Not Running on all cylinders

[Blue]

Why are no.3 & no.4 downpipes not getting as hot as the other 2? I removed plug no.4 & turned engine over, the plug sparked. I then swapped it with no.1 plug but still cylinders 3 & 4 downpipes are much cooler. 

Edited September 21, 2017 by Blue

[Gixer1460]

If its a pair of un-matched cylinders, its unlikely to be electrical - unless both coils, plug leads, plug caps or spark plugs are duff at same time! Which leaves carbs - everybody's favorite subject - i'd start with a strip and see whats blocked - pilots. idle air, float valve would be candidates!

[Blue]

Carbs have been off recently because I discovered I had dynojet tubes & factorypro needles, so I bought a set of standard tubes & fitted 147.5 jets (I think)

[colinworth79]

if its a gsxr then there is 2 petrol pipes maybe one is blocked. As above start with cleaning the carbs and then check there balanced .

[Blue]

I was gonna go to a dyno this weekend, I wasn't sure if I'd balanced them so I checked that's when I noticed it wasn't  running right 

Edited September 21, 2017 by Blue

[Blue]

Can I rule out electrical even though I've just rewired the bike ?

[Gixer1460]

2 hours ago, Blue said:

Can I rule out electrical even though I've just rewired the bike ?

If 1 and 2 are running then both coils are working and so 3 and 4 will be getting sparks (or see my post above). If you have sparks and you have air and it still ain't running then it ain't getting the last bit - fuel !

[Oilyspanner]

Some very good advice given -  has to be intake side, could be air leaking in via seals in intake boots/pilot screw seals (often doesn't show when balancing carbs) - or as been suggested, pilot system/float height etc   - what colour are the spark plugs on 3 & 4 ? 

Edited September 22, 2017 by Oilyspanner
spark plug condition

[Blue]

Didn't check 2&3 but no.4 looked untouched after I'd initially cleaned them & no.1 was black

[Gixer1460]

If #1 was black - dry black or wet black or oily black? If dry - then potentially v. rich. If wet - then potentially leaky float valve / v. rich. If oily then could be leaky valve stem seals or rings. Poor electrics / bad sparks could also cause 1 and 2 as well due to poor combustion. Dirty plugs - particularly NGK's - don't successfully clean up...... so best replace to eliminate that as a symptom! 

[Blue]

Managed to get some time for n this today, pilot jets were blocked or restricted & I've lowered the needle due to the fact I have the needle straightening widgets fitted 

[andydrinkell]

Had a "mate" tell me about the carb problems on these bikes. He then stated, in a very loud voice, that anyone who bought one of these bikes wasn't all there and should be locked up as they weren't exactly firing on all cylinders.  This from a guy with an MZ..... Treated it with the contempt it deserved, lol.

[Beevis]

Have you fixed it? from recent experience of a similar problem I found pilot jets blocked and a low fuel level in the tank caused 1 and 2 to stop working before 3 and 4, no idea why.

 

[Blue]

Yes Beevis, as mentioned above, some pilots were blocked & some restricted