By Steve M. on Unrecorded Date: Edit

Hello all,
After some restoration of my 1972 Amphicat (the only one here in Australia) I am strongly considering replacing the Sachs 270cc slimer with a modern 4-stroke motor, mainly for the noise reduction benefit.

There are two choices available to me here, the Honda GX390 13hp motor and the 13hp Briggs & Stratton Vanguard.
Firstly, is a 13hp motor going to over-power the vehicle? I don't intend to either go fast nor climb steep hills. Would a 9hp or 11hp motor be better?

Secondly, I can't find from either the Honda nor B&S websites the direction of crankshaft rotation - would anyone know this?

Thirdly, has anyone put one of these into their 'cat. It looks like I'd have to trim the end of the inside hull to fit either one in.

Fourth, what fluid do I use in the transmission? I don't think I have a T20 unit, but a b9 unit. This is the one with a long centre chain casting rather than the ones that have all the strange plugs(?) sticking out of it. I suspect there is gear oil in there, rather than trans fluid.
Thanks for any help,

Steve in Oz.
steven@phaedra.apana.org.au

By daveyoder on Unrecorded Date: Edit

to steven
from dave y
i own a71 scrambler and my dad own 67 amphicat
rare b7 model you can call your nearest small engine
dealer and ask them for the numbers toboth
briggs and honda both are 1800 number and
call them and ask them to send you a brocture
on how the crankshaft rotate
try that shouldwork
both engines are great engines
thank dave y

By mike abbey on Unrecorded Date: Edit

hi!steve,boy thats gonna be a tight fit,the chain adjusters are also right there beside the recoilstarter,you will also need a clutch for the fourstroke as the rpms are a lot different,i looked at this option too,removing recoil on the new engine might give you enough room,we havnt got the sachs engine in my brother inlaws yet,but i am familier with you machine,i would do some careful measuring before comitting to the moter change.rotation is counterclockwise at drive end same as fourstrokes,gearbox oil looks and smells like 90wt gear oil,we havnt drivin this one yet but she looks like she would turn one a dime, ps dave yoder go get a job!

By Steve on Unrecorded Date: Edit

Dave and Mike,
Thank you both for your suggestions and help, and to those who contacted me offlist too! Dave, I am a bit confused about your comment on the recoil starter, as the measurements of the Honda engine at:
http://www.honda-engines.com/gxgx390dim.htm
indicate that width doesn't seem(?) be a problem. It's the length that is, though. The cylinder leans over and this would intrude on the tranny gearbox casing. The top built-in fuel tank would be removed so it might *just* slip under the inside edge of the body. Also, an extension pipe from the muffler wound need to be fitted (with perhaps a secondary muffler to make it even more quiet?).
Thanks again,

Steve.
steven@phaedra.apana.org.au

By dakota on Unrecorded Date: Edit

2 Years ago I was a Honda industrial engine dealer . Honda does not warrenty any engine used in a go cart, atv etc..Also the engine is timed and carberated to run at full throttle 3600rpm , or idle but not in between . When engine is run at other than these two rpms you will experience spark plug fouling , alot of spark plug fouling . The honda is a good engine , but you should know the down sides too.

By David Keeso (Argomag) on Unrecorded Date: Edit

When you buy a new engine to put in an AATV such as an ARGO, do you have to buy a new tranny or can you use the existing one providing that it works.

By Alfred on Unrecorded Date: Edit

Dakota, where have you been? The New Honda GX 670 series, 24 HP are the best yet. The Keihin 2 Barrel Carb makes the difference.
As for Warranty issues, not exactly right, you must be an OEM and go through a testing phase and be "blessed" by Honda.
Word of advise, always run 89Oct. Gas from a Major Supplier in any small engine.

By dakota on Unrecorded Date: Edit

If you are coverting from a 2 stroke to a 4 stroke , you need a different clutch . because of different opperating rpms of the diffent types of engines.as far a tranny goes be it the T-20 or the Argo gear box , that doesn't need to be changed at all. Also make sure the belt that your new slower rpm clutch takes is comapable with your driven cluch , If the pitch is wrong performance will be terrible , and or destroy belts . I belive Richard relices on this web site has all the specs you need to be aware of , and probably the parts too.

By Steve M. (202.63.50.228) on Friday, January 14, 2005 - 05:24 pm: Edit

G'day all,
Steve in Australia here again, who posted the start of this thread.
I'm now in a position to repower my 500121 Amphicat, and have taken the above advice about concerns with Honda throttling, so I'm going with the 16HP Vanguard V-twin.

My question is, it's a much larger motor - will it fit? Has anyone sucessfully put a V-twin into an Amphicat?

There ware some photos in the Route6x6 photo section (that I can't locate now) of some fellow about to put a V-twin into a Cat, I wonder how he went?

Regards,
Steve.