Craftsman GT3000 "MUTT"

I mean i probably could've, but you know there's a +$20 premium for anything that's brass. Besides, the hard part is just not breaking off the drill. Besides that it's just a thread, some turning, and cutting a screwdriver slot with a hacksaw.

No it did it with the previous stock air box. The hose is.kind of corrugated, I'm not sure how to describe it. The hose that comes with cheap backyard above ground pools.

Not dead, yet!

I put a thing on to help stop my foot from sliding off the clutch

Nice simple mod!

Rolled mutt in the shop today. I'm tired of fighting to make this engine run well, i think it's just clapped. Low compression, bad valves, weird carb issues. Smokes a lot. Just a pain.


Honestly, if i had a good vanny I'd go to it in a heartbeat. But i don't, so my next best option is an oppy with few shared parts- and hopefully few shared problems.

So it's back to the 20hp oppy that was once on her. I have another of the same engine with the governor still on it that I'll take the intake and carb off of, just to be sure. The only thing major that's being swapped over is the other starter onto this one.


That's as far as i got tonight, feeling a bit tired.

Put the 20hp back together and in, still some stuff to hook up but i got to see if it runs.


aaaaaand it does, but won't idle. I imagine it would surge if it were governed. Go figure, this is a 3 screw with fixed jets. I've not been able to get either of those i have to run well either.

For those that don't know, a fixed idle jet on a 3 screw replaces the screw with a screw in sort of jet. A normal needle screws in but I'm not sure if all the internal geometries are the same, though i got this to idle just by replacing it. The carb is probably still dirty so I'll look into that again.

Oppys are just confusing ...nice job on the swap tho!

Carb stuff is only complicated because of Al Gore. Environmentalists are lame when they're only taking political action. Although any ideology is lame if no one is actually willing to step up and get some attention and results. I mean, take a look at Ted K. Rad guy. Only environmentalist worth caring about.

Just bought a 34mm mikuni clone. I'll pick up a pulse pump here soon also. We're gonna see if i can get mutt to run well again.

Finally doing something- machined a carb adapter on the mill.

I've got a 19.5 hp oppy that's running rough, just like yours. I bought a full carb/pump rebuild kit for it (just arrived last night) & I'm gonna give that a try, but I have to say that Mikuni idea is VERY intriguing! I'll be following this with interest!

My engine is still completely stock, with the governor still hooked up & functioning properly (as far as I know ), but I'm wondering - **will the Mikuni's carb connections permit the governor to still be hooked up??**

It won't. Mikunis connect with a cable, no linkages.

I am doing this swap with a horizontal oppy intake- if you don't have one you'll have to do it a little different.

Ah, okay.  I hadn't planned on bypassing the governor (and don't have a clue how to do it on this motor) due to exploding flywheel horror stories.  My intake manifold looks exactly like the one in your pic above, with the Mikuni on it.  I could certainly machine an adapter, and I suspect I could locate a good used Mikuni (motorcycle shop nearby that I'm on good terms with).

I'll be interested to see how it works out!

By the way, what size Mikuni is it?  As my engine (and yours, as well, I expect) is a 688 cc engine, I'm thinking maybe a Mikuni off a Kawasaki 650KLR or something might work...although I'd still have to figure out a way around the governor.

It's not hard to bypass. I've never seen an undamaged flywheel explode.

It's a 34mm mikuni clone. It's a 20hp oppy, so 46ci. Can't remember what cc that is.

Cool! I'll look for how to bypass the governor, then! Thanks - I'll be watching for your updates!!

So i actually finished the carb adapter tonight, minus cutting a gasket it should bolt right on. Thought I'd go into a little more detail as to how it works.

In this picture you can see i measured the bolt spacing of the intake and just drilled and tapped that into the adapter so i didn't have to find space for nuts. Here you can also see one of the set screw holes that keep the carb in place.


I drilled a pilot hole and got my boring head set up and bored the smaller hole to match the inside diameter of the carb, and the larger bore the outside diameter of the carb mounting flange. Make note of the groove in the carb on this picture.


In this picture you can see the other side of one of the two set screws. Actually, not the set screw, but the BB i put in there for the set screw to push on, so the end of the set screw doesn't mar up the carb so much. Below that is an O ring that seals on the face of the carb. The set screw holes are placed so that they draw the carb down into this O ring to provide a good seal.


It sounds like a lot of engineering, but really this was something i just threw together as I went along.

NICE JOB!! Lots of thought went into that!

So i go to mount the carb up with the intake and realize that it's not gonna clear the winch transmission. Great. I found four nuts to space the engine up and really just moved a spacer on the pulley to make it line up again. I might end up turning some spacers on the lathe, or i might just leave these.


So now having enough room, i mounted it up and hooked everything up. It ended up a lot lower than i expected, but I'm planning on a snorkel of some sort anyway.


I spun her over with a drill as the battery was dead, and before too long she caught prime and fired right up. I have the fuel needle at the richest setting and it runs like an alarmed hominid. Very responsive, and starts easy. I think it's running rich but I'll just have to read what the plugs say after i run it a while.

I think some spacers with a bit bigger foot print might be a good idea. I dont think the bottoms of these engines are machined clean across, but around where they bolt down, maybe across some casting webs. Its been a while since Ive looked at one.

Maybe not all that big of a deal though.

Putting a dirt bike carb on Rusty is my favorite mod to date, I fought and fought to get the factory one to even acceptable performance and I bolted the dirt bike Caen on and it’s been so much easier to tune, so much more responsive and allot more power

TheBeal wrote:

I think some spacers with a bit bigger foot print might be a good idea. I dont think the bottoms of these engines are machined clean across, but around where they bolt down, maybe across some casting webs. Its been a while since Ive looked at one.

Maybe not all that big of a deal though.

You're absolutely right on that. I have some aluminum bar ends that will make some better spacers.

Creepycrawler wrote:

Putting a dirt bike carb on Rusty is my favorite mod to date, I fought and fought to get the factory one to even acceptable performance and I bolted the dirt bike Caen on and it’s been so much easier to tune, so much more responsive and allot more power

Dirt bike carbs run better even when they aren't jetted right. It's wonderful.

I have been trying to get a good air cleaner setup for a while now so i can actually jet the carb right. It seems the air box i made a while ago just doesn't get enough flow.

Nice having a lathe to make adapters.


I really need to get one of my spare 820s doc locked and in this thing. The old trans is screaming, lol.

Nice little adapter there

Ok, I'm new to all this and have just built my first machines (governed with foot throttle.) I understand why this mod is desirable (more power, better response, tune-ability,) but how do you drive ungoverned like this? I mean on my machine, especially in higher gears, the throttle seams almost too responsive and jerks with the smallest Mostly because of my foot bouncing on the throttle as I bounce around so I kinda grab a gear, pin the throttle down, and hang on. This would be disastrous if ungoverned.

So is my foot throttle too sensitive? I have way more throw to my pedal than a bicycle brake throttle. Or when ungoverned, do you have to pin the throttle and let off when the rpm gets too high and on and off as you boogy down the trail?

well really depends on the machine my small craftsman with a 12hp flathead i run it governed and the pedal hooks to where the dash throttle used to hook to, its jerky when you grab a gear and it drives like a manual car does it jerks if you let off the clutch too fast or something like that but takes off with throttle in 6th but will stall without throttle. my jerks a bit but i wish mine was ungoverned it would fly!