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Timing in a t140 cam in t120 bonny #433384
05/05/12 12:19 am
05/05/12 12:19 am
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vancouver,b.c.
black13 Offline OP
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I posted this before and got great advice . I just have a few questions . How do i start , do i need the head and cyclinder on or just cyclinder . Also can i use the bonny intake cam wheel and put it on the slash instead of hole ? Or do i need to tim it in . Do i put the degree wheel on the cam shaft ? Thanks ready to do this . Thanks


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #433405
05/05/12 3:34 am
05/05/12 3:34 am
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Fit the camwheel in the standard position,to start with.Use the keyway closest to the timing mark,and line it up with the long dash.
You don't need to have the head fitted,as long as you can find TDC.
Attach the degree wheel to one end of the crank.It will be easier if it's on the primary side.Attach it to the rotor stud,or screw a 7/16" UNF stud into the rotor nut.

Set up a dial gauge to take readings at the top of a pushrod.

You might find the timing is right.If necessary,you can change it in 5 degree increments by using the alternative keyways.

Re: Timing in a t140 cam in t120 bonny [Re: Pete R - R.I.P.] #433410
05/05/12 3:56 am
05/05/12 3:56 am
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vancouver,b.c.
black13 Offline OP
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well Pete when i line up the cam it is at its highest position on the lobe when it is lined up with the dash ......i think iam close no ....as usual pete thanks ! for the advice ...first time doing this ....but really wanna learn .....thank you


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #433420
05/05/12 7:08 am
05/05/12 7:08 am
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The pistons will be at TDC when the timing marks line up.
Make sure you use the correct keyway,when you time it by the marks.

The timing-side intake tappet will be lifted about 0.180" at TDC (approx 1/2-lift).It won't be at full lift until about 100 degrees after TDC.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #433521
05/06/12 12:14 am
05/06/12 12:14 am
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black13 Offline OP
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Do i want that ? I lined up the marks exhaust cam on dot , intake on hash mark not dot . Idler gear lines up with pinion . So now i have dial set up do i put it at 0 since we are at tdc ? Then what value on disk do i find at full lift ?


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #433652
05/06/12 11:16 pm
05/06/12 11:16 pm
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First thing you need to to do is to zero the degree wheel at TDC.
The timing plug will get you very close to TDC.You could measure 1/2" or 1" down either side of TDC,and compare readings on the degree wheel.
A solid stop bolted across the top of the barrel would do the same thing.Turn the engine either way until the piston hits the stop.Both readings should be the same number of degrees from TDC.

Then turn the engine intil one intake tappet is fully lifted.Set up the pushrod and dial gauge on the other tappet,and zero the dial gauge.
Turn the engine forward and take a reading on the degree wheel wheel,when the pushrod has lifted 0.020" and another reading at 0.080" lift.Turn the engine until the the pushrod drops again to 0.080" lift and 0.020" lift and record those readings.You could also take a lift reading at TDC.

Take measurements on both intake lobes.The 0.080" figures will give you the best indication of timing.The lobe centre is 1/2 way between those readings.If the lobe centre is close to 100 degrees ATDC,that's good enough.


You will still need to check piston-to-valve clearance later.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #433656
05/07/12 12:01 am
05/07/12 12:01 am
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vancouver,b.c.
black13 Offline OP
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Awesome ! Many thanks ! .


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475163
02/01/13 7:24 am
02/01/13 7:24 am
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black13 Offline OP
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Hey Pete , so can i do the cam timing with the rocker boxes on and the tappetes set to the correct clearances ..is the 0.020 the same as clearance or is that start of lift of tappet .. i guess it is better to take the lift readings at the pushrod with the rocker boxes off ? .....thanks


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475166
02/01/13 9:18 am
02/01/13 9:18 am
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Have you got a degree wheel attached to the crankshaft?
Is there a pointer which indicates TDC on the wheel,when the pistons are at TDC?
You can check the cam timing with the rocker box fitted,but you won't be using 0.020" valve clearance to do it.

First adjust the valve clearance to zero,then back off the adjuster to 2 turns or 2-1/2 turns clearance.Lock the adjuster with the lock nut.
You can use a feeler gauge,about 0.005" or 0.010",between the adjuster and the valve to check timing.
Turn the engine forward until the feeler just becomes tight.
Take note of the degrees on the degree wheel;how many degrees before TDC.One degree either way from there,it will become very loose or very tight.
Leave the feeler out and turn the engine forward.The valve will open,then begin to close.When the rocker arm becomes loose again,put the feeler between the adjuster and the valve.Turn the engine backward until the feeler just becomes tight.
Take note of the degrees on the degree wheel;how many degrees after BDC.

