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Cam timing help #368634
04/17/11 7:00 pm
04/17/11 7:00 pm
Joined: Jun 2007
Posts: 15
UK
Enigma Offline OP
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I hope some of you guys out there can help regarding cam timing figures.

I am rebuilding a pre unit engine which I have fitted with E3134 cams and "R" followers, all the parts are either new or reconditoned. The timing figures I am using are IVO 34 ~ IVC 55 degrees, EVO 55 ~ EVC 34 degrees both at 100.5 lobe centres all done at 0.020" lift mesuring off the pushrod (rockerbox removed). The cam wheels have 3 keyways.

Degree wheel set up 0.100" either side of TDC.

The trouble I am having is I am struggling to get "close" to these figures and ballancing between the two. These are the figures I am getting:

Keyway 1 Inlet
IVO 31 ~ IVC 56.5 degrees with 102.75 LC timing side.
IVO 31.5 ~ IVC 61 degrees with 104.75 LC drive side.

Keyway 2 Inlet
IVO 36 ~ IVC 51.5 degrees with 97.75 LC timing side.
IVO 37 ~ IVC 50 degrees with 96.5 LC drive side.

Keyway 3 ~ miles out.

I feel as keyway 2 would be best as the inlet valve will be opening early (safe) rather than keyway 1 which is opening later.

Do any of you guys think this is right?

I have misplaced the paper with the exhaust figures on so will post them later.


1969 BSA A65 Lightning
Triton (in build)
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Re: Cam timing help [Re: Enigma] #368653
04/17/11 10:41 pm
04/17/11 10:41 pm
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hampshire, england
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t120mike Offline
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Looks like your keyway 1 is the best fit.
The best way to measure is either side of the point of maximum lift; measured at least 30 crank degrees either side and get that right. 102 degrees LC is what Dave Nourish recommends for his cams, and would be about right with E3134 cams.

Lets face it, one whole tooth of movement represents 14.4 crankshaft degrees. Using different keyways gets the increment down to 4.8 degrees. You might be lucky and get closer, but if you are unlucky you can be up to 2.4 degrees out with nothing you can do about it but choose whether to be that much advanced or that much retarded. Be sure to mark up the camwheels clearly, correctly and indelibly when you have reached your best fit, and keep a safe record of the markings.

Unless you are stock through-and-through, when you have decided on the best "fit", I recommend you check the piston to valve and valve to valve clearances. I did on my project and found to my horror that the inlet valves were too near the piston crown (one actually touched!) I had them recessed by 0.050". The exhaust valves and the valve-to-valve were OK. I measured every which way, but the acid test is with head, head gasket, push rods and rocker boxes assembled but with carb springs in place of the valve springs and measure with a dial gauge on the top of the adjuster and then depress the valve with a screwdriver until it hits the piston and measure the depression. BTW, do it for both cylinders and do not be surprised if they are quite different. You only need to do it at 1 degree intervals for 20 crank degrees either side of measured TDC.
It is tedious in the extreme but brilliant for peace of mind.

HTH

PS. There is plenty of backlash in the timing side pinions and it's a good idea to measure everything coming from both directions of crank rotation just so you are "aware".

Last edited by t120mike; 04/17/11 10:52 pm. Reason: Added PS

mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: Enigma] #368667
04/18/11 12:21 am
04/18/11 12:21 am
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Asheville, NC
Mike Baker Offline
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I will be at the point of putting my 71 back together soon.
I've marked the camwheels before removing them.
Question: Were the camwheels installed at the best position at the factory. Is it worth going through the motions of looking for the optimum timing numbers when reinstalling the stock setup?

Thanks, Mike

Re: Cam timing help [Re: Enigma] #368704
04/18/11 6:54 am
04/18/11 6:54 am
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triton thrasher Offline
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Looks to me like keyway 2 is better: closer to manual opening and closing figures and slightly advanced.


