Cam and valve question

[feket663]

Hello! I have K4 Busa with about 38000 miles. On 28000 miles I installed an used, but good pair of Yoshimura ST-1 camshaft set. Some days ago my mechanic checked the valve clearance, and he found on the intake 0 clearance. I asked him to take off the cylinder head, and he saw, the all intake valve worned out, almost torn the valve (the exhaust valves in good condition). What do you think is this normal wear, or this may be the camshaft's bigger wear? I used the bike only the street, don't used on racetrack. What do you recommend, need reinstalling the original cams, or use more the Yoshi. I will buy Kibblewhite Black Diamond (stainless steel) intake valves, what do you think about these? Thanks for help and sorry for my bad english. Istvan from Hungary.

 

[Commuta_Busa]

what part of the valve itself is worn?

 

[feket663]

what part of the valve itself is worn?

The valve head thickness close to zero.

 

[Draco1340]

I honestly don't know what you mean by valve head thickness.
Perhaps you mean valve clearance as measured between cam and follower?
High lift cams do wear much faster, and the valve seats tend to recess faster as well.

 

[feket663]

I thought this

 

[Jay]

Early busas had very weak valve springs. With the updated Yosh profile, you could have been getting "bounce" which will hammer the valve faces.

Put some good valves in it, and some good valve springs and you should be good to go.

 

[feket663]

Early busas had very weak valve springs. With the updated Yosh profile, you could have been getting "bounce" which will hammer the valve faces.

Put some good valves in it, and some good valve springs and you should be good to go.

The valve spring's higher seat pressure don't increase the valve seat, the camshaft and valve's wear? 'cause i'm using this bike on the street, and don't like change the valvetrain components every half year...

 

[Marc Salvisberg]

Early busas had very weak valve springs. With the updated Yosh profile, you could have been getting "bounce" which will hammer the valve faces.

Put some good valves in it, and some good valve springs and you should be good to go.

Jay's right -

If you run higher lift cams, rev it too high (for the cam and springs) and the springs are not strong enough, the peak (nose) of the cam will launch the valve further than the lift of the cam.

Then, the cam still rotates, the valve begins to close, but it never quite catches up to the cam profile.

The springs do close the valve, but when the valve hits the valve seat, it bounces a bit and ends up hitting the valve seat many times before it stays closed.

When that happens, the valve face gets peened (hammer tap) in and and the valve "face" depresses - letting the valve sink deeper int the valve seat - and - reducing your cam/valve clearance.

Your mechanic can catch that by noticing that your valve clearance gets less every time he checks it.

Another way to catch valve float is to inspect the bottoms of the valve spring, where they go into the head -

If you are close to valve float and valve seat "pounding", but not quite there (maybe 100 - 200 rpm shy of float), you'll see the face of the spring getting smooth and polished. That's a warning that your springs are right at the bad edge of valve control.

In racing setups, we would spend a couple hours matching and hand prepping each set of 16 - 20 springs.

Titanium valves are pretty soft and prone to pretty quick damage if they "float". "Stellite" faced steel valves are heavier but def. tougher.

Your Yosh cams, with some Yosh springs and new valves and valve guide seals should be just fine.

I only use Japanese "kit" springs in the Japanese bikes - They usually weigh a bit more, but, you rarely have to worry about them breaking, even in race use.

Word to the wise - don't skimp on valve springs - don't buy the cheapest brand. From the Road to Enlightenment... buy the Yosh springs..... :-)

As far as the stronger spring rate of the race springs, yes - there is more tappet / camshaft pressure, but the I've had a fair number of Suzuki's with Yosh or Megacycle cams and springs running around for years without trouble.

Higher spring pressure does not increase valve seat wear. We used to run even .020"/.5mm wide full width valve seats and full radius valve jobs with just a "line' for a seat and the valves and seats stayed fine - as long as we didn't get valve float.
So - it's not the seat pressure that hurts seats and valves - it's the valves bouncing.

On the other hand, I've had a gsxr1100 with some cheap valve springs come in with 8 broken valve springs after 2 years.

I think that "valve head thickness" that he was talking about is called the valve "margin".

Best regards,

Marc

 

[feket663]

Jay's right -

If you run higher lift cams, rev it too high (for the cam and springs) and the springs are not strong enough, the peak (nose) of the cam will launch the valve further than the lift of the cam.

