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Cams / timing / articles

5K views 32 replies 7 participants last post by  Old Cafe Racer 
#1 ·
Can anyone direct me to a previous thread detailing cam timing from the ground up - ie not using any direction from the manuals since I am attempting this on a bike with somewhat unknown cam wheels so I cannot rely on the markings. Plus, I want to get my own head around the theories and get it spot on. A book would suffice too.

I have a degree wheel on order but have failed to find an appropriate dial gauge. Can anyone recommend the latter that would compliment a T140e (79') engine?

This is for a 79' T140e with T120 Inlet/Exhaust cams (70-3134 / 70-9989).
 
#6 ·
Noted and profile updated...

Engine on the bench and ready to roll.
Timing disc ordered and just need some advice
on which dial gauge is recommended? Heaps out there
but figured from some of the photos I have seen of this
procedure, the gauges probably need to be somewhat
specific to the job.

With my setup, should I be looking at the T140 dialling
or T120 dialling. I am guessing the latter from the cams
I am using.

Current stage of engine assembly - cranks cases together
and barrels ready to be fit. Cams waiting to be dialled in.
I have a somewhat technically minded thought process
so I am keen to get my teeth into this. Thanks so far for
the references... any further tips welcome.
 
#10 ·
I was hoping not to bring up the bearing issue, but I will now, and then run for cover!

I have communicated with a number of experienced Bonnie owners and they suggest the 'new' standard bearings ARE up to the job of the 3134 inlet profile cam torque which is lower down the rev spectrum, as opposed to the 'old' less robust standard bearings. Before I get slated for this comment, has anyone any first hand experience of a blown standard timing side bearing using my proposed setup? Please back up any advice with real time evidence/experience.

Thanks thus far for the great info..
 
#11 ·
by "new" standard bearing are you referring to the 3 piece roller bearing as fitted to the last T140s out of meriden ? or just a new ball bearing -- I have no experience of the 3134 profile cam used for exhaust (yet) but i am about to go into an engine i have that is supposed to have a 3134 exhaust cam and a superblend bearing conversion to the timing side -- all i have read is that ball bearing will not stand up to a more potent T140 - in addition when reading opinions generally on main bearings in T140s it seems that "if it ain't broke don't fix it " is the current rule - that is ; when rebuilding a motor if the main bearings are good don't change them as they are possibly better quality that those currently available --- as you say , it will be interesting to find if anyone knows for sure if the ball bearing cant handle a 3134 ex cam

don't know about you but i have been reading all i can about cam timing - my head is about to go bang - so much info - so much info written for people who know what they are doing - very little "cam timing for dummies" --- but i think i am getting there the more i read / re-read
-- i did check the cam timing on a T160 following the same instructions suggested in this thread and that made sense eventually
 
#12 ·
I hear ya regarding the cam timing issue - this is probably the only place I have managed to solicit any information on this subject, hence my thread. Many books out there, but like the information one receives on this website, you have no idea of the quality of information - and very subjective. I dare say those who frequent this particular forum are avid experienced bike engineers who know their stuff - it can sometimes be a bit overwhelming but that is my problem.

When I say new bearing, it is not the upgrade but the standard bearing, but new. I was advised this would suffice. I am still waiting for any first hand experience with failures but nothing thus far. Anyone....? Opinions or has this just become an assumed upgrade with this 3134 intake?
 
#13 ·
my thinking on the subject is - why take the chance - the 3 piece bearing is only a little more expensive than the ball bearing - if the ball bearing does fail then the expence in rebuilding will be far more even if no other parts are damaged by the failure -- I believe Norman Hyde endorses the bearing change and he knows his stuff
 
#16 ·
7.4 : 1

Does anyone know why the intake cam on a T140 model (as opposed to the T120) does not have installed on the left side of the cam shaft, a rotary breather valve and spring? What changed between the 120 and 140 that enabled the item to be omitted?

I am making some good progress on the assembly of my engine - however, how do I identify which push rod tube O ring is which, and the sealing ring. Is there a colour code or dimension I should be considering when identifying the correct type and to where it fits? Sorry, basic stuff but unable to get an answer from my manuals.

Lastly, is there a specific length the dial gauge can operate ie how much travel is needed when dialling in the cam timing? Need this info before I purchase some gauges.

Thanks to all..
 
