Valve Spring Discussion (groan!)

[andy230]

Hello to interested parties!

The ongoing saga continues.  I mentioned a lack of clearance between the inner and outer valve springs. 

The "indestructable, uprated, stanless valve springs" are... destructed!!

(Although the collets are new, and the retainers are certainly ally, possibly titanium, if such a thing exists.  Very light, and not at all marked by the spring compressor.)

Flats on the inside of the outer springs, and correspondingly the outside of the inner springs.

I am presuming with the Stage 4 cam, they MUST be uprated springs, especially if the motor has been raced as a 690, and made good power on the dyno...

Anyway, I was not sure what make/rate/etc the springs were, so measured them, and compared to the standard SRX data, all I had.

Outer: 42.2mm to 42.7mm  (41.8 to 43.

Inner 37.6mm to 37.7mm (38.1 to 40.1)

Will have to find XT600 2KF data for this, as its not actually a SRX head.  But I'm betting the standard data is the same.

So... Let the stupid questions begin!!   

1) How do I know if these are uprated springs??  Any way of telling?  Are std springs stainless??

2) Which uprated springs have others gone for?  May go to Kedo, as they have been kind enough to offer a discount.  How much are we talking here??!

2) Should uprated springs be longer?  Or just a higher rate??  Surely NEVER shorter?!

3) Do the springs get "fatter" as they get worn, ie. more compressed, thus explaining the lack of clearance between the inner and outer?

Cheers for now, will have a look at the valves tonight.  One appears not to want to come thru the guide, I think maybe its a bit mashed at the tappet end... Will try a bit of heat first, before crying.    I they they are standard too, from the "34K" and "5Y1" on the inner (combustion chamber) face.  Will measure and compare to SRX data, or XT if I can get it...

Cheers all.  I can hear the sound of money, going "plop plop plop" down the drain...!!   The scotsman is in dread!!!

a

[Steve H]

Andy,

I checked the springs fiited to the head that came with the Yoshi Stage II cam I have. There is no contact between the two springs. I dont know what make they are.
The springs are required for two reasons.
1- Increased lift. If you attempted to use the standard springs with the increased lift of your stage 4 cam they would just become coil bound and probably stop the engine turning over.
2 - It depends upon the grind but the extra duration may come at the expense of steeper closing/opening profiles, this will need strong springs in order to avoid float and keep the rocker in touch with the camshaft (or as close as possible).
Some cams also need modified guides to clear the spring retainers, but since your engine has already run with this cam presumably this isnt a problem 

As for makes of springs, I have used R+D in the past on an XL500. These were fiddly to fit and specified an installed height along with modified guides. A few aftermarket cam grinders seem to recommend Yoshimura springs, Ive no idea were to get them though. Do you know who did the grind ?, they should be able to recommend suitable springs.

[andy230]

Andy,

I checked the springs fiited to the head that came with the Yoshi Stage II cam I have. There is no contact between the two springs. I dont know what make they are.
The springs are required for two reasons.
1- Increased lift. If you attempted to use the standard springs with the increased lift of your stage 4 cam they would just become coil bound and probably stop the engine turning over.
2 - It depends upon the grind but the extra duration may come at the expense of steeper closing/opening profiles, this will need strong springs in order to avoid float and keep the rocker in touch with the camshaft (or as close as possible).
Some cams also need modified guides to clear the spring retainers, but since your engine has already run with this cam presumably this isnt a problem 

As for makes of springs, I have used R+D in the past on an XL500. These were fiddly to fit and specified an installed height along with modified guides. A few aftermarket cam grinders seem to recommend Yoshimura springs, Ive no idea were to get them though. Do you know who did the grind ?, they should be able to recommend suitable springs.

Hi Steve,

Thanks for that.  Hadn't realised std springs would become coil-bound.  Will compare with std SRX springs tonight.  I strongly suspect that the XT600(2KF) and SRX600 std springs will be the same item.

And yes, the cam has a very steep opening profile.  And generous overlap.

And re the guides, I think that because one isn't keen to come out (will try some heat first), maybe there will have to be some work done there anyway.  The exhaust valves are a bit "hammered" at the stem (from the tappet) so I think should be replaced.  Seats maybe very slightly burnt??

Inlet side is very clean tho, and the valves look good (cooler I spose).

Re the tracts, would you remove the (extensive, slightly "chipping") carbon from inside the exhaust port??  The inlet is very clean, exhaust is rough, with build up, etc.

a

[Steve H]

From memory my springs are made from thinner wire and have less turns.
Why are you replacing the guides are they knackered ? Can you grind the head of the hammered/mushroomed stem down/off to stop the stem damaging the guide.

[andy230]

Why are you replacing the guides are they knackered ? Can you grind the head of the hammered/mushroomed stem down/off to stop the stem damaging the guide.

Steve- I'll try not to replace the guides if I can get away with it.

I had thought about grinding.  Is it hardened? Could I file it down??  Or hacksaw off at the little collet indent?  I dont even want to think about a slipped grinder!!!   

a 

[guest146]

Andy

Send you email  and your home address to here kennethbooth@tiscali.co.uk I have a book that will make interesting reading you can have loan of I shall post it to you.

ken

[Steve H]

I had thought about grinding.  Is it hardened? Could I file it down??  Or hacksaw off at the little collet indent?  I dont even want to think about a slipped grinder!!!   

