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Discussion Starter #1
Just swapped motors on a CBR929.
Motor I got from E-bay and the bike I picked up as wrecked.
It was orginally going to be a parts bike for my track bike but
when I got it home I realized I had everything in my garage to get it going.
Anyway....Put it all together and it starts fine, then it when it
starts to reach operating temperature it backfires through the throttle body
and almost stalls. It is the second cylinder in from the right side of the bike. I have the airbox off and I can feel hot gas being pushed out of the throttle body.

I think it might be the plug that is only occasionally firing..
I used the best looking plugs out of the two motors but not new ones.
Will get new plugs tonight. If it is not that, any ideas....

Any help would be greatly appreciated.

Thanks
 

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Registered
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29 Posts
Just swapped motors on a CBR929.
Motor I got from E-bay and the bike I picked up as wrecked.
It was orginally going to be a parts bike for my track bike but
when I got it home I realized I had everything in my garage to get it going.
Anyway....Put it all together and it starts fine, then it when it
starts to reach operating temperature it backfires through the throttle body
and almost stalls. It is the second cylinder in from the right side of the bike. I have the airbox off and I can feel hot gas being pushed out of the throttle body.

I think it might be the plug that is only occasionally firing..
I used the best looking plugs out of the two motors but not new ones.
Will get new plugs tonight. If it is not that, any ideas....

Any help would be greatly appreciated.

Thanks

check the vacuum hoses on the throttle bodies, i had a very similar problem when i swapped motors on my bike. i thought they all were just vacuum, but they go to different parts of the throttle body inside. i had 3 hoses in the wrong spots and it made the bike run on 3 cylinders down low. i pulled my hair out for a week! the factory manual has a good diagram in it, if you need a pic of it, email me-
 

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34 Posts
Discussion Starter #3
check the vacuum hoses on the throttle bodies, i had a very similar problem when i swapped motors on my bike. i thought they all were just vacuum, but they go to different parts of the throttle body inside. i had 3 hoses in the wrong spots and it made the bike run on 3 cylinders down low. i pulled my hair out for a week! the factory manual has a good diagram in it, if you need a pic of it, email me-
Thanks, I'll check the hoses.
I am taking into a shop next week and let them
sort it out.

Regards,
Marcelo
 
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