Bike lunging under acceleration

I've got a 2000 VFR and had it a week now. I noticed that while under acceleration it lunges. At first I thought it was a tire out of balance. I installed two new tires this weekend and changed the plugs but its still doing it. I did check the air filter and found a nice rodents home. I cleaned it up and will have to order a new filter. Anyway, the bike cruises fine at any speed, its just during acceleration getting there its lunging. The tach looked to be bouncing some too. Any ideas what could be causing this? I did notice the chain is loose but cannot be adjusted anymore. I've got a new chain and sprockets on the way. Could this be causing the problem?? Its got 27500 miles on it. Starts and idles fine. Has a Two Brothers slip on exhaust.

 

Hmmm...A rodents nest, huh? The tach bouncing (I'm assuming erratically) makes it sound electrical. Check your battery terminals and make sure they're tight. It's possible the varmint chewed some electrical wires. Find any colored wire insulation in the nest? It's also possible the your air filter looks clean but is clogged anyhow...look at it through some light source. There's a good chance your lunge is related to the nest.

 

sounds like it could be as simple as a bad plug or ign wire. i've seen bad wires cause tach to bounce, but it could also be erraric due to a ignition miss which could be causing the lunging

 

I changed the plugs hoping that would help it but it hasn't. The old plugs look good which surprised me. I figured it would run lean with the rodents nest but all was good. The plug wires look to be in good condition with no cracks or anything visibly wrong with them. I am going to wait on my chain and sprockets to get here and installed before riding it anymore. I did place an order for a new fuel filter which could be the culprit. I guess its one thing at a time till I get it figured out.

 

Suppose it could be dang near anything. I highly doubt it's the fuel filter though. I personally would take a close look at battery connections (all the big cables both ends), wiring, vacuum lines...that sorta stuff. Last summer I worked on at least three fuel injected Honda's that would lunge and the tach would be really erratic in association...sounds like Slacker's description to me...every one was a loose battery terminal. Suppose it could be poor connection elsewhere as well.

 

The surging is gone!!! When I replaced my much worn out chain and sprockets I checked the battery connections. They were both loose!!! I remember the guy telling me he just put a new battery in it right before I came to pick it up so I guess he didn't get them tight enough. It runs like a champ now!!!! Thanks a million Dizzy!!!!

 

I'm glad you got it sorted, slacker, but for future reference a clogged airbox will result in a -rich- condition, not a lean one. Lean = too much air relative to fuel, and it's kinda hard to suck an air surplus through a rat nest.

 

Ya fixed it slacker...good job. The connection at the source is often overlooked.

 

I was thinking a rich condition was when there was more fuel present than whats required where a lean condition is when theres less fuel than needed??? So if the air is restricted and the same amount of fuel is being delivered wouldn't this be a "rich" condition????