problems at 70-80 mph

[okie_dog]

I installed the S&S dual runner intake about a month ago and finally got it out on the highway and higher speeds today. around town it runs great, and all the way to 65mph. above that the problems start, around 70 it slowly develops a vibration, like a tire out of balance, then after a couple of miles it will start popping and stuttering just a little, if I ease into the throttle it will hesitate for a few seconds before taking off. at 75-80 mph held steady it will cut out after a couple of miles, it has a full tank of fuel but feels exactly like what happens when its running out of fuel, it starts surging. It all seems to have started after the install of the dual runner, I tuned the carb according to the directions and removed the aux bowl vent screw. around town its really responsive and runs great, no problems until the higher speeds. First im gonna check the fuel filter in the morning. after that is it maybe a jet problem? I didn't rejet it when I put the intake on, just adjusted the idle mix and pump screw like it said to. and ideas or suggestions?

 

[HMAN]

Your probably gonna have to re jet, check the rubber caps on the top of the carb and make sure they are still in good shape. They tend to deteriorate with age and heat to develop cracks that will suck air. Keep looking an tweaking....you'll get it right. Also make sure your gaskets on the new intake aren't leaking.

 

[Little-Boo]

Bad instructions, especially if you went from a stock intake to the dual. You need to re-jet the carb and all will be good. Do a search on the dual runner and you can try some of what they did.

What jets are you running now, ????? 29.5/72 or what ????? If you dog is stock with no exhaust change just the intake I would take it to a 29.5/74 if you run after market exhaust and the intake I would go to 31/76 and see how it runs with that. After that check you plugs after about 10 minutes of steady speeds between 60 to 65. If your plugs are black it rich, if they are white to lean if they are tan you are OK. Use new plugs when you do this test. From this point you can go up or down one step or number on the main jet to get it where it will run good. Be patient and you will get it right.

Carlos

 

[francoblay1]

Get rid of the "Bowl Vent Plug" in the Carb when going from stock to an After Market Air Cleaner (as per S&S Instructions)

also, what elevation are you at? It does makes a difference in jetting http://www.bigdogbiker.com/forums/fuel-air/14439-what-jets-do-you-run.html

 

[francoblay1]

here ya go.... as Little-Boo said, "Be patient and you will get it right."

see attached.

 

[okie_dog]

ok here is where im at today, put new plugs in and retuned the carb. same problem still, pulled plugs, they look tanish/ golden-brown. it has has had vance and hines big radius exhaust since I got it and I took off the stock intake and went to dual runner. it has 31/72 jets in it. the trouble area seems to be right at 2800-3000 rpm range, has very light popping at those rpm in 3rd gear. 6th gear at those rpm is around 75 and that's where it wants to start missing and popping.

 

[HMAN]

Fatten ur main. You were OK until you changed the air intake.....now it wants more fuel. Try a 74, but you may find you can go bigger.

 

[claw]

Yep. Bigger main jet.

 

[okie_dog]

nobody open today here that has them so will find somewhere online and order a few sizes in main and intermediate to play with an see what does it.

 

[paleskin]

I am dealing with the same issues on the dual runner. These take a great deal of patience and a little luck to dial right. I can tune mine to be sporty around the hole shot or stable for a long ride at hiway speed but haven't found a good all around tune. I wish you the best of luck. I have had the best results with ditching the chrome spear covers and running the filters only for what it's worth.

 

[okie_dog]

thanks for the advice and will let you know how mine turns out after I get the jet kit in and try some different sizes and adjustments. Mine didn't come with the spear covers, its the s&s dual runners withkinda an oval shaped filter and chrome caps on the end

 

[Brew]

Contact McGroom, he sells jet kits...

 

[okie_dog]

dang it, didn't even think to check with him. I went through all the vendors listed in the section and Fury had them so I ordered from them.

 

[V]

You mentioned "fuel filter" in you first post. If this is a aftermarket inline filter, some have had probs with minor fuel starvation with these.

 

[slam]

I have the same setup(big radius exhaust and dual runner intake). I'm running a 32 intermediate and a 78 main. I have a decel pop sometimes but very responsive at any speed

 

[okie_dog]

no I just meant the fuel filter in the tank that came stock, no aftermarket inline, sounds like to many had troubles with those on the carb models. gonna try bumping the intermediate up one size first an see how that does, seems to me like its around 2700-2800 which from what im reading sounds to be the top end of the intermediates range and its starving out.

 

[francoblay1]

no I just meant the fuel filter in the tank that came stock, no aftermarket inline, sounds like to many had troubles with those on the carb models. gonna try bumping the intermediate up one size first an see how that does, seems to me like its around 2700-2800 which from what im reading sounds to be the top end of the intermediates range and its starving out.

Air Bleed jet, change it to a 48 or a 50. :up: