Had a ton of power loss recently, after working on the front end of the bike, replacing the fork tubes. The bike struggled to reach 60 mph. Since then, I have cleaned the carb, and replaced the diaphram/piston that had some damage in the area of the choke/enricher channel. I also installed a CV air mixture screw and a number 45 idle jet (as advised previously by a Harley tech). Sportster is stage 1 with a heavy breather air filter/clear and vance and hines short shots exhaust. I could not tell what number idle jet was in there originally, its mangled. It does have a 180 main jet.

I installed the CV air mixture screw most recently, and once I got it seated and adjusted correctly, I am able to ride it. Still the carb spits occasionally when riding, mostly on deceleration. Sometimes I can get it to spit in the garage but that's rare, it will shoot fire out of the exhaust...which is very cool, but probably not good. My top-end speed has dwindled. It's now a struggle to get over 70, and tops out at 78.

From what I've read and heard from others is an air leak, but I haven't been able to find it yet. I've sprayed both carb cleaner, and brake cleaker around the intake, while running hot and initial idle with no change.
/
I was leaning toward it possibly being the Crank Position Sensor, but the bike doesn't have a code. Should I try that anyway?

In the least, the bike is running better, I just need to determine where the loss (air?)is happening.

Side note - the weeks before I decided to work on my forks, the bike started running rough. It was after I had ran some non-ethanol gas. It never sat, ran completely through. I treated several tank with Techron, and it was running great before I started work on the forks. Parts issues came up and the bike sat a week. One back together, I've been trying to discover where I am losing power. Bike was on a lift and jack.

 

My guess is carb issue. Perhaps check the voes also.

 

Maybe it needs some silcone grease on the seal between the intake and carb? I was just reading about that. I first time I removed the carb, I pinched the carb on the intake somehow on reassembly. I've carefully smoothed the sharp edges since then, nothing too deep.

I am about to perform the propane test and see if I get any indication of a leak.

It could be something I am missing in the carb. A had a shop help me get it back on the road, they rebuilt it. I would think the seals and springs are new, but if I reopen it up, that will be next I guess.

Keep the ideas coming, Thanks!

 

Also, the VOES? I'm unfamiliar but did I read correctly that if I have a MAP sensor that it doesn't have a VOES?

 

If you have a MAP, you don't have a VOES. Sounds to me like your pilot jet circuit has some crud in it. Also, did you get all the parts out of the mixture screw hole? There is a spring, washer and O ring, in that order.

John

 

Same jet sizes as mine according to the receipts I got when I bought the bike . Also among the receipts was one for a new crank position sensor . So maybe they are prone to failure .

 

Thanks Guys!

Yes I did get all parts out of the mixture screw hole. I didn't initially have the new CV screw in all the way, though I didn't ride it but once that way. I got some machine oil and worked in it there without pulling it out completely. Plan to remove the carb again soon and check it fully. I just put some seafoam in it with premium and I am going to try and ride it out. I feel like I cleaned the carb out well, but then again everything takes a second or third round with me.

I've got my idle and mixture screw set right now at warm idle the best I've ever heard it, but I am definitely losing power around 3rd gear. Tops at 70, 78 if I kill it 😂

And I am wondering if I should just replace the CPS even though there's no code?

 

Just a wild guess but if you think it ran rough after getting non ethanol fuel, maybe the fuel tank has water in it. Non ethanol gas will not make it it run poorly but water in the gas will. Run all the gas out of it and clean tank then add good fuel. Water will be at bottom of tank and you need to get that out. And it costs zero dollars to clean out tank. Ig you ran tanks empty did you run it to empty with reserve on. If not that is where water will stay and this will cause intermittent problems for a long time.

 

Are your throttle cables adjusted so you get full open on the carb butterfly? Also, check that your slide piston is going up and down properly. Good luck.

John

 

Fire out the exhaust? isnt that running rich or "dumping fuel?