Heavy buildup on intake valves

[Mick]

Bike has been running a little sick lately. Pulled the air box and throttle bodies to have a looksy.
Air filters are nasty. Not sure what color they were 8 years ago, but my gut is telling me they weren't brown and black. And the front intake valves are looking grimy. I would have thought both front and rear valves would look close to the same, but this isn't the case. Rear valves are squeaky clean.

Using the "SEARCH" function, it looks like a number of guys recommend Sea Foam...am I correct? But I do have a question...can I drown the valves in a good cleaner like 'brake cleaner' and maybe vacuum / wipe out the residue. My good sense doesn't want me to allow the gunk to travel any further than it already has. But again if the intake valves look this bad how much worse might the exhaust valves be? And is it even worth trying to "clean" the valves without removing them?

Last thought...BMC filters. Again "SEARCH" says they aren't for shit in terms of performance. But are they straight in terms of OE replacement? Price and filtration heavily reguarded in this application.

[MDRC51]

uhhhhh....8 year old filters?????? Thats gross........don't use brake cleaner....buy some fuel additive...gumout, STP....lots og products at Pep Boys to clean intake systems available......and buy some new OEM filters...like before you run the cleaner through it......8 years....oh the horror.....

[Nacho2059]

If you just replace the filters more than once every 8 years that could help.

Just a guess though.

try running the same filter in your car for 8 years and see how far you get.

IMO and most others, just run the stock filter and if you want try this.

RC51 Stock Air Filter Mod

[dstewart]

The fuel additive rarely does any good. You are more likely to just remove the varnish in your tank and what the fuel filter doesn’t catch the injectors will. I have not seen any additive that effectively removes carbon build up. I would give the GM Top Engine Cleaner a try (available at your GM parts dealer). You pour it in to the throttle bodies a little at a time as to not stall the motor until about half is used. Then pour more rapidly until you do stall the motor, let it sit for 10 or 15 min and soak in. Start her up and finish off the bottle. We used this all the time and it really does clean all the carbon and buildup from the top end. You may need a buddy to rev the bike just a bit to keep from stalling as you pour.

[bladerunner]

Alright lets all take a deep breath and relax a little bit.

You mention the air filters have 'eight years' on them. O.K., big deal. The question I have is, how many miles?? Yes, if they are brown/black/dirty change them, but age alone means nothing.

As far as the intake valves being dirty, that too is absolutely normal. Have any of you ever seen the inside of a (dry) intake manifold of a modern, fuel injected car?? Dirty as hell, and coated in black, carbon deposits. But why/how?? Nothing but air (filtered at that) flows through the manifold, and fuel is not introduced into the equation until just before the cylinder at the injector; so where is all the carbon on the inside of the intake manifold coming from??

In any/all internal combustion engines, there comes a time during the RPM cycle where wave propogation moving through the intake/exhaust tracts will FORCE combustion gases back into the intake system, even if just for a fraction of a second. There are many factors that influence when in the RPM cycle this is likely to occur, mainly camshaft valve overlap, injector/ECM fuel enrichment cycles, and exhaust design determine this negative wave propogation back into the intake tract, but the point being it will happen.

Not only does the intake manifold become (benignly) comtaminated with combustion by-products, namely in the form of carbon build-up, but the intake valves themselves can become blackened or discolored.

Yes, I am making some assumptions to follow, but since the RC51 has such extremely short intake manifolds leading to the combustion chamber(s), I would hazard a guess that the air filters would become fouled over time by not only by the incoming air, but also due to the phemomena described above.

Before adding any fuel system additive (which HONDA strongly discourages), or assuming something more mechanically sinister is afoot, you could have some very basic checks performed on the bike such as a leakdown and compression check to make sure no exhaust gases are getting by a valve, or due to lack of ring seal, excess combustion gases are flowing past the piston rings, into the crankcase, through the PCV system and back into the airbox? This could also be causing the filters to become very dirty. Again, how many miles are we talking about.

How does the bike run? Does it miss anywhere during the RPM scale? Does the engine cut out or backfire? What kind of fuel mileage are you seeing? Do you have a PowerCommander, and if so, what map is loaded into it? Are you the original owner of the bike? If not, did the previous owner ride in dirty/dusty conditions? Did the previous owner attempt at some time to coat the filters in some BS material/oil/whatever he heard about through some other misinformed jackass on an internet motorcycle message board?


As stated above, the difference in appearance of the valves from the front cylinder to the back is also NOT a conclusive point for making an arguement that something is not right with the bike. Each cylinder has its unique exhaust routing, operates at different temperatures front-to-rear, and has different rates at which it heats up and therefore cools off as well.

