[cakey]

I've been trying to apply some recently won knowledge and tools to a badly beaten fleet of 20 or so STIHL backpack blowers, all but one is a BR600 the other is a 550. I know that the 550 and 600 are very similar so i think this particular question would be interchangeable between the two models.

I was reassembling the BR550, i adjusted the valves and did a compression test, it was 88 psi or 6 bar. I readjusted the valves and to my surprise the compression went up to 142 psi or 9.8 bar. I wasn't expecting a 38% change from what i felt to be a minor adjustment, however my question lays in that the guidelines I believe are 7.5 to 8.5 bar or 108 to 123 psi. The blower seems to start and run fine but is their a down side to running at a compression 13% greater than the guidelines? Or is this a boon and I should be glad with it?

 

[Sharpcut 1]

If you have a good cylinder, but some carbon build-up on top of your pistons, you are going to see an increase in compression, because the top of the piston is now "domed" with carbon, compressing into a smaller chamber. I would'nt worry about it. Should be running 89 octane in today's 2 strokes/ 4Mix. Does it spark knock?

 

[cakey]

It runs smooth, no knock and we only use 89 octane fuel. I can't imagine that the fuel oil mix has always been ideal though. I also did a leak down test on it and got almost no leak. 4% or less i think, although my process for testing leak is poor and needs refinement so the validity of that measurement is suspect.

 

[Jeff in AL]

I wouldn't waste the time on a compression test... Compression reading will vary depending on amount of carbon build up in cylinder anyway. But if you insist on doing so, Min compression would be 7.5 Bar or 109 Psi. Specs are 7.5-8.5 Bar or 109-123 Psi. IF higher then 10 Bar, you have a problem with the decompression on the cam.

The better way to test any of the 4-Mix units is to do a leakdown test. As long as there is no more than a 10% loss, the upper end is fine! You can also determine at the same time where the loss is from if more then the 10%!

By the way, there is a tool that is used on the 4-Mix units that will lock out the flywheel once set at TDC on compression stroke... Thus you will get a correct reading each time. The same tool is used on ALL 4-Mix units!

 

[cakey]

I've started doing both tests on our blowers, I'm the curious sort and much of the time the time it takes to perform the extra test in inconsequential. About 20 min ago i ordered that part to stop the flywheel after reading Jeff in AL's post. Currently i use a pair of vice grips, a socket and a 3" extender. It leaves much to be desired. Thanks for the help guys. I'm left to assume its just carbon build up. Next time that particular blower comes across my bench i will treat it with EDTA acid to see if that has any effect.

 

[tigerepairdotcom]

Try to do the compression test on that same 140 lb blower warmed up. I have 2 br 600's both test at 150 or so psi and drop to about 125-130 or so after running for a sec. Super rare and hard to find Technical data sheet All kinds of goodies. Theres also a decompression cam inside the engine to facilitate easier starting.

http://2.imimg.com/data2/UM/WS/MY-1817209/garden-blowers.pdf

 

[tigerepairdotcom]

another thing i only run stihl HP ultra oil in my br 600's heres why http://www.stihldealer.net/stihlhpultraoilcomparison-dealer-_e4y4ea.aspx

 

[cakey]

Thank you tigerepairdotcom i hadn't though to warm it up first although i should have. I have recently been switching crews over to HP Ultra oil, focusing on the crews with new blowers. this particular br 550 has been around for years, as have many of the blowers and in the past the crews used whatever oil was around. I'm trying to change old habits but it is what it is, at least i can give them the tools.

 

[Jeff in AL]

I've started doing both tests on our blowers, I'm the curious sort and much of the time the time it takes to perform the extra test in inconsequential. About 20 min ago i ordered that part to stop the flywheel after reading Jeff in AL's post. Currently i use a pair of vice grips, a socket and a 3" extender. It leaves much to be desired. Thanks for the help guys. I'm left to assume its just carbon build up. Next time that particular blower comes across my bench i will treat it with EDTA acid to see if that has any effect.

cakey,

Which lockout tool did you buy, the 4282 890 8600 OR the 5910 890 8600?

 

[Jeff in AL]

Try to do the compression test on that same 140 lb blower warmed up. I have 2 br 600's both test at 150 or so psi and drop to about 125-130 or so after running for a sec. Super rare and hard to find Technical data sheet All kinds of goodies. Theres also a decompression cam inside the engine to facilitate easier starting.

http://2.imimg.com/data2/UM/WS/MY-1817209/garden-blowers.pdf

Have you ever asked a Stihl Dealer for them?

 

[tigerepairdotcom]

I have paper copies the pdf was for the benefit of the over 206 people that have read this thread and don't have a clue they existed. Thats 206 up to this second. Years from now thousands and thousands of people will have read this forum and if I help 1 of them find that pdf I have succeded

 

[Jeff in AL]

I have paper copies the pdf was for the benefit of the over 206 people that have read this thread and don't have a clue they existed. Thats 206 up to this second. Years from now thousands and thousands of people will have read this forum and if I help 1 of them find that pdf I have succeded

Just a little FYI for ya there Tiger... Read the lower left corner of the last page on that file you reposted a link to... © ANDREAS STIHL AG & Co. KG, 2005... That is the reason the info is hard to find on the net, unless you are a dealer!

