Stihl BR 600 Backpack blower vibration

[Raker]

Blower starts and runs fine but has developed a severe vibration. No obvious visual signs of problems. My buddy, the owner, often has high school kids working for him and therefore it is possible that it got a drink of straight gas but he doesn't know that for certain. Would straight gas cause vibration or just seizing?

Any ideas are appreciated.

 

[husqvarnaguy]

I dont think straight gas would make it do that. If I remember correclty it has AV springs on part of the housing. Check those some one might have dropped it and knocked something loose.

 

[XSKIER]

Broken impeller (fan blade)?

 

[Raker]

Well since my original post I have had a chance to run it myself and take it apart somewhat.

When I ran it I didn't experience vibration and much as it just plain ran rough.

I took the exterior housing off and looked for obvious signs of damage and couldn't find any. AV mounts were in tact and so were the motor mounts. When I took the spark plug boot off I discovered where the issue might be coming from. The end that goes into the plug had wire coming out of it and the other end came easily disconnected from the end going to the coil. When I took the plug out, the electrode was jet black. I put it all back together and it ran very similarly, adjusted the carb as best I could but it was still rough. I think I'm going to suggest a new coil and plug for it, agree? I'm no mechanic.

 

[watsonr]

It's not from the coil wire. It sounds like its running very rich... jet black plug indicates that it is rich. Check to see if the spark arresting screen in the muffler isn't plugged solid with carbon and re-tune it.

 

[greg409]

severe ignition misfiring will cause a sooty plug - just sayin'

But I doubt it really needs a new plug

luck,greg

 

[watsonr]

severe ignition misfiring will cause a sooty plug -

And in chainsaw terms.... four stroking, to rich, lean it out.

 

[XSKIER]

And in chainsaw terms.... four stroking, to rich, lean it out.

Any BR550, or BR600 will four stroke at any rpm, at any tune, because they are a 4-MIX ENGINE.

 

[Raker]

It's not from the coil wire. It sounds like its running very rich... jet black plug indicates that it is rich. Check to see if the spark arresting screen in the muffler isn't plugged solid with carbon and re-tune it.

I took your advice and removed the screen. It was clean. I took the wire brush to it for good measure.

 

[Raker]

severe ignition misfiring will cause a sooty plug - just sayin'

But I doubt it really needs a new plug

luck,greg

Sooty is a perfect way to describe how it looked. Even if the plug wire problem I described isn't causing the rough running engine, it can't be good. In my experience (which is much more with sleds than with chainsaws) the boot shouldn't easily separate from the wire like that.

 

[greg409]

tru enough, I'd come up with a method to remove said secondary wire @ the coil and replace it with a new one(or replace the coil/wire ass'y

since it's compromised already (high school punks, LOL)

luck,greg

 

[LegDeLimber]

Teenagers running it?
I'd check the air filter while I was at it.
from a quick google, I'm assuming it's paper, so if it's been damp or wet it'll swell shut
and give a rich condition.
Fuel spills, careless handling, getting hosed down, etc.
Someone here that owns one (I don't) could tell you what ways to get something in the filter compartment.

I see it a lot of oil wetted filters and plug fouling in recent years, on push mowers, now that Briggs has gone to paper filters.
People tip the mower up with carb on the low side and the crankcase breather drools into
the filter box, then in about 2 weeks the oil has spread through the entire filter and gags the mower.

 

[Mountainman6288]

Any BR550, or BR600 will four stroke at any rpm, at any tune, because they are a 4-MIX ENGINE.

I have this blower also. If the plug was sooty, watch your oil mix. Previously i ran a bit extra oil, maybe 40-45-1, thinking it would be better for engine. These days, its just plain WRONG. These engines are made to run 50-1 or thinner. Extra oil causes carbon, which causes the engine to hold extra heat, which is BAD. This from a Stihl rep. So watch the oil mix also.

 

[Silverado 2500]

New to this site. Was trying to start a new post,but can't figure it out. Figured I'd try this. I also have a br600. Not much use on it. It has an issue of not being able to get up to full rpm. Would have sworn in was a fuel( or lack of) concern. Started off with rebuilding the carb. Made no difference. Replaced carb with original Zama carb. No difference. Checked emulsion tube- ok. Cleaned out fuel tank and lines. Replaced fuel filter and tank vent. Checked and adjusted valves. Checked for vacuum leaks. I can start it and within the first minute it operates fine. After that it won't go full throttle. I have heard about faulty ignition coils causing problems. Don't want to spend more money unnecessarily.

 

[scottfarm]

If it kicks back when starting and becomes hard to start the valves need adjustment

 

[jmyren]

Blower starts and runs fine but has developed a severe vibration. No obvious visual signs of problems. My buddy, the owner, often has high school kids working for him and therefore it is possible that it got a drink of straight gas but he doesn't know that for certain. Would straight gas cause vibration or just seizing?

Any ideas are appreciated.

I know this is a very old post but I’m replying in case others found this site (as I had) when having a similar problem. I just fixed my BR600 and I wanted to provide my solution. the muffler was loose. It is held in by three bolts. I thought it sound rough when running recently and I checked the mounts to see if one had broken. Then when I went to start it yesterday and put it on the ground I heard the muffler clunk and it was not fully detached! When I disassembled it I found the three bolts that secure it all just sitting in the bottom, fully detached. The bolts must have loosened up over time leading to the muffler moving more than it should and that was the cause of the “rough” sound I was hearing. The good news is I had all three bolts and none of them or the holes they went into seemed to be stripped.

The disassembly process was very easy:
1. Remove three small bolts holding the rope starter
2. Remove four small screws holding the orange plastic housing (I also loosened the two small bolt holding on the air filter but I don’t think these need to be removed)
That’s it!
3. Remove the black rubber cover from the spark plug (just pull it off) this is the thing on the top center
All screws/bolts are loosened/tightened with the same torx screwdriver tool including the three that secure the muffler on!

While at it, might as well check the air filter and spark plug.