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Thread: Big Twin flathead transmission oil loss

  1. #31
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    Re: Big Twin flathead transmission oil loss

    A quick update.

    I completed the job today, adjusted both chains, set up the clutch biting point and adjusted hand change linkage and rear brake. Then I spent ages getting rid of the oily mess that was my gearbox and rear frame. Then a short test ride and I still have an oil loss problem, but not now from the main shaft oil seal. So this job was a success - thank to you all.

    The oil is now coming from a later type vent screw which has been fitted to the leading edge of the top cover second in from the primary chain side (see pic with vent screw on the top cover). It looks like this is the only leak, but I'll clean it all up again tomorrow and check again.

    Attachment 30736
    Attachment 30737

    Chatting to the marque expert at the VMCC I should have a hexagonal type vent screw on a boss cast into the transmission case on the starter clutch side. I have the boss, but it hasn't been drilled and no vent screw. So my next task is to find the correct vent screw and I'll probably fit it to the starter clutch cover away from the main guts of the box.

    Currently when the engine is running and gears turning I get a constant drip, drip, drip under the bike and it looks like it's all coming from this incorrectly located vent screw. I don't know if this will solve the problem but I have no idea how much on issue it is to have a vent screw located directly over spinning gears.

    I'm not overfilling the box and I'm using straight 50.

    Does anyone know where I can get hold of the correct type vent screw please?

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  2. #32
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    Re: Big Twin flathead transmission oil loss

    Quote Originally Posted by topper View Post
    Paul, the manual says ' tighten securely. Strike wrench with a hammer to make sure sprocket nut is very tight' I use a clutch holding tool ( chain off) to hold the sprocket.
    Cheers Topper
    Thanks for this - I did it up tight and used the lock washer to secure it.

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  3. #33
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    Re: Big Twin flathead transmission oil loss

    From the 'For What its Worth Dept.'
    Your vent screw ?'s were gone over here. Seems the bloke had a oil-going similar to your own.
    http://www.hydra-glide.com/phpBB3/viewtopic.php?t=7354

    You would, of course, have to register to see the pics; but what of that?
    And do you register, you might ask if there is a specific torque/pounds on the nut. Personally, I'm antsy about not using a torque-wrench on that particular nut. The 70-78 Scriptures call for 140-150 foot-pounds; which is a lot. Now, I don't have access to the Parts and Service manuals for those [early] years but it seems that the main drive gear didn't change much over the years, save for a change in bearings set-up. Without the books to verify, I could be mistaken on the latter.
    Last edited by last shovel; 06-07-2018 at 01:13 AM.

    When in danger or in doubt, run in circles scream and shout!

    A common mistake made when trying to design something completely foolproof is to underestimate the ingenuity of complete fools.

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  4. #34
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    Re: Big Twin flathead transmission oil loss

    Time I thought for a quick update as the weather really isn't encouraging me to ride today.

    After replacing the mainshaft oil seal using one of the clubs tools kindly loaned to me the only oil leak was from an incorrectly located vent screw. I established that the correct location for a vent screw on my box is actually through a boss on the starter side of the main casing and would required a box removal to tap a new hole and do the job properly.

    So I swapped the incorrect vent screw location from the leading edge of the casing where it was in direct fire of the main gears and all the oil being flung around to one of the top plate screws closest to the correct location and problem instantly solved. I get a small amount of oil loss still though the main shaft, but not enough to worry about and no oil loss from the better located vent screw. I've dome over 300 miles this week without any need to top up, which is great.

    The box will probably get a rebuild over the winter and if I can find the correct type of vent screw I'll tap a new hole in the gearbox casing so it's correctly location - but that doesn't stop me enjoying this fine summer.

    Thank you again to all who offered invaluable advice and copies of parts books and loan of tools.

    Malcolm

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  5. #35
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    Re: Big Twin flathead transmission oil loss

    Nice work you did Malcolm on the bike and many thanks for all the pictures and write up,I am sure this will help other club members,now the next best thing Malcolm is to meet up for a cuppa,you must be near Loomies cafe on the A32,so if you are up for a meet and a breakfast let me know and may be anybody else who fancies a ride, great.cheers.

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  6. #36
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    Re: Big Twin flathead transmission oil loss

    Hi Andy,

    That's a nice idea - I could meet up this Saturday for breakfast or coffee if that fits, other than that I'm away until week beginning Aug 13th,

    Let me know

    Cheers
    Malcolm

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  7. #37
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    Re: Big Twin flathead transmission oil loss

    Saturday is fine by me,so what about time say 11.00am at Loomies,or earlier let me know,I will buy the tea or coffee.cheers.
    PS.if anybody else wants to come on saturday morning get the old Harley out for a run,weather should be on our side.yes.

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  8. #38
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    Re: Big Twin flathead transmission oil loss

    Quote Originally Posted by andy_brown View Post
    Saturday is fine by me,so what about time say 11.00am at Loomies,or earlier let me know,I will buy the tea or coffee.cheers.
    PS.if anybody else wants to come on saturday morning get the old Harley out for a run,weather should be on our side.yes.
    I'm happy to meet earlier if you are. It's nice to be out on the bike early and Sat looks to be another hot one. How about 10:00am at Loomies?

    Which direction are you coming from?

    Malcolm

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  9. #39
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    Re: Big Twin flathead transmission oil loss

    10.00am is fine by me.I will be coming along A3 then onto A31 (Guildford) then head towards Alton turn left onto A32,see you there.

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  10. #40
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    Re: Big Twin flathead transmission oil loss

    OK great - see you at Loomies on Saturday morning.

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