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Dilemma - I've got my engine apart to replace valve seals. I've got some pretty serious carbon buildup on backside of intake valves. Not sure if this is normal or excessive (think it's excessive though).

So, curious as to whether it is normal or not?
How do the piston's look - normal?
And how can I clean this without damaging sealing surface?
Can I clean the head's sealing surface without damaging it? How?

Gurus.....please take a look at these pics and let me know...

P1040903 on Flickr - Photo Sharing!

P1040907 on Flickr - Photo Sharing!

P1040908 on Flickr - Photo Sharing!

P1040875 on Flickr - Photo Sharing!



Little Background....
1995 GPZ1100. 13000 miles.
A while back I replaced my plugs and had oil on a couple of them.
Asked around and was told to check compression. If this was good to go after valve seals.

So, I checked compression. I'm thinking it's okay, but not perfect...
I've read online that they should be within 10psi of each other, but my manual only specifies that it be withing 128 - 196 psi. Don't still have the numbers, but they were within 15 psi of each other (155 to 170 I think).

On to taking the whole bike apart for valve seals and a good bit of learning and experience. (Good thing I also have an FZ1 and a DR650 to keep me moving :)

Thanks in advance,

Mic
 

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Judging by the pics I would say the valve oil seals are your problem. While you have the head off maybe do a hone job and get some new rings. Those valves need lapping too.

The way I clean a valve is to chuck it in a drill and spin it while I hold a knife to it and scrape off the carbon. A bench grinder with a wire wheel works well too. Or you can get a wire wheel to fit in a drill and do the head too.
You would have to be really sloppy to damage the sealing surface. And those valves are hardened so no worries there either. I also use a drill to lap the valves. Valve in head, stem in chuck, valve grinding compound on seat. Check frequently.
 

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Discussion Starter · #3 ·
Thanks KawPaul. For my own learning sake, how did you know the seals were the cause? Purely from the buildup on the backside of the valve? Or was it something in the appearance of the buildup?

I read online that the intake valves will have more buildup on the backside because that is where the fuel comes in and this was the case for mine.

Not questioning your judgement, just trying to learn.

Thanks in advance,

Mic
 

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well a bad valve seal well let a little amount of oil pass through and get on the valve stem and trickle down to the face of the vavle and set there.if there is carbon build up from fuel the oil will soak into the carbon pile and give it a dark black look and kind of a oilly feel.

the way i clean valves is this... i take a good cleaner(seafoam) and soak all the valves for a few days.this will soften the carbon up to clean with a brass bristle brush or a tooth brush works well also.scrub them clean.you dont want to scratch the valve or its stem puttin it in to a drill chuck or usein a power tools to clean.

say if you used a bench grider wire wheel to clean and you slip and it gets drug into the wheel now the valves damaged (done that one time not prety)that why i clean em by hand with cleaner and a brass brush or tooth brush.
kerosene works well also to clean them valves up.

oh yeah how does the exhaust valves look?do they have black soot on the also?if they did then that is another way to tell a bad valve seal but your engine would smoke like a 2 stroke with to much oil in the mix out the pipes.plus the piston would have signs of oil deposits on it also if it was a bad valve seal leak.but a minor leak would give you what you have on your vlaves now .but keep in mind it had to have a mad amount of carbon from un burnt fuel settin on the valve in order for oil to soak in.

after your top end rebuild might want to have the carbs clean and adjusted to help with a rich fuel mix that would cause excessive carbon to build up.and maybe even start usein seafoam every few tank fulls.to help keep them valves and combustion chamber clean of carbon-
 

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One of my early career projects was to study IVUDs (Intake Valve Underside Deposits) as a function of lubricant composition. Both fuel and lube play about an equal contributory role. IVUDs are the main reasons for aminic detergents in gasoline. Your valves ain't bad at all with respect to IVUDs. Wire wheel them clean and do a light lap with fine grinding compound. Then ride the 'ell out of the big Kawasaki.
 

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Thanks KawPaul. For my own learning sake, how did you know the seals were the cause? Purely from the buildup on the backside of the valve? Or was it something in the appearance of the buildup?

