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72 T120 eating exhaust cams #435488
05/17/12 4:46 pm
05/17/12 4:46 pm
Joined: May 2002
Posts: 688
Winston-Salem N.C.
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D.W.R. Offline OP
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D.W.R.  Offline OP
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Posts: 688
Winston-Salem N.C.
Put a cam and tappets in this bike a year ago because of one of the lobes being worn (replaced with good used cam/tappet). A couple of months later installed a Morgo 750 kit, noticed it didn't have the passage drilled for the tappet block oiler, dealer said it wasn't needed! Both lobes and tappets shot in about 2,000 miles, intake looks great. Engine is totally stock except for Morgo cyl./pistons/oil pump. What's up here?
Don R.

Last edited by D.W.R.; 05/17/12 4:49 pm.
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Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435495
05/17/12 5:14 pm
05/17/12 5:14 pm
Joined: Aug 2001
Posts: 7,419
scotland
triton thrasher Online content
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scotland
Could be you didn't have nitrided cams.


Amateur Loctite enthusiast.
Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435496
05/17/12 5:15 pm
05/17/12 5:15 pm
Joined: Nov 2008
Posts: 2,794
Bishop, Calif.
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desco Offline
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Bishop, Calif.
With out the oiler you will need hardend cams and tappets. New is preferred. On that used cam, if you did not get the same tappet on the same lobe and in the same direction as original that can screw them up pretty quick even with the oiler.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435521
05/17/12 7:03 pm
05/17/12 7:03 pm
Joined: Mar 2005
Posts: 10,130
Boston, Massachusetts
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John Healy Offline

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John Healy  Offline

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Posts: 10,130
Boston, Massachusetts
Where did you get the cams?

Did you use a good cam lube during installation?

You didn't turn the engine over without any lubricant on the tappets and camshafts?


Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435533
05/17/12 8:57 pm
05/17/12 8:57 pm
Joined: May 2002
Posts: 688
Winston-Salem N.C.
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D.W.R. Offline OP
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Winston-Salem N.C.
Thanks, my first thought was a non-nitrided cam. Thought '72 should have them, someone else was in there before me so who knows what was in there(first cam that went)? Don't know the year of the second cam, only that it was the same stock grind. And yes John I use good lube and no, I didn't turn anything without any, not a nube smile! I was however trying to save my buddy some money frown. I've suggested a NEW cam, tappets and tappet block just to cover all the bases. Valve springs are stock, correct installed height and all that. No problems what so ever on the intake side. How can I be sure I'm getting a nitrided cam? All vendors are not created equally, sadly!
Thanks
Don

Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435535
05/17/12 9:22 pm
05/17/12 9:22 pm
Joined: May 2010
Posts: 2,579
Illinois, USA
TR6Ray Offline

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Illinois, USA
Speaking of cam lube, I have read on here that there is a big difference between regular assembly lube and cam lube. Anybody care to explain what the difference is, and what is a recommended brand of cam lube?


'64 TR6R Plus some Twins from other countries (U.S., Germany, Japan)
Re: 72 T120 eating exhaust cams [Re: TR6Ray] #435562
05/18/12 12:06 am
05/18/12 12:06 am
Joined: Nov 2008
Posts: 2,794
Bishop, Calif.
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desco Offline
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Bishop, Calif.
http://www.megacyclecams.com/

They've been making cams for Triumphs for 50 years.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: 72 T120 eating exhaust cams [Re: desco] #435566
05/18/12 12:36 am
05/18/12 12:36 am
Joined: Sep 2011
Posts: 976
New Zealand
Excalibur Offline
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Excalibur  Offline
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New Zealand
It's good insurance to hardness test cams. Usually I get a toolmaker to check the Rockwell hardness. In recent years, there's been lots of new cams which are soft from the word go.
I test both new or used, because you just never know and often times the parts people don't care.
I'd make it clear to your parts supplier that if it doesn't pass Rockwell, it goes immediately back.
Every time I go to get some cams tested I have to scratch my head re the satisfactory Rockwell figure. I think it's 50something. Can someone please correct me with the satisfactory figures, thanks.

Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435615
05/18/12 10:44 am
05/18/12 10:44 am
Joined: Jul 2009
Posts: 3,549
Vic. Australia
P
Pete R - R.I.P. Offline
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Vic. Australia
Originally Posted By: D.W.R.
I've suggested a NEW cam, tappets and tappet block just to cover all the bases. Valve springs are stock, correct installed height and all that.


I'll suggest that you don't use the "corrrect" installed height,as found in the manual.It's just unnecessarily high pre-load (Seated: 87lbs EXHAUST,75 lbs INTAKE),and I haven't found those pre-loads on a stock engine.

I believe 75 lbs EXHAUST,65 lbs INTAKE is more than enough.70lbs,65lbs would probably do.You will easily see 8000 rpm with that,if everything else is OK.I've gone close to 8000 in top gear with around 55-60 lbs intake,65-70 lbs exhaust.

Re-ground tappets,cam lube and not less than 2000 rpm for the first 20 minutes should do.Cam part nubers should tell you if they're nitrided.I like the idea of a hardness test too,although I've never had to.I did test one a long time ago,but I forget what the results were.The depth of hardening was around 0.017"

Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435625
05/18/12 12:24 pm
05/18/12 12:24 pm
Joined: May 2006
Posts: 509
melbourne, australia
7
76degree-triumph Offline
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Posts: 509
melbourne, australia
Interesting question.
Did cams and followers last more than 2000 miles in any pre unit trumpy using the 3134 cam and/or 'R' followers.
I suspect they did.
Where nitrided cams needed or was it piss poor heat-treatment from the factory?
Stock springs to much for the lobes?
Nah.
Regardless of the Morgo kit, if all else is STD triumph and the exh cam/ followers are stuffed within 2k miles then you have coil binding or guide/keeper isues.


