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t120 Cylinder head dilemma
#713990 11/06/17 12:11 am
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slofut Offline OP
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Got this head off eBay, nice plug and play it said, less than 200 mi, unleaded conversion by Rask Cycle etc. Got an invoice with over $600 worth of parts and labor, new valves, seats and guides I think.

https://www.eBay.com/itm/Triumph-650-Twin-Carb-T120-1966-Cylinder-Head-Rask-Cycle-Unleaded-Gas-Conv-/282659059723?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=3uAWpsvJLqV4Qkf1oXXIW1nEW3s%253D&orig_cvip=true&rt=nc

First thing I noticed was the divots in the valve stem ends. The exhaust side doesn't feel deep at all, the intake side the divots are perceptible with the fingernail, but barely. My question... is this kind of wear common for less than 200 mi? Is it ok, or can or should the ends be flattened? A message to the seller revealed that the head was on a bike with aftermarket adjusters and cam. Could this be a valve train geometry problem?

Now, also the valves look much closer to the chamber surface than normal, like they could be too high? Almost proud of the surface. Am I worrying for nothing?

[Linked Image]Untitled by Bill Smith, on Flickr

[Linked Image]Untitled by Bill Smith, on Flickr




[Linked Image]Untitled by Bill Smith, on Flickr



[Linked Image]Untitled by Bill Smith, on Flickr


Here's a link to the Flikr album where you can see the rest of the pics.
https://www.flickr.com/photos/[email protected]/albums/72157684457096686/with/38167155422/


'68 Bonnie, '70 TR6r
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Re: t120 Cylinder head dilemma
slofut #714000 11/06/17 2:04 am
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I would be inclined to contact Rask Cycle with a link to your pictures.

Maybe those valves needed lash caps but removing the valves and taking a look at the seats would not hurt, you would then know how they are and stem to guide could be checked.
A quick check with blue (or fine compound I guess) would soon show you where the margins (placement and width) are on the valve faces.

Re: t120 Cylinder head dilemma
slofut #714003 11/06/17 3:01 am
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"A message to the seller revealed that the head was on a bike with aftermarket adjusters..."

The top end of Triumphs need very little oil to run properly, but it does need to be deposited in very specific places. One of those places would be the valve tips.

Are the rocker boxes set up with the thrust and thackery washers in the proper order? Are there divots machined in the sides of the rocker arms?

Perhaps the engine was started after rebuild with no oil or or assembly lube used in the top-end?


Steve


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Re: t120 Cylinder head dilemma
Les P #714022 11/06/17 12:32 pm
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Originally Posted by Les P
I would be inclined to contact Rask Cycle with a link to your pictures.

Maybe those valves needed lash caps but removing the valves and taking a look at the seats would not hurt, you would then know how they are and stem to guide could be checked.
A quick check with blue (or fine compound I guess) would soon show you where the margins (placement and width) are on the valve faces.


Les, that's a good idea to contact Rask. I'd rather not have to send the head out to them. Hopefully they will remember this head. I do have their invoice detailing the work too. This is the third head I've bought trying to get a plug and play head
you'd think I'd have learned my lesson already. crazy I thought this was one I could use and not have to disassemble but obviously I do need to check valve seats. One thing for sure, all parts here are new, and the seller says it actually has about 100 miles on it. ...which brings up obvious questions.

Last edited by slofut; 11/06/17 3:45 pm.

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Re: t120 Cylinder head dilemma
JubeePrince #714026 11/06/17 12:44 pm
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Originally Posted by JubeePrince
"A message to the seller revealed that the head was on a bike with aftermarket adjusters..."

The top end of Triumphs need very little oil to run properly, but it does need to be deposited in very specific places. One of those places would be the valve tips.

Are the rocker boxes set up with the thrust and thackery washers in the proper order? Are there divots machined in the sides of the rocker arms?

Perhaps the engine was started after rebuild with no oil or or assembly lube used in the top-end?