A grinders the way to go, I doubt a file will make much impact. Think about the damage a slipped hacksaw/file will do to the head/cambox dealing area. Clamp the head down, and lock the valve somehow and softly softly with a grinder, would be my approach.

[themoudie]

Aye Andy,

Assume nothing! It made power on the dyno, but that was before it was raced.

Himalayan cams will hammer valve gear and if the springs have become coil bound/or lost their tensile strength, the hammering will have been worse. Added to this the heat in the head will reduce tensile strength and a few missed gears with over revving just further exacerbates the attricion.

DO NOT WAVE A BLOODY GRINDER ANYWHERE NEAR THE TAPPET END OF THE VALVE

If the grinder slips, carnage! 

Hacksawing the end off the valve assuming you get the blade to bite, is almost as bad.

Use a small oil stone or diamond sharpening stone to ease the hammered deformaties away and make sure you rinse all that dust away and then wash everything in hot soapy water and rinse and dry it, BEFORE ASSEMBLY. If you are replacing the valve guide then just heat the head and drift the whole lot out in a oner and deal with the valve in a vice if you intend to re-use it

Flaky carbon in exhaust port, clean off but don't remove metal unless casting flashes and sproos. Doesn't need to be polished, a clean machined surface is fine. Slight surface roughness behaves the same as the dimpled surface of a golf ball and helps exhaust gases escape.

Spring lengths and other valve spring data I sent, was taken from Clymer, Yamaha XT600 & TT600, 1983 - 1989 handbook. May I suggest you need to speak with whoever made the cam, about follower angles and valve spring rates and lengths.

Whilst the Norton 4S cam was a stonker at the top end the cam that worked and held together was the 2S I believe. Hare and tortoise and you have to cross the line to win mentality. More upper mid range and less thrashing around with the gears, might be the way to go! But then thats why I don't race, no bottle and slow reactions.

Look after yursel' and don't neglect........ 

My regards, Bill.

[Steve Lake]

I agree with Bill on this one.....a grinder is a 'sledgehammer to crack a nut' and any slip would indeed be catastrophic, and in any event you would render the valve useless.
It's not unusual for a valve stem end to foul the guide when removal is attempted...it indicates several things, a lot of use, strong springs, agressive cam.
The area causing the problem is the stem head above the collet slot, on the one hand the top is hammered by the tappet and the top lip of the slot is burred by the force of the collet acting on it.
I have a piece of oil stone (formed by some wizzened old woodturner in the year dot) about 5x2x1/2" with different profiles on each edge used for de-burring the inside of curved woodturning chisels (anyway, you didn't need to know all that stuff, a small bit of oilstone is all you need, my grandad was the ancient woodturner by the way)

Anyway....with the head held firmly, and one hand holding the valve head. with the other hand gently wipe the oilstone over the burred stem tip, at the same time rotating the valve in the guide, only let the stone come into contact with the area above the collet slot, it'll take a while, keep testing to see if the valve is free to remove, no force should be needed, and keep the stem/guide well oiled whilst all this is going on, this way, you will end up with the valve and guide in an undamaged state, you're wad intact, and a bit further down the road to a tuned and reliable motor (it says here) 

[Steve H]

I was assumming valves were to be replaced, a 1mm cutting disc straight through the stem below the collet would reduce potential damage to guides.

[andy230]

Hi all,

The valves are probably getting replaced anyway.

I'll try to file it, and let you know how ai go.

SteveL:

It's not unusual for a valve stem end to foul the guide when removal is attempted...it indicates several things, a lot of use, strong springs, agressive cam.

All of the above I think!


Bill:

If you are replacing the valve guide then just heat the head and drift the whole lot out in a oner and deal with the valve in a vice if you intend to re-use it

Flaky carbon in exhaust port, clean off but don't remove metal unless casting flashes and sproos. Doesn't need to be polished, a clean machined surface is fine. Slight surface roughness behaves the same as the dimpled surface of a golf ball and helps exhaust gases escape.

Spring lengths and other valve spring data I sent, was taken from Clymer, Yamaha XT600 & TT600, 1983 - 1989 handbook. May I suggest you need to speak with whoever made the cam, about follower angles and valve spring rates and lengths.

Ok, will try to reuse the follower if its ok

Will clean loose carbon, otherwise not touch.

Spring lengths look all the same : XT or SRX.

Cheers

a

[guest27]

Being a tight wad myself.....

dress the valve carefully with an oil stone as described until it slides out of the guide - then there are no scores etc on the guide.  Guide only needs replaced if worn.

Valve no matter how bad will act as a pattern IF is is different to std.  Cutting the valve stem will leave a burr - which you  need to dress off, the heat of cutting will harden the stem - so may as well spend the time dressing the uncut valve.

Springs - a number of things effect the spring rate. The length of the wire they are made from and the diameter of the wire they are made from - long wire is easier to bend than short, thin easier than thick.  The spring manufacturer / cam man may specify a fitted length or an unfitted length.  Have fitted springs to Triumph head in the past that were shorter than std but higher spring rate and we needed to make up collars to sit under them to get the correct fitted length.

The temper etc on the spring will affect its rate, so testing a used spring to see what a new one should be may not be the best option.  As the man says - if you can find the grinder of the cam they may have advice on the springs. Basically they need to be strong enough to hold the valve against the cam and no more - but testing this at high speed is kinda difficult and destructive.

R