RedMax BC3400 brushcutter questions.

[naturelover]

Here is a RedMax BC3400 trimmer I got as a freebie helping a buddy put some plugs in his car. He found it in the junk, some older man apparently brought it in to recycle, its only 12 years old, and seems in good shape.

Muffler was plugged with mud daubers, but was, and is, running well. Compression is 120psi, seems a little low, will at least refresh it with rings.

Are these pro grade trimmers? How much were they new? $60 will pretty much get me everything I think I need for a rebuild and some other parts like the guard and air filter cover and top cover.

Doesn't seem much lighter than my FS-250, but since the Shindy T-20 isn't running as of now, plan on using it as my trimmer for when the grass gets too tall for my cheapo Bolens and other grass/brushcutting duties when needed.

PO has filled the whole shaft full of grease, so much that it squeezed out into the clutch. Don't really know how it even worked.. Bet there must be 2lb worth of grease in there. Got some of it out of the top of the tube to keep it out of the clutch, guess will leave the rest in there.

Here is the P/C. The piston still has the machine marks on it in most spots, but is shiny in others. I was thinking that was normal wear, is that true?

Is this normal? A new piston is $25, does it need one? I will get one if ya'll think it would be needed.

Apologies for the bad pictures, thanks for any info..

 

[naturelover]

Welp, got a few parts for it. Decided to skip the piston, and just re-ringed it.

Compression is a little low, around 120psi or so with the new rings, but will check it again when its cold to confirm. Don't know why really, everything looks good inside. Ring gap looks good, the crosshatching is still on the piston, cylinder is as smooth as can be. It started easily, even when it was warmed up.

Getting it mated up with the shaft again.

Lost the throttle adjusting screw, didn't even remember exactly what it was. Looked at the IPL and it looked familiar. Dove into my old bicycle parts and found a brake cable adjuster. Fit perfectly after a little trimming and drilling out the center of it so the cable end would slide through it.

Got a new top cover and air filter cover, new plug boot too, just to spiffy it up a little.

Cleaned up nicely for a junked trimmer me thinks..

It starts easily and runs well, though without the guard (on backorder), didn't really get to try it out that much. Sounds different than my Stihl or Shindy though.

Have only about $40 worth of engine parts in it, but the dang guard and the trimmer head cost around $60, guess they make up for the cheaper engine parts somehow.....

 

[morgaj1]

Those older Redmax units are really nice. I would put the quality up there with Stihl and Shindaiwa. And, you can't kill those Zenoah motors. I wouldn't sweat 120psi compression when warm. These little trimmer motors don't have the compression of a chainsaw. As a matter of fact, the lower limit of normal on the old 25cc Stihl motors (FS75, FC75, etc) was 110psi. I just did a top end rebuild on my old Stihl FC75 edger and it only has 115psi cold. After break in, I'm sure my numbers will rise a bit. And, I'm sure cold, your compression on the Redmax is well within specs.

 

[naturelover]

Thanks for the info morgaj1. :smile2:

Went and checked the compression again when cold, 120psi. Must have not been as warm as I thought when I checked before. Dumped some oil in there and checked again, no difference.

Thats all its gonna give me I reckon.

But feel a little better about it now, was thinking it should be up there around 150 or 160 or so.

Another thing is that I can NOT get the tank screws out, which means I can't split the case if I ever need to. That is how the upper fin got broke off, had it centered on a board pushing on it, but it of course slipped and bent the fin over. Just broke it the rest of the way off, filed and saved what I could of the fin for cooling purposes.

But couldn't stand it any more, got on my full coveralls, gloves, safety glasses and such and tried it out.

It certainly doesn't run like its low on compression!! Runs really well, plenty of power to boot. Its not quite the FS-250 (course, what is!), but its got way more oomph than the T-20. Really smooth too, at speed and idle, anti-vibe works well. Like the exhaust note too, as said, its different than the Stihl and Shindy trimmers, a little deeper or something it seems.

Nice unit indeed.

Bad part is that it is heavy, and that is without the guard. Speaking of, tis a little backheavy too without the guard, had to move the handle and strap back toward the engine, but may have to readjust when I get the guard back on.

All that is left that is needed is a new plug, thought I had one on hand, but will have to pick one up.

I gots too much junk though, couple of months ago to get ready for the season, I spent $50 on plugs! :hmm3grin2orange: