Low speed jerkiness

[lancialulu]

I think most 35 PHH were originally specked with 47.5 pilot jets for the 1300 engine but now it seems a larger one now works better. I assume It must be the modern fuel.

The PHHE3 is in reality not the same inside as the previous C35PHH's. It surprised me that the standard pilot had increased to 52.5 (remember this carb was c1974). I doubt the increase was anything to do with modern fuel.... That carb needed more fuel in transition possibly due to  the main jet (115) being smaller than normally fitted to PHH (120). If you look at the first iterations of the emission carbs (E1 & E2) jetting is all over the place.... I still believe if you hesitation that you can easily drive through it is worth increasing the pilot jets by say 5 or 7.5. (Regarding servicing the Solexes then only "jet" that is changed as a matter of course is the float jet).

If however there is a bigger hole in the torque curve it could be down to valve timing not being quite there....

[andyps]

Where do you recommend getting the jets from? I've got a spare pair of carbs which I'm planning to rebuild to hopefully cure a hesitation and it sounds like changing the jets at the same time would be logical!

[Spider2]

Yes, definately. If either the shafts or the body through which the shaft rotates is worn there will be an air leak that will cause variable mixture and lumpy idle and various other running woes. Unfortunately in most cases it is the body that has worn so changing the shaft does not fix the problem, although it may reduce the problem slightly. The solution is to sleeve the body and reem it to make the shaft fit snugly. This is quite a tricky task to do correctly and probably best left to a machine shop or send the carbs to a specialist such as Euro Carbs.
A bodge experiment one can do is seal the shaft/body interface with a fairly lightwight silicon. If this produces a significant improvement in engine smoothness then the problem has been idenified although obviously not a permanent fix.
The so called overhaul kits do very litle apart from supplying new gaskets and maybe the float needle valve and acelerator diaphram. They certainly do not supply any new jets or needles. An easy start would be to change the pilot (slow/medium running) jets first for larger ones. How much larger? That is the question. They are about £10 each so £40 could be quite an expensive mistake, I have no wear in the spindles but get a hesitation from stationary. I have standard 47.5 jets and think I will first try 52's. 
The other common problem is that the idle mixture adjustment screws have been damaged by someone being heavy handed and "bottoming out" the tips by screwing them down hard against the stop. If this has happened it will be impossible to get the mixtures correct. Check by removing the screws (4) and examaning the tips. NOTE count the turns clockwise before resistance is felt before unscrewing. This will ensure you can put the scews back in exactly the same position but of course there is no guarantee that they had been set correctly in the first place but at least you will be putting the back in the same place. For most 35 carbs I think the correct position is about 1 1/2 turn out from fully in but this will vary with carb and pilot jet size. The correct seting can only be determined by tuning the carbs when the engine is really hot. That's a real game of fiddle and tweak.

[lancialulu]

If you are lucky to have the E3 version of the 35mm then shaft wear is unlikely due to the design having ball races supporting the shafts.

[Scott]

Thanks Simon - and Tim - for those helpful comments.

I'll put this down as a winter job to investigate as whilst I can 'drive around' the issue it isn't ideal and mares the driving experience a little.