If you want to do it by measuring lift at the pushrod,that's easy enough too.Set your dial gauge on the pushrod and zero it when the tappet is fully down.The other intake tappet will be fully up.
Rotate the engine forward until the pushrod has lifted 0.080".Note the degree reading.You can take a reading at 0.020" lift also,out of curiousity.

I'd also be interested in how much pushrod lift you get at TDC.

Turn the engine forward past full lift,until the pushrod returns to the 0.080" lift again.Take note of the degree reading.
Turn the engine forward until the pushrod drops to 0.020" lift,and read the degree wheel.

The 0.080" figures are the accurate ones.The 0.020" figures may or may not be.
Each 0.080" reading is an equal distance (in degrees) from the lobe centre position.

Measure the timing on both cylinders.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475181
02/01/13 12:35 pm
02/01/13 12:35 pm
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PeteR,I commend you on your patience. You are a guy that we all depend on.Thanks Dick

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475224
02/01/13 6:18 pm
02/01/13 6:18 pm
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vancouver,b.c.
black13 Offline OP
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Thanks peter ! really i can't thank you enough . There would be a lot of broken engines and broken hearts if it were not for you people who really know the stuff and are willing to share . I myself feel the same way . i Share what i learn along the way . World peace one triumph at a time !..haha thank you Kind sir ! and yes Dick i agree !......Dean Wadella ....i'll post tonight what i get ...


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475439
02/03/13 5:48 am
02/03/13 5:48 am
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black13 Offline OP
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ok i think iam not doing it right . i adjusted the tappets to .005 ...turned motor till one intake valve was at its lowest point ..adjusted the other intake valve tappet to .005 . moved the engine till the other valve was down and adjusted to .005 .clearance . Now ...Then i put the engine at tdc on the degree wheel i have on crank .{already check tdc with dial guage} ok now i moved engine forward{ crank degree wheel is on primery side }...degree wheel rotates anti clockwise . feeler guage in one intake tappet {riders right intake } i get 80 btdc .....i keep rotating engine till it becomes loose agian . sticjk the feeler guage in the same tappet turn motor backward till i cant pull the feeler guage out and get 80....it will not pull out 75 is tight but still if i yank hard it will move .....does this seem right ? Many thanks Pete !


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475441
02/03/13 6:09 am
02/03/13 6:09 am
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black13 Offline OP
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ok i rechecked and my degree wheel was wee bit out so i took a dial guage on the piston and re did the guage looks like around 85 it is real tight . i'am a bit confused "sorry never done this " do i set the .005 at tdc both rockers because one looks like it is on its way down .....i have a stock 750 intake cam in my 650 bonny ....running a morgo 750 kit ......intake cam wheel is timed to slash not dot .....thanks ......


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475444
02/03/13 7:07 am
02/03/13 7:07 am
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It sounds like you have the head and rockers fitted.
Firstly,does the engine turn safely with nothing jamming?We don't want valves crashing into pistons.

You have a degree wheel on the crank.How did you set it to zero at TDC?You wouldn't be able to use a dial gauge on the top of the piston.You could use a positive stop,like a bolt screwed into an old spark plug body and turn the engine both ways until it hit the stop.
You could use a soap bubble on the spark plug hole of whichever cylinder is on compression at TDC (some people have trouble with this,but it works for me).

Once you have the degree wheel set,adjust the intake valves to about 2 to 2-1/2 turns of clearance on the adjuster.That's 0.080" to 0.100" of valve clearance.
Then take readings of the degree wheel,when a 0.005" feeler just becomes tight.Even one degree change will make a big difference on how tight or loose the feeler becomes.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475447
02/03/13 8:18 am
02/03/13 8:18 am
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black13 Offline OP
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i set it to zero at tdc when i had the head off and a dial indicator on the piston . ...i adjusted the intake valves like i would do at a tune up . rotate engine till one intake valve is fully open , adjust gap at one that is at rest . and vice versa . So after i did that i rotated the engine to the tdc mark on the degree wheel . So then i put the feeler guage into one of the intake valves and rotated the engine forward or anticlockwise . my feeler guage got tight {could pull it out } at around 85 aftertdc ...then i moved the engine the other way clockwise and and it got tight agian at around 85 bftdc ...?....is this correct ?


