Keihin PD46a - missing arm

[SpannerBrat]

Hi there all,

1st time posting on here so, hello, here goes - some time ago (years) I bought myself a "project" - a completely disassembled '76 CB550 (de-tabbed & already hooped bare frame with EVERYTHING else in boxes & bags) that's been sat waiting patiently for me to get my backside in gear. I've no experience of building anything like this & only a basic mechanical knowledge but I'm armed with a manual, a box of tools & a big bag of enthusiasm so what could possibly go wrong???

There are parts that aren't CB550 (the forks look like they could be from a CX & the rear brake looks like it's from a 750) & there are definitely parts missing - some could be more of a challenge to find than others - such as the petcock, rear brake switch (in fact the entire wiring loom needs starting from scratch) & loads of nuts & bolts etc. etc. but nothing - other than the subject of this post - that's particularly fazing me (yet).

Well my backside's in gear now & I've finally got round to doing something with it (it's going to be a cafe racer - think Seaweed & Gravel, Brady Young Black & Tan / similar kind of thing) with much of the work so far being cleaning, tidying & painting of the "big" bits. The bottom 1/2 of the engine is built (with the top 1/2 painted & ready to bolt back together) but I've picked up the carbs & there seems to be an arm missing in one of them as can be seen here...

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I think I've tracked down that the part that's missing is (at least part of) the arm set but I've no idea about the significance of it not being there (hope that doesn't sound too stupid a question). And if it is needed, what the parts do I need exactly, how difficult an issue it is to fix & how I go about fitting whatever's required (I wasn't planning on taking the carbs apart to that degree but if absolutely necessary, I suppose I'm going to have to have a go)?

You can assume a healthy dollop of novice confidence at spannering in terms of tackling jobs.

Many thanks for any help you can offer.

[Trigger]

Welcome to the mad world of the SOHC.
Never assume that the previous owner had the bottom end of the engine all together and working. It is a false economy to think the bottom end is all OK.
The carbs you have are a nightmare to get running right, the 550F1 or F2 are a much better carb.
Pic's of the forks and rear brake would be helpful

[SpannerBrat]

Hi Trigger,

Thanks for the response. Aside from them being a nighmare to get running right (they would be), have you any advice on the missing part?

I've no major issues in principal with the forks / rear brake (I imagine they'll work & I'm more than fine with a "frankenstein" build) but if they prove troublesome, pics will be no problem.

[Clunker]

Hi Spannerbrat, I may have a spare arm for you if the carbs are the same as a CB650. Can you measure the centres of the bolt holes and let me know. On the main carb body just above the float bowl on the right side, there should be a number stamped. Regards, Clunker.

[SpannerBrat]

Hi Clunker,

Thanks for the offer of the arm.

Is that the centres of the bolt holes across the tops or?

I'll go number hunting this evening.

[Clunker]

Centre to centre of the bolts are 76mm on the carbs I have, trying to find my camera cable to upload a picture.

[Clunker]

Ooops! Didn't notice you'd put the carb number in the title

[Clunker]

These carbs are PD40A but the arm may still fit.

[Clunker]

I think the penny has just dropped as to which arm you mean You mean inside the carb body? If thats the case then there is nothing missing, that is your number 2 carb which is your base carb, it isn't adjustable but the others are. The only part I saw missing was the link arm.

[SpannerBrat]

Hi Clunker,

You're penny was right on the money (sorry   ). I hadn't realised I'd taken the photo before I had refitted the brace.

Great news that - at least for the purposes of this "issue" - I don't have to pull them apart....phew.

Thanks for the knowledge (it did seem rather strange that something like that - so far into the carbs - was "missing").

1st post RESOLVED! Cheers.

[Clunker]

No problem mate. Looking at those carbs though I'd be inclined to strip them and ultrasonic clean them while they are off. Don't know if rebuild kits are available for them but steer clear of anything from Taiwan (ask me how I know). Stripping them isn't anything to worry about, putting the buggers back together is the tricky bit! No, seriously, they are a doddle and nothing to worry about.

[SpannerBrat]

That's a bit of a blow. They've been through ultrasonic cleaning.....twice! The 1st time, they stood for too long without lube & the sliders stuck so needed freeing up but after the 2nd clean, the sliders are moving smoothly.

Would it be a full "strip & separate" job you're suggesting? I'd like to avoid that if possible (but would also like to put most things back together once rather than twice......or more times).

[Clunker]

If they've been cleaned twice then I wouldn't bother again as they won't have been used to get dirty inside. When I do carbs I strip them just so much that they fit in my cleaners tank but stripping them right down isn't hard, its just laziness on my part. I take everything off them that I can. I've just done mine but I left the middle two together as they fit in my tank totally immersed. When they are finished in the tank everything gets a really good rinse in the sink then taken out to the shed for a massive amount of compressed air through every single hole, then I do it all again, just in case.

[SpannerBrat]

That's a relief.

I'll give em a go as they are & see how they get on.

Thanks again for your help.

[Bryanj]

Even with ultrasonic the push in pilot jets need removing and cleaning seperately