waterpump seals

Post your Kettle problems here and cures
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yeadon_m
Posts: 7401
Joined: Sat Jan 02, 2010 7:10 am
Location: Canterbury Kent

Re: waterpump seals

Post by yeadon_m »

Hi John & welcome!
I’ve been lurking for quite a while but I used to post very often.
I’ve a GT750A which was rebuilt by Ray the previous owner. I believe he replaced the water pump as he was in that line of business back then.
Unfortunately I’ve noticed over this winter that it’s leaking every so slowly from that weep hole in the pump cover. If I place some white paper kitchen towel underneath, there’s one or two drops overnight, perfectly clean, pink coolant. If I was ever to fix it, and I might not, I think as Iain says, swapping the whole pump unit is the way I’d go. Apparently it can be difficult to get the old pump out fron the underneath, exhausts off, but someone worked out the precise coordinates to permit drilling of a tiny hole in the upper crankcase and then to use a slim drift to drive the pump out from the top, tapping that access hole with a grub screw. I recall the dimensions are on oldjapanesebikes.com?
Good luck & let us know how you get on.
Cheers,
Mike Y (Canterbury, Kent)
Ps: I too reach 60 also, soon though not until later this month. If your J has more one key for its ignition, tank cap & steering lock and if that bothers you, I can probably recode some of your locks such that you end up with a “wonkey bike”. Just PM me through the forums if you’d like to know more. No worries if not!
teazer
Posts: 1035
Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: waterpump seals

Post by teazer »

Baz and Ian are correct. The early crankcases not only do not have an O ring, they also don't have enough metal to fit one. There is a boss inside the cases that carries water from the pump upwards into the barrels and head. Presumably, that metal to metal joint slowly leaked and part way through K production, the castings were changed slightly to create a wider sealing face which was machined to accept an O ring.

Try Bars Leaks first and see if that does the job and if not, the cases have to be split to re-seal the cases.
johnbennettgt750j
Posts: 7
Joined: Sun Apr 05, 2020 10:41 am

Re: waterpump seals

Post by johnbennettgt750j »

It is a long time since my last post and since the receipt of the valuable information re- my J's coolant leaking into the gear box. So I thought I should post an update especially to Baz and others who gave great advice back in the spring. Following Baz's recommendation I added K Seal to my coolant and touch wood, this has cured my leaking coolant problem. I drained and refilled the gearbox with suitable motor oil and added a half bottle of K Seal at first. The bottle of K Seal was around 200mls size. About a month later I did a further oil change. I was a little disappointed to find the old gear oil to be 'cloudy/milky' and so I added the rest of the K seal to the coolant, which in total {full 200mls) is supposedly enough for a cooling system of capacity 10 litres. A further month later I changed the gearbox oil for a third time this year and this time there was a marked improvement in the clarity of the old oil. Since then I have found no need to top up the cooling system and when I have dipped the gearbox oil with a long thin screwdriver blade through the fill hole the sample of oil extracted on the screwdriver blade appears to be golden and clear. So job done! At least I have got another good season's use out of the bike and very much enjoyed every mile! So thanks once again for your help and advice. I'm sure my nearly 50 year old bike will eventually need a crankcase split and an engine rebuild but I see no need to hasten it unnecessarily. It continues to runs well and it would have been a shame to have had to loose this summer when biking has been my principal escape from the horrors of the world situation and news!
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BAZ
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Joined: Thu Jun 18, 2009 7:35 pm
Location: Dudley west midlands
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Re: waterpump seals

Post by BAZ »

Thanks for the update great to have a result..
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