Vance & Hines

[Cushman91]

Has anyone who installed a Vance and Hines Exhaust system still had issues with backfiring? Running on stock jetting?

 

[jetlee]

You cannot use stock jets with any aftermarket exhaust. Use 45/175 (pilot/main) combination.

 

[Cushman91]

hey jet i need your advice on this one, so i got the vance installed, new exhaust port gasket, new intake boot from hd, new hd spark plug, jetted the carb to 45/175, and im still getting back fires/coughing/ hesitation while going down the highway at 65, im friends with the service manager at the local hd dealership and he thinks im just hitting the rev limiter but ive ran 65mph in 3rd 4th and5th and it still happens, i had the guys at hd do the jetting so im at a loss Im guessing something with timing or the carb didnt get put back together exactly right, the new exhaust system and jetting helped but did not resolve the issue entirely, what should i check next?

 

[jetlee]

Turn your idle mix screw down till it soft bottoms, then back it out 2.5 turns.
Shim your needle .050"

Some how-to videos are here:
http://buellridersonline.com/forum/forumdisplay.php?f=122

 

[Cushman91]

i watched your video's on youtube and they were very helpful haven't had time to do any work on it for the last couple of days [up]

 

[jetlee]

If you haven't shimmed your needle, do that.

If it pops on decel (engine braking), turn out the idle mix screw little by little until it stops popping. If you're over 3.5 turns out, you need a larger pilot jet (46 is the next one up).

If it doesn't pop on decel, turn the screw in until it does, then back it out until it stops.

Adjust your idle speed as necessary, only after there is no more popping.

There's another trick for setting the idle mix, but I'd rather you use the popping (popcorn) method first, as it's the easiest.

 

[Cushman91]

The biggest problem is it cutting out at constant speed not so much the backfiring through the exhaust... it pops back through the air box... i loose power for half a second then it comes back and runs fine for a little while, then does it again, i cant go more than a few miles without it happening half a dozen times... i read on this site a description of similar things happening to another guy and he ended up having to change his ignition module and I'm hoping that i don't have to do that

 

[jetlee]

Popping through carb (carb cough) means lean. Backfiring on decel means lean on your idle/decel circuit. When you're cruising, your throttle is barely open and using a good bit of your idle/decel fuel circuit. If it's too lean, it can cause carb cough during light-throttle cruising.

Get your idle/decel circuit set properly before diving into the ignition.

 

[ezblast]

Also you could be hitting the rev limiter.
EZ

 

[Cushman91]

alright thanks, great advice as always, in your how to change jet video you talked about underneath the emulsion tube theres the needle jet, if that was upside down could it cause problems? is that a pretty common mistake for someone to make while doing carb work? the friend i mentioned earlier at the harley shop was the one that did my rejet because they were short handed that day and then later informed me that was his first re jet so im wondering if he didnt get the needle jet in backwards

 

[jetlee]

Also you could be hitting the rev limiter.
EZ

True. In 3rd gear, you're on the rev limiter at 67mph.

alright thanks, great advice as always, in your how to change jet video you talked about underneath the emulsion tube theres the needle jet, if that was upside down could it cause problems? is that a pretty common mistake for someone to make while doing carb work? the friend i mentioned earlier at the harley shop was the one that did my  rejet because they were short handed that day and then later informed me that was his first re jet so im wondering if he didnt get the needle jet in backwards

Yes it would cause problems. It's unlikely you even get moving before the engine dies, let alone to 65mph. It's easy to tell...look into the carb and see if you see the silver thing sticking up about 1/8" into the air path. This is the correct way.

If it's not sticking up, or the top surface is perfectly flat, it's upside down.

 

[Cushman91]

okay another question, if i put on one of those bent series intakes eliminating the air box, what size jets would i need to use then?

 

[Cushman91]

its not the rev limiter, its happened to me in 3rd and 4th going around 65-70 and 5th faster than that, it just always seems to happen when im going at a constant speed for a while, almost like the spark plug isnt firing but its got a new plug and the wires look fine, i dug into the carb tonight and im going to swing by RnR tomorrow and grab some washers to shim the needle, the needle jet is infact sticking in the throat of the carb the right direction i also checked that a little bit ago

 

[jetlee]

Don't do the intake until you get this figured out.

3rd gear at 67mph IS the rev limiter.

 

[Cushman91]

i was just wondering about the intake.. future plans.. on test drives it happens going exactly 60 mph in 3rd, tried it lower rpm in 4th doing 60, still coughs back through the carb, so its not rpm specific, its still running lean, i turned the air mix screw out to 2.5 turns tonight and im going to get some #4 brass washers tomorrow to shim the needle and then ill put it all back together and take it for a test ride

 

[Cushman91]

alright Mr. Jet I shimmed my needle as close as i could get to .050 and i turned my air screw out two and a half times from soft bottom and you were 100% right, it ran perfectly... for about 5 or so miles, then it coughed back through the carb a couple times and died out completely ,I rolled to a stop on the side of the highway, sat there tried to start it a few times.. nothing... then i called for a ride, loaded the bike up and took her back to my shop, around half an hour passed between the time it died and getting it back to the shop, when i got back to the shop, i hit the starter and it fired right up and idled just like its supposed too, so my question is.. is there something wrong with the coil or the ignition module? if this is any clue the kick stand safety switch is apparently messed up because it used to start with the kick stand up and now it wont start if the kick stand is down and engine dies if you flip the kick stand down, I'm at a loss as to what to change next

 

[jetlee]

Could be your ignition.

First, clip the wires to your kickstand switch and twist them together.

Also, have you checked flow from your fuel valve? Blow backwards into the tank to dislodge anything that might be obstructing the fuel flow.

 

[Cushman91]

fuel is flowing fine, i checked that, the guys at the hd shop took the tank filter out cleaned it all out, they told me the tank had some junk in the bottom of it and they had cleaned it out, I was planning on cutting the kickstand wires anyways but I havent yet cause I figured i would forget and do something smart like driving off without flipping it up... anywhoo Im going to run some seafoam through it, I saw some coils on ebay for pretty reasonable I thought about ordering one, seeing if that did the trick considering between the module and the coil the coil is the cheaper out of the two, I have a meter at the farm i could use to check the resistance but i feel like i would need to get it to act up first before checking it, could the crank case vent possibly cause this? and how hard is it to change the module? I checked out the coil and I could handle swapping one of those

 

[jetlee]

The coils rarely go bad. If anything ignition-related it would be the module.

 

[Cushman91]

Alright so I picked up a brand new ignition coil at a local dealership for twenty bucks, figured 20 bucks isn't bad if it fixes the problem, I installed it and went for a ride, sure enough the bike died out on me on the side of the road about 20 miles from home but I brought and extra spark plug with me so I popped off the wire and put the spare plug on it and grounded it, sure enough I wasn't getting any spark so I guess I'm looking at getting a new ignition module