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Discussion Starter #1 (Edited)
I've only owned the bike for about 6 months and I'd take it for a couple of rides a week. Then one morning a few months back I couldn't get it to start and it hasn't started since. I haven't been able to figure out the problem.

It just keeps turning over and nothing else apart from the occasional back fire.

Things I've tried:


  • Tried starting with full choke/no choke/half choke and with some throttle etc.
  • Fuses all look good and all ignition lights are lighting up as usual.
  • Fully charged the battery many times while trying to find the problem so dead battery isn't the issue.
  • Thought it was a faulty fuel pump initially so I replaced that and have made sure fuel is flowing through the lines.
  • Checked the two spark plugs on either side which both appear to be giving a spark. I haven't checked the inner two plugs because they look difficult to get to. Even if one spark plug was completely stuffed wouldn't the bike at least show some signs of starting?
  • I've just replaced the ECU box because the old ones plugs looked corroded and covered in what looks like glue.

I don't know much about bikes so really keen to hear anyones ideas/suggestions! :idea:

Here's a video of me trying to start it just now:
https://www.stuartb.nz/misc/cbr250r-cranking.mov

I know the battery sounds dead again but it does the same thing with a fully charged battery, just louder...
 

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404 - file not found!

We had a similar issue on our MC19. Turned out to be a failing indicator relay causing a dodgy earth.

Had cleaned the carbs and replace spark plugs and install fuel pump back to standard (previous owner used gravity instead...)

In the end I replaced the failing indicator relay with a generic branded one from eBay, fired up fine since.

Found the link: https://cbr250.com/forums/cbr250-fo...e-oem-indicators-relay-go-led.html#post303673
 

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Discussion Starter #3
I've fixed the video link now, sorry.

Failing indicator relay.. that's interesting. I'm getting a good reading on the multi meter when checking resistance between the battery and the rest of the bike.

Would that rule out a dodgy earth or do you think that could that still be a potential problem?
 

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Discussion Starter #4
Since posting two days ago a friend of mine came to have a look. He discovered that one of the throttle cables has snapped and is missing so I'm thinking this is mostly likely the problem.


From what I can see the top throttle cable pulls while the bottom cable pushes. The bottom cable is the one that's missing. My question now is are both cables absolutely necessary or is the top cable capable of doing the job on it's own?
 

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One cable opens the throttle and the other closes it. Both are pull. There is a spring for return but there is a safety aspect to having both.
 

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How old is the fuel inside the tank? Put 91 in it, don't put 98/premium.
Is your fuel pump priming the carbs with fuel?
If you open the drain screw at the bottom of the carb does fuel come out?

After trying a few times pull out a spark plug and see if it is 'wet' with fuel. If not then you have blocked jets not letting fuel in.

Open up all connectors, clean them with contact cleaner or wd40 then reconnect them.
Find your earth points on the frame and give them a good cleaning as well.
Clean out your switchblock on the handlebars.

We had to check the resistance working back along the earths and ended up finding the high resistance on the indicator relay, that's how we came to that conclusion.
 

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Discussion Starter #7
I replaced all the spark plugs with new ones today and now it runs better than ever! :D


Didn't think sparks was the problem because they looked ok when I tested them. I guess they must've been weak?
 
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