AMT 626 Engine Swap

[Mr. Moose]

I bought my Gator in the spring 2 years ago, it was in for some engine work as it smoked really bad and was blowing oil out of it somewhere, when I got the side cover off it I noticed a crack in the case that went all the way down to the other side, pulled everything out and had it professionally welded and got it all back together and still smoked like a son of a gun but I worked it on the farm everyday and it was good, I took it apart again to fix the smoking problem and fixed up the exhaust valve and guide and replaced a seal on the main crank. Now it still smokes worse than ever and its got some piston slap and I'm not taking it all apart and paying somebody to bore out an engine that's on it last legs anyway so I want to drop a new engine 10-20 Horse. I know it can be done and I know people have done it so to those people that have what did you use?It's a short space and it's proved to be a pain in the arse to find anything that will fit it and put out enough to power to move this thing. Any help or insight is welcomed. Here's some pictures

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[Mr. Moose]

Well I have finally found an engine that is going to work, To anybody that wants to drop a new engine in one of these the Honda GX390 is the best engine for the job. Its a 12 hp cranking out 19.5 ft. lb compared to the the 10hp 14.47 ft. lb of the original Kawasaki.

The Honda has an option to come with an electric start and it has a standard 18 amp charging coil. With the Gas tank, muffler and air filter removed form the top of the engine it will fit into the space and will only need a muffler fabbed up to it, the air filter run out somewhere fairly clean and dry and an electric fuel pump, then it should work better than new.

[frochevy]

Hey thanks for the info on using the Honda GX390 engine. I have been thinking about pulling my stock engine and rebuilding it, or thinking of upgrading it. What is the best place you have found to buy your Honda GX390 engine? Have you completed your swap yet? Will the clutch work? I'm also in need of clutch work. Any ideas where I can get clutch parts at? Thanks

[Mr. Moose]

So instead of the GX390 I've got a 390cc 13hp Powerfist engine, almsot an exact copy of a GX390 except cheaper...
Today I pulled all the fuel tank, muffler and airbox off it and played around a bit. To get it to fit the mount holes in the base plate are going to need to be elongated forward and a longer belt used because this engine is longer and if it sits back where the old 290 did then the head hits the tranni. It will need an electric fuel pump and a bit of fab work, the throttle has a place to make it cable operated but the choke is a little less friendly and is going to need to be played with. It will need a new muffler flange welded to the stock pipe and routed out the side to the stock muffler, also the intake is going to need a tube much like the one on the 290 engine to mount the filter to.
Dad has pictures, I'll add them when I get them.

[Mr. Moose]

Well I' back and the engine is finally in the machine and running, the belt is too tight right now because of clearance issues so it doesn't stop but once i get a longer belt it should go good as gold, also I have noticed that this engine seems to have a little extra vibration to it but maybe I'm just imagining things.

[juttu]

Pics pls :)

did you find a longer belt eventually?

I did the same, some pics here http://www.johndeeregatorforum.com/showthread.php?12040-AMT-600-Gets-Reborn!&p=25200#post25200

Now opened up the project again, due to clutch (Drive pulley) function, GX rpm is not high enough for the Salsbury 780 spider to work - so additional weights needed:

http://i573.photobucket.com/albums/ss175/roverjuttu/JD/WP_20160330_001_zpsun82jbcn.jpg (http://s573.photobucket.com/user/roverjuttu/media/JD/WP_20160330_001_zpsun82jbcn.jpg.html)

Original rollers+axles were 35grams, new ones total 60gr - engagement is now low, maybe 1500rpm?
Driven pulley gives up too soon though, power is lost at mid-speed already - too much weight!

I tried to estimate the weights according this source: http://forums.bajasae.net/forum/uploads/78/QDS-09BajaSAECatalog.pdf page 8
-> springs are yellow, but the weights mentioned are from another planet..


http://i573.photobucket.com/albums/ss175/roverjuttu/JD/WP_20160330_002_zpsrffmbjnl.jpg (http://s573.photobucket.com/user/roverjuttu/media/JD/WP_20160330_002_zpsrffmbjnl.jpg.html)


New parts made from Brass (dims in millimeters)
- "rounded" roller B16 d12h7 D19-19.7 (middle)
- side weights B6 d6.5 D15 (result:too heavy!)
- roller axle Stainless B16.5 d6.5 D12H7
- shaft plain M6 screw+nut

IF longer belts are not to be found? one could make a spacer / Shim disc between the plates of the driven pulley - I just estimated some 5mm or 6mm thich plate would do to keep the belt deep enough. Driven axle is D35mm, so a disc with 35.2/60 would be nice to fit in.