Again, a leakdown and compression check is the only way to know if you have any problems, and as to why the air filters are so dirty?

Hope some of that just made some sense.

[mascar]

Im in the Sea Foam camp. I love the stuff, no ill effects to my knowledge. Ive run it everything for years. Even freed up some sticky lifters in the street car with it. Never had a water in the tank problem using it either. It saves me removing and cleaning the carbs every season on an old Kawi I have, 4 yrs now. Still runs great. Im not saying it will make your valves new again , just my experience with it. Please don't fry me T

[Trace]

Originally Posted by bladerunner

Alright lets all take a deep breath and relax a little bit.

~~~~~

Hope some of that just made some sense.

I totally agree with Bladerunner's take on this.

If it were me, I would replace the filters, replace the pluggywuggs, drain tank/get fresh gas, and then see how it runs before I go dumping stuff in the intakes. Actually, I still wouldn't go dumping stuff in the intakes.

The GM Top cleaner does work, but it is more intended for combustion chamber deposits (to eliminate a chronic ping problem).

[reddevil]

Probably has nothing to do with it, but how did the airbox look? After I bought my bike w/ 10,000 miles on it I noticed alot of oily film in the airbox. The PCV system was one of the first things to go. Don't know if it leads to valve deposits but venting that gas to the outside tends to keep things cleaner and probably helps gets you a little more power.

[Vitza]

id be afraid of hydrolocking the engine by using the cleaners...

personally id follow bladerunners advice... find the root of the problem instead of "mickeymousing" and just cleaning things up

[Mick]

Wow! I really screwed up the communication here...

I'll be more clear this time...I was just curious if what many of you do to clean intake valves and if it was a waste of time to use additives. And also if BMC or any other aftermarket air filter was worth a shit. The sick running symptoms were quite obvious when I put the stand under the triple clamp. But I continued to pull the bike apart...just because I like getting eyes on what's happening inside from time to time.

Thank you Bladerunner anyway
That does help me understand the differences between the two cylinders much better.

8 years on one filter!! I'm the 3rd owner of this bike. I found it completely stock without even a finger print on it. It's got 10,700+ miles now. 1300 short of Honda's recommended service interval. I did however ride in some nasty weather lately, which is why I had a look at them.
Paired, flapped, Sato lows and DK's map with 15/41 520. It runs pretty good. But changing residencies caused a badly bent rotor in a U-Haul trailer. Most of you would notice immediately, but I hadn't touched this bike in months. So it was difficult for me to notice just how bad they were actaully bent. Put the bike on the stand, and I can hardly get a 180 degree free spin on the front end! But it was also shocking to see how dirty the filters had gotten in such short time. I havn't ridden the bike much since the last time I had them out. I vaguely remember them being a light orange color? But no doubt...they're toast now.

[bladerunner]

Again, O.K., more information is good.

From what little we now know, it sounds like your bike is in good mechanical knick. I think the best solution at this point is for you to simply replace the shit BMC filters with stock HONDA filters (they flow the best anyway), give the bike a good tune-up, which includes having the valve clearances checked. This is where a Factory Service Manual really pays off.

Don't go dumping anything into your cylinders via the intake tracts, or spraying them with any cleaners. Whatever gunk you remove at that point (which will just fall down into the cyclinders/not good!!) will simply re-appear within a few hundred (or less) miles operation. Use some common sense, ride your bike like you caught it cheating on you, and be happy.

[Mick]

No I havn't got BMC filters. I was wondering if they were a decent OE replacement. I guess not.

I'm beginning to think maybe garbage was coming in under the air box between that rubber oring and the throttle body. The top of the butterfly valve has a little gunk on top of it as well. The rear throttle body is clean as a whistle. But again, maybe that too has something to do with what you're talking about?

I'm a little fuzzy about checking the compression on the RC. The leak down tester I have records the highest and lowest levels. On my other bike I screw it in and cycle the kick starter a couple slow times...But umm...I didn't know how to slowly cycle the RC so I threaded it into each spark plug hole and fired the bike up one end at a time?? Should the bike be warmed up before you test compression? Because I'm getting 180 on the front and 186 psi at the rear...a little higher than I think Honda says it should be? The bike will hardly idle but it will for a couple seconds. Like 425 rpm?

[RC Cola]

Alot of the old school guys used to suggest running a tank of CAM2 racing fuel to clean up your "top end" don't know if it works or not and, if it could damage anything such as sensors.

[bladerunner]

None of the cylinders should be 'firing' during a compression test.

