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1973 GT80 issues

23 May 2020 01:06 23 May 2020 01:07 by Gr8uncleal.
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1973 GT80 issues #1
Some run their bikes on premix. It's not ideal, as the oil pump delivers the right amount of oil at the right time, but is liveable with.

You are obviously very competent mechanically and comfortable reading manuals, so probably worth spending a little time reading the oil pump adjustment section of the manual, just to see if it's a simple fix.

If you are in the US, DEET here on the forum offers an oil pump repair service and I know of someone here in the UK who does the same.

I'm pretty sure that I read somewhere that it's best to plug the oil line if running premix, otherwise excess air will be sucked in via said oil line - I'd rather others confirm this though.

Yamaha do sell a blanking off plate (not expensive) if the oil pump is to be totally removed.

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23 May 2020 20:39 23 May 2020 21:12 by KadeFS. Reason: additional info
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1973 GT80 issues #2
Thanks for your advice. I will investigate the oil pump issue a bit further.

There is also the issue of the on/off switch. I'm not so confident at electrics and would appreciate some guidance here.

In the images here I have marked the wires as I have found them.
There is an existing switch wire with a B/W and B wire. It has no switch attached and ends are just loose.

I was given a generic switch to fit but am very unsure as to which wires to hook up.

At some point this bike had the black switch wire soldered onto the condenser wire and the B/W switch wire grounded, so the bike could be started without a switch.

In the image there is also a Yellow wire with female end, a green wire with female end and a light blue wire male end.

The new switch I have has a red/yellow wire I assume is + and a black wire - .

Can anyone advise me on which wires I need to connect up to get the switch working?


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23 May 2020 20:51
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1973 GT80 issues #3
Grounding the B/W wire kills the spark.

1963 YG1-T, 1965 MG1-T, Allstate 250, 1970 CT1b, 1971 R5, 1973 AT3MX, 1974 TS400L, 1975 RD350, 1976 DT175C, 1976 Husqvarna 250CR, 1981 DT175G, 1988 DT50, 1990 "Super" DT50, 1991 RT180, 2017 XT250

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