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Cutting out at WO Throttle

Brutal FXDX

Brutal FXDX

Active Member
On my way to work this morn and runnin about 80mph and lovin it, then gave her more throttle. Speed climed to about 95 and held it there for a few sec and speed started falling and bike was acting like it was running out of fuel. eased off for a few miles then wacked it again and same thing. Its a 02 fxdx with 95ci htcc heads and cams, mikuni hsr42 with 170 main.
Got to work and checked the petcock that is stock and has 65k on it. flowed good in ON and RES. cap is venting properly.and i just replaced the vaccum hose 2 weeks ago. Any ideas?? havnt removed the float bowl yet.

Just got done puting bike on dyno and as soon as it hits 3500 rpm afr goes off chart lean. bike will rev to 5000 then cuts out. Guess ill remove carb and floatbowl now.

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Im lost. nothing in the float bowl but gas.No trash in bowl and jets clear Not going to change jets until i find out whats going on. Is it possible the vaccum petcock is just not flowing all the time? It flowed good when i put a mighty vac on it. Also i did just fill up after i left the house this morn, but from the same station i always do. :( Bad Gas?? if so it would run poor all the time.
 
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How long have you had the bike ? Have you done anything before this happen? Does it have a upgraded ign. mod that raises the rev limit, I think stock was only about 5200 rpm. Was the bike ran on the dyno before for tuning? Is it possible the fuel tank vent is plugged restricting fuel at higher rpm?
 
Ok after closer examination i found a very small piece of trash sitting in the plug on the float bowl. removed and cleaned the bowl. good to go. made 92hp and 97 ft lbs.
 
From what you've said it does sound like a fuel shortage problem
if the vent in the tank is good and the fuel valve in the tank is flowing enough fuel
provided there is no blockage or air bubble in the fuel pipe (check the routing of the fuel pipe there should be no dips should be down from petcock to card)
then the problem must be in the carb
is there sufficient fuel in the float bowl (plug a length of clear pipe window washer/ fish tank airline is good for this on to the float bowl drain tape the pipe on to the carb and open the float bowl drain the level of fuel in the bowl will be seen as the level in the pipe as a rough rule of thumb the float bowl should be about 3/4 full)
is the needle jet partially blocked remove and clear
is the slide needle in the correct position
There is no easy answer to this one just methodical steps of checking the flow of fuel from start to finish

Brian
 
Graph was ok could be better. really rich at 2500 to 3500 then leans out a bit on up. It has a 165 main and i know it could use a 170. Prob adj accel pump too. But im on the clock and cant mess with it too much. Tq has always had a big dip at start but i think thats from the bassani 2-1 pipe. Had a thunderheader and then a pro pipe and all had the same dip.

I have a set of 110 heads that have been ported, flowed and decked. they are the ones that came on stock cvo bike that the factory had replaced on touring bikes b/c the valve guides were coming loose. Changed the guides and springs. My guy that did the heads said i need a hsr45 or 48 carb to get all the potential out of the heads. Also will be running A s.e 260 cams until i have the cash to get t-man 647. should be around 110 on both hp and tq. Also will be splitting cases and truing flywheels and welding crank pin so i dont have to worry about them shifting. Cant wait, likei need any more power.:bigsmiley11:
 
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