[NCMtnRider]

2007 Heritage, all stock. Most of my rides have me making the same turn up-hill that is about 1 mile from my house. When I make this turn I can count on one backfire as I roll back into the throttle. It doesn't only happen in this particular turn but it only happens when the engine is not completely warmed. I have never heard or felt a backfire when the engine is warm.

I know that one answer is to let it have more time to warm before riding but what I want to know is whether this is simply the nature of the beast with the EPA-spec tuning or is it more likely an air leak in the intake path.

If its the nature of the EPA-approved beast, is there any value in installing the PowerCommander3 with a better tune on a stock bike? I already have the PC3, it came with a set of pipes that I don't use. Its not an issue now but I am also hoping that the new tune will lower the summer temps a little.

 

[Armin]

I would sell the PC3 on Ebay and get a PowerVision to analyze the problem. I suspect that the IAC is acting up to some degree.

Armin.

 

[Thermodyne]

How many miles are on it?

If it only happens in the transition from cold enrichment over to closed loop, then most likely its a fuel mix issue. Too lean just as it switches off of cold enrichment. As they age, the engines often need a little more fuel to make up for internal wear. Try warming it up for a longer period of time and see if the pop goes away.

A tuner would fix it. But I would want to have a hard look at the temp sensor output before I spent the money. And prolly would check the fuel pressure also.

 

[JayFL726]

Just a shot in the dark here but make sure have no intake or exhaust leaks .. Easy enough to check ..

 

[NCMtnRider]

Milage is around 36K. Also, I didn't notice this problem as consistently during the summer months and this is the first fall that I have owned the bike.

I will soon be pulling the rockers off to do some work in there. I suspect the intake manifold will be fully exposed one the tank is off. Should be easy to check for leaks and will have access to the IAC.

Is the ~$100 "fueltool MC500" my best option to check fuel pressure? My simple rocker locker installation keeps growing but if the result is a better bike then its all good.

That PowerVision great to have but its a little pricey. I haven't seem the PC3s sell for anything close to that. Plus, I already have the PC3. It doesn't do all the things that the vision can do but it should be able to deliver more fuel. Maybe the PV can go on my wishlist.

If there is a leak in the intake track of exhaust, I'd rather make that right before tuning around it. Wouldn't an exhaust leak be hard to miss? I have heard leaking header gaskets on V8s and those are pretty obvious.

 

[MFXDB]

You should check for intake and exhaust leaks before you start taking things apart. Unless it's really bad you can't hear an exhaust at the head. Use smoke from a cigar, incense or something like that and check around the exhaust flanges. For the intake use propane or carb cleaner around the manifold and if there is a leak you will get a change in engine speed.

 

[Thermodyne]

Milage is around 36K. Also, I didn't notice this problem as consistently during the summer months and this is the first fall that I have owned the bike.

I will soon be pulling the rockers off to do some work in there. I suspect the intake manifold will be fully exposed one the tank is off. Should be easy to check for leaks and will have access to the IAC.

Is the ~$100 "fueltool MC500" my best option to check fuel pressure? My simple rocker locker installation keeps growing but if the result is a better bike then its all good.

That PowerVision great to have but its a little pricey. I haven't seem the PC3s sell for anything close to that. Plus, I already have the PC3. It doesn't do all the things that the vision can do but it should be able to deliver more fuel. Maybe the PV can go on my wishlist.

If there is a leak in the intake track of exhaust, I'd rather make that right before tuning around it. Wouldn't an exhaust leak be hard to miss? I have heard leaking header gaskets on V8s and those are pretty obvious.

Your best option on the fuel pressure is to pay someone to test it for you.