Fresh crank rebuild problem

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VintageKiwi
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Fresh crank rebuild problem

Post by VintageKiwi »

Hi everyone.

I have recently put a new crank in my GT750., new seals bearings etc.
Well the left and centre cylinders run well, except the right side which smokes really badly then cuts out, there are masses of oil all around the exhaust where it bolts up to the cylinder, I removed the bottom right hand side SRIS valve and to my shock engine oil came dripping out so
Is the crank incorrectly installed or has a crank seal let go , just wondering or if you have any ideas before i take it apart again
thanks,
Jim
Vintagekiwi
GT750Battleship
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Re: Fresh crank rebuild problem

Post by GT750Battleship »

:up: Hi,before expecting the worst..this could be nothing more than the oil pump set to high? how much oil did you put in the gear box ? Who did the crank? the crank seals need to be inspected to make sure their not rubbing on anything before closing the crankcases!
If the motor has been apart you'd expect it to take a little more than the 2,200ml/cc that figure refers to a normal gear box oil change,not a bone dry transmission.The right hand crank bearing is splash fed with gear box oil..that's why I'm asking about oil quantity ? The oil coming out of the right hand exhaust port may be nothing more than a leaking exhaust gasket ? I suggest you leave the SRIS valve out on that cylinder,remove all spark plugs,disconnect fuel supply,& pump her "dry" with the electric start,then have another try 8)

Cheers,
Roger
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tz375
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Re: Fresh crank rebuild problem

Post by tz375 »

Most likely a leaky oil feed line that we often refer to as the octopus even though it only has 6 legs. The check valves tend to leak over time and allow the crankcases to fill with oil.
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Coyote
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Re: Fresh crank rebuild problem

Post by Coyote »

I think the correct word for the octopus thingy is manifold.
I was born with nothing and still have most of it left.

.
1978 GS1000C
1976 GT550 ongoing money pit.
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ConnerVT
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Re: Fresh crank rebuild problem

Post by ConnerVT »

Coyote wrote:I think the correct word for the octopus thingy is manifold.
Sextapus?
titan performance
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Re: Fresh crank rebuild problem

Post by titan performance »

I went out with one of those once.........happy days !
Keeping old 2 strokes alive !
GT750Battleship
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Re: Fresh crank rebuild problem

Post by GT750Battleship »

:up: I'll stick with Octopus,seems to be the term used by the lads in the UK ? PS I have a "NOS" Octopus.never been on a bike!!! (GT750)
Cheers,
Roger
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Re: Fresh crank rebuild problem

Post by Vintageman »

VintageKiwi wrote: I removed the bottom right hand side SRIS valve and to my shock engine oil came dripping out
could you tell if it was gear oil or two stroke oil. I mean are the two in your bike a different color and smell?
Current registered, inspected, and running well 2 stroke motorcycles
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),
73 Kawasaki H1 500
VintageKiwi
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Suzuki 2-Strokes: meanstreak, husaberg 300 yz250
Location: Wellington New Zealand

Re: Fresh crank rebuild problem

Post by VintageKiwi »

Sure was gearbox oil dripping out of the SRIS valve, I am wondering if the gearbox was over filled and the bike then lent over
(to repair the gear position switch) then is it possible that gearbox oil can seep into the RH side crank.
I have done what was suggested by GT Battleship and cranked it dry, when i started it again there was less smoke and oil spurting, so will crank it up again to today and check again.

thanks everyone for your help.
Jim
Vintagekiwi
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Re: Fresh crank rebuild problem

Post by Vintageman »

When you rev it up driving down the road does gear oil come out the crankcase vent weep hole by oil Pump?

I think the far right seal is dry. So not there

The inner one blocks gear oil since PTO for clutch other side of it.

Cases halves must be tight fit I suppose too, but not sure why it would not be,

Try again. look at crankcase vent for blowing out gear oil when after hard run.

What year is your gt750?
Current registered, inspected, and running well 2 stroke motorcycles
74 GT250 (T350 upgrade),
76 GT250 (T350 upgrade),
71 T350,
70 T350,
74 GT380,
75 T500,
73 GT550,
75 GT750,
72 Yamaha DS7 (R5 upgrade),
77 Yamaha RD400 (Daytona Cyls),
73 Kawasaki H1 500
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