Carburettor Jetting

[screwy]

Hello!

Greetings from Latvia, Riga!

I recently bought a 2000 XJR SP. Silver top carburettors.

It has 36Y inlets, Remus 4-1 full exhaust, modified airbox, but with stock carburettor settings.

It was running quite weak, with a big flat spot at 4000rpm. The power was too weak. So i raised the needles 1 step. And fitted 102,5 main jets and 42,5 pilot jet. Stock jets are 95 main and 40 pilot. Cleaned the carburettors and put everything back together. The bike now runs great! The power is superb.
But the problem now is that when ride it with full throttle after some 3-4 seconds is starts to stutter and the acceleration stops. If i let off the gas and then rev it again it goes again for 2-3 seconds and starts to stutter again. I put in 115 main jets, but the problem still was there and the bike was running too rich.

What could be the problem?

I checked the floats and fuel level, and everything is good. Changed the fuel filter. Changed the spark plugs.

Maybe someone can help me... unfortunately no XJR forum in Latvia...

[maras954]

Hi, i haven’t got carbed xjr but this looks like fuel starvation. I would rise fuel level slightly above recommended and check what is happening. I bet someone will get back to you with other ideas.
If you got Facebook i would sign in to yamaha xjr grups, there are few there and all english speaking lads are really helpful

[screwy]

Thanks! I was thinking about the same thing. Will try and see what happens. Got rid of the airbox and put on Pod filters, it will be much easier to take off the carbs now, the airbox made it quite hard. I hope the pod filters will not make the whole problem even bigger...

Already asked on Facebook groups, looks like no experts there, no answers recieved.

[shishqa]

If You get rid of air box to switch for air pod filters You will add huge amount of air into your carbs. A lot of adjusting in front of You, won't getting right with a stock needles.

[screwy]

Yes, that will be an even bigger problem. Will give the carbs for ultrasound cleaning, just in case something is clogged up, that i missed. Will fit the pod filters and see what she does.

[shishqa]

In my case I couldn't get more than 6k rpm.