The bike should be warmed up (but not so hot you get burned) so the oil flows well and provides a good seal between the piston rings and the cylinder wall for the most accurate results. Then screw the compression testing adapter into the respective spark plug holes, one at a time, the other cylinder should still have a spark plug threaded in, but not connected to a coil lead, so the cylinder NOT being tested will NOT fire!

Once hooked up and ready to go, turn the bike over using the starter motor. Turn the engine over for 5-7 seconds at a time. What you are looking for is the highest readings during the test. I don't have a service manual infront of me, but the highest pressure readings should be about 2%-5% of each other. If you were getting 180psi on one cylinder and 186psi on the other, then you are well within that % of change.

A leakdown test is a little less complicated, although you will need a source of compressed air. Again, once connected to the engine via the spark plug hole, and with both intake and exhaust valves closed and the piston at BDC, compressed air can be introduce into the cylinder and PSI monitored. The PSI should remain constant indicating a good piston/cylinder/valve seal. Again, consult the factory service manual for exact procedure and values you are trying to acheive.

[MDRC51]

I would get new plugs, OEM airfilters, and check for vacuum leaks someplace. If a sensor was bad you should get a fault showing. Did you check for that?

As for the carbon...the guys at AF1 give prillers the Italian tune-up to burn carbon away....Whats that? Put it on a dyno and run the piss out of it to generate enough heat to burn it off.....They have pics of Prillers with glowing headers...PIgy would overheat though....seems to work on Prillers though.

[RVTMAVERICK]

When doing an engine compression test, engine should be warm as "Bladerunner" said BUT so you don't have to worry about sparks from the S/P wires just hit the "Kill Switch", then you can just leave the spark plug wire on the cylinder that is not being tested
So now as you are ready to test the compression, just hit the starter botton, the engine will turn over without trying to start, You should also be "Holding the Throttle Wide Open" as the engine is turning over!

Lets us know what you come up with...

Peace

[hokkane4]

Originally Posted by Mick

Bike has been running a little sick lately. Pulled the air box and throttle bodies to have a looksy.
Air filters are nasty. Not sure what color they were 8 years ago, but my gut is telling me they weren't brown and black. And the front intake valves are looking grimy. I would have thought both front and rear valves would look close to the same, but this isn't the case. Rear valves are squeaky clean.

Using the "SEARCH" function, it looks like a number of guys recommend Sea Foam...am I correct? But I do have a question...can I drown the valves in a good cleaner like 'brake cleaner' and maybe vacuum / wipe out the residue. My good sense doesn't want me to allow the gunk to travel any further than it already has. But again if the intake valves look this bad how much worse might the exhaust valves be? And is it even worth trying to "clean" the valves without removing them?

Last thought...BMC filters. Again "SEARCH" says they aren't for shit in terms of performance. But are they straight in terms of OE replacement? Price and filtration heavily reguarded in this application.

I wrote to this forum last summer abut same thing. My bike was just 4 months old and 2300km driven. And intake valves were really dirty. I tried some valve cleaners and they helped cleaning a little. But what I have been reading about intake valve getting dirty, it's normal.
I live in Japan and I think petrol quality is high here. But one thing which maybe helps valves to get dirty is engine running too hot and sitting and vaiting in traffic lights/traffic jams. And that you can not avoid in tokyo..
Here is few photos of my bike valves from last summer. Does it look same in your bike?
Exhaust valves on Flickr - Photo Sharing!
Dirty intake valves on Flickr - Photo Sharing!

[Mick]

Yes that's exactly what the front intake valves looked like. Just the ones in the front though...I was a little confused about that initially.

[RVTMAVERICK]

Front and rear intakes on mine look just like this picture of yours...

Good quality by the way...

[glockem45]

My valves look eggzactly like this as well. I have just stripped down my bike again to get it ready for the track season, and I am sitting here looking at the rear valves and they are caked in soot/deposits of some sort, while the front ones are ashen and very clean looking.

My bike only has 7k miles on it, about 3k of which is track mileage, maybe more. Several things I have changed on my bike obviously like the Thorsten air box, Sato Banzai exhaust, PC3USB. I have still not tuned the bike on a dyno which I know I still need to do, but the bike was running very, very hot last year. I always run Shell 93 gas in it. The front spark plug is ashen/ clean looking, while the rear plug is wet and sooty.

I need to also check the valves for clearances, etc, and go through the entire bike this season. I am about to get the bike Dynoed, so I am looking forward to that.