swapping motor 91 for 93

I'm swapping motors in my ST I't a 93 and I think the new motor is a 91.I have a water hose that I replaced on the 93 that goes thru the head to the water pump but the 91 doesn't have a nipple on it ,can I just cap it?Also on the back of the motor by the transmission there are 2 nipples I don't know what connects to them(are they vents or water)?Thanks for any help!

I’m not exactly sure what you mean, but the 91s have an external crankcase breather chamber. Black box on the right side by your shin. All other ST1100s have an internal chamber that vents through the water pump casing (lower right side nipple) with the hose leading up and between the banks to the nipple on the bottom right side of the air cleaner. The 91s vent from the rear of the engine case to the chamber and the hose from there runs forward to the air cleaner.

HTH If not, pictures would easily confirm the correct identifications. I have a few of my 91 if needed.

John

The first 2 pictures are the hose that was on the front of the motor 93 don't know were it goes on the 91.The second 2 pictures are the back of the motor I don't know what connects to the 2 nipples.HELP

As I described, the crankcase breather hose in your first two pictures doesn’t exist on the 1991s. The water pump in a 91 engine doesn’t have the nipple for the hose. You can install a 93 water pump on a 91 engine, but its crankcase nipple and hose just don’t serve any purpose.

Did you get the external crankcase breather chamber with your 91 engine? Here’s a couple of pictures of mine:
http://www.st-riders.net/coppermine/displayimage.php?album=33&pid=830#top_display_media
http://www.st-riders.net/coppermine/displayimage.php?album=33&pid=831#top_display_media

Here it is (item 18 - Breather, Tank) with associated parts on the Fuel Tank fiche: https://www.ronayers.com/oemparts/a/hon/50540f6df870021c54bedbd1/fuel-tank

You must have these parts for your 91 engine to run properly.

I would need to dig into my archives on my desktop (on my iPad Mini now) for other pictures that may show the vent hose routing to the external breather chamber. My back is killing me right now so I won’t be pulling tupperware or crawling under the ST. From the chamber to the air cleaner is a straight route.

Edit: this image shows the vent hose from the engine (lower right) to the breather chamber. And you can see the hose at the top of the chamber that goes to the bottom of the air cleaner housing:
http://www.st-riders.net/coppermine/displayimage.php?album=38&pid=1139#top_display_media

John

Thanks for the help I will have to try to find a breather tank then I'm sure I will have more questions.

It’s inexplicable to me why anyone would sell you a 91 engine without the crank case breather chamber. Good luck. Please keep us (me) poSTed.

John

Got a breather chamber not sure what hoses go were attached is a picture, thanks for the help.

jhassevoort said:

Got a breather chamber. not sure what hoses go where. attached is a picture. thanks for the help....

Click to expand...

Sorry, the pictures’ links I posted above are the best I have. Click/tap on them for a higher resolution version. Good luck.

Edit: just found this picture of Gunnar Reed's (STOC 44) 1991 in my old alternator upgrade files:



John

David Silver Spares US says they will special order the three hoses.
https://www.davidsilverspares.com/parts/by-part-number/
I don’t know if that means they will definitely deliver eventually...

Generic fuel or coolant hose could be substituted I’d think. Anything that can handle oil vapor under a bit of pressure. Dunno why the lower OEM one is so “beefy.”

I have another question about the swap,on my 93 there was a hose that went thru the head and hooked to the water pump.The 91 doesn't have a nipple on the water pump, can I just plug the hose or does it go somewhere else on the 91?Thanks for the help Jerry.

jhassevoort said:

I have another question about the swap,on my 93 there was a hose that went thru the head and hooked to the water pump.The 91 doesn't have a nipple on the water pump, can I just plug the hose or does it go somewhere else on the 91?Thanks for the help Jerry.

Click to expand...

Jerry, the 93 vents crankcase breather air out a hole in the front of the right cylinder head area, through the water pump housing to a nipple that the hose connects to which then is routed up between the heads to the bottom of the air cleaner housing. The 91, as I have previously mentioned, does not. Only the 91 engines do NOT have the INTERNAL crankcase breather and do not have a hole in the front of the engine. Its breather chamber is EXTERNAL (the black plastic box on the right side). Find the two nipples on the 91 engine at the rear/side. One is the vent to the breather box, the other the captured oil return to the crankcase. The top nipple on the breather box routs the crankcase air, which has had the oil removed, to the nipple on the bottom right side of the air cleaner housing. The online schematics show all three of the 91’s unique hoses and their clamps.

I do have some more pictures somewhere on my hard drive. Email me if you’re still completely lost and I’ll see what I can find. But not until next week as we’re about to leave for my sister’s funeral in Minnesota.

John

Thanks again.