Hi,

I am giving the carbs a clean and refurb after they filled with mud and grass following a (race) bingle.

I have had them ultrasonically cleaned. They were done in what I understand was a mild citrus based acid.

Apologies for the barrage ... but I have some questions.


#1 Powder forming on carbs after ultrasonic

After ultrasonic cleaning now I have a powder forming all over. On everything aluminium I think - including needles. I am guessing it is oxidisation - what can I do?



#2 Carb piston scoring - How much is too much?

Just wondering how much scoring on the carb diaphragm piston and cylinder is too much?

Here is an example of one of mine. Admittedly, the pic probably makes it look a little worse than it is, but still, it is scored.









#3 Carb needles have no markings.

Any idea what they are? I read that the front and rear needles are supposed to be different - but this is a race bike, so looking for guidance here. They all have a 0.5mm shim.





#4 Pilot screw washer and oring - in or not in?

At the base of the pilot screw hole there seems to be a little 'ledge' - I can hook a piece of wire underneath it.

I am not sure if this is actually the fabled washer and oring just stuck down there or not.

Confusingly, two pilot holes actually had orings come out. And a single anonymous washer seemed to have dropped from somewhere - but only one. Pic below. Not sure what it is. 5mm outer, 3mm inner, 0.5mm thick.



So, do the carbs have a little ledge down there?

An d... if I am missing the orings and washers .... they are not a honda part .. so I chase a Keihin supplier then. Anybody know the part numbers?

#5 What needs oiling?

Now that every trace of oil has been removed from the carbs during ultrasonic cleaning ... what do I need to relubricate? I am hesitant to just oil everything - so as not to cause grime collection in some place that should be dry.

Hi, you'll have to wash the carbs in hot soapy water with a stiff toothbrush or something to wash the acid off, then spary them with wd40 or something like that, will stop them oxidising more.

I'd give the slide bores in the carbs a light sand with some fine wet and dry (prob best do this before washing them) just so there smooth, but try to not to take much off tho. i'd leave the slides unless there well ruff but if they are again a light sand with wet n dry but i'd do them wet.

Off memory (and its quite a while ago) in the pilot jet holes there should be the screw, oring, washer then a spring, thats how carbs usually are. I dunno if there on the microfisch, i'm sure one of the others can help with that.

Needles look standard to me, but without numbers on them your never gonna know, if its running ok i'd be leaving them alone. Have you got the airbox/ filter in place?

Lightly grease all the linkage pivots, choke linkage etc.

Cheers
Ian

O rings and washers can get really stuck and be a right pig to even see.

Have you tried shining a light in there, somtimes it helps, I fish them out with big needles and all sorts.

LiteTek blair sells a good kit, I believe Rick O has them instock or new float bowl gaskets and rubber o-rings for the carbs, well worth the price (cheap) and great for the rebuild.

The correct order is (Left most is the slotted (screwdriver) end of the pilot screw)

[Pilot Screw -Spring - Washer - O ring ----> Into the carb.

Chapter 6 of the Honda service manual has the exploded diagrams and related info on carb servicing.

Im sure the grease info is in there too, probably under general maintanace.

As for the carbs in the pictures they look fine. I wouldnt worry about light scoring, assemble them first and make sure they slide and return.

I spray the joints on the linkages underneath the carbs with a bit of white lithium grease but thats about it.

How much diassembly is needed before ultrasonic cleaning, do you have to take the carb assembly apart? What should I use as a liquid, hot or cold?

Ian/Neo,

Thanks. Krisztian, it might be worth making a new topic rather than injecting new questions into this one. But in short, I had them disassembled, but not separated. So, all four carbs went into the bath as a unit, but had a internals removed from each carb.

Re the pilot spring. Actually, what I am trying to determine is if the washers and orings are already down there. I can hook a wire underneath the 'ledge' and it seems pretty immovable. I can see down there with a torch and I also got me one of those FANTASTIC desk lamps where you flip the lid and it has a magnifying glass (like jewelers and watch repairs guys use - get one. Once you use one of these things you'll wonder how you ever managed without!) ... but I cant really tell.

Weirdly though, I got some orings out (only one washer) - so I am unsure if the others are stuck in there and when it was put back together at some earlier date.

I think I'll just order me a set and be done with it.

Thanks for the tip on the Honda service manual.

I set those carbs up a couple of years ago with the previous owner. The needles are Rick Oliver hrc replicas (carbs are running complete hrc open carb setup), he colour codes them with a marker on top to distinguish which sort. I imagine the colours have been removed through the cleaning process. From memory I think the 8zf were fitted.

I would be concerned at the corrosion, it could cause all sorts of gremlins when the build up is dislodged (if any of it is internal?). You could try wiping it off and applying some acf50 to the carbs, could take some time to work it in!

I have plenty of spare pistons/diaphrams if you ever need any, just PM me.

Thanks Cammo,

I found some notes that came with the bike, they are 8ZG front and rear.

Re the corrosion, I contacted the bloke who did it and he said he forgot to crc them when done, so now I need to bathe them, clean then and crc them. And ... as an added bonus, the throttle mechanism has now lost its springiness and is sluggish (despite carbs being aligned) - probably down to same thing ... so here is the irony ...

I took the carbs to some bloke with an ultrasonic bath large enough to clean all carbs at once so I didn't have to bother with a) cleaning then and b) splitting them .... but down $100 I am today splitting them and cleaning them.

Oh, and the ultrasonic cleaning looks like is has removed some plating on a number of the brass-like arms and so on.

For $100 I could have bought an ultrasonic cleaner that will fit a single carb.

Again, just another entry in the "if you want it done properly, do it yourself" book.

oh, and "acf50". Never heard of it ... but I have now .... I'll keep that in mind. Looks very handy.

The pilot screw assembly looks like this. This example is from a mikuni but same for the Keihin.

Neosophist wrote: The correct order is (Left most is the slotted (screwdriver) end of the pilot screw)

[Pilot Screw -Spring - Washer - O ring ----> Into the carb.

LiteTekBlair wrote:

Much better than my text :)

Are those your o-rings too?