RH Cylinder Outer Seal Leaking GT750

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burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

RH Cylinder Outer Seal Leaking GT750

Post by burgs »

Hi All
I had covered about 1800 miles on my recent rebuild of my GT750 L, had a few small issues.
Set out on a 5 day ride of 1122 miles, all was going okay until having to divert through Sydney, with all the stop starts for traffic lights etc, the right hand cylinder started missing.
I had to keep going unfortunately with some serious missing popping and back firing.
Swapped plugs around and the engine ran better, but blowing a lot of smoke.
Fitted new plug and same again, ran good but still lots of smoke.
I then started to hear a noise coming from the alternator cover, not loud but audible when stopped.
Removed the alternator cover and started the engine to see where the noise was coming from, the noise was very loud, turns out the crank shaft seal was leaking bad, so refitted the cover as many miles to get home.
I plan on checking the gearbox oil level first, to see if the oil from gearbox was entering the cylinder making the smoke.
Then remove the alternator and see what the crank shaft seal looks like, I stuffed I know.
A question I have is, has anyone successfully changed a seal with out splitting the engine?
I am thinkin no, because of the raised rib locating the seal in the crankcase? :(
Made it home though, 2 more plug changes, did not loose too much ground on the modern bikes, but I don't think they were too impressed with the smoke screen, I was putting up. :D
Good time had by all though, two old bikes mine and a Yamaha XS.
Burgs
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: RH Cylinder Outer Seal Leaking GT750

Post by teazer »

At least you got home in one piece. Hope the trip was still fun.

The crank has to come out to change that seal unfortunately. What was the noise you mentioned? Was it the outer bearing failing or just the sound of gas blowing past the seal?

When the crank comes out, look for signs of a failed bearing just to be sure.
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: RH Cylinder Outer Seal Leaking GT750

Post by burgs »

Hi Teaser.
Had enough pressure to pop the gasket in the end, I reckon because it had the cover containing the pressure it was still able to keep running, just as long as I kept the revs between 4000 and 5000.
Only new crank build about 3000 Miles or so, so not expecting any bearing issues, he said with his fingers crossed. :D
Got another rally coming up, end of May so might have to take the Norton 650SS and give it a run.

Burgs
bosco659
Posts: 21
Joined: Mon Aug 09, 2021 4:33 am

Re: RH Cylinder Outer Seal Leaking GT750

Post by bosco659 »

With the right crankcase seal failure, was the engine smoking badly out of all cylinders or the Center? I thought the right crankcase excess oil from the gearcase would get burned off by the SRIS on the Center cylinder?
Last edited by bosco659 on Mon May 02, 2022 3:53 pm, edited 1 time in total.
1976 Yamaha XS650C, 1975 Suzuki GT750M
burgs
Posts: 70
Joined: Mon Feb 06, 2012 9:07 pm
Location: Hunter Valley NSW Australia

Re: RH Cylinder Outer Seal Leaking GT750

Post by burgs »

#3 Cylinder R/H much smoke when wound on hard.

Burgs
bosco659
Posts: 21
Joined: Mon Aug 09, 2021 4:33 am

Re: RH Cylinder Outer Seal Leaking GT750

Post by bosco659 »

Mine is smoking heavily (Center) especially on start up so now I’m suspecting might be the check valves in the banjo area leaking and dumping oil in the crankcase overnight.
1976 Yamaha XS650C, 1975 Suzuki GT750M
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