#18 ·
When timing the valves, you will be measuring the lift at TDC on the rockers above the valve stem with nil clearance.
The rocker arms are not 1:1 so its important to measure at the valve end.
No Push-rod tubes makes it easier to do.
The lift will be around 0.2", depending on which cams are fitted.
If the duration needs to be measured, this figure will be about the difference between the cam lobe peak and its nominal diameter.
All clocks should be able to measure this.
 
#19 ·
Great.

I was lead to believe 8.6 : 1 was the standard compression?

I have seen a couple of cam timing guides that discuss working out the TDC on the crank, which is obviously needed during the calculations. Are they referring to older bikes that may not have the markings in the crank flywheel, or are they not terribly accurate on those such as mine, that do have them?

How are these Cu head gaskets supposed to be heat treated before they are installed?

Lastly, should I be using some specific cam grease when installing especially since I will be dry running/turning the engine over during the timing procedure?

Questions questions, but I am looking for some inside knowledge and know how!
 
#20 ·
No, 7.9.

Mine is 8.5 now

Cam lube is a good idea, although I didn't use any when I did my cams years ago.
Don't replace the bushes without seeing if the current ones are ok. They probably are.

You should have two notches on the crank
Also the timing cover has a pointer to idicate 38 on the rotor

Anneal the gasket
 
#21 ·
To find TDC accurately use a degree wheel.
Turn the engine with spanner on the alternator or crank nut.
Forwards and backwards at TDC to find the mean and set the degree wheel appropriately at 0 degrees.
Bear in mind if you use the alternator to mount the timing disc.
Forwards is anticlockwise.
 
#22 ·
To be absolutely sure of exact TDC -- take an old spark plug and knock out the ceramics and centre electrode - fit a nut and bolt into the now hollow spark plug - fit the spark plug with the bolt end poking down towards the piston - use a bolt long enough to stop the piston near the top of its stroke -- fit your degree wheel with a fixed pointer- slowly turn the engine until the piston touches the bolt -- make a note of the degree reading -- now rotate the engine the other way until the piston again touches the bolt - make a note of the degree reading -- TDC will be midway between the two readings -- now you know the true TDC you can check against the factory marks for TDC and 38deg BTDC to see if they are true

annealing copper head gasket - heat to cherry red and quench in water (or allow to cool slowly ) -- I always quench not convinced about the slow cooling
 
#23 ·
I'm going to do all the timing on the bench and as such will have to dismantle again before installing the engine in the bike. Surely if I torque down the gaskets for the dialling in procedure, they cannot be used again?

I had read somewhere that it is not a good idea to slow run new cams and followers, and they need to be up to speed asap to bed them in?

NExt job is to lap the new valves in - plenty of oil down the valve guides to facilitate?

Thanks for all the replies guys...
 
#24 ·
You don't need to torque anything down to set valve timing, just finger tight on a short spanner.

Coat the cam lobes and followers with a moly engine assembly lube and keep the motor at 2000rpm minimum for the first 20 minutes.
2K is quite slow really.

Just a light smear on the valve stems when lapping is all you need, I use 3 in 1 oil for minimum drag.
Just keep the grinding paste away from the stems
I fit a #10 O ring on the stem just below the valve head to make sure no grit runs down there whilst lapping.

ocr
 
#25 ·
All noted with thanks..

I just did a piston ring tolerance check (LF Harris) - compression all fine and in tolerance measured at 1/3 intervals up the bore. Oil ring on the other hand!! Can't even fit it into the bore, too big. I figured with the amount I paid for these products they would at least be plug and play! Small items so I guess I need a very fine file to fix this issue. Anyone done this before?

BTW, I like the idea using the holed out spark plug with a bolt inserted to find TDC - should save me some $$$ instead of using another dial gauge. O ring on the valve stems also a good idea I would probably not have considered. The head is obviously currently off so TDC could be calculated now too with the dial gauge directly over the top of the pistons. The rest can come once the head is installed.

More titbits if you all have any??
 
#27 ·
Its possible to file the ends of the oil ring carefully in a vice to get the desired gap.
When they are manufactured the outer periphery is ground in a top grind machine.
1 thou off the periphery opens the gap by pi thousands of an inch.
I made thousands of them.
Then they are put into a gauge tool with a wide gap and `gapped`.
Something has gone wrong if they are too big.
 
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