CBR 600F2 1991 - 1994 CBR 600F2

Backfire whilst startup

  #1  
Old 07-04-2018, 02:25 PM
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Join Date: Jul 2018
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Question Backfire whilst startup

Hi guys and gals.

New CBR 600 F2 owner and new to the forum.

I just recently bought a F2 from Poland and I love it.. till today.

Little history from the bike:

Doesn't idle without choke, dies straight away. Choke keeps it running, but at 3000 rpm. Fluctuates under that ( by adjusting the choke up and down )

I was replacing the battery yesterday, and thought why not check the plugs. Took them all out and they were NGK CR9EH-9, except 1 in sylinder #2. It was a D plug ( 18mm ).

I didn't manage to get hold of the CR9EH-9 plugs today, but ordered CR9-EK. I tried fitting CR9-EK on all 4 cylinders, but the previous owner / mechanic had installed the D plug and the threads are much larger. I also saw that they grinded down the thread for the socket from the plug head 18mm->16mm to make the socket fit.... wtf.

I did the same to the plug and installed all of em. Marked the spark plug cables with a sharpie whilst removing them 1 by one and they are all in their correct position, snug.

Now, it doesn't start. Cranks and cranks, then makes a pop. Perhaps I need to adjust the carbs, or adjust the gaps on all the plugs? I am not sure if I should match the 3 plugs to the 1 in cyl #2 or opposite :/

I am good with Mercedes CDI engines, but petrol and especially bikes... I am 0.
 
  #2  
Old 07-05-2018, 07:14 AM
Phil314's Avatar
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Join Date: Sep 2008
Location: 45.2521, -93.5612
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I've got a couple thoughts and since you asked...


If the bike doesn't idle without the choke, your carbs need cleaned, they are pluged. Take them off an clean them, then clean them again, finally clean them a third time. You get the idea, carbs can't be too clean. Make sure all the passages are open, blow it dry with compressed air.


I also really dislike the idea of different spark plugs. Either a different part number, I googled those 2 and they are different. And after you changed them, now the bike doesn't run. Or whatever a 'D' plug is, not 100%, but I am 100% sure it's wrong and doesn't belong in your bike.


So since the threads are larger. I'd get one of those heli-coil kit or equivalent. There are several kinds. It's the correct way to fix stripped threads, which is what it sounds like happened to your head. It should reduce the size of the current hole back to original size. Then get 4 of the correct CR9EH-9 spark plugs and put them in.


Then I'd try starting the bike, see what happens and go from there. But it's hard to diagnose any other problems until you fix these first.
 
  #3  
Old 12-25-2018, 07:46 PM
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Join Date: Dec 2018
Posts: 1
Default CBR back fires when you try to start

I've a CBR 600f I had the same problem then I found out I was holds the throttle to far try using the throttle a little bit. It worked for and not had a problem since
 
  #4  
Old 01-04-2019, 05:20 AM
squale147's Avatar
July 2013 ROTM
Join Date: Aug 2010
Location: warren county N.J
Posts: 665
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Originally Posted by phil314 View Post
i've got a couple thoughts and since you asked...


If the bike doesn't idle without the choke, your carbs need cleaned, they are pluged. Take them off an clean them, then clean them again, finally clean them a third time. You get the idea, carbs can't be too clean. Make sure all the passages are open, blow it dry with compressed air.


I also really dislike the idea of different spark plugs. Either a different part number, i googled those 2 and they are different. And after you changed them, now the bike doesn't run. Or whatever a 'd' plug is, not 100%, but i am 100% sure it's wrong and doesn't belong in your bike.


So since the threads are larger. I'd get one of those heli-coil kit or equivalent. There are several kinds. It's the correct way to fix stripped threads, which is what it sounds like happened to your head. It should reduce the size of the current hole back to original size. Then get 4 of the correct cr9eh-9 spark plugs and put them in.


Then i'd try starting the bike, see what happens and go from there. But it's hard to diagnose any other problems until you fix these first.
+100
 
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