Refurbishing carbs, what parts wear

[Fastmongrel]

I am going to pull my carbs apart for a thorough winter clean and I have decided to replace any parts that might have worn out.

What wears out on the VHB25 carburetors I am guessing slide, needle and needle jet wear but anything else I should look at replacing.

The carbs seem to be fine but I am one of those people who likes everything to be spot on and I feel that the mid range could be better.

[3potjohn]

Those items are subject to wear as you say. Other things to verify are working correctly include float height, float needles, choke piston ends as the seal eventually degrades)
And of course you can check HT leads, caps, spark plugs and ignition timing.
Apparently many men slope off to the garage on Christmas day for some essential DIY……,

[72degrees]

The carbs seem to be fine but I am one of those people who likes everything to be spot on and I feel that the mid range could be better.

Ah, the mid range flat spot

Running standard exhaust system and air cleaner?

Be thankful it hasn't got PHBH28's on. Though oddly mine is a lot better since I upped the idle jet size.

[3potjohn]

On the other hand round carb slides don’t wear as quickly as flat slides. My Sport has standard everything fuel wise apart from Sito silencers and has never had a flat spot except for a rear tyre once.

[Fastmongrel]

The carbs seem to be fine but I am one of those people who likes everything to be spot on and I feel that the mid range could be better.

Ah, the mid range flat spot

Running standard exhaust system and air cleaner?

Be thankful it hasn't got PHBH28's on. Though oddly mine is a lot better since I upped the idle jet size.

Aftermarket el cheapo chinesium silencers, standard pipes and standard airbox.

I wouldn't call it a flat spot I call it a mid range fart.

Chokes have new seals but I will order float valves, main jets, needles, needle jets and check the float heights. I might order the atomisers as well I remember they were pretty manky when I first got the bike.

[Fastmongrel]

Apparently many men slope off to the garage on Christmas day for some essential DIY……,

It's amazing how there are so many urgent vital jobs that need doing in the shed at Xmas time. Particularly when relatives arrive.

[125H]

Emulsifier/Needle jets tend to wear stock up, these parts are running low for old VHB carbs I could not find a needle jet for my 125H and have resorted to having one made and beware of cheap Chinese copies use only Dellorto parts.

[MickeyMoto]

The worn parts have done many miles, more than anybody will put on the old clunkers between now and being banned, so 'stocking up' means fewer for others to obtain with a consequent price rise. Did you horde toilet rolls in 2020?

[George 350]

Re Flat Spot.
Firstly, the Sport is significantly worse for this than a Strada due to the cam overlap.
I can't recall my sport having a flat spot when it was new, perhaps it was the way it got ridden I never noticed?
Fast forward 20 years and unleaded fuel, and perhaps a more relaxed riding style in the 90's I found the 'flat spot' at around 4500rpm, especially when accelerating. Testing with a gas analyser showed it going extremely rich at this point - around 10:1 afr, even at 1/2 - 3/4 throttle.
The 'fix' (if you can call it that), was to install #42 pilot jets (std =#50) and there was a significant improvement. Never fully cured, as I had neither the time or money to afford enough jets, needle jets or needles to really play, but it was good enough, and 25 years on, I'm running the same set up.
Worth a try if you are going through the carb refresh thing.

[Martha]

I am getting towards the completion of getting my Strada recommisioned. A PO had fitted a Sachse ignition system; I added new PVL coils, BP7ES plugs, and ultrasonically cleaned the carbs to get it going, though there was still a pronounced stutter at around 4k rpm. The bike appears to be fitted with a L5 cam and has a stainless exhaust system.
Revisiting the carbs, I made sure there were no air leaks (standard air filter system fitted with new filters), reset the float height to within 0.5mm with new float needles, reversed the choke plunger rubbers to get the unworn side, added 43 pilot jets and new standard slides, needles and emulsion tubes.
With the carbs balanced using a Morgan steel rod type balancer I now have no stuttering nor flat spots and a steady 1300rpm tickover!
I am of the opinion that the new slides, emulsion tubes and needles were as much of a factor as the 43 pilot jets but it has been a bit of a journey getting to this point!

[Fastmongrel]

I have stripped the rear carb and spotted the atomiser is a 260D when it should be a 260K according to the blue book. It's also tarnished and corroded.

Going to order a pair of 260Ks and a pair of needles plus float needles which are worn. Anything else I should order.

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[Fastmongrel]

Eurocarb has two options for float needles hard spring or soft which should I order the original is solid with no spring.

[Fastmongrel]

Right done a bit more reading I have VHBZ25HS carbs which have the vacuum pipe connecting the carbs.

If I understand it properly the HS carbs with vacuum connector have a 260D atomiser
The BS carbs without vacuum connector have a 260K atomiser.

I am buying new atomisers anyway but good job I checked

[Fastmongrel]

260D atomisers seem to be unobtanium stumped now.

[Fastmongrel]

260D atomiser seems to be unobtanium I might have to fit a 260K