I need some help with cleaning my older ASP .80 4 stroke. I had trouble this summer keeping the engine running, so I‘ve decided to rebuild and clean it. I found a lot of carbon build up on the exhaust valve and even a little on the intake valve. I believe this is part of the problem of losing compression and stalling.

How do I clean these surfaces without damaging the finish and have them re-seat themselves properly?

What chemicals can I buy to do this? Carburetor cleaner, Acetone, Lapping compound….etc.

I’ve never done this before, so the easier for me the better. Thanks reading and any input would be appreciated.

Steve

It is hard to clean the exhaust valve stem without removing the valve.

You can use the solvents you suggested to clean the engine

Regular valve lapping compound is to coarse. You need to use a finer grit like red or white rubbing compound

I have removed both the intake and exhaust valves. I could use the red or white compound but I just don't want to ruin the valve seat surface. Would soaking them in the carbuerator cleaner or Acetone work just as well?



Steve

You can try but the wire brush on a Dremel treatment is usually required

You have to stay away from the seat in the pocket. It's usually pretty clean anyway and this is where you use the rubbing compound to lap with just to clean the mating surface.

I would get myself some cotton buds and methanol or model fuel. Just keep rubbing those seats until they are nice and shiny again.
Regarding the exhaust valve, you can scrap the stem with a piece of sharp plastic, like a APC prop, to remove the carbon, but never with a knife, as the stem needs to have a good workign surface on the valve bushings.
For the valve face, I would sit it on the head, with springs and collets assembled to keep it closed, and give it a pass with the wire brush of a dremel, as suggested.

Assemble everything up and check for hissing when pulling on the compression stroke to see if there is a need for valve seating with the rubbing compound. Of course, put a few drops of oil on the parts first or model fuel.

After the clean-up try to cut down on the castor content in the fuel, that way you woun`t have to do it again. I have the ASP .90 fourstroke and it is my most used engine and have never had the need for a carbon clean-up. 2-3% castor of the total oil content is enough if you insist on using castor. We run our ASP engines and every other brand too, on synth only and the engines look like new inside and out. I don`t mind if my fuel is a synth/cast blend, the price at the moment of stocking up desides what fuel I buy and lately the synth only have been the least expensive

I thought Castor had the higher flashpoint and if anything would be the last lubricant that would burn and leave carbon deposits. Supposedly this is one of the key factors making it a superior lubricant and the reason so many manufacturers recommend it.

Varnishing would be another matter.

Do I have this backwards?

Clay

Although the castor that is in contact with the metal of an engine won't burn, the castor which is part of the swirling combustion gases will.

A small amount of that carbon (from the burnt castor) will likely be laid down on the head, piston crown and exhaust valve.

A good synthetic seems to help keep the engine clean by stopping relatively small percentages of castor from sticking to the engine's internals when it gets converted to carbon during combustion.

As Asmud says, 2-3% seems to be "just right" as far as castor percentages go. There's enough to give a worthwhile improvement in film-strength but not so much that carbon will build up at any appreciable rate on valves and other hot parts of the engine.

I have never done valve work on a four cycle model engine. Full scale engines, yes. I would use a soft Dremel wire wheel on the valve stems - easy does it. Do not touch the valve seats. I understand that the valve seats in model engines are cut in the aluminum head material. I would purchase 400 and 600 grit loose abrasive dust (lapping compund on a web search). Do not use automobile valve lapping compund because it's too coarse. Mix the lapping compound with water thined corn syrup. and apply the 400 grit to the valve face and gently rotate the valve in it's seat with the eraser end of a new lead pencil wiped off with lacquer thinner. Lift the valve 90 degrees and rotate and again until you have done 360 degrees. Your valve seat will probably have an even grey tone, do this again with the 600 grit. Apply a thin coat of Prussian blueing or cobalt blue artists oil base paint, available at an art supply store, to your valve face and insert the valve onto it's seat and twist the valve. If you remove the valve and the oil based paint has left an even blue ring on the valve seat you are done. If not, lap some more. Do not over do the lapping because you will wind up widening the valve seat which is good for heat transfer but is not as good a seal as a thin seat. Don't overdo the lapping as the valve seat is aluminum, most other engines have a hardened valve seat insert if the head is aluminum.

Bill

I have heard that "whitening" toothpaste ( the type that contains bakingsoda) can be used as a lapping compound for model engine valve seats.

As for lapping compound, I use Copper bottom cooking pan cleaner...it's an extremely fine white (liquid ) polishing compound. You only need about a drop, at most.

I don't know 'bout you guys, but I have several X-Acto knives with #11 blades in various states of dullness (is that a word? "dullness" )
I use the dullest (least sharp?) one that has just the very the tip broken off, and very carefully scrape the carbon off w/ that....then polish the valve head and stem w/ 1000 wet/dry paper and light oil.

Thanks everyone for your input on this. Here's what I have on the Dremel side of things, I have 2 small nylon brushes, the first one is just a straight brush and the larger one is a cone shape. They are both the same consistency of a tooth brush but, the bristles are smaller in diameter. These feel like they would take the rough high spots off the carbon, but not polish. The other two white round discs are more of a hard packed fiber material, but it feels like if they would catch an edge it would fray, but soft enough to do some final clean up.


I know my wife has some cooking pan cleaner around here so I'll ask her what she has. If not, I'll try and get some this weekend. Also, talked with our shop manager and he has a parts cleaner that will clean the head and valve but may not remove much of the carbon, but worth a try.

I'll post some pick this weekend to let you know the progress.

