When the bike cuts out......if it kind of hesitates and slows before stopping.....that indicates a fuel problem.  Try shutting your manual petcock off and run the carb out of gas on purpose, and see if that feels the same.  70 mph might be just faster than your fuel system is able to flow fuel and keep up.....so there could be some kind of a fuel or air restriction.  Electrical problems tend to be more sudden, and generally don't come back on just because you slowed down.

The stalling might be a result of your idle being set too low.  Check that your idle speed is such that at idle in 1st gear you are traveling about 9 mph on level ground.  Try bumping the idle speed up a little bit.  Your idle air mixture might also be a little bit lean.....or your TEV valve in the carb may not be working and the carb should be cleaned.  Maybe the 70 mph fuel flow and the stalling at idle are related.....the carb may need to be cleaned.

The muffler of choice is the DYNA muffler....with baffles intact and not drilled or knocked out.

You changed the coil? & Plug? & didnt ask this monumental library of brains first?
What muffler are you using? Is it stock or have you messed with it? Whats your elevation above sea level?
Yes, the Dyna, unmolested, is the muffler of choice. Its sexy, it weighs a lot less than stock, it sounds good & it breathes easy AND,, heres the Kikker!

Its Cheap! You can get a take off for about $20.00 usually. Make sure theres no crossover hookup.

FWIW, I dropped the $$ & went with the Supertrapp.. If I got a better HP boost than the Dyna woulda given me, it was negligible & the cost was waaay too much for the difference, AND, the Trapp isnt pretty like the Dyna.. I wish I had saved that $$$ for tires & gas,, & the K&N filter is not worth it, either.. stay stock paper.,.save hassle & $$$

Thanks for the reply's. First thing, My muffler is a stock sportster one unmolested. The fuel tap (pet thingy) is the raptor one that is recommended on this forum. I changed the coil, plug and module out of frustration and there was no change. There is no hesitation at 70 engine just cuts out which is what made me go the electrics way. unfortunately I didn't ride the bike when I first got it when standard because it needed a cam chain change. As I was pulling things apart I did all the mods at once.. I have asked about these faults before on the forum as I thought there might be a rev limiter as that is almost what it is like. As for the stalling Ill try the crawling and see what I get. Does anyone know what the revs should be set at ??
Cheers      

I'm probably silly, but just be sure that the K&N has blocked off part of you air intake.

Last time I had something like that, it was on a dirt bike and turned out to be a fuel issue.  At WOT, you're pulling a lot of gas out of the bowl.  It might not lean out and miss...just stop...then back on again.

I see you've got the raptor petc0ck. Running 5/16" line? Inline filter? Have you removed the needle valve and its seat and made sure the little filter screen in there is clean? Anything slowing fuel delivery a tiny little bit could contribute to intermittent running out of fuel at speed.

there is also, i guess, the possibility of a little water in the system.  Have you opened the bowl drain and emptied the bowl just in case?  If you do, drain it into something so you'll be able to tell if there was any water...It's a longshot, but could be.

I don't think it's electrical.  It should act up at pretty much any speed or at the same rpm (vibration related) if it were.

[quote author=7263776E68220 link=1390769969/0#8 date=1390858938]verslagen1 wrote on 01/27/14 at 12:54:57:


Would you say it's "bucking" ?
I'd say it's a fuel delivery issue, I'd pull the raptor and check for any debry... did you say it was used?  and I'd pull the carb, check the screen above the float valve.

But the electrical stuff is easier, bypass the clutch safety and kickstand switch and give 'er a go.

Run it up till it starts to buck, shut the fuel off & flip the switch ( kill switch) off,,Roll to a halt & drain the bowl,, if its not full, it should be,
Id hit a rough road & see if it acts up. Or just make sure the sidestand isnt moving,, that thing can sure cause it to shut off for a sec, BUT, it should backfire like a cannon when it lites off again,,