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Yamaha XS 1100 missing cylinder 3...


othel
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Hi to all you bikers

I am new here

I have a problem with cylinder 3 that wont run, temp on exhaust manifold is aprox. 60degree C and the other ones are 300degree C. I have tried to clean the carbs, swobbed the ignition cables 2 to 3, swobbed the sparkplugs.... when I look down in the sparkplug hole I can see gasoline on the piston... I asumed that when cylinder 2 has a spark then cylinder 3 also would have... Compression is fine on all 4 cylinders

Hope that anyone of you can help me

Thanks..

Regards Henrik :shakeno:

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  • Moderator

Have you actually proven the spark on cyl 3?

You need to dry off the fuel in the cyl too. If it hydraulics you will be looking for a new motor.

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As Cynic say's check you have a spark, might be just a duff HT lead or spark plug cap. :jossun:

P.S check cap to see if you have tracking (silver like) lines down the inside of the cap or it's cracked.

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First clear the fuel from cyl3 by pulling out all the plugs and crank the eng over. and making sure you have good spark on #3

and remove the vacume line to the fuel tap to stop any more fuel getting to the carbs.

then try and run the bike with the vacume line pluged the bike should run and fire on all cylinders ,if it does then hook up the vacume line if the problem comes back you need to clean the carbs sounds like the float is stuck in carb #3 over fueling the cylinder and fouling out the plug.

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Hi... Thank you for your reply's

Yes I have a spark... this model shares the coil between cylinder 2 and 3 and i have tried to swab them.. same result.... Moderator: can you tell me what you mean by hydraulics..?

/Henrik

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there is not that much fuel in cyl 3.. it's only so I can that'it's wet... I tried to plug the vacuum line as you said and run it til it stopped and... the temp never got over 80C... the others about 400C....

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  • Moderator

Hi... Thank you for your reply's

Yes I have a spark... this model shares the coil between cylinder 2 and 3 and i have tried to swab them.. same result.... Moderator: can you tell me what you mean by hydraulics..?

/Henrik

The actual gap at the top of the piston stroke is really quite small, it is possible with a badly flooded motor for there to be enough fuel to fill the gap and some.

Fuel as water is not compressable. ie it maintains its volume under pressure. So if you have more fuel than space you have rods bending and cranks failing due to the piston not being able to pass top dead centre causing the motor to stop cold, no slow down so all that momentum in the crank etc becomes destructive force and bang.

Its why motors flooded in fords and floods are in most instances dead, if they were running when the water got them they have rods out the side, snapped cranks. Not good.

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What are your compression readings. They need to be over 125 psi and not varry by more that 10%.

After running is the cyl still looking wet.

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Sorry I am realy busy today.. but yes I think you should be looking at the fuel end of things. Mostly the air flow circuts of the carbs me thinke you have some junk in thiere. But it should be dry after running the bike if you can get the plug out qulckly try it again with the vac line pluged and see if it come out dry on 3 .

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Hi there...

I took the out carbs again and cleaned it thoroughly... specially the 3'rd... It is beginning now to run a bit better...The temp is op around 170C now so I guess some kilometers can make it god...

Thank you to all that helped me in this process... It is very nice to get some input.....

Best regards Henrik

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