Steve

Bill, the valveseat in model engines are made of bronze.

Can use the polishingpaste from the Dremel kit or polishingpaste for Chrome.

The later model Saitos (most of them now that don't have brass sleeves for cylinder walls) have aluminum seats. But the seats are chrome plated

The OS, Magnum, ASP, SC, etc are bronze

Yes, it is quite clear. Disadvantages with the valve seat of aluminum with chromium, it can not be repaired and will be ruined of lapping. As long as the compression is good, it's best to let the valve seats in Saito in peace and remove carbon with great care.

Merry Christmas and Happy new year to all folks!

I was going to say that's how I do it yesterday. For fear of getting lambasted I decided not to. Model engine valves are very hard and it's hard to scratch one. If a wire wheel works, anything will work. The key is to avoid the sealing face of the valve. I think most model engine valves are made of stainless. OS valves are only slightly magnetic.

In my opinion the engine pictured above doesn't have enough carbon on it to cause running issues.

Before lapping, check to see if there is excessive valve stem to guide clearance. If there is, lapping will not help.

Newer OS engines appear to be doing away with cast in bronze valve seats/guides.

Well, I'm done cleaning the exhaust valve and head. Here is a before and after photo, the valve definitely looks and feels much better. Here's what I did:

I took the head to our parts washer at work and cleaned it with Acetone and a nylon brush. I then brought it home and used the dremel with a nylon brush and polishing compound to the area around the valve seat @ 15,000rpm's. I then took the valve itself and used a dremel fine wire polishing brush to remove the build up on the valve. I then put a small amount of polishing compound on the valve face and re-inserted it into the valve head and rotated the valve around to make faces seal better.

So, now it's time for reassembly tonight and a valve adjustment. If the weather is good this weekend here in Ohio I may take it out for a start up.

Thanks for everyone's input, I really appreciate it.

Steve

Do you need any help with the timing or valve adjustment?

It's going to be below freezing both days and colder Sunday

I went ahead and re-assembled and found top dead center on the cylinder head and push rods. Is this were I put my feeler gauge in and adjust my rocker arm? Wy8e, what is the photo trying to show with the red line? Also, I noticed the feeler gauge you show is stating a .04mm gap? Is this correct? I thought it was .002" (.05mm) min to .004" (.10mm) max. for a gap? My feeler gauge only goes down to .002" (.05mm).

And thanks for the weather report, sometimes I wish I lived further south to fly more.

Steve

There is a dot timing mark on the cam. With the crankshaft at top dead center insert the cam with the dot in line with the push rods/cam followers. It is easier to get it right with the dot at the top/ The red line indicates the alignment of the timing dot with the pushrods/camfollowers. The cam twists when it goes in because of the gear teeth. Make sure it is aligned when fully seated.

The valves can be set with the piston top dead center on the compression stroke. The piston might be on top dead center on the overlap stroke where both valves are partially open but you don't want this position.

It may be easier for you to set the valves with one valve completely open and the other completely closed? You set the closed valve and then turn the crankshaft to swap the valve positions and set the other valve

The valve setting tolerence is .002" to .004"

Here's the engine disassembly/assembly sequence that was originally written in French. A few words were misspelled and so the words didn't translate

http://74.125.93.104/translate_c?hl=en&ie=UTF-8&oe=UTF-8&langpair=fr|en&u=http://epervier.sudluberon.free.fr/moteur4t/index.html&prev=/language_tools&usg=ALkJrhilJ2bs5gz_Grg6Q7MmToGRKxg RmA

W8ye
Lee Clearance wrote in the Engine Clinic in MAN: The engines from Sanye: the dot straight down against gear at crankshaft and the OS engines the dot in line with valve follower.

In doubt, i can scan the copy of the article about timing in 4 stroke in Engine clinic in Man.

My engines from Sanye (Magnum, ASP, SC and Kyosho) has dot straight down against gear at crankshaft.

Edit: added pic..

Jens,
If you think about it, there's no difference whether the dot is up or down as long as it is in line with the pushrods/camfollowers

But the crankshaft must be at top dead center

What would make you think that Clarence Lee knew any more about a Magnum four stroke than you or I? I wouldn't say that about the engines of his specialty like the Veco/K&B's. He is the King there.

Here is a quote from the Just Engines web site on how to set the cam timing on a ASP 91
I'm sure the 80 is the same? And I have confirmed this setting on a Magnum 61 as well as a ASP 91.

http://www.justengines.unseen.org/ac...FS__Ring_.html

Yepp, I can confirm that W8ye are correct. I have used the dot in line with the cam followers on ASP 61 fs, 91 fs, 180 fs even YS 110. I think this is a kind of universal method of setting the timing. The dot can of course point downwards too, but not 90 degrees too the crankshaft, because then it will be off by a tooth or so. It still must align with the pushrods and therefore it is more easy to just line it up right under the camfollowers. Piston must be at TDC in either cases

Edit: I think you are correct too Jens but it is a little harder to be spot on when the dot is pointing down. If the dot is at the tip of the purple arrow in your drawing instead of in a 90 degree angle to the shaft then it will be the same as the above method. I have tried the "dot down" method but found it much harder to get the timing accurate that way, it only takes just a little bit of wiggeling of the crank shaft to be off. It may seem like the dot is pointing straight down, but if the piston really is at TDC and one examine carefully one will se that the dot actually lines up with the cam followers/pushrods

If they wrote something else in the magasine I think they should edit it, it wouldn`t be the first time someone makes a mistake in a magasine

I completely agree with this as this has been my experience also.