Did they change to a Keihin carb because they were having issues with the Mikuni carbs? Looks like the keihin is only on the 2008 bikes before they brought out the Evo. 

Yes, 2000 to 2007 was Mikuni as was the Techno's before.

2008 had the Keihin as do Evo's.

 

I remember their old Zero's from the 90's had Dellorto's.

 

Don't know why they chopped and changed, probably cost lead.

 

I changed my 2007 Rev3 to a flatslide Dellorto VHST, it did highlight the limitations of the Mikuni.

It was like chalk and cheese, the improvements were astonishing, a lot smoother and crisper, though filtering needed constant attention as pilots in Dellorto's are prone to blocking with the smallest grain of grit.

Edited June 18, 201511 yr by goudrons

Beta used the Mikuni from '86 to '94. Dellorto was only on the '95. I hated it because you couldn't get jets then. Swapped it out for a Mikuni. Ran much better. At the time the Delorto was a new design and had two piece pilot jet assembly. Beta went back to the Mikuni in '96 and stayed with the VM26-208 until 2008 when they switched to the Keihin PWK.

Does the noise change when you pull the clutch in?

 

Is it knocking or a sort of chuckling, pinging noise?

 

on mine the noise changes when i pull the clutch in, what could it be?

That's likely to be the clutch basket.

The basket spins free on the gearbox input shaft on a bearing and sleeve, there's always a little bit of play there.

When it's all under tension (clutch disengaged) it's all clamped down to the clutch centre that is bolted to the same shaft, so it's quieter as it's all held tight to the shaft.

Pull the clutch in and the tension is released from the plates and the basket wobbles a little producing a chattering noise.

It's a fairly common noise, particularly when cold and unless it's really noisy, just leave it.

If the noise is bad try replacing the sleeve and bearing first.

Though I think a little too much play for a any length of time may introduce a bit of wear to the inner surface on the basket as well, where the sleeve/bearing fits into.

Edited June 29, 201511 yr by goudrons