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-   -   Lots of backfiring, won't start (https://cbrforum.com/forum/cbr-600f3-17/lots-backfiring-wont-start-146515/)

jhag09 May 2, 2013 07:46 PM

Lots of backfiring, won't start
 
Pulled the carbs out in my first attempt at cleaning them (think I did a pretty good job) replaced air cleaner and got new spark plugs. Put everything back together and all I get is a bunch of backfiring. It sounds like its soooo close to starting but just backfires. Anyone got an idea?

thanks

Duck62 May 3, 2013 07:56 AM

Are you sure you have the spark plug wires in the correct order?

jhag09 May 3, 2013 12:22 PM

Yep, just checked em again. They're connected in the same order they were before (aka pre-everything aka when it was working lol). Can backfiring can be caused by too rich AND/OR too lean of a mixture? From what I've gathered I may need to tune the carb, when I cleaned it I removed the jets and cleaned them and put them back in but didn't touch the adjustment screw...

jhag09 May 3, 2013 07:24 PM

I just pulled the carbs out again, I was advised to use an air compressor to clean the carbs and that there is probably still some gunk in the jets

IDoDirt May 3, 2013 07:26 PM

I'm not sure what "adjustment" screw you're referring to, can you be more specific ? After cleaning the carburetors, it's often hard to get fuel into the bowls and full. It can take a lot of turning over, and can drain a battery while doing this.

Something I do after having the carburetors off the bike and the bowls drained is to follow the procedure in the shop manual on page 18-17 (chapter 18, page 17) for bypassing the Fuel Cut-Off relay. It's under the Discharge Volume Inspection. This will cause the fuel pump to run continuously when you turn the key on. This should prime the carburetors and fill the bowls. Make sure you put everything back. You only need to let the pump run for about 10 to 15 seconds and you're done.

jhag09 May 5, 2013 11:16 AM

Well I got it started, but it still backfires infrequently. I also noticed a substantial loss in power... my mechanic buddy said my timing is probably off, anyone know how to check that?

EDIT: Still reading other posts and noticed that when I cleaned out my carbs, I neglected to remove/clean the D-shaped pilot screw and didn't take off/clean the black parts that hold the gaskets/needles in them. If those were real dirty and gunked up would that cause the power loss/backfiring?

IDoDirt May 5, 2013 01:28 PM

2 Attachment(s)

Originally Posted by jhag09 (Post 1230833)
Well I got it started, but it still backfires infrequently. I also noticed a substantial loss in power... my mechanic buddy said my timing is probably off, anyone know how to check that?

EDIT: Still reading other posts and noticed that when I cleaned out my carbs, I neglected to remove/clean the D-shaped pilot screw and didn't take off/clean the black parts that hold the gaskets/needles in them. If those were real dirty and gunked up would that cause the power loss/backfiring?

No, it's not the timing being off. Not to say that it may not be firing at the wrong time or order. If that's what it seems like, then I have to say go back and check the plug wires and the wires that connect to the ignition coils. Timing is not adjustable on the F3's (not without aftermarket parts) and is controlled by the ICM.

Both coils have a Black/White wire going to them. The coil that fires cylinder #1 and #4 has a Yellow wire with a Blue stripe. The coil that fires cylinder #2 and #3 has a Blue wire with a Yellow stripe. Their close together and easy to get mixed up. Also, the plug wires are numbered, verify the right one goes to the right plug.

Attachment 33275

I'm a firm believer in doing things right the first time. If you're not taking the carburetors completely apart, then it's easy for people to miss things. This is how they look when done fully.

Attachment 33276

jhag09 May 5, 2013 04:40 PM

Ohhhhhhhh man. Thank you so much for the pics and everything. Just got it running, you were 100% right my plugs were outta order, I didn't even see the numbers on the cables. :D

IDoDirt May 6, 2013 06:34 PM

Well congratulations on getting it running again. I'm sure it feels good. Sometimes you just have to take a moment and verify what you're looking at and what it's supposed to look like.

Very good...

Duck62 May 8, 2013 08:10 AM

There ya go!


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