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475460
02/03/13 9:46 am
02/03/13 9:46 am
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Originally Posted By: black13
i adjusted the intake valves like i would do at a tune up . rotate engine till one intake valve is fully open , adjust gap at one that is at rest .

So then i put the feeler guage into one of the intake valves and rotated the engine forward or anticlockwise . my feeler guage got tight {could pull it out } at around 85 aftertdc ...then i moved the engine the other way clockwise and and it got tight agian at around 85 bftdc ...?....is this correct ?


OK,it sounds like the degree wheel is zero at TDC.
You adjusted the valves to about 2-1/4 turns clearance (roughly 0.090" valve lash)
When the 0.005" feeler just becomes tight,turning the engine forward (normal rotation),you read 85 ATDC.The rocker arm has moved about 0.085" from the zero-lift position and is now just tight on the feeler.

The timing is obviously not right.
You got 85 ATDC just opening (at 0.085" valve lift).
You got 95 ABDC just closing (at 0.085" valve lift).
Lobe centre position would be (85+95+180)/2 = 180 degrees ATDC.This means the lobe centre is at BDC,instead of 100 degrees ATDC.Out by 80 degrees.

I wouldn't expect it to be this far out,if you used the camwheel keyway closest to the timing mark and lined up the dash with the idler wheel mark.The error is equivalent to 5.5 teeth on the camwheel.

Please check again.I would have also expected about an extra 60 degrees duration between the opening and closing points.
If it was opening (feeler just tight) at about 25 BTDC,
it should be closing (feeler just tight) at about 45 ABDC.

Last edited by Pete R; 02/03/13 10:25 am. Reason: "I would have also - - - ABDC."
Re: Timing in a t140 cam in t120 bonny [Re: black13] #475538
02/03/13 5:48 pm
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will recheck thanks


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475597
02/04/13 12:04 am
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ok uhhhh.. sorry if iam an idiot but i'am trying to teach myself this ! ok , i took the rocker boxes off .....way better . ok so something seems weird ...i looked at my time marks on the cam . idler , cam and they did not line up at tdc ?. i know it only lines up every 90 revolutions ?...anyway i took the idler out and redid the whole thing again checking also the flywheel mark was in the position thru the bold whole . . then re - tdc'd the piston with the dial guage . ok now i mounted the dial guage and rotated the engine foreward till one intake pushrod was full up position or max lift ! . then moved the dial indicator to the other intake pushrod which was at rest or lowest position . Zero'd the guage ...did not move the engine ...Then i moved the engine foreward till my .001 guage hit 20 on the dial .took a degree wheel number which was 46 btdc ...then another at 0.080 i got 21 on the degree wheel btdc seems like max lift at push rod is86 bbdc ....is this correct or close or should i lay off the booze ?

Last edited by black13; 02/04/13 2:43 am.

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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475600
02/04/13 12:50 am
02/04/13 12:50 am
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That's looking better.
Take a pushrod lift reading at TDC.

Take readings after BDC,where the pushrod has 0.080" lift (probably around 40 degrees) and 0.020" lift (probably around 65 degrees).

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475606
02/04/13 1:54 am
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on which pushrod ? one is slightly up one is at rest ...the one at rest?
thanx pete


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475608
02/04/13 2:01 am
02/04/13 2:01 am
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black13 Offline OP
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how do i do that ? do i put it back to tdc and go the other way ?
{turn engine}


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475617
02/04/13 2:55 am
02/04/13 2:55 am
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It would be a good idea to take measurements at both pushrods.
*Opening points (0.020" lift,0.080" lift)
*Lift at TDC
*Closing points (0.080" lift,0.020" lift)

If your dial gauge has enough travel,you don't need to turn the engine backward to find the closing points at 0.020",0.080" lift.You still need to make sure the tappet is pushed against the cam lobe,and not sticking in the up position.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475618
02/04/13 2:59 am
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i think i get 60 at .020 lift and 35 at .080..


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Re: Timing in a t140 cam in t120 bonny [Re: black13] #475620
02/04/13 3:24 am
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The 46/60 @ 0.020" and the 21/35 @ 0.080" both give a lobe centre of 97 degrees ATDC.
That's reasonable for good mid-range torque.
102 degrees would make a little more power at high rpm.

What was the lift at TDC?
Check both cylinders,to make sure timings are equal.There is often a few degrees difference.

Re: Timing in a t140 cam in t120 bonny [Re: black13] #475676
02/04/13 6:09 pm
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how do i check lift at tdc ?


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