Running Lean / Hard to start / Stalls

[Ingah]

My CB500 is once again, being a problem child. Have had a terrible time with the bike since foolishly buying it ~18 months ago, but at least in doing so it's been the best teacher of mechanics i'll probably ever have.

A month or so ago, i derestricted it, and had some good fun and games with the carburettor even then (probably irrelevant as i have used it plenty without a hitch since it was sorted out, but i'll link it just in case): https://www.bikechatforums.com/viewtopic.php?t=196122

Now today, when i went to ride to work, the bike wouldn't work properly. It started on the choke as normal, but any attempt to use the throttle/rev it resulted in the revs dropping rather than increasing, and cutting out if the throttle was not released within a second or two. As it warmed up i gradually reduced the choke but it wouldn't idle at a constant RPM (this is fairly normal when it's less than 100% warmed up anyway though), and repeatedly cut out. On the multiple occassions i had to start it again whilst playing with the choke/throttle, starting the engine was difficult, it kept turning over for extended periods without "catching". So much so that i was concerned that the battery could run out (now on charge to be sure). At a couple of points i did manage to get the bike to revv up to 6-8K RPM (most of the time it wouldn't do this at all, preferring to cut out instead) and the choke partially on, but it would soon drop the revs and die when i reduced the throttle. I also heard popping noises etc (especially when i was able to rev it), which as far as i'm aware indicates it's running lean (so either too much air, or not enough petrol - it's got to be a carburettors-off job again )

Most people would probably have sold it on long ago, but i'm determined to fix this, and equally determined to avoid garage bills, i've had it with taking my bike to the garage now, it's just too costly.

So err... any ideas? (otherwise i'll be purely relying on the Haynes troubleshooting section)

Note: Video file showing the bike's behaviour, sorry for poor quality as it was made by a cheap mobile phone, and converted online: https://media-convert.com/convert/?xid=12-gefklpcv

Edit: It's got petrol in it (at least a few litres in the tank) and i did switch it to reserve, but this didn't help (so i've left it on reserve).
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-- Ingah

[swampy]

Sounds a bit like the symptoms of flooding, so too much petrol, rather than not enough...

Prob not that though... I've just read your other thread, and I wouldn't bet against it being summat to do with the problems you were having then....

Edit:- Would it be possible that the choke cable has snapped or come undone at the carb end leaving the choke permanently on ??
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[temeluchus]

Yeah sounds like flooding. Try these:

1) drain the float bowls-if there is shit stoping the float valves closing, this may shift it.
2) Remove the carbs, take off the float bowls, floats and valves and give it a damn good clean with some carb cleaner.
3) Replace the float needles and seats (if the seats are removeable) at about a tenner a piece.

Inspect the float needles
https://i241.photobucket.com/albums/ff26/Dalhan/FloatNeedleSeat.jpg

This one has a rubber coated tip, but you can plaintly see the line where it has worn closing onto the seat. If yours has no rubber tip (many dont) the wear line will be even more obvious. If this is apparent, they MUST be replaced.
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Some shite cruiser. Now with guns and FREEDOM!

[Ingah]

[temeluchus]

Can be tricky as very rich and very lean have similar symptoms.


If the needles are fubar:
https://www.wemoto.com/bikes/Honda/CB_500_V/97-98/picture/Carburettor_Float_Needle/

Be thankful you have a twin and not a four
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Some shite cruiser. Now with guns and FREEDOM!

[paddlesat16]

Check your carb rubbers for cracking, try the old soapy water and look for leaks trick your carbs rubbers could be expiring and letting in too much air.
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I once saw a bloke shagging a donkey.... in Saudi arabia. Theory Test Passed 26/10/09 Mod 1 Passed 26/4/10, Mod 2 Passed 7/6/10 Current Bikes Suzuki GSX1400 K5, Aprillia Pegaso 650, Suzuki DR350T.

[0l0dom0l0]

i woudnt bother with taking the carbs off yet. first thing i would do is change the plugs, and also change the air filter. then if that doesnt sort it, then resort to the carbs.

[Ingah]

Have now taken the carbs apart.

Main jet on one side was partially blocked (noticeably smaller hole than the other side), which blowing through it fixed immediately.

That, i assume, was the problem?

However, there is also a wear line in the float needles both sides of the carb (as originally demonstrated by Temeluchus) so i guess i'd better get replacements rather than wait until they fail and/or cause whatever undesirable effect leaving them will cause.

I feel i should get new rubber O-rings and gaskets (Haynes says so anyway) as the bike is so old and the carb has been taken apart at least 3 times now! I do not want to pay for that gasket set from Honda though, as added to the cost of the float needles i expect i wouldn't be seeing much change from £60! (could get a set of carbs off eBay for less i think - obviously i'd hate to do that though as god knows what would be wrong with them) Surely there is somewhere else to get these O-rings from, after all they're only bits of rubber. I'm going to give this company a call tomorrow and see if they can come up with something more competitive for me: https://www.nrp-carbs.co.uk/index.htm. I'll also have a good search on the web, but does anyone know somewhere that provides these carburettor rubbers or other carb bits at a more reasonable price?

HOWEVER, i also decided to check the fuel filter (according to Haynes in the random plastic tube thing in petrol tap/lower tank), and well... i'll attach a few images.
To inexperienced old me (please correct me if i'm wrong), it looks something similar to my sub-air filter when i checked that - the filter itself has disintegrated into mush many moons ago. This i suppose, would explain the original cause of the blocked main jet?

For the purposes of information, one other area of possible concern i've remembered (noticed previously when derestricting) is on the air filter housing, where it connects to the carburettor, all the rubber around there has cracked and was (possibly?) letting in air, and so i superglued it (previously). I'll attach an image as that doesn't read terribly clearly.
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-- Ingah

[temeluchus]

NRP should have overhaul kits for about a tenner a carb hopefull, including the needles.

Plastic metal is a better idea than superglue generally, as superglue will dissolve in the prescence of petrol vapour. This may be an idea f you decide to overheaul the airbox.
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Some shite cruiser. Now with guns and FREEDOM!