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Discussion Starter · #1 ·
First CBR and first post, so here goes!
I bought a CBR250RR with engine problems a couple of weeks ago and was told that the pulse generator is faulty. Have checked the pulse generator and found the coil resistance to be within spec. The bike turns over but sometimes hits a "Hard Spot" and struggles to turn over. When the battery is fully charged and the engine is spinning outside of the "Hard Spot", there is spark. However once the engine speed slows, there isnt spark. Have measured ignition coils and resistance is within spec, have tried starter relay/solenoid off friends bike, but nothing changed. Have tried different battery but this didn't change anything. Any suggestion as to what could be the problem?:-/
The previous owner said he came off the bike at low speed and damaged and replaced the left engine cover that houses the pulse generator and also replaced the pulse gear.
 

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Spark plugs or Reg/rec.

At low revs, you are not getting enough voltage to spark as the alternator is not kicking over enough current.

If the plugs are dirty, you need more voltage to spark, if the reg/rec is faulty, then that will have an impact.

Check the plugs first.
 

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Discussion Starter · #3 ·
Thanks for the suggestions. I dont think it is the regulator/rectifier as I repaired a friends CBR250rr about a month ago, and he had a faulty regulator rectifer aswell as a shot stator. His bike still started fine but eventually died once there wasnt enough electricity stored in the battery to keep the spark going. Im thinking that maybe it is a combination of slightly carboned plugs, along with something or a few other things. Still can't figure out why the starter will turn it over easily then suddenly struggle to turn it over then sometimes turn it easily again. I will clean up the plugs tomorrow and see if I get a more consistant spark. Thanks for the suggestions
 

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Turn the engine over by hand via the crank bolt under the small caps on the rhs side cover. This will tell you if the starter is dropping out causing a perceived hard spot. Or if there is actual resistance in the engine itself.
 

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Discussion Starter · #5 ·
Thanks Aduro, I have just tried what you said and found that the small cap has been absolutely rounded and cannot use an allen key to remove it. I instead removed the whole RHS cover and like you suggested, turned the crankshaft. I used a 1/2" ratched to get some leverage to turn it and found that little effort was used to turn it (Spark plugs are out). I could feel a slight tight spot but nothing that seemed too bad. I am thinking that the bearings could possibly be on the way out but I dont think the tightness was that bad to make the starter struggle to turn it over. I will try a friends starter on the bike tomorrow and hope that this might be the sollution to the starting problems which could be due to lower turn over speed.
 

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Discussion Starter · #6 ·
Turn the engine over by hand via the crank bolt under the small caps on the rhs side cover. This will tell you if the starter is dropping out causing a perceived hard spot. Or if there is actual resistance in the engine itself.
Thank-you very much Aduro. I originally had my suspicions about the starter, and since performing your test last night, I swapped the starter motor with a friends. As soon as I did this, the bike turned over so much easier and sounded like it was turning faster. I did a spark test and found that i was continually and consistantly getting spark. I didn't put the whole bike back together and try to start it as i had limited time and I drained the oil last night in order to feel how the crank turned over. I am going to order in a new starter from Hong Kong for about $60 AUD and put that in, reassemble the bike and see if it will start now that there is spark. While both starters where out of bikes, I turned the shafts on them and found the my suspected faulty started make a slight pinging sound as if something was ticking on the outer case.
 
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