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  1. #1

    Join Date
    Jul 2015
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    Chattanooga, TN
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    82

    Rebuilding an SBT GP1200R (66v) Motor - Need Tips & Advice

    So I pulled the motor because it had an air leak. After tearing it down, it was pretty easy to determine that this engine needed to be rebuilt. It's an SBT motor in pretty rough shape. Crank is missing thrust washers, looks pretty bad. Cylinders need to be resleeved, pistons are shot, powevalves are worn down from the pistons hitting them. Originally I was going to use it as a core and send it back to SBT for a new one.

    I then came to my senses and decided that I could probably rebuild this motor to a higher quality, cheaper than I could purchase another SBT motor.

    I got a deal on a low-hour OEM crank, and three OEM nikasil plated cylinders, with the OEM pistons, and powervalves.

    An online engine rebuilder has offered me $175 to send them my old SBT cylinders and crank. Is that a fair price?

    Currently there are no gaskets on the engine since I was intending to use it as a core. I'm going to order a complete engine gasket kit. I know I'll need some sealant when I put the cases back together (which one?).

    What do I need to know about rebuilding this motor? Although I am mechanically inclined, this is my first time doing a complete rebuild of a motor.

    I've split the cases to get the old crank out. When I get the new seals, what is the proper/best way to seal the two halves back together to ensure it doesn't leak?

    What else do I need to know?


  2. #2
    There's a bunch to it, challenging, but not impossible for your first engine. There's a bunch of 66V rebuild threads on here and other sites that are good to look through. Rich (WFO) is also a great resource for pretty much everything. You'll need a service manual for your ski, yamaha oem crank seals, oem gaskets (yamaha has a complete gasket kit for the 66V), threebond 1211 for sealing up the cases. Everything on sealing surfaces needs to be spotless clean and grease free. Old sealant comes off with nylon brushes or just picking at it with your fingernails or rubbing it off. Go over all metal surfaces with acetone on a rag to degrease (NOT on crank seals), then thin coat of 1211 on surfaces and a smidge of 1211 where the crank seals will sit in the cases. Fercho's guide here is useful: http://www.hydrotoys.com/gpr/tuners/...f?lbisphpreq=1

    Crank seals going onto the crank will be a bit nerve wracking for your first time as they do not want to go on easily, even though you've applied grease (grease makes them pop off when you don't want them to lol). Take your time and slowly work them onto the crank. They'll go on eventually.

    Be careful of the crank seals, my service manual pictured one backwards. Two have tabs on one face of the seals, those two seals have the tabs facing out of the crankcase (one on mag, one on PTO). Third seal is the inner seal on the PTO side. Torque bolts w/ red loctite in the order and torque listed in manual. Wipe off squeezed out 1211 with a rag and I try to get the stuff out of the inside of the cases with a q-tip so there aren't blobs of 1211 hanging out inside (no biggie, they just bug me) and wrap the thing up with saran wrap to keep dust out of it for a week to let the 1211 fully cure. Once cured, put pistons (gap your rings of course), cylinders, and exhaust on and pressure test. If you're meticulous about cleanliness and use OEM crank seals (and of course can follow directions in the service manual), the pressure test is easy to pass. You must do the pressure test (leakdown test), do not skip it. Don't forget waveeater clips on power valves.

    Might as well rebuild the carbs w/ mikuni kits and set them up per oside bill's specs on this forum. Also might as well do the fuel return mod too.

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  4. #3

    Join Date
    Jul 2015
    Location
    Chattanooga, TN
    Posts
    82
    Quote Originally Posted by awh4992 View Post
    There's a bunch to it, challenging, but not impossible for your first engine. There's a bunch of 66V rebuild threads on here and other sites that are good to look through. Rich (WFO) is also a great resource for pretty much everything. You'll need a service manual for your ski, yamaha oem crank seals, oem gaskets (yamaha has a complete gasket kit for the 66V), threebond 1211 for sealing up the cases. Everything on sealing surfaces needs to be spotless clean and grease free. Old sealant comes off with nylon brushes or just picking at it with your fingernails or rubbing it off. Go over all metal surfaces with acetone on a rag to degrease (NOT on crank seals), then thin coat of 1211 on surfaces and a smidge of 1211 where the crank seals will sit in the cases. Fercho's guide here is useful: http://www.hydrotoys.com/gpr/tuners/...f?lbisphpreq=1

    Crank seals going onto the crank will be a bit nerve wracking for your first time as they do not want to go on easily, even though you've applied grease (grease makes them pop off when you don't want them to lol). Take your time and slowly work them onto the crank. They'll go on eventually.

    Be careful of the crank seals, my service manual pictured one backwards. Two have tabs on one face of the seals, those two seals have the tabs facing out of the crankcase (one on mag, one on PTO). Third seal is the inner seal on the PTO side. Torque bolts w/ red loctite in the order and torque listed in manual. Wipe off squeezed out 1211 with a rag and I try to get the stuff out of the inside of the cases with a q-tip so there aren't blobs of 1211 hanging out inside (no biggie, they just bug me) and wrap the thing up with saran wrap to keep dust out of it for a week to let the 1211 fully cure. Once cured, put pistons (gap your rings of course), cylinders, and exhaust on and pressure test. If you're meticulous about cleanliness and use OEM crank seals (and of course can follow directions in the service manual), the pressure test is easy to pass. You must do the pressure test (leakdown test), do not skip it. Don't forget waveeater clips on power valves.

    Might as well rebuild the carbs w/ mikuni kits and set them up per oside bill's specs on this forum. Also might as well do the fuel return mod too.
    Thanks, this is exactly what I was looking for. Especially about the crank seals. Re-sealing the motor and making sure crank seals are in right gives me the most jitters.

    Motor failed the pressure test pretty bad, had a leak near the starter. As I tore it down, I realized how bad of shape this thing was in.

    Carbs are rebuilt with the fuel pressure returns drilled out and a jet (don't recall the size anymore) installed in the return hose. I've bumped up the low speed jet, but have not installed t-handles yet (they're sitting in a bag on a shelf in the garage).

  5. #4
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    Rebuilding an SBT GP1200R (66v) Motor - Need Tips & Advice

    Fantastic advice in this thread, you should post pics and have it made sticky

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