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Discussion Starter #1
Hi Guys

i picked up a CBR250rr bike a couple months back working on it has been on and off as im still learning how these things work.
problem is the bike won't start, yes i have read multiple forums, and service manuals and i still haven't had any luck.
what i've done so far...

- Inspect spark plugs
- Attempted to clean carbs (not feeling 100% confident that i did a good job on this)
- Emptied fuel tank - put new fuel in with a cap of Methalayted spirits
- Sprayed 'Start Ya Bastard' into the carby trumpets
- Removed Auto fuel cock and cleaned it out ensuring none of the tubes or passage ways were blocked

the most noticeable difference when trying to start it now is after i spray 'Start ya bastard' i can hear popping and i see smoke coming out of the exhaust it almost wants to start but just isnt enough... :(

im feeling as though my attempt at cleaning my carbies might be at fault as i took it all apart and just let it soak in clean petrol im sure not sure if i applied the right turns and so on for the jets/screws when it came to putting it all back together, if anyone could elaborate on this that would be great!

and also i just want to double check that this brown nipple is where i connect my fuel line coming from the auto fuel cock(tank) right?
1617525_10152197935382708_2065035107_o.jpg
(this is a spare carby)
 

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Discussion Starter #2
after trying to start the bike a couple times i've found myself removing the carbys again and opening them and it doesn't seem to be much fuel inside? actually very little fuel to be honest.... the walls are abit wet and thats about it
 

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Yep that is where the fuel line goes, you should get yourself an inline fuel filter as well. Pilot screws should be set to 1 and 3/4 turns (make sure you remove these as well and give the opening a good clean as it can become gunked up), disassemble the floats, pins, main and secondary jets and give them a good clean with carb cleaner spray - literally drench them with the stuff and blow compressed air through the tiny holes to make sure that there are no blockages. Get yourself a rebuild kit if you've noticed that your rubber gaskets are brittle or cracked.
 

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Discussion Starter #4 (Edited)
Yep that is where the fuel line goes, you should get yourself an inline fuel filter as well. Pilot screws should be set to 1 and 3/4 turns (make sure you remove these as well and give the opening a good clean as it can become gunked up), disassemble the floats, pins, main and secondary jets and give them a good clean with carb cleaner spray - literally drench them with the stuff and blow compressed air through the tiny holes to make sure that there are no blockages. Get yourself a rebuild kit if you've noticed that your rubber gaskets are brittle or cracked.
do any of the other jets inside the float chamber need to be set to anything?
i believe the pilot screw is the one that sits outside the float assembly? ahh i think that might be my problem i screwed it all the way in and went 2 3/4 turns is that why theres a lack of fuel inside my carby after trying to start it so many times? when i opened it up to inspect it
 

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By what you've said you sound as though you've just pulled it all apart, cleaned it, and put it back together without doing the proper turns for jets/pilot screws?
If that's the case, it is absolutely crucially important to get these done properly. I don't know what the turns are, but find out the proper amount, and definitely do it.
I think you need to follow a manual.
 

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Discussion Starter #6
Yeah I followed a guide on cleaning but not 100% certain with the instructions I followed in regards to the pilots is it just the pilot screw outside the float chamber that needs to be adjusted?
 

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Discussion Starter #7
Just an update I checked the carbs over again set the pilot screws right still didn't start after that I then tried checking that the fuel flow wasn't blocked so I fed fuel via a funnel into the carbs that didn't work either right now I'm basically out of ideas..
 

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Fuel will only flow from your tank when a there is a vacuum (that is what that little tube going from the carbs to the petcock is for).

Are your pilot jets screwed all the way in? if so, back them out 1 3/4 turns.

When you cleaned the carbs, did you just soak them and reassemble, or did you look through each jet and blow with compressed air to remove blockages?
If you just soaked and reassembled then chances are that the jets are still blocked
 

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Discussion Starter #10

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Fuel will only flow from your tank when a there is a vacuum (that is what that little tube going from the carbs to the petcock is for).

Are your pilot jets screwed all the way in? if so, back them out 1 3/4 turns.

When you cleaned the carbs, did you just soak them and reassemble, or did you look through each jet and blow with compressed air to remove blockages?
If you just soaked and reassembled then chances are that the jets are still blocked
took it all apart left the jets and so on in petrol to soak in blew compressed air into openings, pilot screws are at 1 /34 turns back. yeah i understand fuel is fed by the small vaccum thats why i completely eliminated that petcock by trying to feed fuel by a funnel just to take it out of the list of things that's stop the bike from starting
 

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If you hook up the tank and try cranking it for a bit, then unscrew the drain bolt on the float bowl does any fuel come out?

Sent from my HTC_PN071 using Tapatalk
 

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Discussion Starter #15
If you hook up the tank and try cranking it for a bit, then unscrew the drain bolt on the float bowl does any fuel come out?

Sent from my HTC_PN071 using Tapatalk
nothing comes out of the drain bolts thats why i thought the petcock might be stuffed up so tried feeding fuel without the tank and theres fuel in my carbs now but still doesn't start
 

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Discussion Starter #17
thats next on my list what are the common issues with these things in regards to compression and spark?
 

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Discussion Starter #18 (Edited)
Have you checked for compression and spark?

Sent from my HTC_PN071 using Tapatalk

thats next on my list what are the common issues with these things in regards to compression and spark?
what i did find strange is the very little vaccum i felt when i was checking the small vaccum tube when i tried cranking it without the fuel tank which might explain why theirs never fuel getting into my carbs when the fuel tank is attached.
 

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thats next on my list what are the common issues with these things in regards to compression and spark?
what i did find strange is the very little vaccum i felt when i was checking the small vaccum tube when i tried cranking it without the fuel tank which might explain why theirs never fuel getting into my carbs when the fuel tank is attached.
if you don't have spark nor sufficient compression it won't start. There's plenty to go thru in that thread I sent earlier.
 
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