Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: flc on November 23, 2010, 02:43:22 PM
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I took my bike for its mot today( it flew thro :))
The fault is that from cold it will start first kick, but if you dont catch it properly and rev it a bit till its warmish.
and it stalls then im in for a sweaty 50 kick marathon even bumping didnt get it to go...
any ideas????
ta flc.
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Checked plugs, leads? sounds either like it's flooding or has a carb issue? plugs should give a clue what's going on.
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Low battery charge/bad spark
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I had an hour today.
so had a nose,
id left battery charging overnight.
still no joy, so pulled plugs and all are dry? ive since wound out the pilot screws a full turn, and she fired up????
not sure if i stumbled on the fault or was on my 50th kick :) wil see tommorow once its had time to cool,
i did notice the left hand conecting manifold hose thing????? is split and the previous bodger/owner has used normal car jubilee clips. i have another set so looks like its carbs off time (my favorite job). thanks for your help so far folks.
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Sounds like an air leak is your culprit then, dry plugs and a split manifold - cause and effect, too much air getting in, lean mixture would make starting difficult. I'd not worry overly about the jubilee clips but the split manifold will need remedying, new ones can be a problem to source but do come up used on ebay. A bodge repair using cloth and gaskett goo can be effective as a bodge to keep things running.
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500/550 up to and including 76
Head to carb rubbers still available from Honda
Airbox to carb rubbers available pattern from Dave Silver
Ordinary jubilee clips are too wide and knacker the rubbers
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Well, its been a while since i was able to play in my shed, and its been hard.. i found that although most of the carb rubbers did have some visible splitting they still held pressure (sticking them in my palms and sucking ::)) !!! not exactly a honda approved technique but it did show that maybe that wasn't the fault.
This was confirmed when i ordered a nos rubber (i found on ebay) and it was the same when subjected to the suck test.
Leaving me stumped and going on mathewmosse post, i had another look at the carbs
blowing air through pipes and a good look over i found nothing conclusive, the float levels were all the same at 17mm looking like who ever set them knew what they were doing.
but i then looked for my haynes and as i suspected this book only covers the earlier type carbs????
and after searching through this site i find that the correct setting for k type carbs is 14.5mm mmmm a good 2.5mm away.
I must say that 20 years as a fitter/mechanic on all types of engine i have never cured a problem by adjusting the float level. but it was the only thing left. so back on today, tried gas in them before fitting :) (been there before) and on the third kick a lovely burst settling down to an even tick over. heaven....
But now leaves me thinking fitting larger pilots, was a plaster over the real fault(and i lost one of the origionals ::)). only a good run out and a plug chop will tell me what i need to know.
i will post the result soon as the snow gives up ta FLC..
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Still no joy,ok through the rev range but still got the starting problem, ive checked this over a dozen times plugs/ tapets/points etc.runs . plugs still seamed dry, so got to thinking carbs again, are they off some strange clean air model or cb 650, i then came across this
http://en.allexperts.com/q/Motorcycle-Repair-837/1978-CB550-K-carburetor.htm (http://en.allexperts.com/q/Motorcycle-Repair-837/1978-CB550-K-carburetor.htm)
hmm 12.5mm float height.... carbs off again and re set floats to what i think is 12- 13mm (has anyone got any pics of these carbs in bits? or info on float height setting)
it start firing on the first few kicks then started, im not sure if its cured it or not, i have thought i had fixed it before.
i will know more after a run out on it...
more later........ flc.
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The only info on the K3 carbs is a crapy Honda supplement to the 500/550 workshop manual with not very good dark pictures.
I have the complete manual with all the supplements scanned onto a CD you can have for postage cost + maybe a beer voucher
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bryanj you have a pm..
Well the bike now starts loads beter and runs strong until warm,
then a bit spluttery at small throttle openings.
making me suspect that the larger pilots are now too large(corresponding with sootyish plugs) and were all along hidding the real fault of too large float height settings. Does anyone have a spare standard push in pilot jet they would sell? ( i lost one of mine when i changed them ::))
more later FLC.
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Now you are being a pain!! I know i have 3 about as i had to buy a set of 4 from canada when one would not clean out on a mates bike, so i suppose i have to turn my desk upside down to find 'em
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hi all, glad its not just me has these carb problems, my pilot jets are completely blocked,i cant even push stiff wire through.Are these available to buy new? regards, Mick
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I think the company that stocks cb sohc carb kits & jets etc is:-
Sirius Consolidated Inc. in Canada.
http://www.siriusconinc.com (http://www.siriusconinc.com)
They are sometimes on Ebay too.
Andy C
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I got my larger pilots from them, about 3 weeks to get here due to customs etc, they did warn me when i purchased a good company to deal with.
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Now you are being a pain!! I know i have 3 about as i had to buy a set of 4 from canada when one would not clean out on a mates bike, so i suppose i have to turn my desk upside down to find 'em
:) i know.... i had one in my pocket whilst hoovering my car on our gravel drive, when i checked my pocket it was gone :o ::) so its either somewhere in the gravel or up the vacuum. i spent a while groveling in the dirt but no joy. I you have one that would be ace :).
