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caranheim
12-14-2011, 09:37 PM
I have used my BR600 for 4 years without any problems. Because I use it for probably a little over 100 hours a year, I have been checking the valve clearance, then Decoking the engine using the STIHL DeCoke fluid. This last time when I went through this valve and decoke procedure, the valves did not need any adjustment, and I only decoked it using the decoke fluid. When I finished, I ran it for about 20 minutes, and the engine just quit like it ran out of fuel. When I tried to restart it, I found it no longer had any compression. I removed the valve cover to make sure the rocker arms and valves were moving correctly, and the piston was going up and down like it should. I tried blowing compressed air in the spark plug hole to see if I could hear where the air was going. All that did was to drive the piston down with great force. The dealer with a lot of experience looked it, felt the valve rocker arms while turning over the engine, and said he could not see any reason for the loss of compresson. He said it was possible that the one of the valves may be chipped, causing the loss of compression. That would be expensive to fix. I took the machine home and decided to check the valve clearance again, even though it felt the same. I found the exhaust valve clearance increased from where it was using the same STIHL gauge I used to check it before I had the problem. I then sprayed some SEA-Foam in the spark plug hole and let it soak for about 30 minutes. I still had no compression. I then tapped on the top of the exhaust rocker with a small hammer while blowing compressed air into the spark blug hole. This must have cleaned out a particle of carbon from the valve face, because the compression came back to normal. I then had to adjust the valve clearance because now it was too tight do to the valve closing all the way. I was amazed to find that the valve not closing by only a few thousands would show up as no compression. I have been using STIHL Ultra oil, and decoking the engine at the end of every year. What did I do wrong? The Decoke must have softened up some carbon that got trapped under the exhaust valve seat after running it for 20 minutes. Is it even necessary to Decoke when using the STIHL Ultra oil? Would it be better to use SEA Foam instead of the DeCoke fluid? It says on the SEA Foam can it can be used to remove carbon. The dealer said most commercial users don't even bother to decoke their engines. I really like the performance of my 600, and want to maintain it the best way I can. Thanks for any thoughts or comments you may have about this.

BigFish
12-15-2011, 10:27 AM
Man, you don't need to decarbonize it as much as you do! Way overkill! As you've found out, you can create more problems than you cure with that stuff. Using good oil and paying attention to the mix is the key!
When I worked for a stihl dlr. I think I only used it once or twice at the most!

piston slapper
12-15-2011, 10:44 AM
Fish.
Is there an easy way to de carbon the valves and cyl's ?
I've got about 20 of the 4mix units in the bonepile at work and was looking for an easy way to sort thru them.
I've done a teardown and it looks like I will have to invent some new tools to reassemble it.
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dutch1
12-15-2011, 11:30 AM
Fish,

Since you worked in a Stihl shop, are you or were you aware of any Stihl general recalls on the early 4 mix BR600's?

The reason for my question is, in late 2008, a commercial guy brought me two 600's that had valve problems. Since they were still within the warranty period I sent him back to the dealer of record. At that time, I called a friend who was also a Stihl dealer(90 miles away) who informed me he was replacing 600's that he had sold that were under a certain serial number. I don't know whether he was doing so on his own then butting heads with Stihl or if there was a general recall.

I am aware of some recalls on 500's and 550's due to fanwheel problems but was not aware of any 600 recalls.

BigFish
12-15-2011, 01:59 PM
I wasn't aware of any general recalls, however stihl did change the exh valve and seat mid- late 09.

As for your 20 units that need work, If you took em apart already the best way is to mechanically decarbonize em. I use a drill bit extension I got at Lowes and a 1/4' shank wire cup brush. The brush shank is held in the extension with a couple of set screws, works good. I just taped up the ext. so as to not tear up the cyl. Works good on honda's also. You can also get small wood handled stainless wire brushes (toothbrush) at a welding supply store.

Den69RS96
12-15-2011, 04:37 PM
since you decoked the engine, I would also check the spark arrestor screen. That decoking stuff removes alot of the carbon and it gets trapped on the screen. happened to my BR550

caranheim
12-15-2011, 04:40 PM
I called STIHL Tech Support to ask how often the engine needs to be De-Coked if I use STHIL Ultra oil. I was told it is not necessary to decoke the BR600 if I use the Ultra oil, and fresh (30 day) 89 Octane fuel. I told the tech I was speaking with that I just purchased a new BR 600 Magnum blower, and the manual still says to decoke after the first 139 hours, and every 150 hours after that. His response was that the document update was behind, and would be corrected at a later release. I asked if I could occasionally use some SeaFoam in the spark plug hole to help remove carbon. He said that would be OK, but still took the position decoking is not necessary if you use the Ultra Synthetic oil. I forgot to ask how often the valve clearance should be checked. I had to reduce the clearance a little the first two times I checked them, but no adjustment was necessary this last time. The exhaust valve seemed to need the most adjustment.

ricky86
12-15-2011, 09:15 PM
Fish,

Since you worked in a Stihl shop, are you or were you aware of any Stihl general recalls on the early 4 mix BR600's?