1950 Speed Twin outfit
1951 Thunderbird outfit (76 degree racebike, or is it 90 deg now?)
1955 BSA D3 minibike outfit
Triumph solo's
Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435638
05/18/12 1:36 pm
05/18/12 1:36 pm
Joined: Mar 2005
Posts: 10,130
Boston, Massachusetts
J
John Healy Offline

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John Healy  Offline

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Posts: 10,130
Boston, Massachusetts
To reiterate what Pete said. There is a popular after market valve spring set that will coil bind at normal valve lift (.345") if installed at 1 5/32" (1.156"). They need to be installed with at least 1.200" fitted length, or a bit more. They are sold under the Aerco Brand - PS104. When fit so they have enough spring travel they will not coil bind (with .060" plus clearance) they perform quite well.

Given that this is the second camshaft that has failed I would start measuring things.


Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435646
05/18/12 2:30 pm
05/18/12 2:30 pm
Joined: Mar 2005
Posts: 10,130
Boston, Massachusetts
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John Healy Offline

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Boston, Massachusetts
I have been looking at issues relating to this for a long time. Recently I have been looking at measurements I have taken over the years, new heads I have, etc. and the only thing I have found to be consistent is the length of the various valves on the market.

There are after market 750 heads in the market that were machined to the 650 condition and which should be using the 650 bottom spring cup. There are 650 heads (late 9 1/2 bolt) that are machined to the 750 condition machined out of left over castings that were in the basement of the old factory across the street that should be using the 750 bottom spring cup.

And factory heads that are machined all over the place. Much to Pete's disbelief I have a 750 head in near new condition that actually measures out so the fitted length of Intake spring is 1 7/32" and the Exhaust spring is 1 5/32". I am going to have to ship it to him in Australia before he will believe me. I agree with him it is an exception!

Then there are heads that have had valve jobs and seats replaced that have all sorts of dimensions. Some 40 years after these bikes were made it pays to look.

I am trying to document some of this stuff for an issue of Vintage Bike this fall... That is, if it is documentable.


Re: 72 T120 eating exhaust cams [Re: D.W.R.] #435996
05/21/12 12:38 pm
05/21/12 12:38 pm
Joined: May 2002
Posts: 688
Winston-Salem N.C.
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D.W.R. Offline OP
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D.W.R.  Offline OP
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Winston-Salem N.C.
I'm going to have to check the actual spring pressure on this thing. I assumed the springs were stock items, but maybe not! The engine had been gone through previously and some "non-factory" bits used, such as the pushrods. They were so long that one of the exhaust valves would just have the slightest clearance with the mushroom adjuster bottomed against the rocker arm! They went into the bin! The cams were supposedly replaced with Megacycle items, they were stock Triumph! I agree with what someone said about even soft (non-nitrided) cams shouldn't look this bad after 2k miles! Thanks to all for the insight and suggestions, we'll get to the bottom of this and I'll report my findings!
Don R.

Re: 72 T120 eating exhaust cams [Re: D.W.R.] #436010
05/21/12 2:59 pm
05/21/12 2:59 pm
Joined: Mar 2005
Posts: 10,130
Boston, Massachusetts
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John Healy Offline

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Boston, Massachusetts
You will also you will need to check coil bind height. There are springs on the market, if fitted to less than 1.200" will coil bind at stock lift (.345")!


Re: 72 T120 eating exhaust cams [Re: D.W.R.] #439868
06/12/12 2:36 pm
06/12/12 2:36 pm
Joined: May 2002
Posts: 688
Winston-Salem N.C.
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D.W.R. Offline OP
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Winston-Salem N.C.
I think I've found the problem! The owner ordered a set of proper valve springs at my request, stock Triumph pieces, green coded outers and red coded inners. Just a glance showed that the inners on the machine were wound of heavier wire though slightly shorter. A simple vice test showed the outers to be comparable in pressure, however the inners were significantly different with the ones previously fitted being at least 30% stronger by my estimation! They were not coil binding, but the pressure difference is significant. The same heavy wire inners were installed on the intakes so I'm not sure why we didn't have issues there, but I'm fairly confident that with the proper springs and a new properly nitrided exhaust cam that this particular problem is behind us! Thanks to all who commented and to John for his expert experience on these spring issues. I'll let you all know in a few weeks how things are working!
Don R.


71 Rocket 3
72 B50 MX
66-71 A 65 Bitsa
96 Trident 900
Re: 72 T120 eating exhaust cams [Re: D.W.R.] #439948
06/12/12 10:15 pm
06/12/12 10:15 pm
Joined: Jul 2009
Posts: 3,549
Vic. Australia
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Pete R - R.I.P. Offline
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Pete R - R.I.P.  Offline
In Remembrance
P
Joined: Jul 2009
Posts: 3,549
Vic. Australia
The standard springs will be at least 1/16" away from coil-bind on the exhaust,and 1/8" away on the intake;unless you shim them to less than the fitted height spec in the manual.

It would still be worthwhile checking the pre-load,once the springs are fitted in the head.This is easily done with bathroom scales.70 lbs seated load is really enough.


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