Steve


Thanks Steve,
Oiling or assembly lube could be a possibility, maybe it's why the motor is without a head after 100 miles, maybe the motor crapped out from poor assembly. I didn't get the rocker boxes with the head so idk about the state of things when it was assembled.
The washers would locate the rockers properly on the shafts, thus placement on the valve tips correct?
Is there a detailed illustration of this? I'm not sure I knew there were different style washers here. It's been about six years since I was into my bike but I'll want to revisit rocker box details before I put them on. I have to sort through push rod tubes and seals too, the head on my bike now is a '72 with roll pins but with early style rocker boxes. I want to make sure I get it all back together correctly the first time.


'68 Bonnie, '70 TR6r
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Re: t120 Cylinder head dilemma
slofut #714032 11/06/17 1:49 pm
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I wish you the best of luck with that head, I've personally always avoided those with replaced seats- but I'm not sure why. Maybe because the only two I've ever seen have failed badly. They still sit on the shelf, and came to me that way.One was done poorly, way off center, and the other the new seat backed out. At least yours looks like it was done correctly. I think Rasks' was around when I was a kid, and that's been awhile, along with Romans cycle.

Re: t120 Cylinder head dilemma
slofut #714033 11/06/17 1:51 pm
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I’ve been warned about some readily available replacement valves that do exactly this in short order. I wasn’t given a brand name but anymore I try to stick with G&S or premium brands like Kibblewhite. Any record of the valve brand used in this head?

Chris

Last edited by Chris Johnson; 11/06/17 1:52 pm.
Re: t120 Cylinder head dilemma
Chris Johnson #714046 11/06/17 3:49 pm
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Originally Posted by Chris Johnson
I’ve been warned about some readily available replacement valves that do exactly this in short order. I wasn’t given a brand name but anymore I try to stick with G&S or premium brands like Kibblewhite. Any record of the valve brand used in this head?

Chris


Chris, the part numbers on the invoice indicate Kibblewhite valves at $36 each.


'68 Bonnie, '70 TR6r
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Re: t120 Cylinder head dilemma
slofut #714049 11/06/17 4:47 pm
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I just put in a set of Kibblewhite valves and guides, they should look like this:
[Linked Image]
The indents on the valve tips will happen with any spherical tip adjuster due to the point contact although yours is severe for "less than 200 miles". You have to grind the tips to remove them or they will wear your new adjusters. You can put on lash caps but have to check there is enough clearance to the cover. Elephant Foot adjusters have a foot that covers the top of the valve so they do not dig into the valve tips.
I would take out the valves and at least check the stem clearance and spring pack. The valve margins and seating should be checked also.

Re: t120 Cylinder head dilemma
slofut #714056 11/06/17 5:22 pm
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Thanks D,
That's what I was afraid of. Talked to the seller again and he said the it was on a running motor with a morgo 750 kit with a megacycle cam with more duration but no more lift. Parting out the bike due to age and retirement. Got an email in to Gary at Rask hoping to get a reply. I may have to send it back to them for a refresh and peace of mind.

I wonder also if those valve spring retainers would cause higher spring pressure and shorter compression length? Compared to yours it looks a possibility.

Last edited by slofut; 11/06/17 5:28 pm.

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Re: t120 Cylinder head dilemma
slofut #714058 11/06/17 5:37 pm
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Originally Posted by slofut

The washers would locate the rockers properly on the shafts, thus placement on the valve tips correct?

Yes.

Originally Posted by slofut

Is there a detailed illustration of this? I'm not sure I knew there were different style washers here. It's been about six years since I was into my bike but I'll want to revisit rocker box details before I put them on. I have to sort through push rod tubes and seals too, the head on my bike now is a '72 with roll pins but with early style rocker boxes. I want to make sure I get it all back together correctly the first time.