Amateur Loctite enthusiast.
Re: Cam timing help [Re: Enigma] #368711
04/18/11 9:16 am
04/18/11 9:16 am
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Pete R - R.I.P. Offline
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There is something inconsistent with your measurements.Using keyway 2,you have advanced the intake an equal amount on both cylinders (as compared to keyway one).The lobes have no choice,but to move an equal amount.
The measured figures show that the timing side advanced 5 degrees,yet the drive side advanced 8.25 degrees.There's at least 3.25 degrees of error there somewhere.
There's not much accuracy in any figures measured at commencement of lift (like 0.020"),closing point,or anywhere around full-lift.
Try taking measurements at 0.080" lift,or 0.100" lift.Then calculate your lobe centreline.At this amount of lift,the follower is moving almost 0.004" for every crankshaft degree.Even a 0.002" error in your measurement,or on the profile of the cam,is of little consequence.This will give you a true picture of where 99% of your lift curve is situated.

Differences between cylinders can be caused by follower blocks not installed dead square:put a straight-edge across the follower block and measure from the straight-edge back to cylinder bores with a vernier caliper.Cam followers can be ground off-centre and cause a difference.If they're new or re-ground ,you can rotate them 180 degrees to make a small change.

So,what is the best cam timing?Is it 100.5 degree lobe centres,as used on T100 race-kit in the early 50's with open megas and about 8:1 compression.
Or is it 96 degree intake,105 degree exhaust as used in the late 60's on T100R (same cam profile),with mufflers and 9:1 compression.Same rod/stroke ratio.

Re: Cam timing help [Re: t120mike] #368790
04/18/11 6:35 pm
04/18/11 6:35 pm
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Enigma Offline OP
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t120mike, thanks for the reply.
My concern with using keyway one is that the inlet valve will be opening late and more likley to contact the piston. I have spent some time trying to get the figures as close as possible so a few more hours spent doing the checks you recommend will bring peace of mind.


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: Pete R - R.I.P.] #368798
04/18/11 6:59 pm
04/18/11 6:59 pm
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Enigma Offline OP
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Hi Pete, thanks for the reply.
I have spent many hours going through the timing of the cams. No matter how many times I check the timing on each keyway I get the same figures within 1/2 a degree so I am happy that I am measuring it correctly. I agree with you that there seems to be an inconsistent reading! The reason I am using 0.020" lift is because that is what the manuals say, I will try at 0.080" and see what I get. If I still find that the figures are not quite right I will lift the barrels and check the tappet blocks.

What is the best lobe centre to aim for? And what opening and closing figures should I am for?


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: Enigma] #368810
04/18/11 8:29 pm
04/18/11 8:29 pm
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triton thrasher Offline
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Originally Posted By: Enigma
t120mike, thanks for the reply.
My concern with using keyway one is that the inlet valve will be opening late and more likley to contact the piston.


Opening too early makes the inlet valve hit the piston.

But you check before you use the engine anyway, don't you?


Amateur Loctite enthusiast.
Re: Cam timing help [Re: Enigma] #368829
04/18/11 10:49 pm
04/18/11 10:49 pm
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t120mike Offline
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I personally wouldn't go pulling the barrels just to check the tappet block allignment unless I knew this was a problem. With the head and PRTs off you can see well enough whether the cam followers are square or not by putting a rule across them both.
I would guess that to get cam profiling accurate between left and right side lobes within, say, four crankshaft degrees (= two camshaft degrees) was a big ask in the days when E3134s were made in numbers. Chasing unattainable accuracy can be dispiriting. Remember the backlash inaccuracies. Every time you rotate the crank twice, the crankshaft and camshaft pinions are in the same place but the idler pinion is not, so the backlsh will be different unless the idler pinion is PERFECTLY symmetrical. How accurate is your ignition timing, left to right? If you are using points in the magneto you will be lucky to get within 3 crank degrees difference between left and right. Even with wasted spark electronic ignition, the usual set-up can give slight differences between the timing of the spark on rev 1 compared to rev 2.
All I'm saying is that you have to live with some inaccuracy and if you get it near enough, and if your valve clearances are ok, you should be fine. I bet at least 90% of amateurs with stock engines go with the factory keyway and cam pinion markings and are oblivious to the issues mentioned here!
However, I fully understand your anxiety. Been there!


mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: t120mike] #368885
04/19/11 7:29 am
04/19/11 7:29 am
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triton thrasher Offline
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Originally Posted By: t120mike
I bet at least 90% of amateurs with stock engines go with the factory keyway and cam pinion markings and are oblivious to the issues mentioned here!


