honda cb250 superdream backfires problem. Help Please.

nclparky26 · L Plate Warrior Joined: 05 Mar 2008 Karma :

I have a 1980 Honda 250na superdream. And back in november 2007 it started to lack power and backfire through the carburettors, since then I have rebuilt the engine which it ran ok for one day then it started to backfire through the carbs again. the carbs are the only thing i have not replaced but they have been stripped down and cleaned. I can rev the engine up to 3000rpm then it starts to backfire through the carbs. So could anybody give me any tips as to solve the problem. thank you.

MillaMeter · Nova Slayer Joined: 24 Dec 2005 Karma :

Check your spark plugs, and whist ya at it, check that the gap on them are the right measurement. You might have faulty spark plugs causing mis-firing then filling the exhaust up with fuel then reigniting making your bike backfire.

Try new sparkies maybe?
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Big Pete · Spanner Monkey Joined: 18 Jul 2004 Karma :

check your cam chain tensioner, they can stick and the cam timing changes, I've seen the pipes on a 'dream glowing in daylight at idle because of this item. take off the rocker cover and push the top of the tensioner down while spinning the motor on the starter. Be warned, there will be oil thrown off the camchain. Reassemble and see what its like. Its also worth checking the cam timing while you've got it apart.

Other than the cam timing it could be a CDi issue, the advance retard on superdreams is done electronically via the pickups, and the timing changes around 3000rpm IIRC.
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Odie · World Chat Champion Joined: 24 Jul 2004 Karma :

stator / cdi problems.
common fault
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nclparky26 · L Plate Warrior Joined: 05 Mar 2008 Karma :

I have tried another set of spark plugs and it still backfires through the carbs. Thank you it was worth a try anyway. I'm going to try the cam chain tensioner on Sunday and see if that does the trick. I will keep you informed. Bye for now.

nclparky26 · L Plate Warrior Joined: 05 Mar 2008 Karma :

HOORAY. Well its took a while but I have managed to fix it. After rebuilding the carbs and still it wouldn't work I decided to check the wiring harness and bingo one broken wire from the CDI unit, so i decided to check the spare CDI unit I have and low and behold that had a broken wire to. The moral of the story is beware what you buy on ebay. Anyway thanks for all your help. Very Happy

Odie · World Chat Champion Joined: 24 Jul 2004 Karma :

what did pete and i say!
wheres the karma
(yes i am a karma whore Mr. Green

)
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You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

stevegbr · Derestricted Danger Joined: 01 Nov 2010 Karma :

hi

how did you find the broken lead as the cdi unit is sealed, only i have the same problem as you.

regards steve Very Happy

cb1rocket · World Chat Champion Joined: 30 Jan 2010 Karma :

he means the wiring that all plugs into the cdi. I think you should find a wire that is intermittent with twisting and moving but you can't see the break due to the sheath covering the bare wires.

Moo. · World Chat Champion Joined: 11 Jan 2009 Karma :

Mine did this, led to cdi failure, bought another one off ebay for a tenner Very Happy

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