valve clearances, valve timing

doublegarage

doublegarage

Junior member
Location
California
I'm trying to work through why my (new to me) 1982 180 Jota is hard to start. There's plenty of evidence why I shouldn't trust the PO's mechanical skills so I thought I'd better give the valve clearances and camchain a quick check.
- Camchain play at the slackest part was 16mm - really loose, but adjusting the tensioner brought it down to 10mm (+/-5mm)
- clearances, not good.
in/ex mm
Left 0.18/0.18
Center. 0.18/0.25
Right. 0.15/0.05
should be 0.20/0.25? So all bar one need adjustment, and one is really bad.

I turned the crank (17mm alternator end nut) until TDC on left & right cylinders with the camchain link between the sprockets. I was going to paint some yellow lines on chain and sprockets to help reassembly, therefore checked the alignment of the sprocket-lines with the caps and found this.

cam sprockets.jpeg
Not easy to get a good picture but the exhaust cam is dead on the mark, while the intake cam is off by what looks like exactly one tooth, retarded. (note: this pic is 2 revs past the chain's clip-link being between the sprockets)

That's just wrong, isn't it? I'll get a new camchain when I order the shims but a worn one can't put the timing out that much, can it?

Also, the workshop manual says to loosen all cylinder head nuts - while the green book says just the 12 on the cam-caps. What does the Laverdaforum say?

Thanks as always,

-Richard
 
Reshim valves and time cams w/ degree wheel. Just loosen the 12 cam caps & be aware that the cam cap studs are two different sizes on each cap & keep the tappets on their original valves. Measure twice, shim once. I'm sure you'll get responses from members far more experienced that I w/ specific timing spec recommendations.
 
My brothers Jota was similar when he bought it. Some german "Tuner" had simply changed one cam by 1 tooth for "performance reasons". Bike had less power than with standard setting...

I'd typically follow the "iceberg" theory here: For every 1 thing you find to be wrong, 8 other things might hide under the surface... I would check this bike through from top to bottom and front to rear, left to right seriously...

be careful on re-tightening the cam bucket nuts. a) you can make the buckets compressing, causing friction for the cam and b) to pull the studs by slightly over tightening the nuts is a lesson many learned before... so please be careful!
 
While you're at it, check the tensioner blade. With so much slack, it's a good chance the rubber friction surface has fallen/rotted off. Clearances are 0.20-0.25 inlet/0.25-0.30exhaust. You'll do your head in trying to get them "spot-on". The clearances in the cam bearing blocks alone can throw many measurements/adjustments out the window. Clearances should be measured with a properly tensioned chain.

For normal road use, simply aligning the timing marks is quite ample, IF all the correct parts are assembled in the correct places.

piet
 
Okay good to know that there's more of a range for the clearances - also because the shim sizes are quite widely spaced. I guess I'm about to find out whether that one at 0.05mm already has a thin shim or not. Expecting the worst with this PO seems like the best policy.

I've been trawling on here and found torque values of 18/25 ft-lbs for M8/M9 nuts - does that still sound all right?

So I'm okay not to undo all cyl-head nuts, just the 12 on the caps? Other engines I've worked on would say you should replace the head-gasket after doing that and I'm not in the mood for that (yet).

-Richard
 
Hi Richard, no need to exchange the head gasket. The 12 for the cam are enough.

Regarding torquing the head, I will send you a link as PM. Make sure that when you re-torque the head before measuring, you first losen the nut you want to re-torque, then re-torque it carefully...
 
Having just performed the shim and valve timing scenario I can highly recommend using a digital torque wrench. I treated myself to one as a Christmas present and as they constantly display the achieved torque they dramatically reduce the bum clenching terror waiting for normal torque wrenches to click. I used 35nm for the M9 nuts and 25nm for the M8. As a further check, when the timing marks are vertically in line on TDC the cam lobes on no.1 and no. 3 cylinders should be either "looking" at each other equally or "looking away" from each other equally, depending which stroke the crank is on, if that makes sense. Ideally you should set up a timing disc and accurately check timing on max lift. Have fun and don't be afraid to ask for advice.
 
