SuzukiSavage.com - Severe carbon buildup on one valve?

JonBiddle

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Severe carbon buildup on one valve?
09/11/14 at 08:09:54

While cleaning my carb I took a peek into the intake port, and noticed some concerning buildup of what looks like carbon on the top of the right valve, although the left valve looks clean.

Clean (left) intake valve

Dirty (right) intake valve

Does anyone know what this indicates? My best guess at the moment is the valve isn't closing all the way and has been building up carbon due to a bad seal with cylinder.

Thanks for any help or insight you guys can offer!

Additional context:

It's a 1995 LS650 that I bought this season as my first motorcycle. I don't think it was well maintained by the previous owners, and I've been working on getting it running right and having a lot of fun learning about motorcycle mechanics along the way! The power seems good, but there is a high-pitched noise with each stroke of the engine that as best as I can tell is maybe an air leak or perhaps a timing issue with the valves.

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Dave

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Re: Severe carbon buildup on one valve?
Reply #1 - 09/11/14 at 08:27:08

Well, it could be one of several things. The valve seal might be leaking a bit of oil, the valve clearance might be adjusted a bit too tight, or it could have a valve or seat face that is not sealing well.

I would check the valve adjustment and confirm they are in spec....then just ride the darn thing and not worry about it. If the issue is a failing valve or seat it will give you plenty of notice that it is going...it will become hard to start and performance will decline due to the low compression.

You might use some Techron in the fuel to help clean the back of the valve. Buy a bottle and mix it with the fuel in the recommended dose, and just keep adding it until you use the bottle up.

For your whistle....make sure the intake is well sealed and there is no air leak. Also check for exhaust leaks.

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JonBiddle YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 19	Re: Severe carbon buildup on one valve? Reply #2 - 09/11/14 at 08:32:15 Thanks Dave! I'm going to try doing a compression test on the engine this weekend as well as the things you suggested. We'll see how it goes
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Serowbot YaBB Moderator ModSquad Offline OK.... so what's the speed of dark? Posts: 28657 Tucson Az Gender:	Re: Severe carbon buildup on one valve? Reply #3 - 09/11/14 at 08:39:19 Great photos... ...
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verslagen1

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Re: Severe carbon buildup on one valve?
Reply #4 - 09/11/14 at 08:54:47

Dave wrote on 09/11/14 at 08:27:08:

Well, it could be one of several things. The valve seal might be leaking a bit of oil, the valve clearance might be adjusted a bit too tight, or it could have a valve or seat face that is not sealing well.

I would check the valve adjustment and confirm they are in spec....then just ride the darn thing and not worry about it.

A too tight valve would cause the valve to overheat, which is very rare for an intake valve. The hot valve would cause the carbon build up.

Any true backfires?

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JonBiddle YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 19	Re: Severe carbon buildup on one valve? Reply #5 - 09/11/14 at 09:33:57 The only backfires I've noticed is if I quickly roll off the throttle and occasionally when I kill the engine it backfires. Recently the bike has been harder to start (I've only put about 100 miles on it), which is why I was cleaning out the carb.
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verslagen1 YaBB Moderator ModSquad Offline Where there's a will, I want to be in it. Posts: 28886 L.A. California Gender:	Re: Severe carbon buildup on one valve? Reply #6 - 09/11/14 at 09:37:41 True backfire - out the carb or afterfire - out the tailpipe?
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JonBiddle YaBB Newbies Offline SuzukiSavage.com Rocks! Posts: 19	Re: Severe carbon buildup on one valve? Reply #7 - 09/11/14 at 09:58:27 Ahh okay. I think they have all come out of the tailpipe, although I can't be 100% sure because I don't have anything to compare it to sound-wise. edit: I should note that the bike has only about 6,000 miles on it, which to me seems pretty low for a 1995.
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Digger

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Re: Severe carbon buildup on one valve?
Reply #8 - 07/13/15 at 14:20:11

FWIW, I'm seein the same exact thing - starboard intake valve dirty, port one clean...

While I personally would not describe the bulldup on my starboard valve as "severe," the OP's pictures look very similar to my situation, with my buildup perhaps being a bit worse than his.

Bike had 13.9K miles on it when first observed. Burns no oil that I can tell, yet.

See my signature block for other specifics on the bike.