I read online that the intake valves will have more buildup on the backside because that is where the fuel comes in and this was the case for mine.

Not questioning your judgement, just trying to learn.

Thanks in advance,

Mic
Yes, the buildup was not dry carbon but had an oily look to it. And on that side of the valve the only way is with leaking seals or valve guides or both.


well a bad valve seal well let a little amount of oil pass through and get on the valve stem and trickle down to the face of the vavle and set there.if there is carbon build up from fuel the oil will soak into the carbon pile and give it a dark black look and kind of a oilly feel.

the way i clean valves is this... i take a good cleaner(seafoam) and soak all the valves for a few days.this will soften the carbon up to clean with a brass bristle brush or a tooth brush works well also.scrub them clean.you dont want to scratch the valve or its stem puttin it in to a drill chuck or usein a power tools to clean.

say if you used a bench grider wire wheel to clean and you slip and it gets drug into the wheel now the valves damaged (done that one time not prety)that why i clean em by hand with cleaner and a brass brush or tooth brush.
kerosene works well also to clean them valves up.

oh yeah how does the exhaust valves look?do they have black soot on the also?if they did then that is another way to tell a bad valve seal but your engine would smoke like a 2 stroke with to much oil in the mix out the pipes.plus the piston would have signs of oil deposits on it also if it was a bad valve seal leak.but a minor leak would give you what you have on your vlaves now .but keep in mind it had to have a mad amount of carbon from un burnt fuel settin on the valve in order for oil to soak in.

after your top end rebuild might want to have the carbs clean and adjusted to help with a rich fuel mix that would cause excessive carbon to build up.and maybe even start usein seafoam every few tank fulls.to help keep them valves and combustion chamber clean of carbon-
I suppose one could lose a valve in a grinder wheel and scratch a hardened valve. Though I have never had the misfortune of doing so. I have been tinkering with engines off and on for 30+ years and I do not recall ever seeing someone scratch a valve with a wire wheel. I run piston crowns into the wheel and we all know aluminum is softer and more vulnerable to heat than hardened steel. But there is a bit of 'touch' involved so not everyone should just jump in without knowing how to be gentle.
 

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Yes, the buildup was not dry carbon but had an oily look to it. And on that side of the valve the only way is with leaking seals or valve guides or both.




I suppose one could lose a valve in a grinder wheel and scratch a hardened valve. Though I have never had the misfortune of doing so. I have been tinkering with engines off and on for 30+ years and I do not recall ever seeing someone scratch a valve with a wire wheel. I run piston crowns into the wheel and we all know aluminum is softer and more vulnerable to heat than hardened steel. But there is a bit of 'touch' involved so not everyone should just jump in without knowing how to be gentle.
this is true i made the error of usein retard strength and not payin attention a lite touch will work not retard strenght lol
 

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wire wheel vales,pistons,chambers etc... use a brass wire brush/soft steel wire wheel and be nice... lap in valves after cleaning and i usually fill the intakes/exhaust ports with water after reassemble and check for leaks..... nver a problem doing it this way myself for the past 5+yrs.... (oh and check how much margin is left on the valve-if its a sharp edge then they are done and should be replaced anyways..as shown in pic.....)
 

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this is true i made the error of usein retard strength and not payin attention a lite touch will work not retard strenght lol
I think most of us have been guilty of using the heavy hand at one time or another.
wire wheel vales,pistons,chambers etc... use a brass wire brush/soft steel wire wheel and be nice... lap in valves after cleaning and i usually fill the intakes/exhaust ports with water after reassemble and check for leaks..... nver a problem doing it this way myself for the past 5+yrs.... (oh and check how much margin is left on the valve-if its a sharp edge then they are done and should be replaced anyways..as shown in pic.....)
I too use the water trick to check for leaks.
 

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Agreed.

If there is any trace of oil, water will be repelled from the leak location by its surface tension. Oppositely, these other solvents will dissolve this oil out of the way and wick like crazy to the other side.
 
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