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RedMax edger hard to pull over

#1

Richie F

Richie F

Have a RedMax edger BCZ260TS (967194302)
Was given to me with no knowledge of it's condition/problem with the cylinder off.
Piston and cylinder wall looked good and could turn the engine over by hand with no issue.
Installed new rings and honed cylinder and assembled.
Now the question:
With the plug out I can pull it over normally like any other trimmer/edger but when I install the plug it's like pulling over a chainsaw. This is without the coil wire hooked to the plug also.
Checked muffler for blockage(found good) and that the coil pickup was not dragging on the flywheel.
Piston is not contacting spark plug also.
Compression after doing rings is 25 psi but yet trying to pull it over feels like it's "150".
Give me ideas and I'll answer you back.


#2

Tiger Small Engine

Tiger Small Engine

Richie F said:
Have a RedMax edger BCZ260TS (967194302)
Was given to me with no knowledge of it's condition/problem with the cylinder off.
Piston and cylinder wall looked good and could turn the engine over by hand with no issue.
Installed new rings and honed cylinder and assembled.
Now the question:
With the plug out I can pull it over normally like any other trimmer/edger but when I install the plug it's like pulling over a chainsaw. This is without the coil wire hooked to the plug also.
Checked muffler for blockage(found good) and that the coil pickup was not dragging on the flywheel.
Piston is not contacting spark plug also.
Compression after doing rings is 25 psi but yet trying to pull it over feels like it's "150".
Give me ideas and I'll answer you back.
Click to expand...
It is a trimmer, not an edger. Edger uses a hard blade. Anyway, did you use oil or assembly lubricant when installing rings and piston? Did you install the new rings correctly? Was there any significant scoring on piston and cylinder? What is the year of the trimmer?


#3

StarTech

StarTech

Unless you miss something seriously.

Yes it going to feel like a lot of compression because it back to normal compression of 130+ psi probably closer to 160 psi. This why you must use a compression tester design for these small engine to check the actual compression. An automotive tester will not give correct readings. There is no compression bleed off device either.

If it is truly has only 25 psi compression it will never run as you need at least 100-110 psi for the 2 cycle to even to start.


#4

Richie F

Richie F

Tiger Small Engine said:
It is a trimmer, not an edger. Edger uses a hard blade. Anyway, did you use oil or assembly lubricant when installing rings and piston? Did you install the new rings correctly? Was there any significant scoring on piston and cylinder? What is the year of the trimmer?
Click to expand...
OK apples to doughnuts, but yes engine was assembled with oil.
Rings where installed correctly, marked location on pin on ring lands before assembly.
No cylinder wall or piston damage.
Year is unknown other than the S/N given.


#5

Richie F

Richie F

StarTech said:
Unless you miss something seriously.

Yes it going to feel like a lot of compression because it back to normal compression of 130+ psi probably closer to 160 psi. This why you must use a compression tester design for these small engine to check the actual compression. An automotive tester will not give correct readings. There is no compression bleed off device either.

If it is truly has only 25 psi compression it will never run as you need at least 100-110 psi for the 2 cycle to even to start.
Click to expand...
Why won't an automotive tester not give the correct psi reading? Never heard of that and I'm a retired auto mechanic of 55 years.
If you say what is true I'll add fuel and hook up plug wire that does make spark.


#6

StarTech

StarTech

First most automotive gauges have the schrader valve at the gauge and not at the end of hose. Due to low volume of compressed air usually around 21 to 31 cc (which is less than 2 cubic inches) it has to fill the flexible hose first to a pressure that would even open the valve at the gauge. Most times it barely opens the valve if at all. So a lot of the pressure it is lost as the piston passes TDC before the valve opens thus giving false readings. And even those gauges with the schrader valve at the end of the hose it takes multiple pulls at build up the pressure to gauge as the hose must first be fill with compress air. Then there is the schrader valve itself, it must be more sensitive to lower air volume unlike the one used for automobile engines.

Even the gauge I have here takes up to 10 pulls to reach max readings due to flex hose used and it is design for these smaller engines so it has a very sensitive schrader valve.

BTW automotive engine cylinders are a heck a lot larger volume wise in the first place.


#7

Richie F

Richie F

StarTech said:
First most automotive gauges have the schrader valve at the gauge and not at the end of hose. Due to low volume of compressed air usually around 21 to 31 cc (which is less than 2 cubic inches) it has to fill the flexible hose first to a pressure that would even open the valve at the gauge. Most times it barely opens the valve if at all. So a lot of the pressure it is lost as the piston passes TDC before the valve opens thus giving false readings. And even those gauges with the schrader valve at the end of the hose it takes multiple pulls at build up the pressure to gauge as the hose must first be fill with compress air. Then there is the schrader valve itself, it must be more sensitive to lower air volume unlike the one used for automobile engines.

Even the gauge I have here takes up to 10 pulls to reach max readings due to flex hose used and it is design for these smaller engines so it has a very sensitive schrader valve.

BTW automotive engine cylinders are a heck a lot larger volume wise in the first place.
Click to expand...
Any compression tester has a schrader valve designed for compression tester. One from a tire valve won't work.
Never have I've seen a schrader valve at the gauge of a compression tester, always at the end of the hose.
As far as volume I've cranked an internal combustion over as many time as I did small engines and got the same results. This applies to 2 stroke snowmobile engines as well.


#8

StarTech

StarTech

I have seen them. Matter of fact the digital compression tester I brought last year had it at the gauge. Moving it to end of the hose made a huge difference, a royal pain to do so. Also the gauge my youngest brother had also had it at the gauge. But didn't modify it as it is a keepsake of his.


#9

Richie F

Richie F

StarTech said:
I have seen them. Matter of fact the digital compression tester I brought last year had it at the gauge. Moving it to end of the hose made a huge difference, a royal pain to do so. Also the gauge my youngest brother had also had it at the gauge. But didn't modify it as it is a keepsake of his.
Click to expand...
What brand was them?


#10

StarTech

StarTech

The digital one is an Azuno but the other one is in the storage unit under a bunch of other stuff and I am not digging it out in this hot weather.

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#11

Hammermechanicman

Hammermechanicman

If you used a lot of oil when you put it together that can cause a high compression issue.
There are lots of Asian automotive compression testers that use 2 hoses the first connects to the guage and has the Schrader valve and then a second hose that adapts the plug thread. Not good for small engines as they always read low.

660.jpg
92cc engine with advanced timing. You need to pull it like you mean it.

They make guages expressly for small engines.


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