1. Missed the live Ask the Expert event?
    Catch up on the conversation about fertilization strategies for success with the experts at Koch Turf & Ornamental in the Fertilizer Application forum.

    Dismiss Notice

STIHL BR600 Decoke problem

Discussion in 'Mechanic and Repair' started by caranheim, Dec 14, 2011.

  1. caranheim

    caranheim LawnSite Member
    Messages: 8

    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.
  2. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,158

    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!
  3. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,335

    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.
    Posted via Mobile Device
  4. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Messages: 2,249


    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.
  5. BigFish

    BigFish LawnSite Platinum Member
    Messages: 4,158

    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.
  6. Den69RS96

    Den69RS96 LawnSite Member
    Messages: 96

    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
  7. caranheim

    caranheim LawnSite Member
    Messages: 8

    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.
  8. ricky86

    ricky86 LawnSite Silver Member
    Messages: 2,123

    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.
  9. piston slapper

    piston slapper LawnSite Platinum Member
    Messages: 4,335

    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
  10. ed2hess

    ed2hess LawnSite Fanatic
    Messages: 14,465

    Can't they be lapped with normal compound?

Share This Page