Question about 1978 Yamaha XS 650 E

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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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If it's just one cyl, then I doubt its timing.
Check to make sure the carb boof is tight and not leaking
also check any vacuum hoses.

Posted on Oct 13, 2010

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Put new distruber in my 1975 ford 351 m I can get

Backfiring through the carb is a timing problem. I would bring it back up to top dead center and reinstall the distributer. Also double check your firing order on your plug wires.

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1975 Yamaha XS650B replace throttle cables

Hi, Zooyorkog07 for this scenario you will need your service/owners manual if you can't find the first and best tool you ever bought for your Yamaha, despair not, for a mere zero $0 you can download another one. For more information about your issue and valuable "Free" downloads that you will need please click on the blue links below. Good luck and have a wonderful day.
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Mar 18, 2011 | 1975 Yamaha XS 650 B

1 Answer

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

1 Answer

Carbs overflow as soon as the fuel is turned on

The needle and seats are not doing their job. Start by checking the float adjustment is correct, if it is, then replace the needle and seat, this should rectify your problem.

Jan 14, 2010 | 1975 Yamaha XS 650 B

2 Answers

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...

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

Nov 13, 2009 | 1980 Yamaha XS 650 G

1 Answer

Poor running 650..My left side exhaust is weak. Good compression

Try and switch the coils and plug wires to rule those out. Can be a clogged up muffler, it is easy to pull the baffle. Should be held in with a small rivet or screw. Remove the rivet or screw, get a pair of clamping pliers and clamp them to the end of the baffle and smack that with a hammer to pull it out. Next would be check your valve settings and adjust as needed.

Nov 11, 2009 | 1975 Yamaha XS 650 B

1 Answer


If you want to see what the service manual says about it
You can download a free one at
Good luck!

Oct 27, 2009 | 1975 Yamaha XS 650 B

1 Answer

Xs650 one cylinder lean

I had the same bike.there is a rubber line that connects the two carbs together.the carb with the lighter lean sparkplug is the one being feed by the other carb with the darker richer sparkplug with the fuel line connected to it i bet.

Mar 08, 2009 | 1979 Yamaha XS 650 SF

1 Answer

Engine idles with choke on only

You either have cracked intake boots/ manifolds or the idle circuit in the carb is plugged with stuff. Spray some brake cleaner around the intake manifolds (air box in place) and see if the idle picks up. If nothing happens pull the air box, fire it up and put your hand over the carb(s) to try to **** it through....rev it up...cover carb with hand...repeat. Next you're removing carbs and cleaning

Dec 17, 2008 | 1978 Yamaha XS 650 SE

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