Having a few problems setting up dellorto phbl 26, information i have is: 24mm float height, 70 choke valve, 200 float needle, 44 pilot jet, 108 main jet, not sure what needle it should have or which notch in needle to use. Have been told 2.25 turns out for base setting on mixture. any help or information welcomed. thanks

There doesn't seem to be a great deal of information around for 300s. I had a 301 which is the model after the 300 and still a piston port 250 ( and I think may have the same top end as a late 300) and the standard carb settings from my black book (its actually blue but....) are:

Main - 102

Pilot - 45

Choke - 70

Needle - X5 (clip in 2nd groove from top - seem to remember it had to be in the 3rd groove to stop it pinking when opening the throttle, but it was a bit sh4gged)

Needle jet/emulsion tube - BN264

Needle valve - 200

Slide - 45

Pilot screw 2 1/4 turns out (as a starting point)

Float height 23.5 - 24.5

If you ring Bill Pye (01642 722378) he will tell you all you need to know.

Think it should it be a PHBH on a 300 rather than a PHBL?

_{yeah, your correct it is phbh, thanks for your help.}

No problem, just wanted to check I was giving you the spec for the same carb. Best of luck sorting it out.

bike is running fine with new plug, but gets carboned up after its run for a while

any ideas?

Edited February 25, 201313 yr by ajock

Mine didn't foul plugs, but a bit rich 'n wooly on std settings. I've dropped the needle (clip in top slot) and all is well.

Think i have found the cause, it would appear that gear oil has been escaping into the crankcase, not sure if its just the seal or if the gasket between the casings is knackered, Thought i would put it on its side and fill the gearbox with oil, then see if any of it made its way to the crank case. Any thoughts?

I would just replace the seal and the two O rings on the clutch side of the crank if I were you. You can do it with the engine in the frame.

Like grib says, do the seals and the two 'O' rings. It's not unknown for the 'O' rings to be left out. Use a puller to get the mag rotor off and check the condition of the key that locates it. Keys are only supposed to locate things, it's the taper interference that provides the grip, but if it shears it can mar the surface.

Have it all stripped in the frame already, rebuilt only 18 month ago, the seal when removed seemed to have lost a bit of tightness on the crank sleeve the o-rings were quite distorted. all parts where bought from bill pye. It is possible that they where damaged about 6 month ago when started with broken carb to cylinder intake hose???? guilty party said it rev'd abit???

Is the sleeve perfectly smooth where the seal contacts it? I don't think starting it with a split intake hose would damage the seal. You may have to split the cases to check the gasket is sealing.

Going back to your original question; I found a 300 user manual the other day, its in Italian but (using Google translate)the carb spec is:

Main jet 108

Pilot jet 45

Choke jet 70

Needle X5 (clip in 2nd groove)

Needle jet BN264

Slide 45

now here's the odd bit;

Air screw 1 turn out ( but the diagram in the manual shows a carb with a fuel pilot screw not an air pilot screw)

If you do actually have an air screw and not a fuel screw then 2 1/4 turns will be way out.

I have attached the manual because there is other useful stuff in it:

Thanks for your help, the manual will be helpful.

The clutch side oil seal needs to be very carefully fitted, because of the sharp edge on the crankshaft, the factory used a taper tool that fitted onto the crank shaft, allowing easy placement of the steel collar and oil seal. I personally use a very thin feeler gauge and carefully roll the feeler gauge round the inside of the seal, to pass the sharp edge.