Ibet 99% of guys who charge money to build engines are twice as oblivious.


Amateur Loctite enthusiast.
Re: Cam timing help [Re: Enigma] #368903
04/19/11 10:50 am
04/19/11 10:50 am
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hampshire, england
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t120mike Offline
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Mike mblab,
QUOTE
I will be at the point of putting my 71 back together soon.
I've marked the camwheels before removing them.
Question: Were the camwheels installed at the best position at the factory. Is it worth going through the motions of looking for the optimum timing numbers when reinstalling the stock setup?
UNQUOTE
To answer your specific question:
The camwheels were set for the optimum for the prevailing conditions AT THE TIME (fuel etc) with everthing "stock". i.e. Probably for ease of starting, smooth idle, mid-range poke and fuel economy (i.e. street "rideability"). The extra keyways were for those who wanted to "tune" their engine for performance at the expense of an easy life!
I would go for the stock settings but check the valve clearances just to be sure. A PO might have skimmed the head or the valves and seats may have been replaced or the cams reprofiled, or, or......


mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: t120mike] #369011
04/19/11 8:19 pm
04/19/11 8:19 pm
Joined: Jun 2007
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UK
Enigma Offline OP
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Hi Guys.
t120mike, I agree with you about chasing unattainable cam timing figures because thats just what I have been doing!

I must admit since seeking help on this forum I have had a rethink and remeasured the inlet timing at 0.080" as per Pete R's advice. Here are the figures I got using Keyway 2:

IVO 11.5 + IVC 31 + 180 = 222.5 devide by 2 = 111.25 - 11.5 = 99.75 lobe centre drive side.
IVO 10.5 + IVC 27 + 180 = 217.5 devide by 2 = 108.75 - 10.5 = 98.25 lobe centre timing side.

Now at this point I started paying a bit more attention to what I was doing and noticed that the zero on my DTI guage was out by about .002". The ramp on the cam lifts my DTI guage by about .002" then stops moving untill further up the ramp, so I reset my zero at this point. I rechecked the timing figures in the direction of rotation and again noticed that on the closing side the zero on my DTI guage was out when fully off the ramp of the cam. So I then reset the zero at this point against the direction of rotation but then rechecked the timing in the direction of rotation on the closing side(I hope you are still following this as its easier to do than type!) and here are the figures I got by doing this again at 0.080" lift using Keyway 2.

10.5 + 32.5 + 180 = 223 / 2 = 111.5 - 10.5 = 101 degrees LC drive side.
10.5 + 30.5 + 180 = 221 / 2 = 110.5 - 10.5 = 100 degrees LC timing side.

Now that looks better for the lobe centre smile (Triumph say 100.5 degrees LC)

I now remeasured at 0.020" lift and here are the figures.

36 + 52 + 180 = 268 / 2 = 134 - 36 = 98 degrees LC drive side.
37 + 55 + 180 = 272 / 2 = 136 - 37 = 99 degrees LC timing side.

Now is it best to keep these figures as the lobe centres are correct at 0.080" lift and the timing figures are within about 3 degress at 0.020" lift or try chasing 34 IVO and 55 IVC figures!!!!!


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: triton thrasher] #369019
04/19/11 8:43 pm
04/19/11 8:43 pm
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UK
Enigma Offline OP
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Hi Triton thrasher.

I am pretty sure if the inlet valve opens late say 31 degrees BTDC as opposed to 34 degrees BTDC there is more chance of the piston hitting the valve, or have I got the numbers the wrong way round?
But the exhaust is better to open late.


