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De-restricting the CB500

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Jameshambleton
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Re: De-restricting the CB500

Post by Jameshambleton on Fri 5 Feb 2016 - 9:26

Mine started up fine with year old petrol in it changed the plugs and started on the first turn over, although I had ran the bike once or twice a month. 

Yup that's the right tube alight. 

Mine were also the same as yours no visible gaps at all but it turned out to be that I hadn't rammed yes rammed the carbs back into the rubbers that go towards the engine. I had to just all my force and a small plastic mallet to tap them into plate and then she fired into life. 

When mine had the air leak I had the choke on and at a very specific point it would fire but then as soon as I touched the throttle or choke it would die because of how lean the mixture was with the air leak .
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Fri 5 Feb 2016 - 11:30

Yeah the petrol would have to be pretty ancient for it not to start at all.

The brass stub does the sucking for you while the engine's running, so yes suck on the rubber tube that attaches to that stub. This opens a diaphragm in the fuel tap.

The fuel tap is switched on isn't it...? (always worth checking stupid things). 

Also check the HT leads are on their respective correct spark plug.

I seem to remember that there's a lug somewhere on the carb stubs which the rubbers have to push right up against and that's when you know they're fully pushed home. I'll have a look on mine later and take a photo so you can compare with yours.

Btw here's the list from the Honda manual of possible reasons relating to the 'Fuel System' for a non-starting engine:

1. Too much fuel getting to the engine
- Air cleaner clogged
- Flooded carburetor
2. Intake air leak
3. Fuel contaminated/deteriorated
- Jets clogged
4. Starting enrichment (SE) valve circuit clogged
5. No fuel to carburetor
- Fuel filter clogged
- Fuel line clogged
- Fuel level misadjusted
- Fuel tank breather tube clogged
- Auto fuel valve malfunction
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Fri 5 Feb 2016 - 11:46

Thanks for the replies- going try sucking that we tube thing this weekend. 

The engine rubbers never moved so are lined up and in place as before. The others I thought I pushed right in- there is certainly no visible gap but will probably take them off and re-do them to be sure. 

I did one plug at a time to avoid HT lead mix-ups. 

Air filter is new. 

I suspect it is a fueling problem to the carbs. It is certainly coming out of the fuel tap. Will try to blow through the fuel line to see if it is clogged- It doens't look easy to get at to fully remove but the tank is coming off again anyway so will take a look. 

The tank breather hose had some crud in that I washed down with brake cleaning fluid. I did open the tank lid so there shoudln't be much of a vacuum but will have another look at the tube- the bike has been outside so it is possible something has crawled up it. Found loads of snails around the engine a week or so ago so something might have gone into a tube!
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eternally_troubled
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Re: De-restricting the CB500

Post by eternally_troubled on Fri 5 Feb 2016 - 13:34

If you have a can of Bradex easy-start it might be worth trying that in the airbox to give it a bit of a kick.

It might not help in getting it started but if it is a fuel problem then it should at least fire when you've added the easy-start - this might help you to narrow down which area is the problem.
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ashcroc
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Re: De-restricting the CB500

Post by ashcroc on Fri 5 Feb 2016 - 15:13

jchesshyre wrote:Yeah the petrol would have to be pretty ancient for it not to start at all.

The brass stub does the sucking for you while the engine's running, so yes suck on the rubber tube that attaches to that stub. This opens a diaphragm in the fuel tap.

The fuel tap is switched on isn't it...? (always worth checking stupid things). 

Also check the HT leads are on their respective correct spark plug.

I seem to remember that there's a lug somewhere on the carb stubs which the rubbers have to push right up against and that's when you know they're fully pushed home. I'll have a look on mine later and take a photo so you can compare with yours.

Btw here's the list from the Honda manual of possible reasons relating to the 'Fuel System' for a non-starting engine:

1. Too much fuel getting to the engine
- Air cleaner clogged
- Flooded carburetor
2. Intake air leak
3. Fuel contaminated/deteriorated
- Jets clogged
4. Starting enrichment (SE) valve circuit clogged
5. No fuel to carburetor
- Fuel filter clogged
- Fuel line clogged
- Fuel level misadjusted
- Fuel tank breather tube clogged
- Auto fuel valve malfunction
Speaking of checking stupid things....
The kill switch hasn't accedentally been knocked to the off position has it? I've fallen foul of that before. Embarassed
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Fri 5 Feb 2016 - 15:15

On these the kill switch disables the starter motor as well as the ignition so nothing would happen at all...
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Fri 5 Feb 2016 - 16:09

I don't have any of the easy start stuff- but could look into it. Where exactly do I put it in the airbox? Sorry if this is a stupid question!

