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TR6 valve spring length #773929
05/16/19 5:47 pm
05/16/19 5:47 pm
Joined: May 2018
Posts: 22
Louisiana
G
GeauxTwins Offline OP
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GeauxTwins  Offline OP
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G

Joined: May 2018
Posts: 22
Louisiana
Hi, I'm rebuilding my 1971 TR6R head.

My workshop manual says Outer springs free length 38mm and 39mm for the Inner ones but it doesn't give any mini / maxi free length.

My Inners are ranging between 37 and 38mm so 1 to 2mm less than the spec. Should they be replaced?

My Outers are ranging between 40 to 41mm so 1 to 2mm longer than the spec. Should they be replaced?

Thanks


Trophy 67, A65T 70, T100C 70, TR6R 71, Daytona 72
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Re: TR6 valve spring length [Re: GeauxTwins] #774085
05/18/19 7:36 am
05/18/19 7:36 am
Joined: Oct 2003
Posts: 3,725
Emsworth, sunny south of Engla...
D
dave jones Offline
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dave jones  Offline
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D

Joined: Oct 2003
Posts: 3,725
Emsworth, sunny south of Engla...
I was interested in this so have been looking through my manuals, etc, and also a special manual written by someone at the Triumph Corporation (USA) for bikes to 67 written in that year so similar to yours. I can't find anything other than if they are not to the book spec then they should be replaced.

Re: TR6 valve spring length [Re: GeauxTwins] #774205
05/19/19 6:33 pm
05/19/19 6:33 pm
Joined: Jan 2017
Posts: 695
Pleasant Hill, California USA
T
TR7RVMan Offline
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TR7RVMan  Offline
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T

Joined: Jan 2017
Posts: 695
Pleasant Hill, California USA
Hi GeauxTwins, I have observed this discrepancy in spring length also, in both T120 & T140 motors. I have reassembled them with the original springs without issues many times. However if you take the motor to 7000 redline, perfect springs become very important.

Also fitted spring length is important as it directly effects tension.

The length test is only part of the spring evaluation. A rough estimation of spring strength at best. Makes it very hard when real life is not matching specs in manual. The more important test is actual spring tension. You can jury rig that on a bathroom scale to get an estimation of tension, but an actual valve spring tester is the way to go.

Most automotive machine shops will have spring tester. If you're wanting a real test, call & see if they can help you.

I worked at an automotive machine shop & we tested every spring during valve jobs. Was interesting at how some passed well & others failed. This could be on same motor.
100% of time we checked fitted spring length.
Don


1973 Tiger 750
Re: TR6 valve spring length [Re: GeauxTwins] #774222
05/19/19 8:30 pm
05/19/19 8:30 pm
Joined: Feb 2014
Posts: 1,272
Lancaster, California
C.B.S Offline

Parts Dealer
C.B.S  Offline

Parts Dealer

Joined: Feb 2014
Posts: 1,272
Lancaster, California
For the average rider or "Joe" I personally wouldn't worry about 1MM

However, I would focus on the installed height and the installed valve seat pressure

If your springs fall short, you can always add shims or booster under the valve spring cups to compensate

There appears to be different specs used throughout the years, I suppose with a stock cam you would want 75-80# @ the installed height figure

Keep in mind seats get cut and will change the installed height figures

I would contact Dan over @ Franz & Grubb with your question and perhaps you can get some new Kibblewhite springs from him

I hope this helps!


[Linked Image]
Re: TR6 valve spring length [Re: GeauxTwins] #774235
05/19/19 9:36 pm
05/19/19 9:36 pm
Joined: Jan 2004
Posts: 4,074
ca, us
D
DMadigan Offline
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DMadigan  Offline
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D

Joined: Jan 2004
Posts: 4,074
ca, us
You can easily make a spring tester using a pressure gauge and a piston with a 1.128" diameter.
[Linked Image]
It does not return to zero due to the seal friction but it is fairly accurate and is repeatable. Comparing 48 lb of lead block on a digital scale it is 1 lb low.
You can measure the spring height for the seat pressure and check the maximum lift force in a vice.

