Fish
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You're right, I wasn't thinking.
Well then, remove the valve cover and take a peek at the rocker arm movement.
That could explain it suddenly shutting down too.
Stihl BR550 blower no spark
- Thread starter glentre
- Start date
Well then, remove the valve cover and take a peek at the rocker arm movement.
That could explain it suddenly shutting down too.
So, I think I finally have a decent spark. The problem was that the coil mounts on two bolts into the engine. Even with the correct thickness feeler gauge between the flywheel and the coil, when tightening one bolt before the other, the coil moves in the adjustment slots so the gap at one end of the coil is too wide and the gap at the other is too narrow, resulting in no spark or, in my case, a weak one. With that resolved, I moved on the adjusting the valves per hammermechanic man's suggestion.
I found the valves to be a little loose and had to close the gap a little to the 0.005" specs. Unfortunately, the engine still won't start. While turning the flywheel slowly by hand, I noticed some clicking noises in the engine that seemed unusual. I have done nothing that I know of to mess with the timing and think it's still ok but it is acting like it is out of timing. The "S" on the flywheel magnet is at the right side of the coil at the top of the compression stroke and both valves are closed. On the power stroke, the exhaust valve starts to open just before 6:00 o'clock at the bottom of the stroke but the intake valve opens slightly starting at about 4:00 but closes again a little after 6:00. It seems strange that the intake valve would open at all during the power stroke as that would blow back through the carb.
On the exhaust stroke, the exhaust valve starts to close at 10:00 with a noticeable "click" sound and the intake valve is fully closed.
On the intake stroke, the intake valve starts to open at 12:00 TDC but the exhaust valve is not fully closed until 2:00. Just before 6:00 or at the bottom of the stroke, the intake valve starts to close but also with a noticeable "click".
On the compression stroke, the intake valve is fully closed at 9:00 but the exhaust valve opens slightly starting at about 9:00 and closes again at 11:00 with a "click". Why would the exhaust valve open at all during the compression stroke. Is this a designed unloader to reduce compression to more easily start the engine?
At those spots where the intake and exhaust valves open momentarily, if I hand turn the flywheel back and forth, the clicking gets louder and if I press down on the rocker arm while doing that, it feels like the pushrod is falling into a depression or a small raised bump on the cam, I can't tell which. Also, at those spots, sometimes but not always, as I slowly move the flywheel, the valve will slam shut with a more pronounced "clack" sound.
All these internal noises concern me but they may be normal if they are from the compression unloading mechanism. And, the opening of the intake and exhaust valves seem to overlap each other. But that would be in the design of the cam and not anything you could adjust. More importantly, the engine will not start. I'm anxious for some reply with suggestions on how to proceed from here to get this blower running. Anyone with ideas, please let me know.
Thanks..........Glen
I found the valves to be a little loose and had to close the gap a little to the 0.005" specs. Unfortunately, the engine still won't start. While turning the flywheel slowly by hand, I noticed some clicking noises in the engine that seemed unusual. I have done nothing that I know of to mess with the timing and think it's still ok but it is acting like it is out of timing. The "S" on the flywheel magnet is at the right side of the coil at the top of the compression stroke and both valves are closed. On the power stroke, the exhaust valve starts to open just before 6:00 o'clock at the bottom of the stroke but the intake valve opens slightly starting at about 4:00 but closes again a little after 6:00. It seems strange that the intake valve would open at all during the power stroke as that would blow back through the carb.
On the exhaust stroke, the exhaust valve starts to close at 10:00 with a noticeable "click" sound and the intake valve is fully closed.
On the intake stroke, the intake valve starts to open at 12:00 TDC but the exhaust valve is not fully closed until 2:00. Just before 6:00 or at the bottom of the stroke, the intake valve starts to close but also with a noticeable "click".
On the compression stroke, the intake valve is fully closed at 9:00 but the exhaust valve opens slightly starting at about 9:00 and closes again at 11:00 with a "click". Why would the exhaust valve open at all during the compression stroke. Is this a designed unloader to reduce compression to more easily start the engine?
At those spots where the intake and exhaust valves open momentarily, if I hand turn the flywheel back and forth, the clicking gets louder and if I press down on the rocker arm while doing that, it feels like the pushrod is falling into a depression or a small raised bump on the cam, I can't tell which. Also, at those spots, sometimes but not always, as I slowly move the flywheel, the valve will slam shut with a more pronounced "clack" sound.
All these internal noises concern me but they may be normal if they are from the compression unloading mechanism. And, the opening of the intake and exhaust valves seem to overlap each other. But that would be in the design of the cam and not anything you could adjust. More importantly, the engine will not start. I'm anxious for some reply with suggestions on how to proceed from here to get this blower running. Anyone with ideas, please let me know.
Thanks..........Glen
Hammermechanicman
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The clicking may be the compression release. Try spraying a small amout of carb cleaner in the carb and with choke open try to start and see if it fires up for a second or two. Are you trying to start it with the valve cover off? If so it won't start. You must have the valve cover on and air tight. The rocker chamber is part of the crankcase primary compression.
