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Old 12-19-2014, 05:19 PM   #1
Banzaibob OP
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Suzuki GT750 Crank Seals Bad; How do YOU replace them?

Recently acquired the water buffalo. It has sat for maybe 10 year? More? The engine was locked up. I filled the cylinders with oil and next day rocked it back and forth and viola! It turns over. Compression is 150 psi on 1 ans 2 and about 120 psi on 3. I rebuild the carbs and it fires up. I take it down the street under load and starts puking oil out of the transmission breather next to the oil pump. I'm pretty sure that it is bad seals on the crank.

There's not a whole lot of info on how to replace those inner seals. Is the crank a one piece and will it have to be pressed apart in order to replace those seals? Looking at parts diagrams it appears that the crank may separate around the main drive gear. If that is the case then I can do it myself.

Disassembling and reassembling the crank is above my skill set. Anyone know of a company that I can ship to and will replace the seals?
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Old 12-19-2014, 05:23 PM   #2
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it is pressed together there is a site called "2 smokers" i would go there
http://www.kenoconnorracing.com/Cran...0Rebuilds.html

kdo58 screwed with this post 12-19-2014 at 05:29 PM
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Old 12-19-2014, 05:26 PM   #3
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I remember smashing the middle piston on my GT380 many years ago, taking out the bearing surface for the needle-roller small-end bearings as it did so. The crank and conrods were sold as a single part by Suzuki then, so I'd think that may be the case with the GT750.

Mike

PS Managed a work-around by fitting a brass bush to the middle small-end on the 380 to get it on the road. Then sold it.
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Old 12-19-2014, 05:40 PM   #4
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You know, $250 for a rebuilt crank is not a bad thing. I just went out and drained off about 6-8 oz of extra oil from the transmission. I warmed it up on my lift, put it in 3rd gear and gave it some brake drag to replicate a modest load. No oil puking. I even put my finger over the vent and no noticeable pressure. Hmmm?
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Old 12-19-2014, 05:50 PM   #5
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Put some seal stop leak down the carb, spin but do not start then engine and let sit. I might just swell and soften the seals a little. Then your normal oil will keep them conditioned if you ride it often enough.

Rod
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Old 12-19-2014, 06:00 PM   #6
kdo58
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http://www.thegsresources.com/_forum...=water+buffalo
not sure if this link wil work for you. there is a guy on the suzuki gs forums named viperg that has a cool build

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Old 12-19-2014, 06:37 PM   #7
baloneyskin daddy
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I don't know where you're getting a 3cyl 2 stroke crank rebuilt for $250 maybe 3 times that to do it right. Anyway,the only seal that would vent into the trans would be the RH side behind the clutch cover which can be replaced without total teardown on most bikes.But... that seal would more likely suck the trans fluid into the lower end of the R cyl and cause that cyl to smoke like hell. Sounds like you found the problem anyway .
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Old 12-19-2014, 07:09 PM   #8
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Ken OConnor did my GT500. Nice guy, does nice work, reasonable price. That is a big engine.....probably won't be as bad as you think. The crank is the easy part, putting the transmission back together is the challenge.

Make sure your carbs aren't just out before you go ripping and into the engine. The carbs take some practice. If the engine isn't leaking from everything I would concentrate on the carbs for a while.

If you do take it apart plan on every seal, not just crank seals.

Suzuki dealer in Limerick, Maine is awesome for parts. Sold my GT500 this summer, just after I got it just right,

It's also tough to get all the oil out during a change. Make sure you drain anything without a Suzuki "S" on it, maybe over filled. Maybe be gasoline from a bad Vacuum petcock or a petcock left on prime.

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Old 12-19-2014, 07:58 PM   #9
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Actually it doesn't smoke very badly at all. It appears to pull strongly and doesn't seem to have any performance issues. Carbs are clean and in sync.

Bear in mind that I've just started reading up on GT750's but the BIG question would be is the drive pinion pressed in to make an interference fit between cyl 2 and 3? OR can they be easily separated? I don't have the tooling to separate, press and balance a crank. On the parts diagrams I have seen it almost looks as if splines can be separated...am I hallucinating?
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Old 12-20-2014, 09:20 AM   #10
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Bring the crank to somebody, they will make pressing it apart look easy.
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Old 12-20-2014, 10:48 AM   #11
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First thing this morning I started it and let it warm up. Sitting in neutral with it running, there was no oil coming out of the transmission vent, even when revved. I live on a long hill so I got to the bottom and started out. In 2nd gear, pulling the hill I got it up to approximately 5000rpm. Oil started shooting out like a small geyser. Under 4500rpm, no problems. Over 4500rpm with no load (neutral), no problems. It seems that once it reaches a tipping point with respect to load x rpm x maybe even intake vacuum, sloosh! Here comes the gusher.

A bad crank seal makes the most sense to me, could it possibly be anything else in anyone else's opinion?

Also, does anyone definitively know that the junction between cyl 2 and 3 on the crank where the drive gear is located NOT simply riding on splines and can be serviced without pressing apart?

Still trying to decide whether parting it out is more cost effective.
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Old 12-20-2014, 12:38 PM   #12
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See if you can find some of the past Classic Bike and Classic Bike Guide mag's from the last 3-4 years. At one point I remember lots of articles about the Water Buffalo. They described the symptoms very precisely. I *think* excessive smoking from the tranny oil getting pulled into the combutstion chamber is the main one, but I don't have one of these bikes, so I'm not entirely sure. If you search their websites, you might be able to find the ones that have articles about them and purchase them. HTH's.
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Old 12-20-2014, 12:50 PM   #13
Prmurat
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Suzuki GT750 Crank Seals Bad; How do YOU replace them?

On my 3 cylinders(kawasaki) dead crank seals does the contrary: suck the gearbox oil! This is more logic as compression in the pre-compression halves push the gas mix up the transfer to the combustion chamber. Have you tried a pre-compression chambers test?
Finally: what kind of oil level do you have in your gearbox?
As a starter:
http://www.dansmc.com/vacuum_testing.htm
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Old 12-21-2014, 09:14 AM   #14
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Try posting your questions on the Sundial Two Stroke Suzuki board:

http://www.suzuki2strokes.com/forum/index.php

Lots of GT750 owners there.
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Old 12-21-2014, 10:05 AM   #15
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I tried doing that. For some reason it won't allow me to register or sign in.
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