Re: TR6 valve spring length [Re: GeauxTwins] #774265
05/20/19 5:38 am
05/20/19 5:38 am
Joined: Jan 2017
Posts: 695
Pleasant Hill, California USA
T
TR7RVMan Offline
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TR7RVMan  Offline
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T

Joined: Jan 2017
Posts: 695
Pleasant Hill, California USA
Hi Madigan, I think I'd like to make one. Do you have a plan you could post? How is piston sealed? How much stroke does piston have? What keeps piston from falling out? What is piston pushing on? Oil, grease or ??

I used the old fashioned ones like a little press with a lever. The dial was calibrated in # of spring pressure not PSI, but I can see what is happening here. I just learned these are commonly sold on eBay. I have both steel & aluminum on hand in suitable sizes so I can make for cost of seal ring & gauge.
Don


1973 Tiger 750
Re: TR6 valve spring length [Re: GeauxTwins] #774289
05/20/19 11:28 am
05/20/19 11:28 am
Joined: Feb 2014
Posts: 1,272
Lancaster, California
C.B.S Offline

Parts Dealer
C.B.S  Offline

Parts Dealer

Joined: Feb 2014
Posts: 1,272
Lancaster, California
The old fashion one is a Rimac valve spring tester, sometimes they come up on eBay

Very handy units


[Linked Image]
Re: TR6 valve spring length [Re: GeauxTwins] #774313
05/20/19 5:52 pm
05/20/19 5:52 pm
Joined: Jan 2004
Posts: 4,074
ca, us
D
DMadigan Offline
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DMadigan  Offline
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D

Joined: Jan 2004
Posts: 4,074
ca, us
I have to see if I still have the drawing. Simple enough, the wall thickness of the aluminum has to accommodate the 1/4 NPT of the gauge. Mine is 2" diameter, 1.55" long. The piston seal is an O-ring but a quad-ring would give less stiction. I left 0.2" for stroke but that is more than needed. It depends upon how much fluid the gauge needs and how much air you leave in the chamber. A 10-32 flat head screw in back is for filling with Marvel Mystery Oil.
Vacuum holds the piston in.

Re: TR6 valve spring length [Re: DMadigan] #774414
05/21/19 10:17 pm
05/21/19 10:17 pm
Joined: May 2018
Posts: 22
Louisiana
G
GeauxTwins Offline OP
BritBike Forum member
GeauxTwins  Offline OP
BritBike Forum member
G

Joined: May 2018
Posts: 22
Louisiana
Hi Guys,
Sorry for my late reply and thanks for the all the great advices.

Yes, I totally agree I should check the spring lengths when valves are closed
Not sure how to do it with a simple caliper with the top and bottom cups/collars installed
I might have to buy one of those special micrometers you fit in around the valve's stem instead of the springs to get that "valve closed length" then check the psi on a spring bench at that same "valve closed length".

I'm scouting around for a spring test bench too. Machine shops have ones but they're asking more than for a set of Kibblewhite! So, I'm going to try putting together a DM set-up or buy one if I fail!
The Rimac or similar are perfect but too expensive just to re-built two TR6 heads (however I have two spare A65 and T100R to do).

On the TR6R 71, I can feel the two exhaust ports are recessed so I can't avoid a "valve closed length" measurement for a good shimming.

So, I need to find a way to measure that "valve closed length", access or buy a spring load tester, buy a set of STD new springs, test them and if bad get the Kibblewhite!

Keep you updated,
Thanks again,
GT


Trophy 67, A65T 70, T100C 70, TR6R 71, Daytona 72
Re: TR6 valve spring length [Re: GeauxTwins] #774461
05/22/19 3:13 pm
05/22/19 3:13 pm
Joined: Jan 2004
Posts: 4,074
ca, us
D
DMadigan Offline
BritBike Forum member
DMadigan  Offline
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D

Joined: Jan 2004
Posts: 4,074
ca, us
If there is interest, I can make the piston and body and you can supply the gauge for the tester. Gauges are usually available on the surplus market fairly cheap. eBay lists a 2-1/2" diam. 200PSI gauge 2-1/2% accuracy for $11.

