Hi my cb1 nc27 wont start ive changed fuel pump and relay but still no joy it trys to fire but then backfires with a vengence ive been told it could be the pick up coil is there any way to check this . cheers al.
I left mine parked up for 5 weeks (in freezing conditions) and had the same problem. Battery went flat trying to start it. I jumped it off the car battery but it took about 15 minutes to get going (give the starter motor a break from time to time so it does not burn out). If you left it out in the cold for ages this might work otherwise I dont know. My bikes running fine now since I got it going.
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Hi It may be excess fuel form the non starting that is giving you the backfire! Change the plugs (if necessary) or at least visually inspect the plugs for sooty deposits and dis similar coloring and condition.Backfiring is almost always a timing issue ! Good Luck
there is not too many combinations of firing order to check. one coil fires plug 1 and 4 the other coil fires 2 and 3 just turn the flywheel past the pick up for 1,4 and make sure the coils are correct the only other things that could happen in a straight engine swap are exhaust and inlet gasket leaks and incorrect fuel line , vacumn hose. I assume all the wiring is replaced in the correct plugs
They can do this from time to time. What can happen is the expansion chamber gets pumped with fuel vapor and then can be ignited, causing a large backfire. I hate to attempt to answer your question with a question, but how old is the piston and ring? A ring won't last very long in a 125. For racing, it's changed every race. For joy riding 15-20 hours of run time and it's time for a ring at least. Weak compression can make it impossible to start. If you have perfect compression the cause for the non-start could be something as simple as a burned up or fouled spark plug.
Start by re-ringing the motor (you can do this for about $25 inside of 2 hours time). Clean the carb out, clean the air filter, fill the tank with fresh fuel and replace the spark plug (NGK B9ES - from Autozone for $1.89). If the bottom end of the engine is good, the above steps should get it fired up - providing your ignition system is good, and based on the apparent backfire, I would say you have spark.
This can either be a Timing problem or bad fire. If you say the plugs are sparking, then it can be that it fires where it shouldn't be firing. The misfire can also be caused by a double fire on the plugs. Time the engine properly, adjust the timing chain, check for proper engine compression as well.. Hope this helps
check compression, the valves may need adjustment. also make sure that the carb is clean and that there are no air leaks or you will have trouble.
From my experience, 80% of old bike troubles come from the carbs being dirty/clogged. Pull the carb off, disassemble any plastic/rubber parts and BOIL in lemon juice for 20 minutes then rinse and blow out the passages. Reinstall and give it a try.
If the valves are out of whack then the piston wont compress the air/fuel mixture and the spark will not ignite the mixture or will ignite it erratically thus getting an occasional backfire. Check valve lash and retry.
If it has spark,compression and getting fuel it should hit,backfire or something.pull out a spark plug and see if its wet with fuel or dry,squirt a small amount of fuel into the plug hole ,replace the plug and see if it tries to run,if so then clean the carburetors then give it a try
My 87 honda has a fuel relay...i jumper'd it and it pumped fuel out pretty good all the time...find a wiring diagram or just try different combination of jumpering the pins ..i used a paper clip..there was only three wires and only two need to be jumped...take the main fuel pump line off and have somethng to catch the fuel in...flow should be a moderate flow coming out, if not, its going bad or you have a clogged fuel fiter or missed up petcock.
Check fuel pump is working(remove seat and tank)Although your bike has carbs,they are fed by a fuel pump(under seat and tank)
if there is no fuel getting pumped when you are cranking over,replace fuel pump relay(cheapest option)If still no joy your fuel pump is u/s.although hondas have a seperate small vacume type hose running off the back of the pump,any pump off a kawasaki zx7/zx9 will do the job(they are all made by the same firm)