Hi
I have 2004 Fatboy (EFI).

I bought it in Aug 2007 with 2200 miles on it.
The owner before me had a big bore upgrade done by a dealership in NY state at 1300 miles.
(88ci to 95ci)

When I first got it ,the engine ran well with very little "sewing machine" noise.
It has a tach on it and the tach showed very little fluctuation at idle; the needle sat at 1000 rpm.

Today I have 4300 miles on it, I have notice a change in the engine sound as well as the idle.

The needle of the tach is still sitting around 1000 rpm however I hear the engine stumble ever so slightly and it seems to be idling a little slower however the tach says otherwise.

I have also noticed a more prominent "sewing machine" noise which I am not overly concerned with.

I have tightened up the exhaust bolts , I have adjusted the primary chain and adjusted the clutch recently and it all seems to be functioning well, however my mind and ears tell me there is a slight stumble in the idle.

I have an occasional back fire but again very occasional.
I have also noticed a slight weeping of oil from the rocker box

It does run well with lots of low end power butat idle I am hearing/sensing a stumble that was not there before.

Any thoughts, or is it just me ; my delusional paranoid self.

 

A V-Twin with a big bore kit will stumble a bit. The occasional backfire can be normal depending on what pipes you're running esp noticeable upon rapid decelleration. If your tach reads fine, all is well. You're probably just getting used to the bike so the noises are becoming more noticeable i.e.: valve train "sewing machine". 950-1050 RPM is normal idle speed. The rocker leak is not going to get better and should be taken care of ASAP.

 

Check your plugs, and the wires. Sometimes, people upgrade everything else except the wires.

Plus, you may need to get it out on the highway and blow it out, so to speak. Summer was hot, so check, and maybe change the oil as well.

Could also be condensation in the tank. It is getting cooler out.

 

All good points...thanks.

I am intrigued about the rocker box leak comment ...could it damage the engine?
It is such a small leak that I thought I would leave it alone until it became a nuisance...Am I looking for trouble?

Also I was thinking of doing it myself over the winter...would replacing the gaskets be an easy enough job? I am worried I will scratch stuff (tank and frame) or have a hard time getting things back into place ?

Thx

 

Any leak is not a good thing. Most likely the leak is between the rocker box assembly and the barrels and not the rocker covers. Tearing down the rocker assembly is easy, but requires a manual and some good tools, like a torque wrench and torque wrench extensions. Do a search here on the boards and you will find pics to help you. The tank has to come off.