Crank case curiosity

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LC Cnd
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Crank case curiosity

#1 Post by LC Cnd » Thu May 25, 2017 12:57 am

Fired the LC up today for the first time this Spring and noted that after running it & shut down, a slow oil drip was forming under the engine which has been rebuild with less than 500 kms. Took a look underneath and noted only one crank case bolt with a drip forming. Was not a problem for the first 350 km break in. Wiped it clean, torqued it tight. Over night checked it and a new drip formed. Looked to see if the case was cracked around the bolt- nope. Whats the solution here - worst case is an engine tear down (don't think its applicable here) or perhaps seal the thread.
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L.B
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Re: Crank case curiosity

#2 Post by L.B » Thu May 25, 2017 2:00 am

See that hole past the nut n washer? Thats the drain from the top case,under the carbs etc. It could be something leaking above. Or keep a close eye on your g/box oil level.
Very unusual spot for oil leak to develop so long after a rebuild.
You used 1211 or some such gasket goo between cases?

LC Cnd
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Re: Crank case curiosity

#3 Post by LC Cnd » Thu May 25, 2017 1:11 pm

Yep, used 3 Bond for crank case sealant. Did a leak down test max pressure 10 psi (test at 7 psi) which held ok 2 weeks ago. Still scratching my head about this one. The crank case is filled with Royal Purple 10w30. Following your comment, I realized the hue of the leak should correspond to the colour in the photo one would think. I'm presently using iPone 2 stroke oil which has that sweet scent (appearently strawberry?). Ck'd the odour of the latest oil drip forming and noted it had that sweet smell and the gold colour matches Ipone. Ck'd the dip stick against my finger and the oil show puple. Hmm, wishing the drip was the Royal Purple because that would make more sence given its location. What else should be examined?

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two-stroke-brit
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Re: Crank case curiosity

#4 Post by two-stroke-brit » Thu May 25, 2017 2:03 pm

my bet would be small overflow from a carb bowl draining through the hole in the cases ending up at the lowest point ,that being the stud.
mark
350LC,Athena 392 big bore,stock porting,swiss cheese air box,stock reeds,spec11 pipes.(now TSA big bore pipes)
She might not be pretty but she will always be a fun ride


1982 YAMA RD350LC
98KDX 220R
1967 TRIUMPH TIGER
2001 TRIUMPH TT600

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L.B
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Re: Crank case curiosity

#5 Post by L.B » Thu May 25, 2017 8:30 pm

What colour is your 2 stroke oil?
Did you "oil up" your clutch cable during the rebuild?only other place is out of the tacho drive or your breather hose

nzminis
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Re: Crank case curiosity

#6 Post by nzminis » Fri May 26, 2017 4:38 am

i have had gearbox oil leak out of those 2 bolts on my 250
but it does have 40,000km and the cases have not been apart
only a few drops on the pipes over a few months

bit of rtv on the threads and retorqued the bolts and it has not leaked anymore

Hooligan
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Re: Crank case curiosity

#7 Post by Hooligan » Fri May 26, 2017 8:41 pm

Is it on left side of the engine?
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

2cycle
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Re: Crank case curiosity

#8 Post by 2cycle » Sat May 27, 2017 7:37 am

Stuff a rag in the hole above the drip to see if it stops. make sure its not coming from an injection line or fitting .
1973 ct70
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LC Cnd
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Re: Crank case curiosity

#9 Post by LC Cnd » Sat May 27, 2017 11:44 am

The oil is a golden colour. I'm thinking the issue is a slow leak in the left carb. The bolt with the drip is on the left. The rag idea is a good litmus test - thx. Just pulled apart the carbs to re-jet/calibrate the bowls to 21mm. Thinking the jet needle left may not be seated properly while mucking about. May have to tap it down the needle for a proper seal is the hope.

Hooligan
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Re: Crank case curiosity

#10 Post by Hooligan » Sat May 27, 2017 1:02 pm

A seal worth looking at is the big one where the countershaft sprocket shaft comes out the side of the cases. From there it is easy for oil to drip down and end up on the left side of the motor.
'82 RD350LC in '81 colours, OEM pipes, UNI filters
'85 FZ750

LC Cnd
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Re: Crank case curiosity

#11 Post by LC Cnd » Wed Jun 07, 2017 9:37 pm

Licenced the bike yesterday so went out for a burn. Left a piece of cardboard underneath to see what would happen. Well a minute drip occurred on the cardboard overnight but on both underneath crank case bolts. With the use of a good LED flashlight, noted a small drip forming on the right carb drain screw and a glistening trail to the upper crank case drain. Ck's both lower bowls for oil residue - negative. Tightend the drain screw but will purchase a New drain screw gasket to be safe. Appears mystery solved. Time and gravity.
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Re: Crank case curiosity

#12 Post by JonW » Wed Jun 07, 2017 9:56 pm

good find Scott!
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82 RD350LC decapitation project
82 RD250LC JDM '251LC' YPVS
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LC Cnd
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Re: Crank case curiosity

#13 Post by LC Cnd » Thu Jun 08, 2017 12:54 am

Actually kudos should go to Mark - he called it and got me thinking in the right direction -up, way up. Colour and odour oil evidence was helpful.

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