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Thanks for the several good suggestions above, addressed in order.
First, I tried spraying carb cleaner into the carb after removing the air filter and cranking with the choke open but got no firing. I did have the valve cover on and tight but did not have a new gasket. But even if this caused a slight loss of pressure, the engine should have at least shown some sign of life.
Second, I don't recall where I got the 0.005" valve setting and will re-do that setting to 0.004". With that slight difference, it should fire anyway. The rockers were at a far wider setting before it suddenly quit.
Third, when I first researched possible problems with the coil, I read where not putting those little plastic washers would short out the coil resulting in no spark. So, I was sure to put them on when mounting the new coil.
Forth. Thank you Fish for your kind offer to send me the service manual but that won't be necessary since I was able to find the manual for the BR blowers on line last night. At this point, I need to read it, paying particular attention to timing and how to run a compression test on this engine. I tried that test yesterday but couldn't get any reading, I thought because of the unloader mechanism. If that wasn't the reason for not getting a reading, then this engine may have some serious internal problems.
Thanks again for all who are trying to help me get this thing fired up. I'll keep you all posted on what I am doing and, hopefully, find the problem myself or get some further input.
Glen
First, I tried spraying carb cleaner into the carb after removing the air filter and cranking with the choke open but got no firing. I did have the valve cover on and tight but did not have a new gasket. But even if this caused a slight loss of pressure, the engine should have at least shown some sign of life.
Second, I don't recall where I got the 0.005" valve setting and will re-do that setting to 0.004". With that slight difference, it should fire anyway. The rockers were at a far wider setting before it suddenly quit.
Third, when I first researched possible problems with the coil, I read where not putting those little plastic washers would short out the coil resulting in no spark. So, I was sure to put them on when mounting the new coil.
Forth. Thank you Fish for your kind offer to send me the service manual but that won't be necessary since I was able to find the manual for the BR blowers on line last night. At this point, I need to read it, paying particular attention to timing and how to run a compression test on this engine. I tried that test yesterday but couldn't get any reading, I thought because of the unloader mechanism. If that wasn't the reason for not getting a reading, then this engine may have some serious internal problems.
Thanks again for all who are trying to help me get this thing fired up. I'll keep you all posted on what I am doing and, hopefully, find the problem myself or get some further input.
Glen
Hammermechanicman
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Double check the flywheel key. The clicking noise could be an issue problem is looking inside the engine requires pretty much complete disassembly of the engine. You can try a bore scope if you have one. Or a leakdown tester.
Yesterday I adjusted the valves and while doing it, verified that both valves were opening and closing properly and appeared to be in time with the flywheel and coil. Today I did a compression test using a high speed drill. All I got was the needle flickering and basically, no compression. To verify the lack of compression, I then tried to do a leakdown test. Before doing that, I pulled the cap off (and then replaced it) the rocker chamber to verify the piston was at the top of the compression stroke and that both valves were closed with play between the rocker arms and the valve stems. Also, the flywheel was locked in place at that point. On applying air to the cylinder, it came out of the muffler. As higher pressure air was applied, it escaped through the muffler in whooshing volume, not a hiss like you would hear from a valve that had not seated well. I found that odd because while looking at the rocker arms, springs and push rods, even at high rpm, everything seemed to be working normally. This is other than the intake and exhaust valves opening briefly during the power and compression strokes which may be part of the cylinder decompression for easy starting.....or not.
I also used a boroscope in the cylinder to try to see if there was any damage to the piston. The resolution was a little fuzzy and while not being able to verify it for sure, the top of the piston seemed undamaged. It was impossible to turn the scope to see the condition of the cylinder walls. I'm at a loss to guess where the pressure is escaping. It doesn't appear to be a hung up exhaust valve because before adjusting the valves, both were closed and the tappet gaps were both about the same. With a hung up valve, the gap on that one would have been much wider. On the other hand, with such a small cylinder volume, a valve that is not seating might let more air escape than I would think. Anybody have an idea what is wrong inside the engine? It seems it must be something in the exhaust valve area. Sure would like to get some input from anybody who has run into this problem before I start tearing the engine apart so I know what I'm getting into.
Glen
I also used a boroscope in the cylinder to try to see if there was any damage to the piston. The resolution was a little fuzzy and while not being able to verify it for sure, the top of the piston seemed undamaged. It was impossible to turn the scope to see the condition of the cylinder walls. I'm at a loss to guess where the pressure is escaping. It doesn't appear to be a hung up exhaust valve because before adjusting the valves, both were closed and the tappet gaps were both about the same. With a hung up valve, the gap on that one would have been much wider. On the other hand, with such a small cylinder volume, a valve that is not seating might let more air escape than I would think. Anybody have an idea what is wrong inside the engine? It seems it must be something in the exhaust valve area. Sure would like to get some input from anybody who has run into this problem before I start tearing the engine apart so I know what I'm getting into.
Glen