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I have a 03 Shadow ace 750. I have a stock air filter. I tore out the baffles in the exhaust. My carb was leaking gas so I went ahead and did a rebuild and rejet. I went with sigma 6 jets I believe it was 115 Front and 120 Rear. I did mess with the float unfortunately. The bike ran fine for a few hours then started bogging down. I think the bike is running rich. At 1/4 throttle is has a bad bog also at idle. I adjusted my pilot screws and the only way I can get the bike to act normal is if they are all the way in. What did I do wrong? Jets to big? Float level not set right? I did not clip my needle do I need to?
 

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2007 VT750DCA7 Spirit - NHB01 Black
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Jets are too big with stock airbox and just removed baffles, you probably would have been fine to leave the stock jets in there as you didn’t change how much air the engine is getting through the intake. Other than the carbs leaking fuel did the bike run fine before you changed the jets? What exactly did you do to the floats?
 

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Discussion Starter #3
Jets are too big with stock airbox and just removed baffles, you probably would have been fine to leave the stock jets in there as you didn’t change how much air the engine is getting through the intake. Other than the carbs leaking fuel did the bike run fine before you changed the jets? What exactly did you do to the floats?
Jets are too big with stock airbox and just removed baffles, you probably would have been fine to leave the stock jets in there as you didn’t change how much air the engine is getting through the intake. Other than the carbs leaking fuel did the bike run fine before you changed the jets? What exactly did you do to the floats?
The bike was backfiring like crazy. So I figured jets would help it. It hasn’t backfired once since the new jets tho. And the floats I measured them to 7mm they were sitting at around 9mm.
 

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Discussion Starter #4
Jets are too big with stock airbox and just removed baffles, you probably would have been fine to leave the stock jets in there as you didn’t change how much air the engine is getting through the intake. Other than the carbs leaking fuel did the bike run fine before you changed the jets? What exactly did you
Jets are too big with stock airbox and just removed baffles, you probably would have been fine to leave the stock jets in there as you didn’t change how much air the engine is getting through the intake. Other than the carbs leaking fuel did the bike run fine before you changed the jets? What exactly did you do to the floats?
What would be my best move? Going back to stock jets? Maybe stock in the front and 115 in the rear? Would the backfire come back?
 

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What would be my best move? Going back to stock jets? Maybe stock in the front and 115 in the rear? Would the backfire come back?
Put everything back to stock other than your exhaust with removed baffles then trouble shoot the deceleration popping properly. Was it backfiring mostly on deceleration? Would it get better and pop less as the bike warmed up or would it get worse? What exhaust is installed? Stock?
 

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Discussion Starter #6
Put everything back to stock other than your exhaust with removed baffles then trouble shoot the deceleration popping properly. Was it backfiring mostly on deceleration? Would it get better and pop less as the bike warmed up or would it get worse? What exhaust is installed? Stock?
The exhaust is the stock all I did was chop it to take the baffles out then welded it back together. It backfired before I fooled with the exhaust. It would backfire while decelerating. It seemed to get worse when the bike was warmed up.
 

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Put everything back to stock other than your exhaust with removed baffles then trouble shoot the deceleration popping properly. Was it backfiring mostly on deceleration? Would it get better and pop less as the bike warmed up or would it get worse? What exhaust is installed? Stock?
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The exhaust is the stock all I did was chop it to take the baffles out then welded it back together. It backfired before I fooled with the exhaust. It would backfire while decelerating. It seemed to get worse when the bike was warmed up.
How much did you take out? I am very familiar with the stock ACE exhaust.
 

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It is completely hallow. I cut a little after the 2 connects into 1 big piece.
That has a lot to do with your popping, you essentially have straight open pipes now with a big expansion chamber just past the merge if you cut everything out of the can like I did. Everything you removed is designed to stop the popping from occurring so you will have a pretty difficult time completely tuning the popping out while retaining the loud sound. For the gutted ACE exhaust there is a lot of volume of empty air space inside that exhaust canister for expansion and the hotter air from the rear cylinder dumps right into it, you will need to get the tuning pretty spot on or it is going to pop on decel. You will need ideal pilot jets and ideal idle mixture tuning as well as ensuring there is no air leaks from your carb boots and that your exhaust gaskets are in good shape and not allowing any air to be sucked in while engine braking... that’s just to start. Welcome to CV carbs with modifications. 👍🏻

Does your stock airbox still have the snorkel attached? You may consider attempting to de-snorkel the intake to allow a small amount more air in and see how the bike runs If you still have the 115 and 120 jets in, but that is starting to get into complicating things more and you would need to balance the carbs again and re-tune the idle mixture at the same time.
 

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Discussion Starter #11
That has a lot to do with your popping, you essentially have straight open pipes now with a big expansion chamber just past the merge if you cut everything out of the can like I did. Everything you removed is designed to stop the popping from occurring so you will have a pretty difficult time completely tuning the popping out while retaining the loud sound. For the gutted ACE exhaust there is a lot of volume of empty air space inside that exhaust canister for expansion and the hotter air from the rear cylinder dumps right into it, you will need to get the tuning pretty spot on or it is going to pop on decel. You will need ideal pilot jets and ideal idle mixture tuning as well as ensuring there is no air leaks from your carb boots and that your exhaust gaskets are in good shape and not allowing any air to be sucked in while engine braking... that’s just to start. Welcome to CV carbs with modifications. 👍🏻

Does your stock airbox still have the snorkel attached? You may consider attempting to de-snorkel the intake to allow a small amount more air in and see how the bike runs If you still have the 115 and 120 jets in, but that is starting to get into complicating things more and you would need to balance the carbs again and re-tune the idle mixture at the same time.
I reinstalled the stock jets last night and fine tuned the pilot screws and did a carb sync. So far it is running good I have the pilot screws at 2.5 turns out. I have minimum back firing not near as bad as it was after the exhaust mod. A few things have me wonder still. It feels to hold on to the rpm after I let off of the throttle before it would decel quick. And it also feels to be getting warmer a lot faster. Any suggestions?
 

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Be sure all hoses and boots to your carbs are tight and sealing well, if you’ve never replaced the two lower boots that connect the carbs to the heads I would pay a lot of attention to them.
 

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Discussion Starter #14
Be sure all hoses and boots to your carbs are tight and sealing well, if you’ve never replaced the two lower boots that connect the carbs to the heads I would pay a lot of attention to them.
I know when I put them back on my front carb boot was not sealing good. I’ll have to order some new ones to install. I scrapped them up pretty good
 
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