Nah have had issues before with kill switch so it was close to the top of the list of things that were checked. It does try to start but can't quite manage it.
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Fri 5 Feb 2016 - 16:11

Have you tried giving it a little bit of throttle? It's not impossible that during your moving of the carbs you moved the throttle stop screw leaving it too low to idle/start.
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Fri 5 Feb 2016 - 16:12

And the easy start goes in where the air filter goes.
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Fri 5 Feb 2016 - 16:47

I did adjust the throttle cable but only to take in the slack/free play. Tried opening the throttle whilst starting but no joy.
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Fri 5 Feb 2016 - 17:13

teamwindsor. wrote:
HT leads are on reasonably well

This also strikes me as worthy of further investigation ;-)

Have you checked for a healthy spark by turning the engine over with the plugs out, HT leads on, and the plug bodies grounded against the engine?

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Re: De-restricting the CB500

Post by Guest on Fri 5 Feb 2016 - 17:25

Is the battery polarity correctly connected? study
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skyrider
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Re: De-restricting the CB500

Post by skyrider on Fri 5 Feb 2016 - 18:15

you would be wise to leave easy start alone vehicles become addicted and wont start without it just keep your bike well serviced
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Sat 6 Feb 2016 - 15:49

Right some (only a little) progress has been made. 

Spark plugs and HT lead are good with nice sparks. 

I managed to get the bike started via sucking on the vacuum hose. I could blow through the fuel line and it is freely flowing from the tank. 

It started but needed a constant small amount of throttle until warm then it was ok. 

It was doing some pretty impressive backfires but idling ok if not a little slow. I sprayed some easy start at the back of the carbs and confirmed there is a leak. I have taken the rubbers off again and noticed the dried orange crusty stuff that must have been used as a seal originally. 

What can I use to seal it again- I suspect plumbers mate or silicon although handy don't have a place here?

I also noticed that the choke although moves the choke plate doesn't do anything. Normally it would only start even when warm with the choke then after 30 sec or so i could ease it back. No choke is normally needed when the engine is warm. I think this may be part of the reason why starting it up has been an absolute pig- it was trying to go with no choke from cold. Although the cable seems ok and the plate moves left to right and recoils I was wondering if anyone had an idea why it would not be actually doing anything. The carbs although opened have not been interfered with internally. 

Thanks in advance!
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Sun 7 Feb 2016 - 12:32

It's odd, this sealant is not mentioned at all in the Honda workshop manual or in Haynes. Are you separating the rubbers from the airbox, leaving them attached to the carbs, or vice versa?


I would have thought some grease might act well as a sealant as really the pliability of the rubber and the tension bands ought to do the majority of the sealing work. But I'm sure someone else on here can give better advice about that. 


I would double check that the rubbers really are pushed fully home onto the carbs. I will put a photo of mine up later today so you can compare. If I recall, there's a point when it feels as if they're fully pushed home but which isn't actually 'all the way' and that they can go further than this with a bit of effort and pushing/wiggling. 
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Re: De-restricting the CB500

Post by Alvi on Sun 7 Feb 2016 - 21:45

I've cleaned this gunk of my cb5 & both my Superdreams & refitted the rubbers without any sealant. As jchesshyre says, if the rubber is still flexible & the recess is thoroughly cleaned out, they should seal ok - that's certainly been my experience. I soaked mine in very hot water to soften them up a bit before refitting.
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Mon 8 Feb 2016 - 9:04

The rubbers seemed to have been covered in an orange crusty stuff that looks like it has been previously used to seal them to the airbox. It's not just dried on gunk it looks like some form of glue. 

The screw clips hold the rubbers to the back of the carbs. The airbox connection seems to rely on as you say the rubbers being flexible and the flange going into the hole in the airbox. Mine are really not that flexible and could do with being replaced which I will get round to post move- if I get the bike running. Small gaps have been plugged up with grease so it looks okayish as a temporary bodge. Will get new rubbers on order!