Then, the cam still rotates, the valve begins to close, but it never quite catches up to the cam profile.

The springs do close the valve, but when the valve hits the valve seat, it bounces a bit and ends up hitting the valve seat many times before it stays closed.

When that happens, the valve face gets peened (hammer tap) in and and the valve "face" depresses - letting the valve sink deeper int the valve seat - and - reducing your cam/valve clearance.

Your mechanic can catch that by noticing that your valve clearance gets less every time he checks it.

Another way to catch valve float is to inspect the bottoms of the valve spring, where they go into the head -

If you are close to valve float and valve seat "pounding", but not quite there (maybe 100 - 200 rpm shy of float), you'll see the face of the spring getting smooth and polished. That's a warning that your springs are right at the bad edge of valve control.

In racing setups, we would spend a couple hours matching and hand prepping each set of 16 - 20 springs.

Titanium valves are pretty soft and prone to pretty quick damage if they "float". "Stellite" faced steel valves are heavier but def. tougher.

Your Yosh cams, with some Yosh springs and new valves and valve guide seals should be just fine.

I only use Japanese "kit" springs in the Japanese bikes - They usually weigh a bit more, but, you rarely have to worry about them breaking, even in race use.

Word to the wise - don't skimp on valve springs - don't buy the cheapest brand. From the Road to Enlightenment... buy the Yosh springs..... :-)

As far as the stronger spring rate of the race springs, yes - there is more tappet / camshaft pressure, but the I've had a fair number of Suzuki's with Yosh or Megacycle cams and springs running around for years without trouble.

Higher spring pressure does not increase valve seat wear. We used to run even .020"/.5mm wide full width valve seats and full radius valve jobs with just a "line' for a seat and the valves and seats stayed fine - as long as we didn't get valve float.
So - it's not the seat pressure that hurts seats and valves - it's the valves bouncing.

On the other hand, I've had a gsxr1100 with some cheap valve springs come in with 8 broken valve springs after 2 years.

I think that "valve head thickness" that he was talking about is called the valve "margin".

Best regards,

Marc

Dear Marc! Thanks for the reply. But I have a problem: I can't find Yoshimura valve springs for this model.

OFF Topic:

Your Factory Pro Shift Star kit works very vell.

 

[GIXERHP]

Dear Marc! Thanks for the reply. But I have a problem: I can't find Yoshimura valve springs for this model.

OFF Topic:

Your Factory Pro Shift Star kit works very vell.

I would use 70 lb springs from Ape, or Carpenter!

I run them with dual intakes, with no problem!

 

[ogre]

beat me to it, i was also going to bring up the APE springs.
CLICK ME!!!

 

[B@DA$$08BUS@]

Cant go wrong with the APE ones. Got the HD in 1441 with massive cams. Went to SS valves intead of the Ti ones. Give APE a call

 

[Marc Salvisberg]

Dear Marc! Thanks for the reply. But I have a problem: I can't find Yoshimura valve springs for this model.

Either can I -
Next best thing is a slightly stronger (than stock) set of springs that haven't broken for anybody -

OFF Topic:
Your Factory Pro Shift Star kit works very well.

Thanks -
The STAR kit decreases shifting time by about 10ms each shift with manual or a quick shifter.

I always wonder why people more Busa people don't use the Evo Shift Star kits - I think that most street people just figure that Busa's shift clunkily and leave it at that and the 'drag" guys throw on an air shifter and call it a day -

I wonder if an air shifter slams the shift drum so hard that it "floats" the detent arm and the trans "shifts quickly", regardless of the detent arm construction or shift star profile?

Or, maybe an air shifter can still only rotate the shift drum about the normal "51% of the way" and the STAR and detent arm still have to finish the shift and maybe a star would help, even with the air shifter. I don't have any way to easily check that.

On the gixxer race engines, typical quickshifter "kill" time with a stock star is 50 to 55 ms - with a Evo STAR kit, it's around 40ish ms in the upper gears.

Maybe start a new thread with Evo Shift STAR -

Thanks -

Marc

 

[feket663]

Today i found, the valve springs 7-8 mm shorter than service limit... My part supplier prefer the Kibblewhite springs, but I'd like the best solution. What do you think? Some experience? And the other question: if i increase seat pressure (e.g. 65 lbs APE springs), can i keep the stock (otherwise good gondition) valve spring retainers?