The assembly of the washers (thrust and thackery) changed when Triumph went from the drilled rocker arms to the solid arms with the machined divot. If you assemble the rocker box with the machined arms using the drilled arms washers, the valve tips won't get enough oil on them.

Drilled arm rocker boxes used three thrust washers with ID of 1/2" and one with ID of 3/8". In order to assemble the machined arms correctly, get rid of the 3/8"ID washer and just use four 1/2"ID. If you don't replace the 3/8" washer, it will foul on the shoulder of the spindle on assembly.

Some parts manuals show the incorrect part # and/or the correct order of assembly (not that we should be relying on the parts manuals for assembly instructions!). The four thrust washers need to be on the ends of the rocker arms. The two thackery washers go between the rocker box itself and the outer thrust washers. This will ensure the divots machined in the arms direct oil flow to the valve tips.

As a final note, the only way to fully ensure the valve tips won't get knackered again, even with the washer change is to replace the rocker box spindles with the ones made for the T140. They have a groove machined in them to help with oil flow. You will need new acorn nuts too, b/c the T140 spindle's threads are UNF, the 650's are CEI.

Good articles on valves and valve seats:

http://vintagebikemagazine.com/wp-content/uploads/2017/07/GSvalvearticle.pdf

http://vintagebikemagazine.com/wp-content/uploads/2017/06/650-750head.pdf

Cheers,

Steve


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Re: t120 Cylinder head dilemma
slofut #714059 11/06/17 5:42 pm
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Originally Posted by slofut

I wonder also if those valve spring retainers would cause higher spring pressure and shorter compression length?


Spring pressure is easy enough to check with an analog bathroom scale and small piece of oak or other hardwood.

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
Re: t120 Cylinder head dilemma
slofut #714060 11/06/17 5:45 pm
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Interesting that "mushroom" head adjusters would do this. It is problem they were supposed to be a solution for. I think Steve is on to something. The proper location of the washers ensure proper oiling.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: t120 Cylinder head dilemma
slofut #714077 11/06/17 7:43 pm
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I never had Kibblewhite valves tips looking like that.
They suppose to have stellit tips much harder than material of any adjuster preventing them from being smashed.
Even my Trident old Kibblewhite valves didn't look like these new ones and Trident valve geometry makes all the ordinary valve tips smashed to smithereens in quick order.
I'd ask Kibblewhite what's going on.

Re: t120 Cylinder head dilemma
slofut #714082 11/06/17 8:17 pm
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Wow thanks Steve, that's a lot of info and much appreciated. Worth the price of admission right there! I'll definitely make sure I have t140 shafts and nuts. And I'll check spring pressure. I'll know more on my rockers when I pull them off my bike and I'll make sure they're correct.

Bob, the seller just said they were aftermarket, he didn't elaborate and I doubt they were mushroom style because as you said, they couldn't really make marks like that on the valve tips. ...unless the mushrooms fell off. But I think you're right, the rockers may have been assembled incorrectly. The pattern on one tip is kind of random, all over the place like a rocker is floating laterally by a few thousandths. I'm thinking too that maybe he had adjusters with pointed tips, and with no oil.

And now I'm thinking the guy had this head work done many years ago... The corner of the invoice with the date has been torn off.


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Re: t120 Cylinder head dilemma
slofut #714103 11/06/17 10:01 pm
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Adam, I agree about the valves having stellite tips. The more I think about it, the more I'm thinking I should send the head as is to Rask for inspection and to make it so I can install it without issues. Although, I'm sure they will charge me going rate to fix it, and in that case I might do just as well to send it to Frank Deihl since he's closer. But then again, Rask installed the valve seats, so they may be more aware of potential problems there and can rectify. [***]... idunno.


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Re: t120 Cylinder head dilemma
slofut #714114 11/06/17 10:36 pm
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Stock adjusters on stock valves make those type of wear marks. Neither the adjusters or valve tips were hardened. A spherical tipped adjuster is a point contact. Triumph went to the Ducati style adjuster with the truncated ball to reduce wear. Porsche used EF adjusters until they went to hydraulic tappets on later 911 engines.
Here are the available types of adjusters:
[Linked Image]
The stock style are the left two, the T160 "Ducati style", the Elephant Foot and mushroom is on the right.

