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Discussion Starter #1
Hey guys,

I got my first bike this year and its an '89. Needless to say with it being that old it has a few little quirks but no real issues until late. I found some threads related to this topic but their issues seemed to be slightly different.

When accelerating at a normal pace I experience no issues in 1st-3rd gear. However, at mid range in both 4th and 5th gear (while steadily accelerating) the engine bogs down quite hard (but will not cut out). This issue is explicitly limited to 4th and 5th. But if while in 4th or 5th I accelerate hard I experience no bog issues and the bike picks right up.

No work has really been done to the bike yet, I did change out the spark plugs today before riding though. Any help on this is much appreciated, thank you in advance!
 

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So you're saying it loses power if you try accelerating "slowly" from 3,000-4,000 rpms while in 4th or 5th....but takes off fine if you crack open the throttle a lot?

Bike idles fine and both cylinders are firing?

Sounds like you might have a torn or leaking diaphragm in your carb(s)

Check your air filters and intake hoses (maybe something crawled in there) pull out the vent hose going into the back of the right ear, cut the end at a 45degree angle and re~insert it.



It's odd that it doesn't do it in lower gears. What rpm do you normally shift at?
 

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When in 1-3 are you giving it as much throttle as you give when you're in 4-5 and it starts to bog? Trying to determine if would start to bog at, say, 65% throttle regardless of what gear you're in, but you just don't open it up that much in low gears. I personally don't use a ton of throttle until I'm on the highway, so I wouldn't notice a mid-to-high throttle problem until I was past the low gears.
Just a thought.
 

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Discussion Starter #4
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So you're saying it loses power if you try accelerating "slowly" from 3,000-4,000 rpms while in 4th or 5th....but takes off fine if you crack open the throttle a lot?

Bike idles fine and both cylinders are firing?

Sounds like you might have a torn or leaking diaphragm in your carb(s)

Check your air filters and intake hoses (maybe something crawled in there) pull out the vent hose going into the back of the right ear, cut the end at a 45degree angle and re~insert it.



It's odd that it doesn't do it in lower gears. What rpm do you normally shift at?
Yes, I wouldn't say "slowly" accelerating, I'm not pinning it, but yes if I do crack open the throttle 75% or more I experience no issues. Also I normally shift around the 5k mark. Thank you I will try to take a look at the carb!


When in 1-3 are you giving it as much throttle as you give when you're in 4-5 and it starts to bog? Trying to determine if would start to bog at, say, 65% throttle regardless of what gear you're in, but you just don't open it up that much in low gears. I personally don't use a ton of throttle until I'm on the highway, so I wouldn't notice a mid-to-high throttle problem until I was past the low gears.
Just a thought.
I intentionally tested this issue out by giving it the exact same amount of throttle through all 5 gears and the issue still only happened in 4th and 5th gear. Honestly I'm usually on the throttle pretty hard regardless, the only time this issue is truly an issue is while I'm trying to cruise down the highway as it starts bogging right at the perfect throttle position for highway riding.
 

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I think the issue is more obvious than we are making it out to be. That's how long it takes for your fuel bowl to run out of fuel. You're running lean. When you start out from idle your bowls are full, after a good run through 1st, 2nd, and into third you have sucked your bowls dry. At least one of your carbs is lean. I'd check your floats and see if one is set to not allow as much fuel in as you need.
 
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I think the issue is more obvious than we are making it out to be. That's how long it takes for your fuel bowl to run out of fuel. You're running lean. When you start out from idle your bowls are full, after a good run through 1st, 2nd, and into third you have sucked your bowls dry. At least one of your carbs is lean. I'd check your floats and see if one is set to not allow as much fuel in as you need.
An empty bowl wouldn't give him power back at full throttle in 4th & 5th though.
 

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FREEBIRDS MC CENTRAL NY
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Question of the day,is the bike stock,earshaved,stock exhaust, degoated?
 

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Question of the day,is the bike stock,earshaved,stock exhaust, degoated?
You all heard the man. No more questions today. We've hit our quota.
 

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Discussion Starter #10
The bike is completely stock with the exception of removed baffles. Also nothing was changed or adjusted prior to this issue beginning.
 

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FREEBIRDS MC CENTRAL NY
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The bike is completely stock with the exception of removed baffles. Also nothing was changed or adjusted prior to this issue beginning.
OK baffles removed alone wouldn't do it.
 
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