Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: Johnwebley on May 26, 2013, 03:25:53 PM
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I have recently been forgetting to add "lead substitute" to the fuel,
and have got what appears to be sticky valve !!!
as the motor get warm/hot,after cruising around 6K rpm for several miles ,the engine runs rough,noisy tappets,and feels like its on 3 only,
spitting in the carb,and spitting in exhaust.I still have 4 - 4 pipes,
after checking,setting tappets at 3th inlet/4th exhaust,and re-using Morris lead substitute again,the bike runs well again,
is it common?
if so,I hope you take notice,and use an additive as well,
John Webley
PS,I should say I have a '74 CB500/4. and the handbook does say it needs "some" lead in fuel
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I got 180,000 miles from my 500/4 on it's original engine for the vast majority of it - the issue that got that motor pulled was jumping out of second and definitvely Not fuel related. The vast bulk was done on unleaded - simply because I have done all my biking in the unleaded era and Honda built the 500 and 550's top cope with unleaded and at the milages I was doing the cost of additive was going to add up. I will admitt I felt it ran a tiny bit better when visiting a garage that ran a 4star pump in Hereford where my mates lived ditto on the 'special' or super unleaded that you can buy and with my current commuter (Honda rebel 125) it runs better or so it seems on fuel from the independant / Texaco garage then when I fill up at Tesco - maybe Tesco run a higher ratio of bio fuel which is more likely to be an issue then unleaded. Maybe the tesco fuel is too horsey ;D ) I must say at this point my conclusions regarding Tesco fuel may be coincedence induced, but on a couple of occasions the bike has run underpowered after about 200 yards riding from filling up at Tesco, then run like a dog until 200 yards after filling up at my regular fuel stop.
I do like to run a bit of redex occasionally to clean the system out a bit - on my 500 I would do so if the floats started sticking causing overflow - roughly every 6 months - it would get a shot in the fuel tank and a bit neat into the petrol pipe after riding the last 200 yars or so with the tap off, then leave it to stand overnight. Far easyer then remving the carbs, and genrally always sorted a overflowing carb - other fix being to tap the offending carb bowl with a screwdriver I went many years without removing those carbs.
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No Honda since the late 60's needs leaded fuel, if you have a sticking valve without you have the start of a mechanical problem mate
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No Honda since the late 60's needs leaded fuel, if you have a sticking valve without you have the start of a mechanical problem mate
OK,its runs well,got just over 52K miles,great starter,etc,
what could be the issue ?
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I'm wondering if a worn valve / stem / bent valve, might be masked by added lube from an additive? I had an engine built from used parts that had a suspected sticky valve - symptoms were a rattly noise once hot and ran rough, once hot and on checking the clearances it emerged that one valve was discoulored from excess heat. I pulled the engine out and intend to get the valve and guide fitted by someone competent and who has required kit.
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I would also say a slightly bent valve mate
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looks like a head-off job !!
just as summer is finishing!! LOL
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OK,update,
so I took the head off,
looked like Foreign object damage in cylinder No4,
lots of marks both on piston,and head,
valves removed,good seals on inlets valves and seats,exhaust seats good,but valves in need of lapping,
not happy about state of No4 piston,so off with the barrells, result,top ring broken,and 50% vanished !!big damage to top ring groove,
and top land,
No3 piston also has broken top ring,???
1 and 2 pistons OK,
no marks on bores,
ordered new (std) piston, 4 X sets of rings,
waiting for them to arrive,
SQ, why do you think the rings went ??
John
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It's quite unusual to break rings on a 4 stroke engine if everything is normal, possibly more influenced by the assembly last time it was built.
Also a possibiltiy if it had been stored for a long time for the bore/rings to rust and cause damage when someone tried to start it.
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Sounds familiar, my first running and taxed 550 had all 4 pistons like this when I bought it, mostly the top rings were completely awol and the gaskett goo pointed to bodged rebuild in the past and the missing rings had scorred the head badly. Ran really well with a good used set of pistons and barrells fitted. I found 1/2 of one ring in the sump, rest either was removed in the bodged rebuild or possibly found it's way out through the exhaust valve which I find unlikely. Appart from being tempremental to start when hot there were no symptoms.
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It's quite unusual to break rings on a 4 stroke engine if everything is normal, possibly more influenced by the assembly last time it was built.