 

[herler]

For those of you touting leakdown tests, I am sure it's the common sense de rigeur procedure for certain mechanics but I don't care how many links you send, not everyone knows how to do that and it is nowhere near as easy a procedure as a straight compression test. Not saying that leakdown tests don't have their place, but what I'm saying is what the compression test doesn't tell me I can't fix anyhow so what difference does it make.

 

[tigerepairdotcom]

Just a little FYI for ya there Tiger... Read the lower left corner of the last page on that file you reposted a link to... © ANDREAS STIHL AG & Co. KG, 2005... That is the reason the info is hard to find on the net, unless you are a dealer!

I don't understand. Im not being dense, I just don't get what you`re saying.

 

[piston slapper]

I don't understand. Im not being dense, I just don't get what you`re saying.

Stihl considers all their technical info Trade Secrets.....
Posting this info on the net voids your dealer agreement...
I thought all technicians knew that..????

 

[herler]

another thing i only run stihl HP ultra oil in my br 600's heres why http://www.stihldealer.net/stihlhpultraoilcomparison-dealer-_e4y4ea.aspx

Hmmm...

Corporate names below used purely for example...

The Microsoft corporation publishes the results of a test they ran between Windows and the Mac OS...
Not being stupid here, but which OS do you think will win this one?
You don't think Microsoft's going to let Mac win, do you?

On to the next...
The General Electric corporation publishes the results of various tests they ran between their gas turbine engines and that of the Rolls Royce corporation...
Once again I'm not being ignorant, honestly speaking which gas turbine do you think is coming out the winner here?
You don't think GE's going to declare Rolls Royce the winner, do you?

I could go on, but do you see why I have little to no faith in test results posted by the Stihl corporation about their oil versus someone else's?
Yes, I realize the Stihl corporation didn't use actual names for Competitors A and B.
You didn't think they'd publish the other corporation's oil as the winner, did you?

The real problem I have is that I own products made by some of these very corporations, and here they are wasting time on test after test that does nothing for me, the end user... Wouldn't they be better off using the time and effort to improve their product?

So...
Why even post the link to these silly tests when I already know the results are no surprise and nothing new is ever revealed.

Perhaps when we stop showing interest in their stupid tests they will realize maybe they should start investing their efforts in more productive agendas.

 

[tigerepairdotcom]

Crucial info up there for everyone benefit and people on this forum (allegedly wanting to help people) trying to shut it down. What are you the gestapo?

Link to Cindy Lauper. True color

 

[Jeff in AL]

For those of you touting leakdown tests, I am sure it's the common sense de rigeur procedure for certain mechanics but I don't care how many links you send, not everyone knows how to do that and it is nowhere near as easy a procedure as a straight compression test. Not saying that leakdown tests don't have their place, but what I'm saying is what the compression test doesn't tell me I can't fix anyhow so what difference does it make.

herler,

It is pretty obvious why a leakdown test is more beneficial than just doing a compression test...

A compression test will only give you an "idea" of ring, cylinder and valve condition... Aside from the obvious, is there any compression at all.

A leak down test will tell you exactly where the problem is!

Lets say you do a compression test and have 40#...What is the problem and where is the problem?

Now do a leak down test on that same engine and see that you have say 60% loss... It would be obvious to determine were the loss was coming from doing a leak down test... Listen for air in the carb (leaking intake valve), listen for air in the exhaust (leaking exhaust valve), listen for air in the dipstick tube (issue with rings and or cylinder). If it's an OHV and you have the valve cover off, you can also check the inside (pushrod side) of the head gasket to see if blown.

As far as being difficult to do, well it's no harder then adjusting valves as you have to put piston at TDC on compression stroke either way.

Have 3 different people pull an engine over and check compression... Likely you will have 3 different readings as they will turn the engine over at different RPM's. Take those same 3 people and do a leak down test and all 3 will have the exact same result!

I would rather know WHERE the problem is on an engine with low compression prior to going into it... But thats just me.

 

[Jeff in AL]

I don't understand. Im not being dense, I just don't get what you`re saying.

The reason the information is "hard to find" is because the majority of it is Copyrighted!

 

[Jeff in AL]

Stihl considers all their technical info Trade Secrets.....
Posting this info on the net voids your dealer agreement...
I thought all technicians knew that..????

Slapper,

Not exactly true... IF it was a trade secret, dealers wouldn't have it to begin with. True that I cannot post any of the Copyrighted material online, I can however give a lot of information to customers that ask!

Now, I don't agree with some things Stihl does, for example, not having a public site for people to look up IPL's... But, it's not my decision!