Vintage Tiger Any Carb Gurus Out There

3K and above is about when the main jets supply the fuel so they should be ok.

I would look at the pilot jets / needles for being dirty and/or adjustment .

 

As David said blocked pilot jets

 

No mate they have the main jets at the bottom the pilots are separate and smaller and undone with small flat head screwdriver to the side of the main look at an exploded diagram on google to locate them

 

Your low tech solution is to ease the carbs off the inlet manifold and back blast the tiny galleries and jets with aerosol carb cleaner.

Your target is the two oblique slots at the bottom of the photo that feed fuel from tickover through light throttle until the slide and needle lift and the main jet comes on stream......at about the point your problem disappears. Stick the aerosol fine tube right in the hole and hose them out........

 

A suggestion to get off the idle jetting a bit sooner , something that @Ron Ashurst has done to. Lift the top off the carbies and do some drilling , there's a small bypass port ,it's located just to one side of the needle. Open this up a little and your carbies will lift/open quicker , better throttle response. To get the best out of this mod lift needles 20 or 30 thousands of an inch ! Jetting is right on the money std , mod requires a little more...!

 

It won’t make a blind bit of difference if the jets are blocked!

I would walk before attempting to run. It avoids a fall....... It helps to have a basic idea of how a constant velocity carb works with butterfly throttles as opposed to variable Venturi types. If I have lost you already put the drill down!

This http://www.bonneville.se/nedladdning/Hur man jettar.pdf
explains how your particular carbs work but the jet and needle details are NOT applicable.

Dirt first!

 

Good man! If you are going in there then you will be dropping the float bowls anyway and should use the opportunity to clean all the galleries. Euro Car Parts sell carb cleaner at half the price of Halfrauds. You will want newish screwdrivers as the screws are soft and easily burred. Many are so scarred by the experience they refit with Allen head cap screws.......

 

I don't know what bike you are dealing with but
I believe a little larger pilot jet would help this. The transition from pilot curcuit to running on main jets can be tricky. I have gone through this with my 2 old T-3's. Raising the needles a notch or two might help also. Of course this is assuming the carbs are already clean and has the proper main jets. ...J.D.

 

If it runs well at open throttle, I would assume the main jets are fine. I would be a little cautious at taking a drill to your carbs as some have suggested, simply because that is irreversible. I only mentioned main jets because thier size will effect changes made to your needle adjustments. I like.to have the jetting all done before I get into the finer points such as needles. If your bike has Mikuni BST36's you have provision for changing the needle height. Just remove the circlip and put them up a groove or two. If you have Keihin's you have to come up with spacers to do this. I have one bike with Mikuni' and two others with Keihin's. Been into all three at one time or another. Needle heights are one of the last adjustments you want to make. This is the finer adjustments. That and pilot screws. If you have to run your pilot screws much more than 2 1/2 - 3 turns out, you need a bigger pilot jet. Hope that helps you out. Just some of the stuff I have delt with owning carburetted Triumphs for almost 18 years. ...J.D.

 

Well, if you are only1 1/2 turns on your pilots, I would first screw them out a bit and see if it helps. You are still in the range of adjustment for that jet. ...J.D.

 

He’s a bit OCD about cleaning them though.

 

Which carbs are you using Ron ? ...J.D.