Re: t120 Cylinder head dilemma
DMadigan #714196 11/07/17 4:52 pm
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Thanks D,
I appreciate the pic, that explains a lot. There's an automotive engine rebuilder across the street from me, or a really nice machine shop/fabricator about 15 miles from me. I think I'm going to pull these valves and have the tips leveled, clean up everything, check spring pressure and height and put it back together. I filled the chambers with kerosene and let it sit overnight with no leakage. I could lightly lap the valves, but I hate to as the contact pattern is fine. I'll get t140 rocker spindles and the ducati or EF style adjusters if they'll fit.

Here are a few more pics...

[Linked Image]


This is in the bottom below the valve spring, I think I know why the seller was parting out the motor.


[Linked Image]



[Linked Image]


[Linked Image]


[Linked Image]


[Linked Image]


[Linked Image]


[Linked Image]IMG_6988 by Bill Smith, on Flickr


'68 Bonnie, '70 TR6r
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Re: t120 Cylinder head dilemma
slofut #714208 11/07/17 6:40 pm
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Hi Bill, I've studied all your Flick pics and posts etc. I must start with the caveat that most of my cylinderhead experience is with pre-unit T120's.

As I understand it, the engine that has been parted to provide this head was somebody's go at a bit of a hottie, with big-bore, mega cams etc, and as it's no longer together may suggest the "more of everything" approach was not a great success.

Looking at the valves in the chambers, they look very big compared to what I am used to seeing.

The valve spring top collars are non-standard of course, I can't tell whether they are alloy or steel, but whatever they look as if they'd result in more preload on the springs.

The springs themselves look unusual, when free the coils seem much further apart than usual, which suggest a heavier spring rate.

The lower spring "cups" look more like washers/spacers. They should cup/retain the spring bottoms to stop them moving about. This may explain the obvious damage in the lower spring cavities, where metal has been ground away, either by the spring or the bottom collar.

Have a look on the sides of the springs and bottom collars, you may find witness marks of this contact. I think this is where your metallic debris came from.

I suspect the PO went for mega cams, mega valves and mega spring pressure. Rapid wear of valve tips/adjusters would be quite understandable.

Possibly the macho venture ended in some mechanical disaster, broken rocker arm or worse. Good motors don't get broken for no reason.

I reckon you could be ok with that head if you go back to standard spring bits from your old head, as long as the "maybe" bigger valves clear the pistons. It may actually turn out pretty good!

Dave

Re: t120 Cylinder head dilemma
koan58 #714222 11/07/17 8:30 pm
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Thank you Dave,
The lower spring cups are "cups" and they do center the springs ok but the springs have made witness marks like they may be bigger. Top retainers are alloy. Those valves do look quite a bit bigger. I suppose they were ok as far as piston to valve clearance as the previous bike ran 100 miles, contact would have been catastrophic instantly. And I did ask him the question of piston/valve clearance along with if a thicker head gasket was required. His reply was that the Morgo barrels came with a different head gasket but that nothing different was required for valve to piston clearance. So I have a head with big ass valves... I can't get a break, like carb jetting and tuning isn't hard enough with everything stock. I'm going to check spring pressure as suggested by Steve, with a bathroom scale. I have some used springs from another head that I'll use to compare.


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Re: t120 Cylinder head dilemma
slofut #714225 11/07/17 8:55 pm
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Bill, I think you're probably ok, assuming everything measures up wear-wise. Use std spring bits and check everything compared with your old head, dimension wise. It may turn out to be rewarding!
I don't think the bigger valves will make much difference to carb jets etc, possibly a little more on the main, maybe not even that. Let us know how it goes. Dave

Re: t120 Cylinder head dilemma
slofut #714233 11/07/17 10:14 pm
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A bit more info...

