Running on 3 cylinders on idle

[fredbcj]

gsxr1100 m ,i have checked valve clearances,compression,changes ht leads ,cleaned carbs ,  it runs fine until slow riding when it will bog down then run on 3 , open it up and it coughs like a 2 stroke ,clears then takes off, 

i am thinking blocked pilot or more likely i think ,perished O ring round the float valve seat ,would it flood a bit ,the plug on this cylinder is black on the electrode,

any help ,pointers would be greatfully recieved,cheers fred

[Gixer1460]

Pretty good diagnosis i'd say! I can't think of other alternatives?

[fredbcj]

I think I have found the o ring sizes, 7.5mm i/d x 1.5 mm , obviously petrol resistant viton ect, does the size sound correct. You can see number 3 rich flooding on idle 

Edited October 25, 2019 by fredbcj

[fredbcj]

[Buzuki]

On 10/25/2019 at 11:08 PM, fredbcj said:

I think I have found the o ring sizes, 7.5mm i/d x 1.5 mm , obviously petrol resistant viton ect, does the size sound correct. You can see number 3 rich flooding on idle 

Yes that small O-ring dimension is 7,5 i/d x1,5mm ,

also is important to check condition of O-ring on each intake manifold boot .

 

[fredbcj]

thank you , bought a screwfix hilca nitrile o ring set to get me out of the problem (edited and corrected) ,and its sweet ,thanks for all the input

Edited October 28, 2019 by fredbcj

[Dezza]

1 hour ago, fredbcj said:

thank you , bought a screwfix hilca viton o ring set ,and its sweet ,thanks for all the input

Interesting. I am sure there are many on here, e.g. me, who would be interested in a source of the correct size viton O'rings for carb rebuilds. What does the kit consist of and how much does it cost? Link please

[fredbcj]

https://www.screwfix.com/p/hilka-pro-craft-metric-o-ring-set-3-50mm-419-pcs/27385?kpid=27385&ds_kid=92700046638549236&gclsrc=aw.ds&ds_rl=1243318&ds_rl=1241687&ds_rl=1245250&gclid=Cj0KCQjwgNXtBRC6ARIsAIPP7Ru3z17I-6mmQEgi9l8V8ZdRTliJQMjBQ1juIaw9sAWmTxtMP4hvDs0aAsI0EALw_wcB

[fredbcj]

£15  for the box 20 odd + of each size 

[fredbcj]

[Dezza]

2 hours ago, fredbcj said:

£15  for the box 20 odd + of each size 

Ok, thanks. I though the viton jobs were green.

[Gixer1460]

Nitrile O rings are NOT Viton O rings - totally different materials with the latter usually more expensive ( like £3.50 odd for a couple of 1mm x 3mm bore types !)

[fredbcj]

I know, all I could get on a Sunday as this motorcycle is my only transport 

[Gixer1460]

1 hour ago, fredbcj said:

I know, all I could get on a Sunday as this motorcycle is my only transport 

Understood that - it's just you described them as Viton - when they aren't!

Others could read this and assume they were getting Viton (for a particular purpose) only for these Nitrile ones to fail / leak with serious consequences!

[fredbcj]

I have edited the post and fully understand, I used nitrile hilka from toolstation, looking for a source of better ones for the future as I have some bst38's to service for my speshial 

[Dorkburger]

Just a bit of an add. I had a similar situation after a valve adjustment / carb synch. I bench synched the carbs as a baseline, but after the vacuum synch, one of the butterflies ended up fully closed at, and off idle, causing a running condition similar to yours.