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: Enigma] #369080
04/20/11 12:58 am
04/20/11 12:58 am
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Pete R - R.I.P. Offline
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Your intake figures look good.Triton is right;opening the intake early makes it more open at TDC (closer to piston).Piston clearance can be a limiting factor,when trying to get the best timing.
Opening the exhaust early means it closes early and is more closed at TDC (away from piston).Advancing the exhaust has other benefits:smoother idle,more low speed and mid-range torque (makes the engine feel bigger).There can be a little loss at maximum power or beyond.
This isn't Triumph,but see what BikeBoy does: BikeBoy.org-Ducati Cam Timing-2V models

Last edited by Pete R; 04/20/11 1:05 am.
Re: Cam timing help [Re: Pete R - R.I.P.] #369200
04/20/11 7:10 pm
04/20/11 7:10 pm
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Enigma Offline OP
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Hi Pete
I will check the piston to Inlet valve clearance at TDC hopefully tommorow, any idea of how much clearance there should be?
I just had a quick look at the link you posted, I think I need a cup of tea when I start reading it as it looks fairly long winded smile
Hopefully all going well I shall sort out the exhaust timing over the weekend!

Now where did I put my beer?


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: t120mike] #369226
04/20/11 9:12 pm
04/20/11 9:12 pm
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Pete R - R.I.P. Offline
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Originally Posted By: t120mike

How accurate is your ignition timing, left to right? If you are using points in the magneto you will be lucky to get within 3 crank degrees difference between left and right.

All I'm saying is that you have to live with some inaccuracy and if you get it near enough, and if your valve clearances are ok, you should be fine.


Ignition timing difference with a magneto is easily fixed,and is rarely caused by the points cam (unless someone has been stoning it).Its more often caused by the points cam not being square to the armature axis.Either:-
*The face of the main body is not square to the axis
*The face of the cam housing is not square to the cam.

If the points gap on one lobe of the cam is bigger,rotate the cam housing 180 degrees and bolt it up again.
If the same cam lobe gives the same bigger points gap,the cam housing is at fault.
If the same bigger gap is in the same position relative to the magneto body,the face of the main body is off-square.
It may be necessary to also check for errors at right angles to the lobes,using similar logic.

Valve to piston clearance: 0.040" intake,0.060" exhaust would be safe.More is better.

Last edited by Pete R; 04/20/11 9:23 pm. Reason: "Valve to piston - - better."
Re: Cam timing help [Re: Enigma] #369230
04/20/11 9:39 pm
04/20/11 9:39 pm
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t120mike Offline
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Just to give my experience of checking valve clearances, I found the closest encounters for the inlet valves between TDC and about 25 degrees ATDC (as the piston is still near the top and the inlet valve is intruding further). Plot the gap from TDC every degree and you will find it bottoms out in this range.
Equivalent area for the exhaust is 25 degrees BTDC to TDC. As the others have said, if you are undecided which keyways and you are worried about valve clearances err on the side of late inlet and early exhaust.


mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: Enigma] #369238
04/20/11 11:05 pm
04/20/11 11:05 pm
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Enigma,
Still pondering!
I am only assuming that this is a 650 motor you are building. If so, where did you get your data regarding the E3134 cams? I only ask because pre-unit 650s, as far as I can tell from the books I have, didn't ever have 3134s for both inlet and exhaust (although this was a very commom upgrade).
Pre-unit T120 had E3134 inlet and E3325 exhaust as stock. I did the sums on the opening and closing angles given in the workshop manual and both inlet and exhaust lobe centres came in at 100.5 degrees. Go for increased valve clearances and, say, 3 degrees inlet late and 3 degrees exhaust early and this shifts the LCs both to 103.5. So getting your LCs in the range 100.5.to 103.5 would seem appropriate.
FWIW


mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: Enigma] #369250
04/21/11 12:37 am
04/21/11 12:37 am
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Asheville, NC
Mike Baker Offline
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T120 Mike
Appreciate your thoughts regarding factory settings. The bike runs fine as is. Perhaps when there is more time available to me I'll dig into the "black art" of cam timing.
For now, I'll put it back together as it was.
And thank you Pete R for your insight on another thread.
Thanks, Mike

