Stupid MV50

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black95

black95

10 Year 15 Year
Joined
Aug 25, 2008
Threads
127
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2,499
Location
Colorado
So I went out wheeling yesterday with a Suzuki Samurai club... Yeah, you read that right-- Samurai's... because I'm not a 4x4 bigot :) Those little Ninja's were kicking butt, I've been searching craigslist for one all day.

Anyway, used my MV50 to air up my tires so I could save the CO2 in my tank, which saves a little money. Well, the love/ hate relationship almost ended, as the ol' MV50 pushed its last breath of air out, thankfully on my 4th tire. The RPM jumped way up, and there was the typical "box of rocks" sound of death. I figured one of the reeds in the air chamber broke, I later confirmed this by breaking it apart and finding all the pieces of the intake reed.
I told myself to walk that thing to the trash can immediately, but couldn't help but pull out my smartphone and google to see if there was a rebuild kit available. There's not-- but, there was a thread about a guy who totally rebuilt his to try and get more flow out of it. I was intrigued. I ended up going through mine, because I'm a cheap, and was bored with my day off- so for those of you that have this compressor, (the Harbor Freight is extremely similar) if yours quits, maybe there's hope before you trash it.

I didn't really get any pictures of the reed block before I started working on it, because I really didn't think I would keep it, so the pictures start in the middle somewhere.

This is the reed block, with the exhaust side reed showing. This reed has a rubber plug that is loosely contained in the reed. Both intake and exhaust ports were 3/16 or so in size, unfortunately, you can't open the exhaust side up because the plug would no longer seal properly. The other port you see is the intake port. I opened it up to 1/4 inch and chamfered the hole to hopefully allow better air flow. In my mind, if you're compressing air, getting air in is more important than getting air out, so I'm happy there's no rubber stopper on the intake port and it could be opened up.

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This is the other side of the block, and you can see that I chamfered the intake port with the same 1/2 inch drill bit, almost all the way through to get it as big as I could, especially since I couldn't enlarge the entire opening. I figure this serves two purposes though, it gets the air moving easier, and creates more volume in the piston chamber. Hopefully that's good logic, but I'm probably wrong :) the exhaust reed and screw that hold it are still missing at this point.

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At this point I started looking at the badly scored up piston bore, thinking I might be wasting my time. But looking closer, it turns out that it is a sleeve and with a little gentle tapping from a hammer, it will move inside the heat sink. I decided to take the sleeve out and flip it over, so that now the piston will use the nicer, not all scored up side of the sleeve. Looking closer though, I think you'd be ok flipping the heat sink over as well.

Once upon a time, trying to make this compressor more quiet, I thought I would get smart and put some Marvel mystery oil in the cylinder and make it more efficient. That turned out to be not very smart, as the heat involved turned the oil into sludge and cake, which bogged the compressor down and the extra amperage burned up the fuse holder in the cord. I think this might be when the scoring happened. When a compressor says "use no oil"... Well, don't use any oil :)

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I cleaned up the piston and Teflon ring, which surprisingly seemed to be OK. Teflon is some tuff stuff. You can see the indent in the piston. This is for clearance for the screw that holds the intake reed. If you take your compressor apart, make damn sure the reed block is clocked right or very bad things will happen...

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In the thread I found on google, the other guy took his compressor apart and bored his intake too large, which caused the reed to suck in and bend out of shape. He replaced it with a five thousanths feeler gauge that he cut off. I stole this idea and did the same. My feeler gauges were all bent up and needed to be replaced anyway. Drilling those little dudes out is tough. Here is the reed block with my new larger .005 intake reed.

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The guy who I got the reed idea from was tackling all the problems associated with this compressor, one of which was the horrible pressure gauge. He ended up tossing the factory unit with metric threads and drilling out the cylinder cap with an 1/8th inch pipe thread tap, then unscrewing the adapter off of a "Slime" brand tire guage and screwing it into the head. Strangely, in the bag with this compressor, I had the exact same tire gauge. I decided to do this mod too. The numbers are much easier to see, as the gauge only goes up to 60 pounds. I don't need to go any higher than that because I don't have a heavy duty truck, and there's no way I would trust this compressor to put out over 40 psi anyway.

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So the old compressor is back together and pumping out air like crazy. It's still loud enough the wake the dead, but I will keep it around as a backup for when my CO2 tank runs empty or I take something besides the Cherokee wheeling. I have a 100% duty cycle Viair compressor sitting in the garage that I STILL have not gotten around to mounting in the Cherokee, but someday I'll get there.
 
Couple of friends of me used to run carnage canyon 4 or 5 times a year had jeeps with stretched wheelbase and 42's had to winch at least once on the exit if not more. They said the only vehicle the have seen make it out the exit without winching was little sizuki either om 33's or 35's. They are bad ass.
 
Ive treated my MV50 like crap for about 4 years.. literally had it just floating around in the back of my cruiser slamming on every bump and its still putting out air! Love that thing
 
So how much faster is it at filling a tire?
 
CO_Hunter said:
So how much faster is it at filling a tire?
Click to expand...

It's probably not any faster. Lol. I feel pretty confident that the little Asian people that designed this thing was a lot smarter than I am, and if they could have gotten more flow out of it, they would have.

Seeing as how we have the same brand of tire, probably with the same carcass, both on a 16x8 wheel-- we could hook them up on the next outing and check the pressures with the same gauge, and after a timed amount of time to see if it is any speedier. Mine is definitely three times as loud as yours, but I doubt it's any faster. Haha.
 
karas said:
Couple of friends of me used to run carnage canyon 4 or 5 times a year had jeeps with stretched wheelbase and 42's had to winch at least once on the exit if not more. They said the only vehicle the have seen make it out the exit without winching was little sizuki either om 33's or 35's. They are bad ass.
Click to expand...

Matt, I'll try and dig out some good pictures of my old Sammy. It was pretty awesome when it was upright. I feel I could build a much better version of it with the knowledge I have acquired over the years.
 
black95 said:
-- we could hook them up on the next outing and check the pressures with the same gauge, and after a timed amount of time to see if it is any speedier. Mine is definitely three times as loud as yours, but I doubt it's any faster. Haha.
Click to expand...

MV50 drag race...bring it on...
 
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