In terms of the choke- could anyone explain how it works as all the cable seems to do is slide a piece of metal over the top of the carbs. I assume it covers/uncovers holes that in turn enrich the mixture? Although the slider moves and recoils the choke does nothing as far as I can see to my bikes idle speed and is probably why it has been such a pig to start. 

I had recently lifted the left side of the choke slider off to clean out gunk around the screw and re-fit the return spring but haven't taken the slider itself off so am slightly puzzled why it is no longer working. I am guessing that if indeed it works with air holes that they are blocked but could be totally wrong? I am thinking in the near future these carbs will need to come off and get a good cleaning but at this point with time being tight i am all up for a quick fix!
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Mon 8 Feb 2016 - 9:10

The slider should be engaged with two brass plungers, one in each carb, which it pulls out of the carb body as the choke lever is engaged.

Part 11 in this diagram
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Mon 8 Feb 2016 - 9:50

Can't see the diagram but I think you might have solved the issue. 

I have noted that there are two small brass things about 3-4mm long and about as wide as a pencil lead that protrude from the insides of both carb pot. The slider impacts these at each extreme of its travel. I just assumed that these were to limit the travel and stop it impacting on the carbs! Is it a matter of lifting off the slider, pulling out one of the plungers and locating it on the top or it is bit more involved and necessitating a carb removal?
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Mon 8 Feb 2016 - 10:29

You *should* be able to do it without taking the carbs off. There should be holes open on one side in the slider that engage with the plungers kind of like a fork. This picture from Haynes isn't 100% clear but the bit I'm talking about is on the left of the carb here, above the throttle linkage spring. It should be pretty obvious if you look at it and look at what the slider is 'trying' to do when it moves across. 


I can't remember how much space there is but it should just be a case of unscrewing the screws holding the choke slider down, lifting it up a bit whilst pulling each brass plunger out far enough then dropping the slider down so that the 'fork' is around the 'neck' of each plunger. I've only ever needed to do this when the carbs were off the bike so not sure how much room you'll have but it should be do-able. 



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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Mon 8 Feb 2016 - 11:02

Brilliant. Have commitments tonight but aim to do it tomorrow assuming the weather is ok/not hosing it down! Thanks very much for your help!
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jchesshyre
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Re: De-restricting the CB500

Post by jchesshyre on Mon 8 Feb 2016 - 11:07

No worries. Can't have a fellow CBer unable to get his bike started ;-)


Btw you probably realised this but in that photo from Haynes, ignore the black arrow, that's unrelated to what we're talking about!
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eternally_troubled
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Re: De-restricting the CB500

Post by eternally_troubled on Mon 8 Feb 2016 - 13:01

If you can't see the brass plungers being pulled out of the carbs then the 'choke' isn't being engaged, which would explain your cold starting problem.

Good luck in hooking the choke slider back onto the plungers.


skyrider wrote:you would be wise to leave easy start alone vehicles become addicted and wont start without it just keep your bike well serviced


They don't get addicted if you only use it for fault diagnoses :)  I wasn't advocating using it on a regular basis...
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Mon 8 Feb 2016 - 13:12

Nah it just slides along the top of the carbs seemingly without doing anything. Will investigate those plungers and hopefully that will be me back on the road! Will try to get it done Tuesday evening..in the dark!

Thanks again for everyone's help!
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teamwindsor
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Re: De-restricting the CB500

Post by teamwindsor on Thu 11 Feb 2016 - 9:32

Choke has now been fitted back on to the little plunger things and I am pleased to report that all is now well again with the CB!

It still is running a little lumpy and I suspect there might be a slight residual air leak. Additionally there is no gasket between on the exhaust box. Both of which are likely contributing. Will get carb rubbers on order and plan to do the work in the near future and hopefully solve the problem for good. Will take the carbs fully off to get at those front rubbers and just replace them too whilst I am at it- they are totally rock hard. 

Currently have the Beowulf exhaust which sounds amazing but has always had the issue that the fit is tight so that a gasket will not fit. I forgot about this fact before I ordered another gasket with all the other parts. Was probably going to stick some high temp silicon as a bit of makeshift gasket when I get a chance- popped into B&Q as I was passing but they had never heard of high temp silicon. 

Anyway thanks so much to all those that posted helping to get the bike back and running!

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