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Discussion Starter · #1 ·
I took my bike out for about an hour ride today and noticed something weird. When I try and hold a steady highway speed or decelerate slightly the bike makes this farty noise and it hesitates slightly. The bike feels like it starts to loose power and is starving for fuel. Whats' weird is that if I get on the throttle the hesitation goes away. So as long as the bike is accelerating it seems fine, but as soon as I level off on the throttle and try to cruise at a steady speed I get the popping. It gets a bit worse when I just slightly slow down, but won't do it at all if I let go of the gas all together.

I have been messing with the timing springs a bit so my first instinct is that I am not getting full advance at a steady rate. As soon as Mike's has springs back in stock I plan on replacing them. My second suspicion is I have a leak at the carb boot.

What do you guys think?
 

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Sensei
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Occam's Razor....Whatever you "messed with" that initiated the problem is likely the point of the potential cure.....

I agree with Bill about the "popping"....Likely a minor exhaust leak .... But the power loss is something else.....What else have you "messed with"?
 

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Discussion Starter · #4 ·
One of the carb boots was a bit loose at the filter side, I doubt that was the problem tho. I could have a leak between the header pipe and muffler in the exhaust, but I didn't think that could cause the loss of power when the popping or missing occurs. Like I said it almost feel like I'm running out of gas.

I have "messed" with about everything on this bike. I've dipped the carbs twice, and replaced almost the entire ignition system. I have only put about 200 miles on this bike since I got it back together.

When the bike is cruising at 4k or so, is the float needle normally wide open to keep up with gas flow? Is there a point where it isn't opening and closing?
 

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drop the float bowls, look for water/crud or rust particles
 

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souperman said:
Is there a point where it isn't opening and closing?
Yeah, when the bike isn't running........

And Steve's right, you mess around with those advancer springs and generally it turns out bad.
Check for advance with a strobe if you can, after staic timing.

Have you checked the compression?????
 

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Discussion Starter · #7 ·
Just an update, I opened up my timing advance cover and found one spring mashed up against the housing not connected to anything. I replaced them both with new springs from Mike's XS and the bike is running great. The timing springs are a tad long so I bent the hooks slightly so they fit snug.
 

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souperman said:
I took my bike out for about an hour ride today and noticed something weird. When I try and hold a steady highway speed or decelerate slightly the bike makes this farty noise and it hesitates slightly. The bike feels like it starts to loose power and is starving for fuel. Whats' weird is that if I get on the throttle the hesitation goes away. So as long as the bike is accelerating it seems fine, but as soon as I level off on the throttle and try to cruise at a steady speed I get the popping. It gets a bit worse when I just slightly slow down, but won't do it at all if I let go of the gas all together.

I have been messing with the timing springs a bit so my first instinct is that I am not getting full advance at a steady rate. As soon as Mike's has springs back in stock I plan on replacing them. My second suspicion is I have a leak at the carb boot.

What do you guys think?
I'm having the same problem you are describing. My bike will rev up fine to 7,000 or so sitting in the garage and accelerates pretty well through the gears but once I get to 60 mph, which is about 5,000 rpms, the bike just bogs down and has no power. It still moves but its not smooth at all...kinda starts "stumbling" or "lunging" down the road and won't rev over 5 grand. I checked the timing advance springs and both of them are on and intact but seemed a bit loose and weak.

I'm ordering a set of mike's xs springs so hopefully that will do the trick.

I adjusted the cam chain, valves, static timing, and rebuilt the carbs and nothing yet has gotten rid of this goofiness on the highway. I'm hoping this does the trick!
 

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try popping open your gas cap when it starts to bog, I had a slow vent that would cause a real similar situation one cylinder would die and air would get sucked into the petcock through the float drain allowing the other carb to get gas, very funny acting, it would take a minute to sort out once you opened the cap then would run fine.
 

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make sure the needle clips are the same and in the correct notch, and that the cables are synced if it is bogging at mid-throttle.
 

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mordantly.....
Because we have many less experienced "mechanics", working on their own bikes here on this site, we HAVE to be extra careful NOT to relate inaccurate information.....
Your response does NOT completely apply to the 450's as the slide needles are non-adjustable...Synchronization IS of course important on multi-carbed bikes.....

I understand you are trying to be helpful, but please read topics carefully and somehow indicate your response is an assumption based on generalized mechanical knowledge if you aren't absolutely certain it applies to the specific model bike in question......

Erroneous information can be expensive (broken parts) and/or dangerous.....
 

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It sounds like Resty's problem arises when his engine is trying to develop high(er) power. Perhaps his engine is not able to breathe properly due to a restriction in either his intake (e.g. clogged filters) or exhaust.

Mike V.
 
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