CBR900RR - Carb Cleaning

[wots]

After running out of fuel the bike can hold back at wide open throttle. Clearly I've dragged some dirt in. I want to strip and clean them, but crucially, I don't want to make a mess of it.

I'm not looking to do a full strip and back to pristine, but I need to ensure I have cleaned everything I can. I have a small ultrasonic cleaner for smaller parts. So:

1) What should I take apart?
2) What should I not even think of?
3) Which bits to replace (Gaskets)?
4) Anything else?

I suspect this bike has been jetted, as it runs a K&N and a Micron exhaust under normal circumstances it's super smooth.

Also, I have a spare petcock, so I'm going to buy the rebuild kit and do that at the same time. In fact I may do that first just in case it caught there.
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[J.M.]

Remove float bowls. Clean any dirt out using something like petrol and a toothbrush.

Carefully remove the jets one by one and ensure that they're clean. Do it using something like pressurised air. Blowing on them kind of works. Make sure they go exactly back where they came from, else the bike will not run right.

No need to replace anything unless the gaskets are worn. Generally if the rubber doesn't look dry and broken, it's fine to reuse.
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2004 R1 & 2018 XSR900

[wots]

Managed to clean the carbs, thank god for my new impact drill, float bowl screws were solid. With the faintest press on the trigger of my impact drill, they freed.

Anyway, all clean, no sign of anything significant. All back together, ran her up, the Mrs was sat behind the bike when it hit about 6K, backfired and singed her eyebrows

Still the same, ran it up with an auxiliary fuel supply. It ran perfect. I've had the tap apart and replaced with a spare as well as stripping both and using the best bits. Same happened on both. The original membrane looked a bit crap, but there was no difference between old and new taps when changed. I cleaned the in-tank filter, it was crappy but not too bad.

I have a tap repair kit coming anyway, I'll do that, but it looks fine. The only thing I can imagine is some other problem with the vacuum on the petcock, I've checked it all and it looks good. I'll replace the pipe tomorrow. Failing that I may look to get a fuel tap from the earlier fireblade which doesn't have the vacuum and try that.

Have I missed something?

EDIT: It is running 126 jets, rather than standard 120
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[Wafer_Thin_Ham]

Kinked vacuum line, giving you a fuel starve at high load?
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My Flickr

[wots]

You'd think, but it's dead straight, it would be almost impossible to kink. They are known to come off, but then it won't run at all. I'll replace the vacuum pipe anyway, as I've got some.
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[wots]

UPDATE: Yesterday had carbs in bits again, cleaned the mixture screws (forget what these are called), tightened and counted turns 2 and 1/4 all of them. All had nasty white crud in the springs and the washers were a bit manky. I previously didn't want to do this as I knew I'd definitely need a carb sync afterwards. Also, removed the Iridium spark plugs and put the standard ones back in. Vacuum replaced anyway. Also, cleaned the slides, there was an amount of dirt in the bowls on some.

It will now rev to the red line in first but stutters a bit on the way. I actually think the iridium spark plugs weren't helping.

Can someone explain very briefly, what each of the jets do and how this would affect running if there is a problem with them. I am happy to replace, but I don't want to replace the lot.

It is running larger jets, looks like 126 main, which seems odd as I haven't seen them available in that size on wemoto. 125 and then another a jump up to 130.

I have a whole new petcock and gauze coming from the states, only cost £20 which is cheaper than secondhand here. Incidentally tried again with the separate fuel feed and it was doing the same, I must've made a mistake there.
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[P.]

This may help.

https://www.iwt.com.au/images/effects3.gif

Ideally, I'd have all the jets out, make sure all are clear.

[wots]

Perfect, exactly what I needed, genius. Previously, all jets had been out and cleaned. I just hadn't done the pilot as I thought I'd screw it (pun intended) and then not be able to proceed further.
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125

[evoboy]

It shouldnt need to be rebalanced if you clean out the carbs and pilot/air/idle mix screws.

The 126 jets might be from a Dynojet kit thats fitted.

Were the idle mix screws all set differently?
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[wots]

[evoboy]

Have you checked all the carb diaphragms for splits/'cracks?

Are all the vac lines in good shape without any splits?

Are the inlet manifolds all cracked and old?
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[wots]

[wots]

It's Fixed!

After a lot of fannying around, I sent the carbs away for ultrasonic cleaning. They came back looking fabulous, noticed that a connector was just barely making a connection. It was a black connector with black and yellow wires IIRC. I pushed this firmly home and re-connected everything. Got all rubbers to seal correctly, pumped fuel through and boom, sounds fantastic. Revs all the way smoother than ever.

I had the carbs stripped (not separated) and ultrasonically cleaned, 4 O rings fitted as these were gone. £45

Very happy.
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Currently: Yamaha DT 125 LC2,Repsol Fireblade, and Bumblebee MSX 125