I need a little help

[GSnoober]

Got an update on this for us? Did you check the carb diaphragms yet?

[CrispThat]

Still waiting on diaphragms. Should be here by Saturday.

I'll update then.

[JAS6377]

Just my $.02, but if it runs on prime and not "on", then it's probably related to the petcock vacuum (as discussed). Might it be worthwhile to check the tank vents before spending too much time and money?

[bombsquad83]

Just my $.02, but if it runs on prime and not "on", then it's probably related to the petcock vacuum (as discussed). Might it be worthwhile to check the tank vents before spending too much time and money?

I was confused why he didn't cap off the vacuum port for the petcock and run on prime as I suggested...

Oh well, new diaphragms can't hurt, and they aren't too expensive.

[CrispThat]

Petcock vacuum line capped, PAR system removed (and capped where needed), and new diaphragms installed. One of these three fixed the problem (most likely the petcock vacuum line cap by sound of the discussion from while I was away). Running on prime I now have good pull over the whole range (with the exception of a flat spot from 5500-6000rpm. Fuel/air mix? Needles?).

So it looks like you've all helped me isolate my petcock. Where to go from here? I took a quick look and didn't see a rebuild kit. I'm guessing there's one out there somewhere out there right?

[bombsquad83]

Flat spot might go away once the bike is completely warm.  If you don't have any small washers shimming the needle up, then try one or two. 

There are no rebuild kits for the vacuum petcocks.  If you want to stay with the vacuum, you have to pony up for a new OEM one.  Retrofitting to a non-vacuum petcock can be done with a little effort.   I recommend the 2007 Honda CRF250X petcock, which can be bought for less than $30.   This petcock retains the main and reserve functionality without the need for vacuum. 

EDIT: See this thread for details, which also links to my build thread with pics.

http://gstwins.com/gsboard/index.php?topic=67433

Using this, you just need to remember to turn it off when done riding to prevent flooding in case your needle valves fail.  And remember to turn it back on when you get on, or you will get a surprise about 1/4 mile down the road  .

EDIT AGAIN:  Not sure how the petcock fits on a 2001+ bike.  If you get it and it doesn't fit even with modification, please let us know.  I'm sure someone else would take it off your hands if it didn't work .

[CrispThat]

I'm really surprised that there's not rebuild kit...

Correct me if i'm wrong, but it seems like all i stand to gain by swapping out my petcock is the partitioned reserve tank. If that's the case, i'll just keep using the one i have and run on prime (switching while stopped). Just will take some careful planning and caution for trips....

Thanks again for all the help. I'll keep messing around with my needles to get rid of that flat spot... (lessened when warm, but still enough to make me want to get rid of it)

Cheers! 

[CrispThat]

After playing with my fuel air mixture for couple days, the best I've been able to come up with is the same setting I originally set it to after all my tinkering (complete fluke of course), 3 turns out.

However, i still have a drop in power when going through 5.5-6k rpm. I keep reading that "rpms don't matter to the carb, only throttle position", but the fact remains I have a drop in power at a particular spot in the rev range, regardless of throttle position. I still have a strong pull at lower and higher engine speeds, but its just hesitating through that same spot every time.

I haven't added any washers yet because i want to be sure that's what my issue is. In all my reading, it seems like washers help more with a drop in power at a throttle posistion rather than particular rpm range. Is this a situation where a washer or two would help?

[bombsquad83]

Rpm does matter in cv carbs like ours, because the diaphragm is lifted by the vacuum created by the engine, which varies by rpm.  The slide isn't going to lift right away as soon as you open the throttle.  So really mixture is dependent on both throttle position and Rpm.

I think you should try added a couple washers.

[CrispThat]

Ok. So. Stupid question. Where on the needle is the best place to add the washers? Below everything that's already on there?

http://rx7.voodoobox.net/images/needle.jpg
(A picture of a needle from elsewhere on the forum.)

[Janx101]

Just a thought. .. how much hesitation at the 5.5-6k point? ...my 06 has a very slight flutter/hesitation in/around that point also.. I've always taken it as normal? .. it's not a pump fed FI system after all!? ... or should I consider my situ a problem also? ... it's only a tiny bobble in the power? ... thought it was jet transition.... my carbs are untouched.

[bombsquad83]

The washers should go directly under the clip on the needle.  Above the bottom donut thingy, and below the clip and the spring seat (the other plastic UFO shaped thingy).