL

[Pigford]

Al.... thats ace matey........ Can I borrow it

[Al]

Its in the post Tuesday (tomorrow) if you e-mail a postal address, should be with you for the BH weekend. You have e-mail too.


AL

[Al]

This is a picture of cam timing for a gpz 550 etc.
It looks like a hy-brid version between early z and later 'J' types.

In any event it does show the droop on the chain which the big Z manual does not.

I measured the difference having the hold down tool makes to cam timing and its approximately 4-7 degrees' when dialing in cams using the lobe centre method.
That would be enough to take you from say 111.5 / 112 degrees to potentially 104.5 / 105 degrees if that was your goal








AL