Backfiring under down shifts
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Joined: Jun 2023
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Backfiring under down shifts
Hi I wonder if anyone can help. I felt great having solved my starter problem. (Bike just clicked when hot on restarts) after checking the regulator rectifier etc I suspected the starter motor bushes. So I replaced the starter motor and she fired up first time everytime.
I’m not a mechanic and learnt by using the Haynes manual (UK Im based), and it was a pain in the **** to get to the starter motor which was easy to switch out. But to get to it I had to take out the fuel tank, air filter, coolant housing (draining the coolant), fuel rail and throttle body (which needed heating and a crowbar to pop off).
Job done, along the way I replaced the battery, oil filter and oil, new coolant and new battery.
Now on the test run the exhaust kept back firing under high revs when shifting down or rolling off the throttle hard.
Quick Look online suggested unburnt fuel due to Fuel/air ratio incorrect due to air leak ( one chap saying he reseated his throttle bodies and it sorted it as they weren’t seated properly and must of let air in), spark plugs (but they are only 12 months old and I didn’t touch them plus I’ve only done about 200 miles on the bike since the new plugs).
Im sure I reconnected all the cooling pipes and engine ones back correctly or at least hope so. To be sure I stripped the bike back to the throttle body today and took them out and reseated them. And re plugged all the pipes. Then all back together, out on test ride and still backfiring.
not sure what to do, it was fine before I started messing with it so it’s nothing mechanical that’s failed.
any help? 2002 Honda CBR fuel injection UK spec so equivalent to USA F4i. 9000miles in the clock.
I’m not a mechanic and learnt by using the Haynes manual (UK Im based), and it was a pain in the **** to get to the starter motor which was easy to switch out. But to get to it I had to take out the fuel tank, air filter, coolant housing (draining the coolant), fuel rail and throttle body (which needed heating and a crowbar to pop off).
Job done, along the way I replaced the battery, oil filter and oil, new coolant and new battery.
Now on the test run the exhaust kept back firing under high revs when shifting down or rolling off the throttle hard.
Quick Look online suggested unburnt fuel due to Fuel/air ratio incorrect due to air leak ( one chap saying he reseated his throttle bodies and it sorted it as they weren’t seated properly and must of let air in), spark plugs (but they are only 12 months old and I didn’t touch them plus I’ve only done about 200 miles on the bike since the new plugs).
Im sure I reconnected all the cooling pipes and engine ones back correctly or at least hope so. To be sure I stripped the bike back to the throttle body today and took them out and reseated them. And re plugged all the pipes. Then all back together, out on test ride and still backfiring.
not sure what to do, it was fine before I started messing with it so it’s nothing mechanical that’s failed.
any help? 2002 Honda CBR fuel injection UK spec so equivalent to USA F4i. 9000miles in the clock.
Thread Starter
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Junior Member
Joined: Jun 2023
Posts: 9
Likes: 1
I take it you mean around the throttle bodies as it’s a fuel injection model? I’ll get some today and try that.
I also ordered a diagnostic tool to see if it through up an error with a sensor causing incorrect fuel/air mixture.
I also ordered a diagnostic tool to see if it through up an error with a sensor causing incorrect fuel/air mixture.
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