Last edited by mblab; 04/21/11 12:39 am.
Re: Cam timing help [Re: t120mike] #369356
04/21/11 7:24 pm
04/21/11 7:24 pm
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Enigma Offline OP
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Hi t120Mike
I should have mentioned that the engine is pre unit with a Morgo 750 barrel running 3134 cams in both inlet and exhaust for my Triton. The information for the cam figures came from "Kim the CD man" Triumph manual CD, which has a collection of genuine Triumph manuals and tunning data. I was going to check the valve to piston clearance tonight but other matters took over. so I will try and do this over the weekend after the Stafford bike show. Thanks for the information on the LC's.


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: Enigma] #369392
04/21/11 10:44 pm
04/21/11 10:44 pm
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t120mike Offline
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Enigma,

Easter Weekend is run by her indoors as a family thing and funnily enough does not include the Stafford Show. Dang!

If you see Hughie Hancox there, tell him "certa cito" from me.

Have fun!


mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: t120mike] #369467
04/22/11 4:02 pm
04/22/11 4:02 pm
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Enigma Offline OP
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Hi Mike
Sorry you can not make the Stafford show always a good turn out.

I have managed to wangle the day off work so I thought I would try and finish of the cam timing.

I have checked both Inlet & Exhaust Lobe centres at .080" lift:
Inlet 101 degrees drive side
Inlet 100 degrees timing side
Exhaust 103 degrees drive side
Exhaust 101.5 degrees timing side

And again at .020" lift

Inlet 98 degrees drive side
Inlet 99 degrees timing side
Exhaust 102.75 degrees drive side
Exhaust 101.25 degrees timing side

The opening and closing figures @ .020" are

IVO 36 IVC 52 degrees drive side
IVO 37 IVC 55 degrees timing side

EVO 58 EVC 32.5 degrees drive side
EVO 57.5 EVC 35 degrees timing side

I have also checked the valve to piston clearance as followes.

Inlet timing side

10 degrees BTDC = .193"
TDC = 132.5"
10 degrees ATDC = .116"
15 degrees ATDC = .126"

Exhaust timing side

10 degrees BTDC = 143"
TDC = .156"
5 degrees ATDC = .180"
10 degrees ATDC = .214"

There seems to be plenty of clearance between valve and piston, also the opening and closing figures are within 3 degrees of the Triunph factory figures for the 3134 cam (Triumph say +/- 2.5 degrees) close enough?

I have to ask what does "certa cito" mean?

Anyway have a good easter break


1969 BSA A65 Lightning
Triton (in build)
Re: Cam timing help [Re: Enigma] #369547
04/23/11 12:35 am
04/23/11 12:35 am
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t120mike Offline
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Enigma,

Strange, isn't it that the LC seems to change with different amounts of lift. Could be backlash or hysteresis or possibly that one side of the cam is not quite a mirror image of the other.

You are there or thereabouts and probably won't get closer by switching keyways. Result!

Also, now you know that you don't have a valve clearance issue, you can sleep better!

"Certa cito" (Swiftly and Surely) is the motto of the Royal Corps of Signals and Hughie was in the White Helmets Motorcycle Display Team during National Service both as a display rider and chief mechanic.

Happy Easter to you, too!

Last edited by t120mike; 04/23/11 12:36 am. Reason: manners!

mike
Member #: 147
1960 T120 Bonneville
1999 H*%^a VFR 800 FI
V4 Triton Project (still keeping me sane (Ha-Ha!))
Re: Cam timing help [Re: t120mike] #369658
04/23/11 6:54 pm
04/23/11 6:54 pm
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Enigma Offline OP
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Hi Mike

Stafford show was packed! and very hot, picked up a couple of items for the Triton project. Sorry I did not see Hughie (if he was there I still would not know him if I saw him)!

I am going to try and get the top end built up this weekend now that I am happy with the timing and the piston to valve clearance, thanks for all the information.

Any chance of posting some photos of your V4 Triton project?

Once again thanks.


1969 BSA A65 Lightning
Triton (in build)

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