Honda-SOHC

Sorry - quite a long post!!

As per earlier posts, following major fuel seepages from around the carb bowls and (as it turned out) the fuel tubes between the carbs and also sporadically from the overflow tubes, I undertook to rebuild them.

With help from comments on this forum and Brainj who miraculously managed to supply me with four springs used on the throttle slider link arms, which had been lost during cleaning, the carbs have now all been re-assembled, bench balanced and refitted to the bike - re-fitting them was a nightmare!

During the rebuild the carbs have been vapour blasted and cleaned in an ultrasonic cleaner as well as having all the replaceable jets etc have been replaced along with the seals and O-rings etc. Taking note from others comments I have tried very carefully to make sure that all the internal passage ways were clear and clean.

The good news is that they look good and all of the fuel leakages have been cured.

To complete the exercise I have just finished carefully making sure the timing is spot on (at least statically), the points are good and the tappets are all correctly set up. (Both the timing and some of the tappets clearances were a little bit off).

The bad news is that the bike will not run smoothly at all!

Actually no-1 cylinder is hardly firing - its exhaust  pipe is still cool after a couple of minutes whilst the other three cylinders are all hot. just to be sure this wasn't anything to do with the plus I have swapped 1 & 4 plugs over but to no avail.

To explore a bit further I did remove the screw where you would attach a vacuum gauge and spray some carb cleaner in and immediately the revs picked and No1 cylinder fired up, perhaps suggesting an issue with the fuel delivery to that cylinder. I have also checked that there is fuel in the cab (by opening the drain screw) and confirmed there is a regular flow of fuel.

Its worth saying at this point that No1 cylinder has always been a bit of a problem in this regard, causing the engine to 'chug' at tickover until the engine has warmed up which makes me wonder if there is possible a more deep seated problem?

I am loathed to remove the carbs again and have another go at clearing them as there seems to be no clear way of knowing if the clearing is successful.

Does anyone have any suggestions - is there anything else which could cause this type of symptom other than the carbs? If I do take them off again what can I do to make 100% sure that all the passageways are clear and there is nothing else causing the problem? Any guidance would be appreciated!

So, managed to eventually remove the air cleaner (earlier post) and after a big struggle actually get the carbs off the bike! They are (as referred to in several other posts) the 'dreaded' PD types (PD 46A).

The original problem was that the carbs were leaking significantly from around the bowl seal and having removed the carbs and set them up on the bench, connected to the tank, I have confirmed this is definitely where the fuel is leaking from.

Having removed the bowls it looks like perhaps the last time somebody did take them apart the seals were not replaced - they looked pretty deformed and in a bad state - also the screws holding the bowls to the main carb bodies were not really done up very tightly - I was expecting a bit of a struggle here but they came undone with very little effort so I am wondering if this 'lack of tightness'  was contributing tot the problem?

In preparation I have already purchase new 'packing' kits for the carbs but here is the first problem - the top gasket in the kit has locating holes in a different arrangement to that which is on the bike (see below). Now the kit was supplied by David Silver as a substitution, so that might be the explanation but has anyone else seen this problem before?

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But now the BIG QUESTION - as the carbs are off the bike should I go for a complete rebuild at this stage or let sleeping dogs lie and just replace the bowl seals?

If the general recommendation is to go the whole way are there any good articles on how to do this - I have found one from the "Vintage Bike Builder" website which looks pretty good but wondered in there were others which I could refer to. I have noticed that both the Haynes Manual and the Honda Workshop Manual I have don't seem to actually cover the PD carbs!. Also is there a recommended kit of parts including all the jets etc - looking on this forum there does seem to have been problems with different jets being supplied which are not always correct!

Any advice on this would be welcome!

I have had some issues with the front brake on my 550 so have had to look at the master cylinder.

Unfortunately (as commonly seems to be the case) the internal circlip was badly rusted but have managed to remove that. I was then expecting the whole internal assembly, piston, cup spring etc to simply come out or at least come out with a gentle push from hose connector end, but it seems locked in place.

Should they simply and easily come out or have I missed something else which needs to be removed first? is it possible that perhaps the washer under the circlip has rusted and this is causing the problem? If so how much pressure is it safe to apply to help it out (I have already applied some easing fluid which help release the circlip)

Thanks for any help - would like to get the bike roadworthy again very soon!

Hi all,

My name is Keith and ride a CB550 K3 (Pic attached). Have just joined this forum after watching the .net one for a while .

Most of my 'bike forum time' recently has been been focused on the UK Honda Superdream forum, as my current project is a complete strip down and re-build of a 1981 CB250N Superdream and the forum is a fantastic source of help and advice.

I am hoping (and am sure) this forum will be at least as good in terms of help, advice and general discussion!

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