GT750A oil feed woes....

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Malcj

GT750A oil feed woes....

Post by Malcj »

IMG_20180319_204749.jpg
IMG_20180319_204913.jpg
I don't know if the photos will work, so a little explanation....

The bike is a 1976 A model, US import, with an indicated 10,800 miles on it. Footrest & gear lever rubbers rubbers, bar grips, etc would tend to support this mileage. As would the very original and unmolested state of the bike. It was seized when I bought it - I'd hoped that it was seized in the bores from standing, but, no.
The big end on the L/H cylinder seems to have completely disintegrated. I haven't got the engine fully stripped yet, but there's about 10mm of vertical movement on the conrod.
This struck me as a bit unusual in such a low mileage engine. As I continued with stripping it down I found that the cover over the oil pump and feed pipes has a little spigot inside the cover which has what looks like a casting 'bump' on it. This spigot/bump combination has clamped the oil feed pipe pretty fiercely and, I suspect, has interfered with the oil feed to a sufficient extent to cause the failure.
I suspect that this situation has existed since the bike was new. It doesn't look as if the covers have been off before (probably have tho....), but , even if they have, I can't see any other route that the oil feed pipe would take to avoid it being squeezed.
Anyone got any experience of this, or even got some photos of the correct routing for the feed pipe in this area ?
Roger Ackery
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Joined: Wed Jul 20, 2011 3:40 am
Location: Sydney NSW Australia

Re: GT750A oil feed woes....

Post by Roger Ackery »

I had a friend who misaligned that cover on his GT750J model seized a rebuilt motor on its first day out :o :twisted: :cry:
He was not happy !!
Same thing crushed the oil line
Don't know why that cover should fit without issues.... if all the retaining bolts line up with their holes unless the oil line has been undone at some point..& is sitting in the wrong position :evil: Will be interesting if anybody else has had a problem ;)
Cheers.
Roger
GT750A.
summer0123
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Joined: Tue Nov 17, 2015 2:58 pm
Location: Neath, South Wales

Re: GT750A oil feed woes....

Post by summer0123 »

http://www.ozebook.com/compendium/techb ... 0001-6.pdf

Suzuki warned of this in one of their service bulletins ' Oil Stavation' therefore it must have happened a lot
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yeadon_m
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Location: Canterbury Kent

Re: GT750A oil feed woes....

Post by yeadon_m »

Malc,
In my humble opinion, unless you track down what caused this LH pot failure, you will find it difficult to trust even a rebuilt (and expensive!) motor. Certainly, I'd be thinking 'might it seize again?'
The key steps are to confirm whether or not the oil pump dispenses oil from all 6 holes in its base, when removed and left connected to the oil tank. If yes, and anyway, is there oil in all 6 lines or not? additionally, can you force oil into each pipe from below the lifted pump and into the motor (confirming the valves are not jammed and oilways inside the case are free flowing)?
I always do this as I build. Also, when built up but the head is still off, I run the engine on the starter with the oil pump lever choc'd wide open and watch for oil drops appearing in the brass tubes projecting up in the barrel intakes! nothing like 'seeing is believing'. (you can tell I've had a seizure).
Good luck!
Mike
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Malcj

Re: GT750A oil feed woes....

Post by Malcj »

Thanks gents, some mega useful information and tips there. I'll certainly be very careful when I rebuild this motor. I may have to bother Mike again for some more detail on his oil pump check regime. Won't be for a wee while tho :D . Thanks again
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malky
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Location: swansea south wales

Re: GT750A oil feed woes....

Post by malky »

I re routed my oil feed pipe via a hole that I drilled in the cover of the oil pump giving the pipe a straight line on to the banjo union - much better idea in my opinion also used clear tubing so that you can see that there is oil in the pipe
Mal.
teazer
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Joined: Mon Mar 07, 2011 8:10 pm
Location: Chicago

Re: GT750A oil feed woes....

Post by teazer »

The guys already identified the issue. For some reason, Suzuki decided to rout the feed pipe around the breather stack and it tends to get pinched. Even if it is not pinched, it can collapse from the tight radius.

It is always a good idea to open up the hole where the pipe enters from the rear to give it a little more wriggle room. I have also slipped a spring around the outside of the tube to stop it from collapsing. The best idea (already mentioned) is probably to re-route the feed pipe. I have not had to do that yet, but I have to be very careful with that feed pipe to avoid it collapsing or getting pinched.
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malky
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Re: GT750A oil feed woes....

Post by malky »

I'll post a pic of the re route tonight if I can find the pics
Mal.
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malky
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Re: GT750A oil feed woes....

Post by malky »

pic as promised
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modified oil pump cover
modified oil pump cover
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yeadon_m
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Location: Canterbury Kent

Re: GT750A oil feed woes....

Post by yeadon_m »

Mal,
Thats a great tip and the visual reassurance is priceless!
Mike
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