Here's a weird question... re: tank position, air filter... and power?

[Johnny5]

Clearly the PO of my bike had a little drop LOL... knew it when I bought it and I used it as a negotiating tool.  No biggie, the front left blinker was bent, handle bars are tweaked a tiny bit, and the gas tank was shifted to the left.

Straightened out the blinker bracket, but here is something weird... the bike runs great since I got it...  But always around 5k RPM, you could hear the air filter make a louder sound, and seemed to be a flat spot there.  Anyway, I got around to taking the gas tank off a bit and reseating it... piece of cake... and... now that sound/flat spot at 5k is GONE... and my bike is revving smoother all the way around, with NOTICEABLY more power, and it sounds great.  Does that make sense?  Does the gas tank form a seal over the air box or something?  It's a K&N... I just thought it strange...

[ben2go]

No, the tank doesn't do anything for the air box.When you have an air leak around your carbs or filter,it causes the mixture to lean out,and causing the problem you described.

[Johnny5]

No, the tank doesn't do anything for the air box.When you have an air leak around your carbs or filter,it causes the mixture to lean out,and causing the problem you described.

I didn't think so... so what the hell did I do?  LOL All I did was straighten out the gas tank.  I looked at the filter, but I didn't touch it.  I can't believe the difference, I just took it out for an hour, it is clearly running and sounding better.  Weird.

[ben2go]

No, the tank doesn't do anything for the air box.When you have an air leak around your carbs or filter,it causes the mixture to lean out,and causing the problem you described.

I didn't think so... so what the hell did I do?  LOL All I did was straighten out the gas tank.  I looked at the filter, but I didn't touch it.  I can't believe the difference, I just took it out for an hour, it is clearly running and sounding better.  Weird.

May have been a pinched fuel line,contamination in the tank petcock screen.If you turned the tank petcock off and back on,it could have had dirt sitting in it.I recently drop my bike on it's right side.I thought my tank was spotless inside.Well when I looked inside,to check the petcock screen,there was some rust down in the right side of my tank.It was knocked loose when the bike hit the ground.I was stopping on wet grass,in my yard,and the front washed out.

[ohgood]

Shook up the water in the tank, accidentally bumped the loose carbs back onto their boots, wiggled a loose plug wire, bumped a electric connection....

Anything can cause a weird power loss at xyz rpm. It's usually a lean-out, but gremlins are everywhere.

[RVertigo]

One Internet Dollar (No Monitary Value) says the hose off the carbs was smashed...  When I replaced my rear shock, I went in through the top (took off the tank and airbox and pulled the old shock right out)...  After putting everything back on, I rode around and noticed a lack of power ~5k-6K, then SMACK it would all come back ~7K-8K, then gone again ~9K...


After new plugs, oil change, valve adjustment... Same problem...  Pulled the tank off again, checked all the fuel hose routes...  Same problem...  Moved the carb-breather-hose-thingy from the top of the air-box to the side... Problem solved.  


It seems like if you smash that poor little hose, the back pressure keeps the gas from flowing as fast as it needs to (I made this conclusion after blowing on that hose and seeing gas shoot out of the carbs**).


** WARNING:  RVertigo actually knows nothing about working on bikes.

[ben2go]

One Internet Dollar (No Monitary Value) says the hose off the carbs was smashed...  When I replaced my rear shock, I went in through the top (took off the tank and airbox and pulled the old shock right out)...  After putting everything back on, I rode around and noticed a lack of power ~5k-6K, then SMACK it would all come back ~7K-8K, then gone again ~9K...


After new plugs, oil change, valve adjustment... Same problem...  Pulled the tank off again, checked all the fuel hose routes...  Same problem...  Moved the carb-breather-hose-thingy from the top of the air-box to the side... Problem solved.   


It seems like if you smash that poor little hose, the back pressure keeps the gas from flowing as fast as it needs to (I made this conclusion after blowing on that hose and seeing gas shoot out of the carbs**).


** WARNING:  RVertigo actually knows nothing about working on bikes.

At least you put a warning disclaimer at the bottom of your posts.

[RVertigo]

The fine print...



Just speaking from my personal experience...  Deductive reasoning...  And some Internet Dollars (No Monitary Value)...

[galahs]

Blocking the breather hose causes the carbs to flood as the only way the air can be pushed out is out of the jets. Which means the float bowls have to over fill.

[RVertigo]

The little hose...  Not the big one attached to the airbox....  The little hose that runs OVER the airbox and attaches to nothing.

[galahs]

Yep, that's the carb breather.

It allows the air in the float bowls to escape as fuel replaces it.

[RVertigo]

And if you blow in it, gas shoots outta the carbs!

[Johnny5]

The little hose...  Not the big one attached to the airbox....  The little hose that runs OVER the airbox and attaches to nothing.

Hmm, I didn't see that in my travels... LOL.  Of course, I wasn't really looking all that hard, the primary thing I noticed was the air filter was open... no tubes running over it that I saw.  Maybe I'll check it again, but it's running so good now I'm afraid to touch it... LOL.  It is really running strong.

Another thing I was thinking, along what ben2go 1st suggested the tank was skewed to the left side, where I could see it was maybe pinching the gas lines coming off the tank against the frame... maybe it was a bit starved for fuel.

[Johnny5]

I just had to bump this post again.  I just can't even believe how much better my bike is running since I moved my tank.  Night and day.  I did check the fuel line coming directly from the petcock and it was a bit wet around the top.  I'm thinking that when the PO dropped the bike and shifted the tank, it had to have pinched that gas line a bit, and when I moved the tank it resolved it.  It's literally like a different bike.  And I thought it ran good before...