Bike won’t run (part 3 of the saga). ‘Carb tuning just not making sense’

[MikeyVeitch]

So I found the electrical problem with the bike constantly fucking up new plugs with death by internal ground. It was the carbs 

1127 lump b12 mk1 bst36ss carbs and a high flow full custom exhaust

If I read the spark plugs.
A 145 main jet needle all the way down is rich

A 130 main jet with the needle all the way down is slightly lean

A 130 main jet with the needle clip in the middle is perfect

So why does it run perfect on a 145 but fuck the plugs after 15 minutes but on the good setup with the raised needles and a 130 jet, it will sputter at 4K and just fucking gives up at 6K.

I am truly lost now and don’t know witch way I should be looking

any replies would be greatly appreciated because at this point, I feel like shooting myself

[TonyGee]

what airfilter setup are you using ? 

[MikeyVeitch]

17 minutes ago, TonyGee said:

what airfilter setup are you using ? 

Forgot to mention that sorry. K&N dual pod filters

[Nik]

How do you read the plugs? On open throttle, the needle position has no/little impact.

130 mains are way too small. No wonder it gives up at 6K.

I have BST36s on an 1127, with dual pod K&N filters and open exhaust. I run 150 mains, and it runs as good as one can expect from CVs with pod filters. 

[MikeyVeitch]

26 minutes ago, Nik said:

How do you read the plugs? On open throttle, the needle position has no/little impact.

130 mains are way too small. No wonder it gives up at 6K.

I have BST36s on an 1127, with dual pod K&N filters and open exhaust. I run 150 mains, and it runs as good as one can expect from CVs with pod filters. 

I read of people jetting the big 5 speed engines saying that 140-160 is the place to be but when I run a jet as big as that, it constantly fouls my plugs. 

[MikeyVeitch]

9 hours ago, Nik said:

How do you read the plugs? On open throttle, the needle position has no/little impact.

130 mains are way too small. No wonder it gives up at 6K.

I have BST36s on an 1127, with dual pod K&N filters and open exhaust. I run 150 mains, and it runs as good as one can expect from CVs with pod filters. 

In terms as to how I read the plugs, if I go up to a 145 the plugs go sooty and black where as with the 130, they stay clean

[Nik]

1 hour ago, MikeyVeitch said:

In terms as to how I read the plugs, if I go up to a 145 the plugs go sooty and black where as with the 130, they stay clean

To read the plugs, you have to go full blast (fully open throttles under load for at least a couple of seconds), turn off the engine with the kill switch, pull the clutch at the same time, and roll to a stop. Then, if you know how to read the plugs, you can evaluate how rich/lean the engine runs at full blast, i.e. if the main jets are alright. 

[george 1100]

Needle and seats leaking? Float height? 

[MikeyVeitch]

3 hours ago, george 1100 said:

Needle and seats leaking? Float height? 

Carbs are in perfect condition. Basically have nee everything. I was also trying to read the spark after idling so that may be m issue

[bluedog59]

You need to do a proper "plug chop" as described, kill switch/shut throttle/clutch in all at the same time to get a meaningful reading.    What is this "high flow full custom exhaust" you're running ?

[Gixer1460]

3 hours ago, MikeyVeitch said:

 I was also trying to read the spark after idling so that may be m issue

Oh! - you think? You can't tune carbs at idle or standing still ! 

[coombehouse]

5 hours ago, Gixer1460 said:

Oh! - you think? You can't tune carbs at idle or standing still ! 

He's not wrong.

At idle, the engine isn't running on the main jet or the needle. It's running on the idle jets (hence the name) & the mixture screws.

[MikeyVeitch]

Right. Don’t ask because I actually don’t know. I put the 145s back in and the bike now runs like a rocket ship. Slightly lean in fact so I might go for a 155 because that’s what everyone recommends. I don’t change anything else about the carbs. Cyl 4 is getting more fuel for some reason but at this point it’s doing 145mph no stress and I feel like it’s got more to give. Fixed by god I guess. Should I go for the 155 jets or just leave it as is?

[george 1100]

I'll bet you had a tiny bit of grit stuck in the needle and seat. Fouling your plugs at idle but running good at open throttle with 145 jets. The grit now gone . Doesn't explain the plugs with 130 jets though