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Superdream CB 250 N

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Kal
World Chat Champion



Joined: 02 Jan 2007
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PostPosted: 17:18 - 15 Jan 2009    Post subject: Superdream CB 250 N Reply with quote

Okay the Superdream is having issues pulling away and anywhere below 5k rpm.

It is crawling away from the lights ata walking pace and really struggling, then at around 5k it suddenly wakes up and punches forward with life.

Although it is making for an interesting ride, I'd like to not get plastered all over the road.

Now the bike itself until very recently had been stood in fields, gardens and garages but the carbs and tanks have been cleaned.

Any thoughts?

As usual Karma for useful suggestions.
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Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).

1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S


Last edited by Kal on 17:43 - 15 Jan 2009; edited 1 time in total
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Howling TerrorOutOfOffice
Super Spammer



Joined: 05 Dec 2008
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PostPosted: 17:24 - 15 Jan 2009    Post subject: Reply with quote

Hi, it sounds like the idle jet in the carb could be blocked slightly or worn.

stick around better advice from the Pros

Pat
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virus
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Joined: 16 Aug 2006
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PostPosted: 18:47 - 15 Jan 2009    Post subject: Reply with quote

Check the carb diaphragms, they can tear very easily on old super dreams, that and spray WD40 etc onto the intake manifolds with the engine running and listen for an increase in revs, this will give away an air leak.

Is it idling ok?

Cheers
John
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own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.
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Kal
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Joined: 02 Jan 2007
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PostPosted: 09:52 - 16 Jan 2009    Post subject: Reply with quote

virus wrote:
Check the carb diaphragms, they can tear very easily on old super dreams, that and spray WD40 etc onto the intake manifolds with the engine running and listen for an increase in revs, this will give away an air leak.

Is it idling ok?

Cheers
John


No problem with it idling. I'll get into the carbs tomorrrow.

Something I forgot to mention yesterday is with the engine off the float bowl overflow runs like a tap.
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Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).

1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S
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virus
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PostPosted: 10:43 - 16 Jan 2009    Post subject: Reply with quote

Ah, You will never get a good mix with a dodgy overflow.

Sounds like float height/valve worn, or could possibly just be crud in the overflow stopping it being tightened enough.


Cheers
John
____________________
own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.
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NiteMare
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Joined: 12 Sep 2008
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PostPosted: 11:43 - 16 Jan 2009    Post subject: Reply with quote

virus wrote:
Ah, You will never get a good mix with a dodgy overflow.

Sounds like float height/valve worn, or could possibly just be crud in the overflow stopping it being tightened enough.


Cheers
John


nearly correct ...

with fuel pissing out of the overflow i'd suspect you have shit in the float valve seat or the float is stuck...

sometimes a quick fix can be achieved by draining the float bowl and then turning the fuel back on which in turn flushes the crap out of the valve seat , sometimes it requires a tap or two on the side of the bowl to help it seat/shift the crap, this doesn't always work tho ...

which then requires removal of the carbs so that you can remove the float bowl, remove the float pivot and then remove the valve to clear the crap, be very careful if you have to do this as the posts the pivot pin goes thru are very easily snapped and the pin usually can only be removed in the one direction (taper fit)
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virus
World Chat Champion



Joined: 16 Aug 2006
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PostPosted: 11:55 - 16 Jan 2009    Post subject: Reply with quote

Good advice there NiteMare, Only thing I'll add to that is the float pin on superdreams isnt tapered, and can be removed from either end. Thumbs Up

Cheers
John
____________________
own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 12:03 - 16 Jan 2009    Post subject: Reply with quote

Hi

From memory the Superdream carbs are CV ones but don't have a rubber diaphragm at the top of the slides. An air leak to above the slides could cause the same issue.

That said the problem with the overflow (almost certainly a dirty / worn / stuck needle) is probably the problem.

All the best

Keith
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Kal
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PostPosted: 16:26 - 16 Jan 2009    Post subject: Reply with quote

Outstanding, thank you to all of you. I guess that's my weekend sorted Smile

Anyone want to lend a hand, or point and laugh? Wink
____________________
Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).

1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S
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NiteMare
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PostPosted: 18:03 - 16 Jan 2009    Post subject: Reply with quote

being as i'm swapping an Escort clutch tomorrow, do you mind if i just point and laugh once i've finished Mr. Green
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Kal
World Chat Champion



Joined: 02 Jan 2007
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PostPosted: 01:13 - 18 Jan 2009    Post subject: Reply with quote

I didn't get the carbs, however the tank sprang a pinhole leak today.

From the sounds of if once I had emptied the petrol out of the tank there was a lot of rust left in the bottom of it.

BTW: The new tank was painted with white gloss emulsion at some point, complete with brush marks and ridges where the loose paint collected.

Given that it has to be started with a spanner does it qualify as a rat? Twisted Evil
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Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).

1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S
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monkeyboy111
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Joined: 16 Dec 2008
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PostPosted: 22:06 - 09 Feb 2009    Post subject: Reply with quote

Hi i have a honda cb250n superdream! first off i had a hole in my fuel tank right at the bottom of the tank half way down the road! so fixed that but then my carbs needed cleaning so spent a day cleaning them then realized that it was pissing out of the overflow! everything keeps going wrong with it!
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NiteMare
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Joined: 12 Sep 2008
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PostPosted: 22:58 - 09 Feb 2009    Post subject: Reply with quote

folks that buy superdreams should realise they're mostly nearly 30 years old ....

that's quite a long life for most things mechanical ...

they'll have suffered neglect, salt, water and all manner of young folks thinking they can fix them with a wood chisel and a set of bicycle tools (if not the cutlery out of the kitchen drawers)...

the few that have survived that onslaught have done really well
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Kal
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PostPosted: 00:06 - 10 Feb 2009    Post subject: Reply with quote

Superdream Picture Thread
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Kal...
I Like To Hoon It Hoon It I Like To Hoon It Hoon It I Like To Hoon It Hoon It Ya Like To (HOON IT!).

1984 GB250 Clubman,1983 CB250N Superdream, 1999 GPZ500S
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Old Thread Alert!

The last post was made 17 years, 4 days ago. Instead of replying here, would creating a new thread be more useful?
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