Here is my problem. I have a 97 F3. 21k. It was doing fine untill my ignition fuse blew. I replaced the fuse and about 200 miles later I noticed a slight "jerk" in RPMs. Meaning it would change RPMs about 500 at a time up and down. It was slight at first but continued to get worse. Now my problem get worse. This bike will rev up no problem out of gear but as soon as I put it in first anf get to about 5000 rpms it will cut out like it's starving for gas. Here is what I did and FYI I'm an aircraft mechanic so I'm pretty sure I know what I'm doing so please lets drop the rookie mech stuff.

1. I replaced the plugs. No change.
2. I check the plug wires. NNo change.
3. I clean the carbs. No change.
4. I ran carb cleaner though thegas tank. No change.
5. Checked the fuel pump. No Change.
6.I took it to a shop. No change

While it was in the shop I became impatient so I asked if I could help. The shop is very cool and let me assist. This is what we did in the shop.

1. Tore the carbs of and had them cleaned and soaked. No change.
2.By passed the full pump. No change.
3.By passed the gas tank with gas/IV bag. No changed.
4. Eliminated CA emissions. No change.
5. Removed and replaced carb with NEW set of carbs. NO CHANGE!

In short, I've eliminated all of the fuel system or more clearly the wet fuel system without out result. All lines and vacuum hoses were removed from the problem. The one good news is we (the shop and I) learned that you can give it some choke and it will punch through a bit through the drop in RPMs but not enought to keep it from stalling. This sounds like a carb problem except with a new set of carbs and a supplemental fuel line (gravity fed) there is NO CHANGE. The bike still will run up fine at any rpm while out ot gear but as soon as I hit about 4500 -5000 rpms (in gear)it will cut out like it is not getting enough fuel. Is there anybody who has had this problem and what else did you do to eliminate this problem. It's summer and I live by the coast. My bike has been sitting in the shop for 3 weeks. I've considered replacing the CDI but because of cost issues I can't take the risk of spending $300-$400 because it might help. I need serious feedback please. I appreciate any help and will pass on any information I get. Please serious mechanics respond. Any additional information need to help give you a better understanding please leave a post.

 

I thought about the cam tenssioner too. Mechanicaly speaking if the chain is stretched then it will be stretched in any position. Meaning it will have the same reaction if it is in gear and at 7000 rpms or doing a 100mph. Besides, if it was the problem then why only when it's in gear? I'm always up for learning so please let me know if I'm mistaken. I didn't metion it above but yes I replaced the fuel filter and air filter and the battery connections and the battery too.

One thing I want to check is the trottle position sensor. I've got to do that tomorrow. Any advice is welcome on that too.

Return fuel regulator? Any help there?

 

Just wondering if i does it in second or third gear or just first gear?

 

i am wondering if its something in the charging system because our bikes start to charge the battery at 5,000 rpms.. do a charginig test on it and see what comes from it???? hope that helps...

still doesnt explain why it wont do it in neutral though..

 

it does it in all gears except when out of gear.

 

Does the bike seem to sputter when you are giving it constant throttle? If that's the case, try tightening your battery connections. My bike was sputtering about two weeks ago. Tightened the screws on the terminals, and the sputtering disappeared. Hope the solution is that easy!

 

Unplug the kick stand start in neutral sensor and try that.

 

wonder if it could be a coil starting to go out.....

 

Alright guys, thanks for the help. Let me be clear about a few things.

1. I checked the battery cables and connection. Ops check good. (besides there is no indication of low voltage and it (problem) is very constant between 4500 and 5000+ rpms and I forgot to mention that we did do an ops check (via multimeter permaintenance manual)
and it checked out good
2. Choking the bike to "push" through helps but indicates lack of fuel not lack of spark and I tested the wires too and threw in new plugs.
3. Nuetral sensor was a thought but why the response with the choke? I will try that anyways.
4. In my experience with coils they just go out. My mechanic agrees with me on that. He's had them go out.

Has anybody tried to disconnect the throttle position sensor before?

I've read through all of the postings here on this site. This problem is not frequent but it happens enough to be posted. Unfortunately, no one has posted how they fixed the problem. Tomorrow I will start calling all the shops in the greater LA and San Diego area to see if somebody knows exactly what this is. Be sure I will post all of my findings here so it will save others a lot of trouble. Hell! I'll even email my phone number just so they can call if need be.

Keep the ideas coming guys. I will try to respond to each idea and give you the feed back

 

Here is an update. My shop is at a loss. I've located a CDI from another shop right down the street and hopefully tomorrow we will be able to replace (temp) the CDI and remove that from the problem. If this doesn't work I'm going to have to pull my bike from the shop and try another place. I really don't have the money to have shops test and retest the same freaking problems. Any help you guys can throw my way will help.

Here is what my mechanic will do in the morning.

1. R&R the CDI. (remove and replace)
2. Disconnect the neutral switch.
3. On my orders blow up the bike and call my insurance company.

I looked at my description above and I think I need to be clear on the symptoms again since I test drove her (bike) again today. The bike will rev up to and rpms out of gear no problem. I put it in gear and rev up the engine to any rpm constant and not still no problem. I can ride the bike and it will be fine in first gear and sometime second but as soon as I hit 4500+ rpms it will cut out and sputter. I can choke her a bit but that only gets me a few more rpms. Under no circumstances can I get enough speed or constant speed to even think about getting on the freeway. About 45-50 mph is about the max.

While I was talking to another mechanic from a neighboring shop he mentioned a resistor in the ignition that is very sensitive and if it even has the slightest influx of resistance it will cause havoc. My bikes ignition switch (key slot)was replaced. (Bike was stolen for a joy ride and that was replaced). Does anybody know if that resistor is located there? I'm not certain if that would be a logical place for it but then I'm used to working on airplanes and simply put... there isn't a place to put a key in and fire a 747 up!

Please keep the ideas flowing.