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**MartyA** · 08-09-2003, 06:58 AM

It just so happens, through no fault of mine, that I currently have my head off, along with many assorted large and small engine parts. This is the first time I have been able to look at the combustion chamber. I was surprised at the amount of carbon build-up. At least 1/16" on the pistons, more in some places, and that much on 2-3-4 cylinders in the head, #1 had somewhat less. It was pretty much evenly distributed over the head and the exhaust valves. The intake valves had just a coating of carbon.

I have had the bike since '96, it has 38,000 miles and mostly unknown abuse prior to my purchase. I know it had a series of young owners who I heard would run the heck out of it around town, then park it for weeks. Then it sat for two years outside. The PO then got it and did tons of work to it, including a somewhat stage II jet kit, K&N indy filters, MAC 4-1. I know I drive it somewhat conservatively, so I expect to see that carbon built up. But actually seeing it was surprising.

Cleaning the pistons was fairly straightforward, chip and scrape with a dull screw driver. I crammed rags into the hemi-head and soaked them overnight with ammonia, that crud mostly wiped out, did not have to chip it out with a screw driver. The exhaust ports are still built up with carbon, but I am leaving that alone.

I did not remove the valves, is not my intention to do a rebuild. I have not moved the valves since I pulled the head, so the seats should be just fine. There was no leak past the valves when I filled the hemi with solvent.

The engine has been flawless for me. It starts all the time every time, never misses, so all that carbon build-up seemed harmless, and only added a little to the compression ratio, maybe.

A weak battery might keep sparks from flying properly. Also you said there was fuel in the float but not in the filter. Clogged petcock?

**dragxs11** · 08-10-2003, 01:34 AM

Have you been reading my posts Ben? Go for the petcocks Ben. Sounds like your starving that cyl. Makes sense doesn't it? Your pilot pickup in the bowl is higher than the main jet. So you can still kick in that main circuit and let er rip. The fuel level in that bowl is high enough for the main, but not the pilot. This is why float level is so important. Hope this helps.
Matt

**Shuriken** · 08-10-2003, 12:17 PM

Thanks for the info. guys. I tore into the carbs yesterday. They had gunk in the bowls from somewhere. I wasn't able to decide what it was. There was still water in there too. I don't know where that keeps coming from, but it seems like every time I have drained the bowls I find water in the bottom of the fuel.

Anyway, I sprayed all the passages clean again and inspected the jets. Number #4 had a plugged pilot jet. That's about all I could find. I checked the needle valve assemblies and they are allowing fuel and shutting it off. The petcock is working too. After I put it back together and rode it, the low end was back to normal as far as smootheness. I could also see some gas going through my inline fuel filter.

I think I saw someone post previously that the height of the fuel filters when compared to the float bowl level was causing bubbles in his fuel feed.... where was that post....

Can I fill the intake chambers with Sea Foam or ammonia to soak and get the crud off of the tops of the valves?

My valves are not to spec. They are much smaller than .008 and .006, which makes me think the seats are carbonized...

Ben

**jchigbee** · 08-10-2003, 12:38 PM

Take this with a grain of salt as I have not tried it. Anyway, local fix it up and sell it fast mechanic told me to try white rice for an excess carbon build up problem, as it worked for him. According to him you take ONLY six to eight grains of raw white rice and with bike running dump the grains into the back of the carb with the problem cylinder. Supposedly the rice is hard enough to break loose the built up carbon but not hard enough to damage the valves or seats. According to him he fixed a misfire on a used bike he sold apx. 4 years ago and is still running good today! Before I tried this though I would like to hear from a few other people to see if they had heard of this and if it actually works?
Good luck

**xssiveone** · 08-10-2003, 01:34 PM

My valves are not to spec. They are much smaller than .008 and .006, which makes me think the seats are carbonized...

If the seats are carbonized, that would make me think that the clearances should be larger, since the valves would be held open and therefore be further away from the camshaft.

Smaller valve clearance is actually a normal thing as the valve wears into the seat.

