"Highspeed" issues

[glynnd89]

Okay guys, so i just recently installed my K&N lunchbox filter, and rejetted to 150 main jets and raised the needles.  Bike run greats, but a little weak in the lower RPM, besides the point though and I just haven't adjusted air mixture screw yet.  Although when traveling in the triple digit speed range, upwards of 110 indicated, the few times I have after rejetting, the bike seems to hiccup, is the best way to describe it. Now under this speed runs great, accelerates hard. It doesn't seem to make sense to me that it wouldn't be getting fuel at this speed, when it gets fuel all the way through the rpm range at full throttle and petcock set to "on" and a full tank of gas. Would it be possible that air blowing past the filters creates a low pressure environment and then acts like a vacuum and suck air out of the carburetor? Just spitting out ideas, any other ideas would be a great help. Also if anyone has an SV650 throttle cable that they would be willing to part with to help me out that'd be cool.

[jeremy_nash]

next time, try it with the petcock set to prime.  havent heard of any fuel starvation issues out of the newer petcocks, but u never know.  I have been 104 mph actual on mine, on the racetrack, without any such issues.  I have lunchbox, v&h pipe, and 147.5 jets, with the newer petcock

[ineedanap]

Sure sounds like a fuel problem.  Don't forget to make sure your gas cap is venting as well.  Is it still stock?  Some of the aftermarket ones need a little "mod" to function. 

Like jeremy said, I never had any problems with high speeds and the new petcock either, but you never know.

[tt_four]

A 150 jet sounds large to me. That doesn't mean it's wrong, but it just sounds a little big.

[glynnd89]

We have thought about going up to a 152.5, but decided that the benefits probably would not be much, It dosnt give the obvious signs of being rich, but have thought about going a step down, but my next lowest is 145, Idk what to do about the fuel issue, stock gas cap and stock petcock. Do you think it is draining the bowls? It seemed to happen on cooler windy days.

[dohabee]

I could be mistaken but I believe I once read that Kerry experienced a similar situation while riding on the highway and attributed it to wind.

It has also happened to me. Sometimes If I'm riding 80+ mph and there is a strong crosswind the bike will hiccup a little.

I believe it is related to the angle the wind hits the bike because it only ever happens on really windy days.

Maybe you could try high speed runs in varying wind conditions and see if you notice any difference.

[ineedanap]

I could be mistaken but I believe I once read that Kerry experienced a similar situation while riding on the highway and attributed it to wind.

It has also happened to me. Sometimes If I'm riding 80+ mph and there is a strong crosswind the bike will hiccup a little.

I believe it is related to the angle the wind hits the bike because it only ever happens on really windy days.

Maybe you could try high speed runs in varying wind conditions and see if you notice any difference.

I used to get that on windy days too.  It always happened on windy days at 70+ MPH with the wind blowing from the right of the bike, and only at a constant part throttle.  

The bike ran perfectly everywhere else and I was happy with the jetting.  I ended up raising my needle one clip position just to see what would happen (adding one washer would be the same) and it took care of it forever.  

[glynnd89]

Interesting... I was debating raising the needles again anyways, not a whole clip positions as I only have one position left, the rest would have to come from the washers. hmmm.