Edelbrock Quicksilver - Tuning Problems

With all the hearty endorsements of the QS having been posted, I bought and installed the new carb before going on vacation last week. Installation was a breeze, but initially I couldn't get the bike started. Came to realize that the "enrichener" was partially on.

With the starting problem behind me, I set out to ride with the adjustments set as they came with the unit. Unfortunately, the bike exhibits a severe flat spot when the throttle is opened briskly from an off idle postion. Even with a fully warmed engine, grabbing the throttle in gear from an idle or close-to-idle engine speed results in the engine quitting. It will recover if you let off the throttle in time...otherwise flat out stall!

I have tried adjusting the mixture leaner and richer to no avail and have tried turning the pumper delivery adjustment screw inward up to a full turn and a half (again with no positive results). Presently, I have it back at the factory mixture setting, and the pump delivery way to the heavy side. All indications are that this is a lean tip-in hesitation. With the tank on and off at least 15 times, I'm out of answers, and would be so very appreciative to hear from others with advice!


Jim Turnure

Maybe an intake air leak? Sounds similar to a Harley with an intake leak. Try starting the bike and squirt starting fluid (with a straw) ever so slightly around intake and listen for idle change.

you can also try a richer needle and adjust it leaner than needed.

When I had the xr6 with the eddy carb, if it ran rich it never that. So I think you are on the right track.

Ummmmm...good thought on the air leak! I did in fact overlook a check for false air, but unfortunately a few shots of carb cleaner revealed no leakage. I just received an email suggesting that I try the richer needle. This confuses me a little...as I'm unclear how the richer needle set leaner would translate into the off-idle flat spot going away. ???

Thanks, Jim

You will not set the needle leaner than the smaller unit. What I mean is that from the stock needle you have now, when you install the richer unit, you will have to adjust the richer needle leaner than what you have now. You do this with the adjustment at the top of the carb.

sorry if I confused you


No confusion here dude...just a little unclear as to why the different needle would overcome the engine hesitation/stall off-idle. I've not looked at the other needles that came with the unit, but suspect that the rich needle has a different overall profile??? and that this is what allows for the off-idle enrichening that is apparently needed.



There are also some special needles that Edelbrock sells.


The larger the number on the needle, the richer the mixture. Needles with "-1" are richer off-idle.

So if you find the rest of the power band off idle is fine, you may want to try a -1 needle.

I have experienced similar symtoms when I adjusted the accelerator pump too rich - thats right, I said too rich.


I found some notes I had on my Edelbrock settings and I believe I ended up at 12 clicks out for the mixture and 2 turns out for the pump, which is a leaner pump setting than stock by 1/2 turn if I remember correctly.

My bike was at my brother-in-law's house in perfect working order with strict instructions to be left alone so I could ride it out there during Thanksgiving and then bring it home afterward. It no longer runs thanks to him and is missing parts. This is yet another case where I can tell my wife...I told you so!

All recommendations followed / all settings tried! This thing came back off the bike last night in order to dry out before being sent back to Barnum's. These folks have really been gems to work with, are sending me a shipper and promise quick turn around. I sure hope that they are able to identify something definitively wrong (or are at least able to point out where "the installer" screwed up).

Thanks to all for your thoughtful input. I will inform the group as soon as I have an update.


As I promised in my last posting, it was my intention to post an update when the 'brock returned from Barnum's. The unit showed up at my door last Thursday, preceded by an email from Rob Barnum in which he explained that the factory had found a problem in the float bowl. Evidently, the float bowl was unable to transfer fuel properly to the pump chamber, resulting in a dead-off-idle condition that could not be corrected through tuning. Rob informed that they replaced the float bowl.

This morning, I had an opportunity to bolt it on and give it a try. The bike started well with the enrichener 1/4 way on and I allowed it to warmup fully while backing the enrichener off. Warmed up, I took it out (20 degrees outside) and it appeared lean with a hesitation and exhaust popping during decel. I gave it 4 clicks clockwise and it now "smelled" like it should at idle! Now, it would respond well to opening the throttle sharply at any RPM except right off idle. Off-idle sharp opening still produced a stall unless you backed off immediately. I tried increasing the pump shot 1/2 turn and the condition is practically eliminated.

Come warmer weather when I get a chance to actually get out and ride, I'm pretty sure that I still need to adjust the pump shot and possibly the mixture, but overall the problem appears to be solved.

Either way, Barnum's demonstrated super customer service and really wanted to make sure that this customer is happy...he is. The exemplary service and follow-up makes me inclined to be much more tolerant about the less then stellar quality control that apparently initially went into the unit.

Happy New Year All!


good news! You will be tunning for a little while and then just be riding! The best thing about that carb is the lack of random caugh outs on the XR6 motors and being able to start it first kick any time.

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