Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: veefour on November 07, 2012, 07:04:12 PM
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Well, my 'new' 1976 CB550f arrived last night ( see Hi from Berkshire ). Started her up for the first time at her new home this afternoon, nice quiet engine no smoke or nasty noises :) Alas the first fault appeared after switching off when petrol started running from the 2 right hand float bowl overflow pipes. Now, apart from starting the engine up regularly the previous owner has only done 150 miles in 9 years, so i can imagine there is probably the need for a Carb clean. Does anyone know if & where i can get a Carb gasket kit from or do they only come with a Full Engine Gasket Set !
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hi vee, you can get them at Dave Silvers among others....
http://www.davidsilverspares.co.uk/CB550F2-SUPER-SPORT-1977/
could also try;
http://www.fowlers.co.uk/parts/from_fowlers_web.shtml
or
http://stores.ebay.co.uk/ClassicCycleCity/CB-500-550-Four-/_i.html?rt=nc&_fsub=293250012&_sid=127779182&_trksid=p4634.c0.m14.l1513&_pgn=2
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Might be also worth a try: http://www.nrp-carbs.co.uk/index.htm
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Plus they don't come in an engine set.
Also worth checking the brass overflow tube for cracks
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Thanks for all the replies, gaskets on their way from the USA.
Took float bowl off of the right hand side carb to find someone has already soldered the overflow tube, ( is there any way these can these be replaced ! ). Also as i removed the bowl the plate that holds the main jet in fell out, could this have somehow come unclipped & was therefore weighing the float down !
Finally, ( until the Haynes Manual arrives ) i have read on here about float levels but can anyone tell me how to adjust the float's !
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Soounds to me like you need the proper Honda manual for the adjustments, as to the standpipe officially you have to replace the complete floatbowl which i think is teh same as the 500 but the only parts book i don't have is the 550f so i cannot be 100% on that.
I was looking at buying brass tube and drilling out and tapping the bowl then screwing in a tube with loctite but that is all still in me ead.
The jet retainer frequently falls out when you remove the bowl as its teh bowl that holds it in tight
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Soounds to me like you need the proper Honda manual for the adjustments, as to the standpipe officially you have to replace the complete floatbowl which i think is teh same as the 500 but the only parts book i don't have is the 550f so i cannot be 100% on that.
Does this help: http://www.dotheton.com/downloads/CB550_Parts.pdf
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It confirms that the floatbowl, otherwise known as chamber set A or B, has a 323 middle part number making it the same as 500 four and all the US 550 K models Up to but not including the 77 K3
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The tubes are very difficult to solder. I have found the most effective method is to smear araldite along the crack. I have one on my bike which was temporarily repaired in this way 8 years ago and still working fine.
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Soounds to me like you need the proper Honda manual for the adjustments, as to the standpipe officially you have to replace the complete floatbowl which i think is teh same as the 500 but the only parts book i don't have is the 550f so i cannot be 100% on that.
I was looking at buying brass tube and drilling out and tapping the bowl then screwing in a tube with loctite but that is all still in me ead.
The jet retainer frequently falls out when you remove the bowl as its teh bowl that holds it in tight
OK, so i am replacing all the little O rings on the jets ( managing to do it with the carbs in situ). It seems like the floats in the 2 right hand carbs are just not cutting the fuel off at all so need a big adjustment. I now have a manual & it states the measurement between the top !! of the float to the base !! of the float chamber should be 22mm when the tang of the float is bent so that it is touching the jet. Could anyone explain to me in layman terms how this is measured ! Maybe a little diagram would help ! Also how could the floats alter so much in general use.
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As a general rule on any carbs, if you turn the unit upside down and let the float rest on the inlet valve freely without pushng it down......then get a steel rule (starts from zero mm with no space before the scale starts) and put the end of it onto the surface which the float bowl fits to.......then read off in mm where the highest point of the float is.....then that's what the reference reading is talking about.
This is a default way of seting any carb IF no specific knowledge is available to suggest otherwise.
"local knowedge" or a specific manual would give more precise descriptions if there is a different system of markings/ geometry that is used.
Hope that gives you a starting method, maybe another contributor has more accurate info.
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Well i have decided to stop fiddling about & to make them easier to work on have removed the carbs from the bike. To do the job properly i have also ordered new jets / needles etc. from David Silvers. Also the floats look like they have been bent about a bit in their lifetime so am thinking of getting new ones of them also, i don't think DS have any of these ( will call them tomorrow ), but if not does any one know where else i could get them apart from paying the horrific prices some sellers are asking in the USA :o.
Although i bought the bike as one i could tinker about with it now looks like i might be having to spend a bit more cash than i anticipated. I did take the indicated ( not guaranteed ) milage of 2,600 with a pinch of salt :D although the Reg doc confirms the previous owner has only covered 150 miles in the 9 yrs he owned it ! Unfortunately the owner before him cannot be traced, so apart from knowing it was sold originally by Broomfields Motorcycles of Chelmsford & looks like NOO483P has spent its 36 yrs in Essex i cannot get any more info. about the bike, unless any one on here knows of course. ???
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Floats rarely need replacing, just careful attention to detail in getting them square to each other and on straight brackets. Worth polishing the pins so they move freely
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HELP, i have almost finished the carb rebuild but i have been & snapped one of the main jet retaining clips >:(.