Re: TR6 valve spring length [Re: GeauxTwins] #774476
05/22/19 6:49 pm
05/22/19 6:49 pm
Joined: Jan 2013
Posts: 223
Frazier Park, CA
C
Chris Johnson Offline
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Chris Johnson  Offline
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C

Joined: Jan 2013
Posts: 223
Frazier Park, CA
Mail-em to me and I’ll throw them on my Rimac if you just need to know on the cheap.

Chris

Re: TR6 valve spring length [Re: Chris Johnson] #774634
05/24/19 10:10 pm
05/24/19 10:10 pm
Joined: May 2018
Posts: 22
Louisiana
G
GeauxTwins Offline OP
BritBike Forum member
GeauxTwins  Offline OP
BritBike Forum member
G

Joined: May 2018
Posts: 22
Louisiana
Chris and DM, thanks for your offers. Appreciate.

Just got the TR6 1967 back from soda blasting and its clear one exhaust valve guide is cracked and all 3 other valves are rocking into their guides. Going check the stems diameter but pretty sure it's the guides. That 67 bike is a barn find I just got for 350$ so never cranked it up yet but bike is 95% complete! The head was off when I picked it up and had a hard time to get both exhaust valves out. Rocker boxes were missing so couldn't look at them but probably an oil feed issue.

On the TR6 1971 head I have a snapped exhaust guide as well. Not cracked up/down like the 67 but in 2 parts inside the springs. Never saw that before.

So let me address those guide problems before looking at the spring lengths and PSI

Few new questions to you all:

#1 - I never removed valve guides from a Triumph. Should I use the special 5/16 drift tool and banging on it or thread those guides at 9mm or else then use a bolt/tube/washers/nut for extracting?

#2 - Do I need to heat up locally the head around the guides?

#3 - On both heads I have cast iron guides. Better to switch to bronze ones?

Best,
GT


Trophy 67, A65T 70, T100C 70, TR6R 71, Daytona 72
Re: TR6 valve spring length [Re: GeauxTwins] #774641
Yesterday at 01:29 AM
Yesterday at 01:29 AM
Joined: Nov 2008
Posts: 2,926
Bishop, Calif.
D
desco Offline
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desco  Offline
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D

Joined: Nov 2008
Posts: 2,926
Bishop, Calif.
The single biggest improvement you can do to a Triumph is a proper valve job. People have, and still do, this themselves. But to get the full benifit today you pretty much need access to the zillion dollars of machines needed to get it right. I have always sent the head out to someone who specialilzes in Triumph heads. Spendy? Yes. But it lasts forever and makes them scary quick. Now that I am retired I will probabley have to learn to do it myself.


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
Re: TR6 valve spring length [Re: GeauxTwins] #774649
Yesterday at 03:39 AM
Yesterday at 03:39 AM
Joined: Jan 2013
Posts: 223
Frazier Park, CA
C
Chris Johnson Offline
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Chris Johnson  Offline
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C

Joined: Jan 2013
Posts: 223
Frazier Park, CA
My thoughts:

New springs are cheap, no need to reuse old ones.
If your guides are that worn, so are your valves. Again, new ones are cheap.
I’m sold on the bronze guides. The 630 bronze guides from kibblewhite are really nice.

Aluminum expands at a greater rate than cast iron. Heat the head a couple hundred degrees, evenly, and they should come out easily. A drift may help. It’s good practice to bead blast any accumulated carbon from the port around the guide first.

You need to be able to measure the guide bore in the head to determine which oversize, if any is needed for each guide. If you aren’t tooled up, have a good shop fit the guides and cut the seats.

Chris


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