HHEEELLLPPP!!!

[old1eye]

just recently fitted a honda cd250u engine into my honda rebel.

had it rejetted and on a dyno and is set perfect.

today though i have found out the twin carbs are leaking feul some how?!, both of them have yellow stains and are wet/smelly.
undid the drain screws and did them back up to let feul through and check it didnt drip. both are fine. seals were fine last time i had it apart which was around 500 miles ago and its only just started it now, put a new feul line on to see if that solves it but hasnt.

also the engine has suddenly started making a really bad metallic sound on the over run when decelerating around 3-4k rpm above and under it stops, it doesnt do it on normal revving or acelerating only when slowing down and more in the 2 top gears?!

the carbs also pop and spit once or twice when engine braking?!

any help would be really great thanks

p.s. duno if this is posted in right section.
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If its loud Be proud!

[stinkwheel]

Leaky carbs is most likely a sticky float. try tapping them with a bit of wood.

I'd be wanting to check your camchain tension quick-sharp, could be a classic superdream death-rattle.

Take the rocker cover off and have a look at it. If it all seems ok, slacken off the adjuster nut then tighten it again while pressing down on top of the tensioner blade. You should be able to hear the camchain whirring at tickover, not clattering.

Popping on the overrun can be as simple as a leaky exhaust joint. or a hole in the exhaust (check at the splitter if it's a 2-1 system) have you torqued down the exhaust manifold nuts since you fitted it? They usually settle a bit after being fitted with new gaskets.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Teflon-Mike]

Many maledies... but those CV carbs are rather notoriouse for the diaphragms cracking up. That could cause all sorts of anomolouse running issues, and I believe that the cure is new slides as they diaphragms are 'bonded'.....
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[old1eye]

[salty21]

the discolouration could be leaky inlet rubbers. my superfour did it when the clamp snapped on the carb side of the rubber, would also explain the revs hanging a bit. not sure about the fuel leak though.
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04 NSR 125(sold) ---- 03 CBR 600rr(sold) ----90 pan euro ST1100 '' ----02 CG 125
94 CB400 Super Four ---- 2000 VTR SP1 (sold) ---- 08 ninja p8f(sold, meh) ----05 CBR600rr

[stinkwheel]

The camchain tensioner on the older 250 twins at least was notorious for not springing down hard enough to do its job properly. It was seldom the chain itself that was the problem.

From the fact that you can tell the carbs are spitting back, I'm assuming you are using no airbox. Again, traditionally superdreams always ran like a bag of spanners with no airbox but this should have been ironed out by the dyno setup.

If it's spitting back significantly, it could also be an issue with ignition or valve timing, or perhaps the inlet valve is staying open a touch? Ignition timing should be keyed on that motor. Worth checking the tappet clearances and timing marks when you check the camchain. A loose camchain could conceivably alter the valve timing a bit between being on and off the throttle.

I don't think the above is likely but it's worth a check for piece of mind.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[old1eye]

Ok cheers dude will do so after work today
____________________
If its loud Be proud!

[old1eye]

Ok. I have adjusted the valve clearence (werent to far off) done the cam chain tension thing. Tightened up the exhaust bolts checked the carbs over. still making the metalic rasping on de accelerating.

Could it be worn pistons? Still got good power but the left exhaust has smoke drifting out of it wuen i switch uer off, slight amount of white smoke when riding around at low revs too.

Could it be something inside the gearbox as when i pull the clutch in it stops and it doesnt do it on accelerating?

Cheers
____________________
If its loud Be proud!

[stinkwheel]

[old1eye]

nope, chain is properly adjusted and nothing to rub on as theres no chain guard and the rear mudguard doesnt exist
____________________
If its loud Be proud!

[Maverick Rigger]

[old1eye]

[Maverick Rigger]