**Geezer** · 08-10-2003, 02:38 PM

Originally posted by jchigbee
Take this with a grain of salt as I have not tried it. Anyway, local fix it up and sell it fast mechanic told me to try white rice for an excess carbon build up problem, as it worked for him. According to him you take ONLY six to eight grains of raw white rice and with bike running dump the grains into the back of the carb with the problem cylinder. Supposedly the rice is hard enough to break loose the built up carbon but not hard enough to damage the valves or seats. According to him he fixed a misfire on a used bike he sold apx. 4 years ago and is still running good today! Before I tried this though I would like to hear from a few other people to see if they had heard of this and if it actually works?
Good luck

This sounds like Voodoo mechanics to me.

The easiest way to reduce carbon is to switch to a brand of gas that has a high (7 to 10%) alcohol content. You can add your own but becareful or you'll lean it out too far.

Geezer

**puttman** · 08-10-2003, 03:04 PM

Does anyone know if the Decarbon spray for two cycle boat motors will help in a four stroke?

I just learned a little about that (new boat) so I was wondering.

Method is to spray in the carb till it stalls then let it soak for awhile then run it.

**Jeff** · 08-10-2003, 03:34 PM

That's essentially what many of us do with Seafoam Deep Creep spray. It will break up carbon deposits.... as will Chevron Techron.

**MartyA** · 08-10-2003, 07:21 PM

If you break up the carbon and then try to blow it out it might clog your baffles. Try a compression test to see if the valves are really lifted off the combustion chamber. I am thinking if you run well and there is carbon built up in the chamber, which is somewhat normal, the actual valve seat surface might be OK.

If you are talking about the gap between the cam and the lifter pads, having a build-up of carbon under the valves would increase the gap, being that they would be unable to seat, therefore be further away from the cams. So the gap would be getting larger. The gap will get larger also as the pad wears. And if the valve seat is wearing the gap will get smaller. So checking the gap might not tell you what you need to know.

I would try a compression test first, see if there is a problem there.

**Shuriken** · 08-10-2003, 07:35 PM

I wasn't thinking, it was too late at night for that...

That's probably what's going on, valve seat wearing, that is. I've done a compression test, though not leakdown, and have screwy compression, something like 110, 60 90, 100 - it's been awhile. Oil only brought the readings up 10psi so there should also be valve wear. I wonder if the head work is something best left to a competent shop?

I've used sea foam when the bike was running but I've never soaked the intake ports with it.

Ben

**MartyA** · 08-10-2003, 08:10 PM

I know if you want to 'touch up' the valve seat, you can use some jewelers paste and spin the valve back and forth a little on the seat. Clymers has a little ditty on that. If you think you need major surgery, spend the money and get the seat done right. You might need the surface trued up also.

When you did the leak-down, did you listen at the exhaust or carbs for noise?

Last time I had my compression tested it was at the dealer and had 145 across all 4. 60 is very low.

**skids** · 08-10-2003, 10:39 PM

It kind of gives a new meaning to "rice burner," eh? :-) Oh yeah, and a grain of salt AND pepper!

Originally posted by jchigbee
Take this with a grain of salt as I have not tried it. Anyway, local fix it up and sell it fast mechanic told me to try white rice for an excess carbon build up problem, Good luck

**MartyA** · 08-11-2003, 03:15 AM

Yeah, got that right off, a bit obvious though.

If you have carbon built up, take the head off and clean it.

**TopCatGr58** · 08-11-2003, 08:46 PM

Hey there Ben,

We've gone over this before IIRC. If you're thinking of pulling the heads, might as well save your $$, get that big bore kit, and do a complete topend. I did mine myself, with simple hand valve lapping tool and compound, simple large 8" C-clamp and cut out piece of pipe for valve spring compressor. Just be sure you have that low scale torque wrench. You'll just need to have somebody perform the cylinder boring, but you should be able to do the rest yourself. Your compression problems will most likely not be fixed by just reconditioning the head, and you can actually cause more problems with just the valves sealing better, can cause more blow by past your compression rings, and it will still run poorly cause the comps won't be balanced until you fix the rings!!!
T.C.

Announcement

I can see crud on the valves.....

I can see crud on the valves.....

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