Tips dressed
[Linked Image]


Hi-po vs stock springs
[Linked Image]



With the bottom cups on each set, there is 1/8" difference. Hi-po is 2", stock is 1 7/8". The diameters are the same on the outer springs, the hi-po springs will fit in the stock bottom cups.
[Linked Image]

The valves are the same diameter...

[Linked Image]

[Linked Image]


But the free length of the springs are much different, the hi-po springs are taller but with a thin bottom cup so the assembled length to the top of the springs are close between the two. But with the top retainers on the hi-po springs are slightly taller. From initial tests, the hi-po springs are a good bit stronger than the stock ones, which could account for the rapid valve tip wear, especially if the guy raced the bike
facepalm


[Linked Image]


'68 Bonnie, '70 TR6r
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Re: t120 Cylinder head dilemma
slofut #714292 11/08/17 6:18 pm
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Interesting extra pics and info Bill! Another interesting one would be the invoice for the head work, assuming it gives some detail of the work/parts?
Just redact anything private.

As far as can be seen, the work appears to be decent quality. That the valves turn out to be std size was a surprise, maybe my caveat applies.

The spring setup is unusual though. The springs look weird, but I'm no expert. I can envisage them being prone to "grow" width-ways on compression, as well as tending to "warp slinky-wise" when fully compressed. The combination of these may account for the wear, where they have been distorting out of cylindrical shape enough to make serious, undesirable contact with the head metal.

Added to this, the bottom collars do not seem to be cupped at all, as you describe they centrally locate the springs. This doesn't fully prevent the bottom of the spring, especially when it has grown under full crush, from being able to wander off-centre.
This could cause tipping imbalance on the bottom collar (the supporting ring of head around the guide is narrow) which would then encourage the spring to "slinky" in that direction and hit the head. I guess Triumph had reasons to make the bottom collar a retaining cup.

On the subject of the head support ring for the bottom cup being narrow (perhaps to minimise heat transfer to the springs?) some of your pics show possible evidence of that cup wobbling, in that the head surface outboard of the guide seems smoothed down. Or maybe it's just that the guide angle is a bit steeper than original (search John Healy's stuff about inserting guides and how they can wander off-course), this could also put the spring assembly closer to that gouging area.

I think you have more measuring and comparison with your standard heads to do, eg how far do the valve stems protrude from the head, are the collett positions at the same point on the valves, wobble of valves in guides etc. I do think the valves would benefit from a fine lap, it's hard to see the seating surfaces clearly in the pics so far.

If measurements are close to normal, I'd say go with std springs and retainers, I think you'll be ok.

Dave

Re: t120 Cylinder head dilemma
slofut #714294 11/08/17 6:35 pm
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just making it a hot rod isnt enough to mess up the motor. my old 72 T120 has the big bore, big valves, way too stiff springs (oops), and a higher lift cam, and it's stayed together for 30 years that way with the head off for a valve job once.

i think the metal particles you found indicate some dirty assembly in its history, and that will certainly cause difficulties.


I would rather be ashes than dust
Re: t120 Cylinder head dilemma
slofut #714297 11/08/17 6:48 pm
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Thank you Dave,
The bottom retainers don't have sides, like you said. The only thing keeping the outer springs in check is the internal spring and it's located by the center of the bottom retainer. Still for the life of me I can't see how the outer springs ever contacted the head casting, but it looks like all four have done it. Even at full squish the spring doesn't grow that much. It has to be dancing around. They have to go, I'll set it up with standard springs from the other good head and see how it looks. In the mean time I'll take measurements to check guide positions etc... I'll look at your point about the bottom collar wandering, that could be suspect. I wonder where these springs and retainers came from? Has anyone ever seen them before?

It is funny how those valves do look larger in the head than standard.


'68 Bonnie, '70 TR6r
'74 CL360
trail 70's and minitrails
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