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2001, Metallic Glacial Blue, Raptor Petcock, Verslavy (first hole) (otherwise, mechanically, the bike is stock), 13,xxx miles
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verslagen1

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Re: Severe carbon buildup on one valve?
Reply #9 - 07/13/15 at 14:54:53

Digger, as Dave and I concur, it's most likely a valve adjusted too tight and not sealing. The valve has to sit on the seat long enough to cool. The carbon looks just like the carbon that accumulates on top of the piston.
If you could, get an eyeball on a stick and look at the top of the piston to rule out oil from below (worn rings) vs. from above (worn guide).
if it's not oil, then it's gas additives. ARCO used to be famous for the sulfur content and build up on sparky.

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justin_o_guy2

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Re: Severe carbon buildup on one valve?
Reply #10 - 07/13/15 at 15:23:22

I was rebuilding a Raptor 650, wasn't sure of the valves. Leveled the head upside down and put gas in it. Gas will go thru pretty quick. All four were leaking. I dunno how the head is designed up there, transmission fluid is pretty thin, need something that doesn't evaporate fast or risk blowing stuff up.
A garage might look like a great place to work on stuff, but if there's a gas water heater or clothes dryer or just some random spark, it can get ugly fast.

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Digger

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Re: Severe carbon buildup on one valve?
Reply #11 - 07/23/15 at 10:46:27

verslagen1 wrote on 07/13/15 at 14:54:53:

Digger, as Dave and I concur, it's most likely a valve adjusted too tight and not sealing. The valve has to sit on the seat long enough to cool. The carbon looks just like the carbon that accumulates on top of the piston.
If you could, get an eyeball on a stick and look at the top of the piston to rule out oil from below (worn rings) vs. from above (worn guide).
if it's not oil, then it's gas additives. ARCO used to be famous for the sulfur content and build up on sparky.

Hi Ver,

Just an update on the intake valve clearances:

Both intake valves showed 0.003" of cleanrance, which is what I set them at almost 4000 miles ago. (FYI, the book says the range of allowable clearances for the intake valves is 0.003 - 0.005 in).

Took a quick peek at the top of the piston, as seen through the spark plug hole. Looked the same color as the spark plug insulator did - kind of a mid-level gray color. No black carbon-y stuff in sight.

Will take another peek at the top of the piston after the head cover is removed and I can get a better angle...

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Digger
2001, Metallic Glacial Blue, Raptor Petcock, Verslavy (first hole) (otherwise, mechanically, the bike is stock), 13,xxx miles
I don't own a cage.
www.astronautbiker.com

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Digger

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Re: Severe carbon buildup on one valve?
Reply #12 - 07/23/15 at 10:49:39

justin_o_guy2 wrote on 07/13/15 at 15:23:22:

I was rebuilding a Raptor 650, wasn't sure of the valves. Leveled the head upside down and put gas in it. Gas will go thru pretty quick. All four were leaking. I dunno how the head is designed up there, transmission fluid is pretty thin, need something that doesn't evaporate fast or risk blowing stuff up.
A garage might look like a great place to work on stuff, but if there's a gas water heater or clothes dryer or just some random spark, it can get ugly fast.

Hi Jus,

I get your idea. One could drizzle some type of fluid on top of the closed intake valves and let it set there for a while (while the head in still on the engine and the engine is in the bike). Then, one could come back later and see if one of the valves looks like it's letting more fluid through than is its twin...

Any other ideas of what type of fluid to use? Tranny fluid doesn't sound like too bad of an idea so far...

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Digger
2001, Metallic Glacial Blue, Raptor Petcock, Verslavy (first hole) (otherwise, mechanically, the bike is stock), 13,xxx miles
I don't own a cage.
www.astronautbiker.com

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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Severe carbon buildup on one valve? Reply #13 - 07/23/15 at 11:15:39 Well, I dunno,, seals inside, what they like, I like the idea, but what to use? Hunting a leak, want it thin. Don't want evaporation to throw you off. Measured amounts, each valve, difference equals leak,
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Art Webb Serious Thumper Offline SuzukiSavage.com Rocks! Posts: 3007 columbus, Texas Gender:	Re: Severe carbon buildup on one valve? Reply #14 - 07/23/15 at 15:53:16 trans fluid is a bit thicker than gas of course, but not too thick for this i think, and it's a pretty decent solvent / lubricant, I'd say it's not a bad choice for what you have in mind
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