I know these are hard to get hold of but does anyone have a spare one they could supply me with please.
Other than that i have seen something somewhere on this site where someone has done a modification using a spring !!
Cheers,
Dave.
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Well carbs all rebuilt & balanced, engine starts on the button & revs cleanly. Problem is when ridden the engine seems to be only running on 3 cylinders, the plugs are new & all have a strong spark. So, what do i try next new plug caps / HT leads, or could it be a faulty coil !! Any clues welcome please.
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Plugs, Plug Caps and vacuum balance of carbs---AFTER all service items done. Coil can't fail to just one plug as it's double ended but one lead can short to frame etc.
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Well i have done all i can think of, new plug caps et all ( all plugs have strong spark ). Balanced Carbs again ! At second thoughts it feels more like the choke is staying slightly on, when ridden it is sluggish but when opened up above 5000 rpm it accelorates quite quickly. Where do i look now !!
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It seems like you've been through all the logical stuf that should be checked and set, so if you're happy that those items are ok then you may having to start looking a bit further.
Next i'd check that you have no valve clearances that are too tight......followed by a compression check if you haven't already done that.
Just a quick check item to give you a lead.....start it from cold and run for about 10seconds then switch off......now carefully check the down pipes close to the head to see if you have any which are cold to indicate which cylinder could be giving you that missfire feeling.
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see my old post "3 cyl 550" as i had similar probs, turned out to be a bent float needle!
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Next i'd check that you have no valve clearances that are too tight......followed by a compression check if you haven't already done that.
Just a quick check item to give you a lead.....start it from cold and run for about 10seconds then switch off......now carefully check the down pipes close to the head to see if you have any which are cold to indicate which cylinder could be giving you that missfire feeling.
I had previously checked valve clearances, & all the downpipes are getting hot. Will try a compression test next.
see my old post "3 cyl 550" as i had similar probs, turned out to be a bent float needle!
All the jets & needles etc. are new, & i have set the float levels as well.
The only thing i have not checked yet is the ignition timing !! Although i have a nagging feeling it is still carburation related.
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Braving the cold yesterday ( looks like we are going to put up with it for a while longer !! ) i decided to take the carbs off & check them all out again. After studying the manual ( again ) it states the needle clips should be in the 3rd / middle groove, now for some reason the original ones were in the 2nd groove ( from the top ) so this is how i had set the new ones. Would this have any effect on the poor running !
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Well I still haven't got to the bottom of the problem. The bike starts on the button, it does need a bit of fiddling with the choke for a minute or so but then idles nicely at about 1200rpm. While stationary it revs cleanly & responsively. The thing is when riding it feels rather sluggish with a burbling misfire sound, but when opened up quickly & the revs reach about 5000 it takes off smoothly & surprisingly fast. Took it for a 30 mile run this morning & apart from this it runs well. Getting a bit peeved now, any more ideas on this please.
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I have just noticed the Choke Flap on the Carb nearest the Choke Lever is not opening quite as much as the others. It's only slightly different but do they all have to line up by the same amount.
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If as you describe it's only slightly different, then it would be unlikely to have such a pronounced effect on overall running.....it would be more typical having one odd setting to notice less peak power I feel.
If you haven't verfied the timing is accurate and the advance is working correctly, then it would be wise to check it through to mke sure nothing fundamental is wrong.
Presumably once it's warm it will run without choke at all? and if so, when you are running at sub 5000rpm (hesitantly) then if you hold the throttle steady and bring some choke in, then does it improve or get worse?
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I am beginning to think I am never going to get to the bottom of this >:( I have just changed the coils for some different ones now & this persistent misfire is still there. So to recap, coils changed, new plugs & caps, points (timing done), valve clearances done, all new carb jets, floats height set, carbs balanced, compression test done all the same pressure. Engine starts on the button & revs cleanly with no smoke & all four pipes get hot, but on accelerating there is this persistent misfire. The No.1 cylinder plug is getting very sooted up so somehow it must be running rich but why !! (Not the plug as I have swapped them around). Before long it will be staying under the covers if I can't sort it soon ::)!!!!!!!!!!!
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Go up a long steep hill and let it pull in top gear wide open throttle for a while, plug chop it and check out the sooty plug. If its feels to be on all 4 flat out and plug has cleaned up..get the carbs off again and check that particular one out. I suspect an issue with that carb. For these little Hondas to run like sewing machines the carbs have to be perfectly clean, set up correctly, and balanced. I have had a simlar issue with blocked primaries. Hold them up to a light and look through them, you should see a pin prick of light. On the later better carbs you have to pull primaries out with pliers. buy a set of cheap micro drills off of Ebay...they are great for poking out any crap. If you use your fingers to twiddle them you wont do any damage. Fairly convinced its the carbs.
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Does anyone know where I can get carb manifold O-rings if I need them, David Silver doesn't list them.
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Same ones in the tappet caps
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Same ones in the tappet caps
Well done that man. Cheers ;D.
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Soounds to me like you need the proper Honda manual for the adjustments, as to the standpipe officially you have to replace the complete floatbowl which i think is teh same as the 500 but the only parts book i don't have is the 550f so i cannot be 100% on that.
Does this help: http://www.dotheton.com/downloads/CB550_Parts.pdf
Thank you so much for this link!
I have been looking for this for ages...