Ta FLC.
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thanks for info have ordered some from siriusconinc hope it solves problem !
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For all you people that are dealing with slow jets... You can clean them, boil them, leave hours in carbcleaner, treat them with lemon juice, have them listening to ultrasound and... well what not. You can attack them with a copper strand. But they don't wear, at least mine didn't in over 130.000 kms, so why buy new?
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Cos ive had two recently that no matter what i did (couldnt get hold of nuclear deterant) stayed stubbornly blocked with something---possibly a PO's attemt at wire cleaning but who knows and Srius don't charge a fortune for them considering the limited maket they have
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i agree with you bryan, mine seem like they are solid in the middle, whatever i try dosn't work, so new it is! It seems carbs dont like to be left for years not used, not for 28 years anyway!
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Thanks to help from bryanj i have now got 4 standard pilots, after fitting the bike runs much better low down, and accelerates strong, BUT....
i still have a mid throttle weak spot which is only apparent whilst cruising.
the only thing left is needle clip position or maybe needle taper,
i hope its the former as i can alter it, the taper means a searching for the holy grail (possibly)
So off with the carbs again.
more later Flc
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The needles could be worn. They get a "step" in them.
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The needles could be worn. They get a "step" in them.
Not thought about that after all they are 30 plus years old... but would that not make for a rich mixture?? i will have a look. are these parts still available?
thanks for your help Flc.
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16012-404-004 if you can find them, the 404 means its a 750 auto part so good old USA may be the best place to search
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Thanks for that byranj, im hoping i dont need them ive lifted the needles one notch (only one more left) and she seems cured lovely cruise at any throttle position, strong acceleration, bit fluffy just off stop but i think the float setting of 12.5 is a missprint as the float looks level at 14mm when im next off i will set them back to 14.
but im happy now and its a blast to ride.
I would like to thank all who have helped, its been a long trial/test.
i have just got home from work and its p~+@?ng it down and i now have a water based missfire ::) you couldnt make it up :D
looking under the tank in the dark was like a scene from star wars, its more like a monsoon out so cant really blame the bike.
more later, a happy Flc.
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Careful how you read the "supplement" the 500 and 550 K3 have different settings
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Back in the 70's we had an ingenious solution for this (well, we were all electronics students...):
- Remove coils (incl HT leads!) and place in nice warm airing cupboard for a few days
- Rough up area around the HT/coil join with sharp screwdriver - makes purchase for...
- Apply RTV (Room Temp Vulcanising) rubber compound to seal join
Worked (most of the time - just make sure you don't leave any gaps)
A saw a CBX1000 with a plastic carrier bag wrapped around the coils once - it was melted!
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OR buy shares in WD40!!!
Did you find the cd usefull?
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To be honest byanj it only seems to deal with the 500,
i may not have looked properly. time is the enemy at the moment. its a keeper tho ;).
and thanks for the jets. Flc.
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Ah, an irsh friend of mine played with the original manual in Adobe and linked all the pages of the 500 manual to the contents page BUT NOT the supplemnts---you have to search those for yourself mate, try page 169 onwards for the K3 supplement---my fault should have told you! They say float height is 14.5mm by the way
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You can download the complete and original Honda Workshop Manual CB500 - CB550 incl. all supplements at
http://www.mediafire.com/?uznwn3ihx0i (http://www.mediafire.com/?uznwn3ihx0i)
It's 77,5 MB.
If you happen to read french, I know another very good one (160MB!).
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Ah, an irsh friend of mine played with the original manual in Adobe and linked all the pages of the 500 manual to the contents page BUT NOT the supplemnts---you have to search those for yourself mate, try page 169 onwards for the K3 supplement---my fault should have told you! They say float height is 14.5mm by the way
Yes thats better i thought it was my error. thank you,
it says second groove for the needle would that be from top or bottom?
mine are second from bottom 5 groove needles.
i may try that steve the other 550 i had was a worse nightmare in the wet than this one.
thanks for the link deltarider pity i didnt listen in french at school :)
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recieved slow running jets from canada only took 2 weeks, will fit soon and try again, wish me luck!
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carbs reassembled and cleaned, still wont go! Scratching my head now!
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are the plugs dry? most of my problems were caused by incorrect float height,(should be 14.5mm)
try to cover one of the carbs with your hand whilst try to start it does it fire?
also look here
http://www.sohc.co.uk/index.php?topic=3074.msg10881#msg10881 (http://www.sohc.co.uk/index.php?topic=3074.msg10881#msg10881)
let us know how yopu get on..
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back to the slow jets, now the new ones are in i sawed an old one in half, the through holes were solid at both ends but clear in the middle, as if they were deliberately blocked, so i checked another one, it was the same, weird! no way to clear them exept to drill so glad i got new ones.