BobSol said:
Having just performed the shim and valve timing scenario I can highly recommend using a digital torque wrench. I treated myself to one as a Christmas present and as they constantly display the achieved torque they dramatically reduce the bum clenching terror waiting for normal torque wrenches to click. I used 35nm for the M9 nuts and 25nm for the M8. As a further check, when the timing marks are vertically in line on TDC the cam lobes on no.1 and no. 3 cylinders should be either "looking" at each other equally or "looking away" from each other equally, depending which stroke the crank is on, if that makes sense. Ideally you should set up a timing disc and accurately check timing on max lift. Have fun and don't be afraid to ask for advice.
Click to expand...
You are so right Bob, I too got myself a nice 'snap on' digital torque wrench for xmas. Its lovely. It glows amber up a little scale as you approach the desired torque setting and buzzes when you get there. No more bum clenching terror in my shed, well not from the torque wrench anyway !
 
Be careful with the tension the outer studs are M8s and the inner main cylinder studs are all M9s
The M8s dont need much tension no more than 18 ft/lb the M9s on the inside of the cam blocks can be 25 ft/lb
It wouldn't hurt to get someone to actually clock your cams those marks on your cam wheels maybe no incorrect!!!
 
Okay sounds like my next steps are
- re-torque head
- re-measure clearances
- split the chain while at TDC - maybe move pistons/valves to safe distances apart
- remove cam-cap nuts only, in sequence and torque-steps
- cams out - measure shims - order shims and new chain + tensioner blade
mauricejota7604 said:
actually clock your cams those marks on your cam wheels maybe no incorrect!!!
Click to expand...

Reading around the forum tappet discussions I think I do have 4/C sprockets - they have 'A' and 'S' stamped on them and the holes line up with tooth peaks not valleys. I need to find the valve-timing article on LaverdaMania that everyone refers to. Then i'll put the degree-wheel on it when I get closer with clearances and a new chain.

I've got a good quality clicker torque wrench although its calibration was a few years (12?) back - might be the excuse I've been waiting for to get a new one!
 
Also never ever tighten the cam block nuts down when there is a cam lobe applying pressure to a bucket. Also if all your markings align correctly and you cannot see the cam chain connecting link you will need to reposition the chain in the crankshaft sprocket. Where are you in California and do you have the 'Green Book' by Tim Parker?
 
78jotadave said:
Also never ever tighten the cam block nuts down when there is a cam lobe applying pressure to a bucket. Also if all your markings align correctly and you cannot see the cam chain connecting link you will need to reposition the chain in the crankshaft sprocket. Where are you in California and do you have the 'Green Book' by Tim Parker?
Click to expand...
I'm near Santa Cruz, up in the hills to the north. Yes I've got the green book - it's great, it just slightly disagrees with the factory workshop manual in this area hence asking what the consensus is.
I'll re-tighten the cams somewhere there's no pressure on a lobe, ok. And with the link, I think I know what you mean - i found it was about 6 engine revolutions (can't remember exactly) for one rev of the chain, so have to find a good position to split it. I don't want to have to disengage the chain from the crank sprocket if I can help it.
 
If you spin it over enought youll eventually see the joining link between the cam sprockets with the timing marks in place.
On the 180 the inlet is off tension and youll need to retard the ex cam a few degrees to free it from spring tension.
Hope this makes sense
 
doublegarage said:
Reading around the forum tappet discussions I think I do have 4/C sprockets - they have 'A' and 'S' stamped on them and the holes line up with tooth peaks not valleys. I need to find the valve-timing article on LaverdaMania that everyone refers to. Then i'll put the degree-wheel on it when I get closer with clearances and a new chain.
Click to expand...
A and S stand for intake and exhaust.
The Laverdamania article on valve timing is an article by Phil Todd taken from this forum I should think.

Paul
 
I did the head re-torque today which produced some slightly different clearance measurements - then removed the cams and shims and measured.

The shims are all on the thick end of what's available, thank goodness. My guess is this is the first time anybody's checked clearances since a machine-shop valve job in 1994 - but I don't know how many miles it's done since then so not very useful.

Table of measurements and what to buy below - looks like I can re-use 2 of them elsewhere so that's always nice. Let me know if you see any stupid mistakes.

laverda tappet table.png

-Richard
 
With the exhaust cam in particular, it’s important to pay attention to the tension of the timing chain, i.e. to load the camshaft when measuring the valve clearance. If one of your exhaust valves had such little play (or probably no play at all with a loaded camshaft), the question of how long the engine was operated without exhaust valve play is allowed.

What do the compression values of the cylinders look like?

Cheers
Jo
 
Jo, the clearances were measured with the timing chain tensioned and the cylinder head nuts etc all torqued - so I think those numbers were valid.

I could have taken a compression reading with it in that state, true, but I didn't and it's too late now - I will do so when it's all back together. Thanks.

-Richard
 
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