Surprising amount of carbon build-up on intake valves - BMW S1000RR Forums: BMW Sportbike Forum
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post #1 of 13 (permalink) Old 05-03-2012, 09:06 AM Thread Starter
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Surprising amount of carbon build-up on intake valves

While I was putting on a bracket to reduce the throttle tension yesterday, I opened the throttle valves & was very surprised to see quite a bit of carbon build-up on the intake valves. Those closest to the center were the nastiest with significant build-up near the base where the stem joins the valve. I run a PC V with Dan's map, and always run premium fuel (93 octane here in NC) so I am wondering what could be causing this, especially with only 4,500 miles on the bike. In comparison, my highly tuned C6, with close to 60k miles looks almost new.

I poured some Techron Complete Fuel System Cleaner into the tank & will do so over the next 2 fill-ups as well (12 ounce bottle @ 4 ounces per fill-up). I hope that cleans this up as it looks like it could easily affect performance.

I plan on taking the bike to a local tuner soon to check the AFR & get a custom map created.
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post #2 of 13 (permalink) Old 05-03-2012, 10:10 AM
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get some pics mate, in all honesty a bit is quite normal...
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post #3 of 13 (permalink) Old 05-04-2012, 09:39 AM
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High octane fuel burns slower. And leaves carbon behind, which increases compression...and hot spots...requiring more high octane...
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post #4 of 13 (permalink) Old 05-04-2012, 10:35 AM
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Burning slower has nothing to do with leaving carbon behind. The simple answer is he's running rich. A proper tune at any octane should have minimal carbon.
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post #5 of 13 (permalink) Old 05-04-2012, 10:48 AM
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Originally Posted by Zed03 View Post
Burning slower has nothing to do with leaving carbon behind. The simple answer is he's running rich. A proper tune at any octane should have minimal carbon.
It's just my experience taking apart an engine that used excessively high octane has a layer of nasty carbon to be removed from the head.
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post #6 of 13 (permalink) Old 05-04-2012, 01:14 PM
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Would you agree that a modern engine running factory tune & using a higher octane gas than it was designed for would leave carbon behind?



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Burning slower has nothing to do with leaving carbon behind. The simple answer is he's running rich. A proper tune at any octane should have minimal carbon.
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post #7 of 13 (permalink) Old 05-04-2012, 02:04 PM
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the OP was talking about valve deposits.

what brand fuel are you using? even though most gasoline in an area come from the same refinery they don't have the same additives.

I use chevron or unocal 76.

took the intake off a bmw (car) with 100k+ miles. valves were almost clean. very minimal deposit. no additional additives were used.

techron or redline fuel system cleaner does work. I've used them in the past.
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post #8 of 13 (permalink) Old 05-04-2012, 03:22 PM
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My experience that even well-running engines will sometimes have these deposits, regardless of fuel or cleaners. I had an early R6 that had significant carbon on the intake valves that ran great and had a true 155 mph top end, so if it was affecting performance it wasn't by much.

I think it stands to reason that if you jet your bike strictly for throttle response and performance, you're probably more likely to be running with excess fuel and this excess fuel is probably going to increase carbon deposits. Whether it is significant, I don't know.

I doubt octane has diddly-squat to do with it. There are rumors that higher-octane fuel has a better additive package, but I'm skeptical that the difference is significant enough to buy higher-than-required octane gas for this reason alone.

Personally, I wouldn't worry much about it. Of all the fuel/additives, I've seen enough data to think that Techron is probably the best, and perhaps the only way that really does much for this problem, but it works better to prevent deposits rather than remove them.

- Mark

Last edited by markjenn; 05-04-2012 at 03:26 PM.
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post #9 of 13 (permalink) Old 05-04-2012, 04:20 PM Thread Starter
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Running out in the mountains, I'm forced to use whatever stations have premium, but I try to stick with top-tier fuels. I would say it's probably 50/50 top-tier/no-name gas.
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post #10 of 13 (permalink) Old 05-08-2012, 10:42 PM
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Quote:
Originally Posted by fast4d View Post
the OP was talking about valve deposits.

what brand fuel are you using? even though most gasoline in an area come from the same refinery they don't have the same additives.

I use chevron or unocal 76.

took the intake off a bmw (car) with 100k+ miles. valves were almost clean. very minimal deposit. no additional additives were used.

techron or redline fuel system cleaner does work. I've used them in the past.
Just as a recommendation, checkout Sea Foam for your engine cleaning/fuel delivery system cleaner...IMHO it is much, much better than techron.

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