help please

[sher4548]

suddenly my 2000 vmax w 24k miles wont run above 4500 or so rpm without missing,sputtering,backfiring out the exhaust and after a backfire she will sometimes die,after stopping and turning off the key and back on she fires right up but will not go above 4500 rpm without major stumbling,starts and idles just fine.Bike is stock except for Dyna 3000 and K&N air filter.I did the shotgun method on the carbs,syncd carbs,ran 2 tanks of seafoam,installed new plugs,battery,fuel filter and 2 new ign coils pulled the carbs off and found one screw had come loose out of the float bowl,screw was laying on engine right below carb,figured that was my problem so re-installed screw and put carbs back on still runs like crap,also checked for vaccum leaks and pinched hoses,nothing.Don't know what to do next,any advice would be appreciated

 

[KJShover]

Sounds like your lid came loose or carbs not fully seated. Did you check to see if they're fully seated and all the clamps tight?

 

[sher4548]

all clamps are tight,does the gasket on the air box lid need to be replaced after so many years,its original?

 

[KJShover]

all clamps are tight,does the gasket on the air box lid need to be replaced after so many years,its original?

Not that I'm aware of.

The reason I asked about the carbs and box being fully seated, cause there are quite a few of us (myself included) that didn't seat the rack or the box fully. You'll still be able to tighten the clamps but they wont be seated all the way.

That not wanting to rev past 4500 rpm, but fine down low and idle are indicative of either the carbs or airbox not being seated correctly. You might still have something clogged in the carbs. Have you tried the shotgun or peashooter cleaning techniques?

 

[sher4548]

Not that I'm aware of.

The reason I asked about the carbs and box being fully seated, cause there are quite a few of us (myself included) that didn't seat the rack or the box fully. You'll still be able to tighten the clamps but they wont be seated all the way.

That not wanting to rev past 4500 rpm, but fine down low and idle are indicative of either the carbs or airbox not being seated correctly. You might still have something clogged in the carbs. Have you tried the shotgun or peashooter cleaning techniques?

did the shotgun a few days ago,do i still need to do the peashooter also or does the shotgun do it all?

 

[KJShover]

did the shotgun a few days ago,do i still need to do the peashooter also or does the shotgun do it all?

It couldn't hurt. Also are your slides moving freely?

 

[twistedmax]

Did you wash it? check for wet wires

 

[TURBOVMAX]

Did you try switching back to your stock ECU?

 

[wildweasel_pt]

Any sync plug not properly in place? Boost sensor hose in good condition? Is the fuel pump working properly?

 

[Redbone]

Check that the carb vent tubes are not pinched/ blocked/ disconnected. They are the 4 hoses that run from the carbs up the back of the airbox (likely pinch area) then split off 2 hoses to each side of the airbox and screwed down near the airbox openings.

 

[sher4548]

Check that the carb vent tubes are not pinched/ blocked/ disconnected. They are the 4 hoses that run from the carbs up the back of the airbox (likely pinch are) then split off 2 hoses to each side of the airbox and screwed down near the airbox openings.

slides move ok and havent washed the bike or got anything wet hasn't rained here in abt 2 months,dont have the stock ECU whe i bought the bike a couple of years ago the DYNA was already on.
I think i'll replace the boost sensor hose and the rubber caps at the sync ports today checked for a pinched vent tube but all are ok,thanks for all the suggestions--any more!!

 

[naughtyG]

checked for a pinched vent tube but all are ok,thanks for all the suggestions--any more!!

Make sure to blow in each vent tube and make sure they are clear! Insect and other such critters can block'em

 

[sher4548]

Make sure to blow in each vent tube and make sure they are clear! Insect and other such critters can block'em

will do

 

[jfeagins]

How about checking your FUEL PUMP for proper flow? IF it ain't pumping right, it won't keep up with hwy fuel needs, but might idle fine for hours.

 

[sher4548]

How about checking your FUEL PUMP for proper flow? IF it ain't pumping right, it won't keep up with hwy fuel needs, but might idle fine for hours.

disconnected the fuel line at the carbs and turned on ignition and pump ran strong for abt 3 seconds then stopped,how else can i check it?

 

[naughtyG]

maybe pull out your spark plugs and take a good look - see anything out of the ordinary?

 

[sher4548]

maybe pull out your spark plugs and take a good look - see anything out of the ordinary?

all 4 plugs looked the same,a light grey color but funny thing is i put in fresh plugs and ran them abt 20 miles pulled them and the look like i just took them out of the box,maybe not enough miles.
After looking at my two rear coils i noticed both had cracks on the bottom i replaced the front two but not the rear,could this be why the bike revs fine when i first start out and when heat builds up a few minutes later she wont rev past 4500 rpm without backfireing?What do u think

 

[naughtyG]

Not sure about the coils although it is possible. At least you replaced the fronts already (a real PITA), the rear ones a dead easy to replace. Do you have a pair to swap them with to try it out? Seems silly to buy two new ones if it ends up being something else - maybe someone here could lend you a couple to try..

Must say though, if it's all fine when cold then not when warm, that does point at electrics..

 

[jfeagins]

The pump should run longer than 3 seconds before shutting off.

Take along a phillips, run it til it sputters and runs outta HP. Shut off the key, pull over and check the bowls for gasoline. That'd prove you aren't starving for fuel when it's coughing/sputtering.