The reason for my question is, in late 2008, a commercial guy brought me two 600's that had valve problems. Since they were still within the warranty period I sent him back to the dealer of record. At that time, I called a friend who was also a Stihl dealer(90 miles away) who informed me he was replacing 600's that he had sold that were under a certain serial number. I don't know whether he was doing so on his own then butting heads with Stihl or if there was a general recall.

I am aware of some recalls on 500's and 550's due to fanwheel problems but was not aware of any 600 recalls.

We have replaced complete units. It depends on the dealer status. If a dealer get paid shop rate, repairing a unit might exceed the cost. It is taken on a case by case basis. There was a recall on valve retainers, but that dates back to 2006-2007. All depends on what the failure is.

piston slapper
12-16-2011, 07:50 PM
I was hoping someone had come up with a caustic solution that would eat carbon and wouldn't harm steel or aluminum.
Guess I should just add it to my christmas list.
Thanx again Fish.
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ed2hess
12-16-2011, 08:24 PM
I was hoping someone had come up with a caustic solution that would eat carbon and wouldn't harm steel or aluminum.
Guess I should just add it to my christmas list.
Thanx again Fish.
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Can't they be lapped with normal compound?

ricky86
12-16-2011, 08:28 PM
I was hoping someone had come up with a caustic solution that would eat carbon and wouldn't harm steel or aluminum.
Guess I should just add it to my christmas list.
Thanx again Fish.
Posted via Mobile Device

The Stihl decarbonizer works wonders. The engine really has to be hot for best results. Depending on the amount of build-up, you can let it sit in the cylinder for 24-36 hrs cold. It won't hurt anything. Heat helps alot.

DR J
12-16-2011, 08:33 PM
May try mechanic in a bottle, we use to decarbon pistons and valves on motor remans and 2 cycle remans very good prod. aslo use it in ultrasonic cleaner with heat to do carb rebuilds.:usflag:

DR J
12-16-2011, 08:36 PM
mechanic in a bottle. also use in ultrasonic cleaner with heat to decarbon pistons and valves on various units, works great also on carb cleaning before rebuild wonderful prod.

piston slapper
12-16-2011, 08:49 PM
All of the 4 mix units in the bonepile have been run on the cheapest mix oil and the cheapest fuel.
The valves were never adjusted. For the most part, the local dealer told them they were blown up regardless of their condition.
In turn the dealer sold them about 50 units a year.
I may try some stihl decarbonizer, as the only way to heat them up is with a torch.
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caranheim
12-16-2011, 09:33 PM
I would think lapping the valves in the 4Mix engine would be very difficut bcause even though it is an overhead valve engine, there is no removable head. You would have to remove and completely disassemble the engine to get to the valve heads by working through the cylinder.

piston slapper
12-17-2011, 08:40 PM
Its not a 5 minute job.
Its just a little easier than repairing a ship in the bottle.
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ed2hess
12-17-2011, 10:32 PM
I would think lapping the valves in the 4Mix engine would be very difficut bcause even though it is an overhead valve engine, there is no removable head. You would have to remove and completely disassemble the engine to get to the valve heads by working through the cylinder.

That is exactly why us guys who want units to run a very long time stick with 2 stroke. And you don't have to be a master mechanic to do the repairs.

ed2hess
12-17-2011, 10:36 PM
Oh and besides not having valves they don't have a lot of other stuff the 4 mix has.

caranheim
12-17-2011, 10:50 PM
When I called STIHL support to ask about decoking the BR600 4 Mix engines, I was told it would not be necessary if you use the STIHL Ultra synthetic oil correctly mixed with fresh 89 Octane gas. I mentioned that the Owners Manual for the new BR600 Magnum still recommends decoking the engine at 139 hours, and every 150 hours after that. He said the manual updates have not kept up with the current recommendations. I did not ask about checking valve clearances. I would think it still should be done every 150 hours. I found the clearance changed the most (Got larger) the first time I checked it. I checked it once each year, two times after that. The third check only showed a very small change in the exhaust clearance. Again, it was a little wider than it should be, using the STIHL feeler gauge. My STIHL dealer now only sells the Ultra oil. I may be wrong, but I suspect few landscapers take the time to decoke their SHIHL blowers. Here in Connecticut, the BR600 seems to be used more often than the other brands.