Question about 1980 Yamaha XS 650 G

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Hi I have a 1985 Yamaha xs 650.It is back firing out both excusts. Left cyl spark plug is wet with fuel. Right hand cyl is running hotter.Bike starts ok but back fires on Idle both cyl... Hope you can help.... thanks

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There are several reasons for backfiring, your sounds like either a faulty spark plug or coil. Another thing to check is the Carby Float Level on the Left Cylinder. This might sound a little funny but if you haven't rebuilt the topend of the engine I would look at a slightly colder spark plug not hotter. When fitting new plugs, check the gap but it should be OK from the manufacturer. Please resist closing the gap by banging it on a hard surface, it can fracture the new plug and you will be back where you started.

Posted on Nov 13, 2009

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Well the most problems are in the carbys {running to rich or to week} and with 2 carbys you must have them in tune with each other by about 98%.
and with a plug getting wet your float level is to high so when your going the fuel is getting to much in that cylinder and putting out a strong mixture and the other one to weak and you could also have a gasket on the intake sucking air or the exhaust has a bad flang gasket or a small pin hole in it some where
WHEN idleing put your hand over the tailpipe and stop the exhaust and see if you can hear a small blow if so fix it and the same the other side.
AS ITS ALL TO DO WITH HEAT AND INCORRECT MIXTURE so L/H is to much fuel,,,R/H cyl is running almost correct but wants tuning.
Have a goodday RON

Posted on Nov 13, 2009


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1 Answer

Had carbs rebuilt on my 1975 Yamaha Xs 650 now the left side cylnder fires infrequently and backfires loudly with new plugs. could this be a timing issue?

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Oct 12, 2010 | 1978 Yamaha XS 650 E

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Xs750 what is the firing order

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Jul 25, 2010 | 1979 Yamaha XS 650 SF

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My 650 yamaha specail has a miss fire on the right side not all the time under power it dont do it just at an idle and when you give it a little gas help

There is a resister in the spark plug caps that can cause a problem, try swapping the caps left to right and see if the miss changes side, the caps unscrew off the leads, if there is enough lenght cut 10mm off the end of the leads, when you screw the caps back on

Jun 02, 2010 | 1979 Yamaha XS 650 SF

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I have been building a chopper out of this model bike, have the bike complete but it isn't starting. It trys to turn over but it wont fire up.

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Check if fuel ( gas ) gets into the combustion chamber.
Try cranking it and thn remove the spark plugs and check if they are wet with gas.
Basically these are two things to check first.
Hope this helps!,
Let me know of the outcome and hope to be of help further..Thks.

Nov 29, 2009 | 1983 Yamaha XS 400 L Maxim

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Jul 10, 2009 | 1980 Yamaha XS 650 G

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May 08, 2009 | 1980 Yamaha XS 650 G

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Apr 10, 2009 | 1981 Yamaha XJ 650

3 Answers

Getting my bike started

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Here is a good site on XJ's
I hope this helps

Apr 07, 2009 | 1980 Yamaha XJ 650

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