My Franken-Mantis

[PhilsSmallEngine]

Never has there been a bigger thorn in my side than my grandfather's Mantis tiller. It has the Echo 2-cycle engine everyone says is awesome and a bulletproof gear box, yet his chews up carburetors. It has gone through 3 C1U-K54A carburetors in the span of 6 years. The factory carb lasted 3 years and to my dismay, I couldn't get it to idle after rebuilding it. Plug a new one onto it and away it went. Got 2 years out of the replacement and same issue. I bought the $8 rebuild only to find I can't get it to idle properly. The third... you see the trend here.

I decided to bypass that amalgamation of low quality plastic and high quality aluminum and go all aluminum. I plunked down less than half the money of the Mantis factory carburetor and spent the evening putting a C1U-K68 carburetor on it. How does it fit? The primer bulb is upside down and I had to take the butterfly/throttle linkage off the old carb and put it on it, but it has never run so well. Throttle response is phenomenal and it revs up like a well tuned chainsaw. I never was able to get the same response with the C1U-K54A. There was always hesitation at the bottom end.

If anyone is interested, I can take pictures/video of the final product since I didn't bother to take shots or video of my rebuild. I also have a customer that wants me to work on their Mantis despite the fact I told them they are my kryptonite. I may do the same with theirs since the problem is essentially a new carburetor from what they describe.

 

[Merkava_4]

How'd you get the idea to switch to the C1U-K68 ?

 

[eljefino]

I wonder if there's a difference in emulsion tubes. These are the little brass things stuffed in with the main jet with various tuned holes in them. A steady speed/ state engine like a generator doesn't need a sophisticated one. They could have assigned the wrong part number to your mantis.

 

[PhilsSmallEngine]

I got the idea taking apart an Echo chainsaw and I noticed the carb was simply an upside down Mantis Zama carburetor. Then I looked at the all aluminum construction and wondered if that will make it more durable. My grandfather's Mantis has never run particularly well so I decided the worst that happens is it never runs again on that engine. I'd rather attempt to mount a more powerful and reliable Red Max engine on it anyway.

The body is exactly the same CU1. That was why I tried it. The only difference is which end the bulb is on and which brass barbs are pressed in. The Mantis factory carb has all 4 small holes tapped on the top. If I tapped the other 2 holes, I could use that body on as a factory replacement.

I'm planning on giving it a hour plus workout today or tomorrow to get a definitive idea of potential issues I could have missed. Then I'll put the correct Echo fuel line/filter kit rather than the low quality stuff I had laying around.

 

[Bud]

Had to laugh when I read the subject Franken-Mantis. Had one several years ago, but never again. The thing was the biggest pain in the neck I ever spent money on.

 

[NH73]

A couple years ago, I spent a little or and got the one with a Honda engine. No problem.

 

[andyd]

My sister and my BIL picked up the Mantis we snagged when the old homestead was emptied. I got it going and tilled my beds with it. My BIL is also my best friend and a great mechanic. It is in good hands. My folks were organic gardeners and had over an acre under cultivation when Dad died. Rick maintained their Troybilt tiller for 25 yrs. He was thrilled to see my brother haul it away to VT.

 

[PhilsSmallEngine]

I know that feeling andyd. I wish I didn't need this Mantis for the dethatching and aerating attachments. It's so useful, but the price paid isn't necessarily worth it. As a tiller, it stinks since my area has really rocky soil. The usefulness is in its versatility. I still have to tune it up as it has a dead spot in the mid to upper rpm range when at temperature, but there seems to be no ill effects from running this carburetor other than inconvenient primer location. Only time will tell.

 

[1duck]

Hi, I just signed up because i'd really love to see some pictures or even a mini video. The official zama carb costs about 5x what I could pay for a clone of another cu1 carb.

How did you get around the throttle being upside down, i flipped my current carb and from the cursory glance i gave it, it looks like the cable would pull the throttle in the wrong direction.

 

[PhilsSmallEngine]

You need to gut an existing C1U-K54A. You need to remove the butterfly (1 screw) and remove the E clip to take the throttle linkage to reuse.

 

[1duck]

Surely the throttle cable still pulls upwards on the linkage though, so with the carb turned upside down it pulls upwards straight into the throttle stop screw? I'm probably just being stupid here and for that I apologise. I'm just having a hard time visualising it.

 

[PhilsSmallEngine]

The C1U body is the exact same. The butterfly moves in the exact same way. The only differences is the location of the primer. It can be mounted either way. The one I used simply made it so it appears to be upside down. All you have to do is simply swap the throttle linkages out and screw the butterfly back on.

 

[1duck]

I've been staring at it for way too long and i think I understand now, it's because i just flipped the carb i had to try visualise it, which was a 5k4a but obviously that doesn't work because then the whole thing is upside down.

Looking at pictures of the carb i'm hoping of getting, either the c1u h60 or the c1u w18, i think it will work.

Thanks for the patience phil, truly appreciated.

 

[Hokiefyd]

So the stock carburetor was all plastic? I would like to see pictures...it's possible that other Echo carbs would fit as well. If it was plastic, I can certainly understand the problems -- little passages inside probably warp with heat. Many Lawn-Boys suffered similar problems -- warping on plastic carburetors.

Both of my Echo products have Zama carburetors, but I think they're all metal.

 

[PhilsSmallEngine]

It's a mix of plastic and aluminum. the CU1 base is still aluminum. The top and bottom covers are plastic and prone to warping. The diaphragm loves to tear when the plastic shifts.

In theory, as long as they use the CU1 base, you can put it on a Mantis. It does require modifying the throttle linkage to the Mantis one, but that is 1 C clip and 1 screw on each.

 

[1duck]

Well I bought the C1U-H60 it took a little more butchering to get it to fit, because it came with its own choke mechanism but that was just one more screw and a touch of light dremeling to get rid of the plastic choke handle.

Brilliant fix though, thanks again phil.