Carb Needle Adjustment
 

Is it possible to adjust the carb needle clip position without removing the carbs?

I removed the baffle from the exhaust over the weekend to see if it could be modified to quieten the bike down a bit and it was obvious that the bike was running well rich.

So I sat and thought about it for a bit and decided that after I stripped the bike the choke had less movement than before, maybe it was not going back to the fully off position? Off came the tank and air filter to check but that’s not it, the choke has full movement and the cable is slack when off.

My next thought is that the carbs were adjusted for the straight through pipe it was fitted with when I bought the bike and that changing to a baffled pipe was the cause. As I spend most of my time at 1/4 to 3/4 throttle I’ve discounted the main jets and I’m concentrating on the needle position

When I had the tank off I’m sure that I noticed that the screws on the top of the carbs were visible - are they accessible enough to remove the tops and get at the diaphragm, slide and needle with the carbs in situ?

Sure, if you can reach all screws for diaphragm cap, should be able to remove cap. Then pull out diaphragm and slides out to adjust needle.

Thanks for that, a full strip down scares me and the quote I’ve had for a professional clean and reset to standard scared me even more - potentially over £500 is more than I can justify.

Well, the answer to the original question is yes, you can access the needles without removing the carbs.

Unfortunately the bike is still fitted with the original, non-adjustable, needles so I still have some thinking to do.

You can adjust them by shimming with 1-3 small washers onto needles before dropping them into slides. This raises them as if there’s grooves & clips.

https://cbrforum.com/forum/attachmen...1&d=1712992233

That OK but I want to drop them as its running too rich :-)

Factory mixtures are always rich under WOT for safety. Many ways to lean out WOT mixtures:

1. Lower float level, unfortunately leans out across board, including idle and mid-range

2. Smaller main-jet

3. Custom needles with custom profile. I used to spin these up micro-lathe. Typically have narrower mid-section for more mid-range fuel. Then thicker tip to remove WOT fuel.

I suspect it's the mid-range area I need to lean out as that's where I spend most of my time - very little full throttle work.

As I understand it changing the main jets would only affect 3/4 to full throttle and adjusting the pilot setting would be zero to 1/4 throttle so it would be the needles I need to alter.

Do the OEM needles come in various sizes or are they all standard?

Factory ones only come in one size I think.

Hi him, back to the drawing board.

At least it runs well enough to ride and still goes like **** off a shovel so no massive rush to fix it.