spotted a Gumtree bargain CBR250R MC19 on Friday, when I see them cheap, I always grab them for parts as the wheels are almost always quickly snapped up by Motard riders. So I popped out to Ipswich and picked her up yesterday, when I got her home, I poured in some fuel in the tank and hooked up the jump pack to see if I could get her to fire up. Alas no dice. I pulled the carbs down and found they were pretty grotty, the slow jets were blocked so all the brass parts went into a jar of 3bond. Several hours later they were clean and free from blockages, so I put her back together and tried again to start her. What I found was a busted throttle cable , the push cable was hooked up to the pull side effectively having it on half throttle. I removed the cable for the sake of trying to get her started. She was almost starting, but was doing a massive backfire. I checked inputs to the coils and they were wired correctly, I used a spare spark plug to check each coil lead for spark, they were all good. I was a bit perplexed, so I started cecking the wiring, after undoing some tape, I have found that someone has run a feed from the battery directly to the fuel pump, effectively have it on the whole time, that's not good, this bypasses the relay !! Will see if I repair the cut wires and put it back to stock and see if she fires up today
You dun did it again with a cheap bike and it seems to be some else who moffed it up.. Should be a quick sale for you once its running smooth again..
If it was backfiring with correct coil order and other things checked that's you said that's a scary sign. I think it could be about 6 things things of which only 4 are likely. 1. Chinese cdi 2. incorrect colour code for wires to coils/wiring 3. spark rotor telling cdi to fire at wrong time/flywheel is loose 4. broken exhaust valve ive never looked at the mc19's wiring diagram though, but from memory of the mc22 you would have to be pretty special to short circuit it in a way that all 4 coils where shooting all it once haha. Unless and lets be fair there was corrosion in the plugs or cdi connection but as that was one of 1 of the 2 extremely un-likelies.
Im thinking because the fuel pump is on all the time, its pushing fuel out the exhaust valves hence the backfire... I think it needs some new plugs before it fires up, its close now
carb overflow would stop that wouldn't it? I did think of plugs causing pre ignition but that has gotta be seriously low on the list of possibilities.
Why would anyone power the fuel pump directly to the battery ??....is the relay functioning correctly ??
the way it was wired, it bypassed the relay, Im not 100% sure why, Im thinking it would start because of blocked jets and they tried to hard wire the fuel pump as a way to get her to run
well, swapped 4 plugs with fresh ones, disconnected the fuel pump and manually filled the carbs with my AUX tank. It took some coxing but she fired up and sounded quite good. Super stoked. I have 3 people chasing mc19 engines , this one is going to be a parts bike as I would need to spend a heap of cash on it and I know I wont see it back when it comes time to sell. MC 19 Parts anyone ?