Also a possibiltiy if it had been stored for a long time for the bore/rings to rust and cause damage when someone tried to start it.
the history,I have owned the bike since 1977,
the barrels have never been disturbed,the head came off about 20k miles ago,after I damages a couple of valve stems while changing
the cam-chain,the bike gets regular use,although only between 2-3,000 a year,
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The old CB/CD 175 and the 250/350 K4's used to do the top ring if they were thrashed a bit too much before they had warmed up----never realy found out why, put it down to differential expansion and warming too quick. If we stripped them quick enough it was just gaskets and rings but if pistons as well normally went 1 size up and rebore as the bore was only a small part of the cost
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haha I remember my old 250k4 doing that, glad it wasn't just me. I did abuse it though!
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ok,further update,
new parts arrived from Mr Silver,
nice new piston,and 4 sets of rings,
slight query,
the rings are 3pt oil,and two plain rings
one looks plain,no markings,seems to be coated in black teflon ??,guess its the second ring,
and I guess the one with grey surface for the bore is a chrome ring?? and is fitted at the top,
again no markings,
do you agree ??
regards
John
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John,
I recently had some rings for the 550 from silvers.
The rings are slightly different if you look at them one is square and the other slightly tapered.
It tells you the installation sequence in the manual if you have one, the rings are marked with a "N" this needs to go to the top if I remember correctly.
Hope this helps.
Regards,
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Silver top black second and there will be a small mark close to the gap and it goes at the top
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John,
I recently had some rings for the 550 from silvers.
The rings are slightly different if you look at them one is square and the other slightly tapered.
It tells you the installation sequence in the manual if you have one, the rings are marked with a "N" this needs to go to the top if I remember correctly.
Hope this helps.
Regards,
thanks,I looked Very Hard,and found the "N"s,as luck would have it,I had fitted them correctly,
as far as the cause,
check out this link,
http://www.motorcycleclassics.com/mc-how-to/project-cafe-rebuilding-a-1973-honda-cb500.aspx#axzz2Vx8B1Md3
a CB500/4 with almost the same issue,
my piston wasn't quite as bad,but the diagnosis is "detonation" ,I guess severe "pinking" ??
my bike never seemed to suffer this,but would over advanced ignition cause it ?
I run Boyer electronic and also a much bigger plug gap,(0.033th) as it supports a bigger spark,
also gives great low/mid range punch,
maybe I should retard the ignition a few degrees ??
thoughts and comments please,
John
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update,
all back together,
started first time.
felt really tight,the new rings are steel,see link,look for motorcycle rings
http://www.npr.co.jp/english/products/p_train/index.html
I expect these to be stronger,less brittle,and more durable than old style cast rings
after about 130 miles,gentle throttle no more than 5k under load,and 6k on overrun
the motor feels much better,still a little tight,but very torquey
will continue till about 500 miles before any serious throttle,increasing the revs under light load
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update,
firstly thank you all for your help and advise,
the bike is back together,just over 600 miles,runs beautifully,got its top end back,
runs up to 9k very willingly,
oil change done,no issues,seems so much more in the lower gears,
I rev it in the 2nd,3rd , and 4th gears,dont slog it in top,
and I am really pleased
John
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Thats not detanation as the cause, what happens is some idiot PO reved the nuts off it when cold and the rings expand to quickly so the top one shatters into pieces, this widens the ring groove then flame passage and heat finish it off.
Used to happen quite a bit on 250K4 and CB175's
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I had exactly this on a 550 years ago. My friend bought a bike that had been standing for a year or so. Unfortunatley, the seller had taken the bike for a blast to make sure all working OK. My friend bought the bike but soon complained that it wasn't running properly and was smoking. When I investigated I discovered that there were broken rings on all four cylinders. Luckily, they had stayed in place and not scored the bore and a new set was all that was needed.
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Thats not detanation as the cause, what happens is some idiot PO reved the nuts off it when cold and the rings expand to quickly so the top one shatters into pieces, this widens the ring groove then flame passage and heat finish it off.
Used to happen quite a bit on 250K4 and CB175's
I had exactly this on a 550 years ago. My friend bought a bike that had been standing for a year or so. Unfortunatley, the seller had taken the bike for a blast to make sure all working OK. My friend bought the bike but soon complained that it wasn't running properly and was smoking. When I investigated I discovered that there were broken rings on all four cylinders. Luckily, they had stayed in place and not scored the bore and a new set was all that was needed.
thanks for the hints !!
I can't remember racing it when cold,
BUT,from now on will keep it below about 5k for a couple of miles at least,
thanks
John