Running rough when warmed up

[jgw1986]

I've searched the forums and haven't found anything. My ride from home to work is about 4.5 miles. I can leave my house running great, and by the time I get to work, i can barely keep it running. If I try to takeoff from a stoplight/sign, I have to rev it near 4k just to keep it from bogging down/dying. Any ideas? I was thinking maybe the inline fuel filters flow less and get sucked dry by the time I get to work, but they're still full when I get there. I had the carbs rebuilt/rejetted for indy filters and stock exhaust, they were also bench synced at the shop, but I have not synced them myself (havent had enough time off of work to build the sync tool). Plus, the bike runs GREAT right out of my driveway, and as long as I stay at high rpms once I get it warmed up. After warm up, coming off of a stop or at low speeds in a parking lot, it feels as if its missing or starving for gas. What are the ideas guys? I'm lost.

[Ken Talbot]

First place I would look is the vent in the filler cap. Drive until it starts action up, pull over, and pop open the cap. If you hear a whoosh as the cap opens, you've found the problem.

[jgw1986]

will do tomorrow morn, Its a brand new cap from mikesxs, but I'll still try it out. Thats what my thoughts are, some kind of fuel starvation issue, but dont know why it takes time for it to develop.

[TopCatGr58]

HEy Justin,

You've got the special right, and you've had the carbs worked on, but have you checked out the Octy? Put the petcocks on PRIME and run it that way. IF it doesn't start to bog down by the time you get to work, then you've proved it fuel starving. Could be problems with Octy, vacuum hose leak, sticking Octy.

However, if PRIME doesn't help, have some water and spritz it on the pipes to be sure all 4 are hot. IF some are cooler than others, depending on which ones will provide further diagnostic direction. 1-4 or 2-3 cool, ignition problems. if 1-2 or 3-4 cool, fuel/carb related.

With a new gas cap, seriously doubt it's vent is clogged. Good Luck.
T.C.

[jgw1986]

I do have the special, but I've removed the octy and gone with inline fuel filters straight from the petcock to the fuel inlets. I will try the spraying water test tonight when i get home from work.

[psycoreefer]

have you pulled the plugs? what do they look like? Rich gets worse as it warms up so maybe the new jets are "to big" or your running rich for some other reason.

[jgw1986]

I just replaced the plugs, old plugs looked decent though, havent pulled the new ones to check them yet.

When I got home, it was starting to act up... So I sprayed the headers and if anything, it looked like #2 & #4 were running cool. Water evaporated off of all four, but on those two it took a millisecond longer, the other two it was steam as soon as it touched.

I also checked the gas cap, no "whooshing" sound. Its intermittent though, when i went to work today I popped the cap to get rid of any vacuum beforehand, and it didnt act up.

I'm starting to wish I had done the carbs myself, now I have no idea what jets are in there.

I have an exhaust leak on my left side where the muffler joins with the pipe, not a large leak but enough to hear it...

[jgw1986]

any ideas guys? still no updates on my end...

[boyat68]

Originally posted by jgw1986
I also checked the gas cap, no "whooshing" sound. Its intermittent though, when i went to work today I popped the cap to get rid of any vacuum beforehand, and it didnt act up.

jgw1986:

As you said above, the popping of the cap did something. It looks like your cap is not letting the tank vent to atmospheric pressure. In order for a gravity tank to allow fuel to flow it must be able to equalize the pressure as fuel is removed from the tank. I suspect that over time you have a small leaking action from the tank that allows enough fuel to fill up the bowls, but the small leaking is not enough to allow the fuel to flow freely. You will see fuel in the lines but the fuel will not flow enough to keep up the demands of the carburetors. The cap is not venting properly. It may not whoosh as Ken suggested since it is venting just a wee bit but It sure sounds as if your tank is not getting the air it needs.