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Dick07

Joined:

Sep 10

Posts: 3

Dick07 says:

Diagnosis Please...! would really appreciate.

HONDA CBF600

Bought a bike that was standing unused for months. The battery could not hold a charge, so I had a new one fitted and a service.

However, when starting from cold the bike struggles. If I increase the throttle quickly the bike dies. If I use full choke and no throttle the bike dies.

To start the bike I have to press starter with no choke and no throttle. Then very slowly try to increase the throttle (too fast and it dies). Then once the revs increase I use the choke to keep the idle high. The then idles fine.

After a no more than a minute I turn off the choke, and the bike is fine. The bike then runs fine, and has no other issues.

What is this. As previously mentioned it has a new battery, and has been serviced recently (which included new air filter)

Please help....Any ideas....?



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  • Posted 5 years ago (11 September 2010 12:17)

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jaffa90

Joined:

Mar 09

Posts: 9004

jaffa90 says:

starter

Welcome D,your bike should start with choke only,it`s either not enough juice coming through or too much when on full choke.When the revs increase you use the choke to keep the idle high,Q,how much choke can you use? Also what`s your tickover speed after a run?

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Dick07

Joined:

Sep 10

Posts: 3

Dick07 says:

Thanks jaffa

Thanks for advice Jaffa. The choke extends around 1 -1 1/2 inch. moving it a small way has no effect. only when fully extended does it have an effect.


I have tried numerous combinations of trying to start -  but it always seems reluctant. I have had other bikes and used choke alone which has worked fine, but not with this bike. Something is wrong.

Scenarios:
a) Trying to start bike with no choke - Bike will start but not tick over until its been started a few times. If you try and increase throttle too quickly it stalls. After very slowly increasing the throtlle the revs climb, and then the idle becomes stable. All ok.

b) Trying to start bike with full choke - the bike starts then stalls immediatley. ( as if flooded)

c) tyring to start bike with half choke - bike will eventually start but tick over does not become stable until throttle is increased and the bike revved.

The best method ive found so far is to coax the throttle so the revs increase, then fully extend the choke so that the bike ticks over fast. One running for a short time i close the choke and all is ok.

Once warm the bike idles at around 1500 rpm. - I have tried adjusting the tick over but this doesn't seem to help starting.

Once bike is warm it runs lovely, just something wrong with start up. 

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jaffa90

Joined:

Mar 09

Posts: 9004

jaffa90 says:

choke

It sounds to me that there is a fuel shortage on full choke,with the bike not been used for months the starter (choke) jets and the pilot jets up to 2,000rpm can be restricted with the residue off rotten fuel.Using the accelerator or a high tickover will bypass any choke being used.I suggest you check the air intake manifolds for leaks also the tickover should be 1,000rpm and use a carb cleaner in the petrol tank like profi-fuelmax or seafoam.If you use this cleaner shut the accelerator off whilst on a run and give it full choke for 5seconds a few times,the full choke should make your revs stay at 4,000 rpm.

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Dick07

Joined:

Sep 10

Posts: 3

Dick07 says:

thanks.

Thanks again Jaffa. Just ordered a bottle of profi-fuelmax online. I have also sprayed WD40 onto the choke cable line in order to free it up a little.


I've also condidered changing the spark plugs, but not sure if they could contribute to the problems I'm having?

I'm sure there problem has arisen from the bike standing unused so long. But I thought that by now the issue would of resolved itself. 

Thanks again!

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mrmarklin

Joined:

Apr 10

Posts: 16

mrmarklin says:

Carburettors

That's a common problem with bikes that have sat for a while.

You should look to a thorough cleaning of the carbs.  Probably a sticky floater or slider.

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bbstrikesagain

Joined:

Nov 08

Posts: 880

Clean fuel?

I presume you've been through a tank or two since this started?  Old fuel is said to go off, but also the composition, and especially the volatility, of pump fuel is seasonally adjusted, so a stored bike may have the wrong season's fuel in it too.  But if you've been through a couple of tanks you can probably rule that out and focus on the carbs.  Have you drained the float chambers in case of any water or dirt?

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paulderekjohnson

Joined:

Feb 08

Posts: 1952

Strip the carbs....

...you have no choice really.

A FULL strip and clean and maybe some new jets needed if they're in poor enough condition.

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