OK, a ton of confusion exists with these. What do you have for main jets ? 70 or 125 ? The problem range is as you describe, partial throttle. However, the slides are very much a part of the fuel feed at that RPM. Can I assume you had these completely apart ? Any chance of having exchanged the slides / pistons ? AND, possibly rotated the caps ? The caps should read from the riders position. (embossed lettering) A possibility is the slides not responding till you apply a ton of force via pressure diff. The problem you are encountering is not a common one. Most often, the glitch is right off idle when pulling out. Please confirm above before we proceed. Check for scaring on the slides. The fit of the slides and caps is a hand selected one and very critical. Under the caps are some passages that bleed air and should be checked for open. The carbs used on the '86 are quite different from others.
--- On Sat, 10/3/09, JFTdiesel <[email protected]> wrote: From: JFTdiesel <[email protected]> Subject: [Nighthawk Lovers] Re: `86 450 carb question To: "Nighthawk Motorcycle Lovers!" <[email protected]> Date: Saturday, October 3, 2009, 12:31 PM Hi Dennis, I appreciate you looking into this a little for me. To answer your question, this bike has one each a VB2EA and a VB2FA (single LH accel pump w/ a cross-over tube to the RH carb). And to clarify the behavior a little more, the stumble seems to be independent of RPM; 3rd gear 3K RPM 35 MPH or 5th gear 6K RPM 60 MPH cruise, the stumble is there until you roll-on power. So, my thinking a this point is that the stumble is tied to throttle plate position (just off idle and approaching part throttle) and thus working solely off the pilot circuit. And playing with the idle screws seems to only affect the low idle. I Hope this is useful info for you. And why not talk about smaller carbs? The way this bike is going to be ridden, it does not need max top end - it's primarily a commuter bike, so great low end / mid-range throttle response/power is really the goal here. JT On Oct 3, 12:27 am, Dennis Hammerl <[email protected]> wrote: > An excellent question. I haven't had to deal with one of those in years. > Since you seem to be quite able to perform changes, I might make a few > suggestions. First off, are these VB2FB carbs ? No 400 / 450 really ran all > that well off idle till engine temp came up. So replacing with some other > carb pack won't be much of an option. You increased the fuel at slow speeds > by 2%, which isn't very much. Another 2% (#42) might help some but you will > encounter a point of diminishing returns quickly. The problem being that > there is insuficiant air speed at low RPM's to atomize the fuel and carry it > in. Two factors are at work here; to provide performance the carbs are rather > large (throat area which causes low air speed at low RPM) and the compliance > with EPA for emmisions (lean)... These are not good companions. It is > essential to have all the air-box parts in place (with filter) for one of > these to run. To achieve "driveability" I prefer to attempt to increase > air speed rather than simply jet larger. Believe it or not, smaller carbs >make one of those fun to ride. Let's not go there. > I'll do some research and see what we have done in the past to correct this > problem. > > --- On Fri, 10/2/09, JFTdiesel <[email protected]> wrote: > > From: JFTdiesel <[email protected]> > Subject: [Nighthawk Lovers] `86 450 carb question > To: "Nighthawk Motorcycle Lovers!" <[email protected]> > Date: Friday, October 2, 2009, 10:53 PM > > I picked up an `86 450 this spring for my wife (newbie rider and > lovin' it!) and have put about 1,500 miles on so far (11K miles at > time of purchase). I went through the fuel system very thoroughly and > am confident that all is working as it should - mostly. But, I do not > seem to be able to get rid of an off-idle cruise stumble regardless > of the gear or speed. Part throttle or more and rolling-on throttle > is fine. I brought the pilots up 1 step to a 40 which improved a few > things but not this stumble. Low idle is perfectly smooth, vac is > 20"+, sync is perfect, plugs are lean(ish) but clean. The little bit > of research that I've done says that these `86 carbs are purposely > very lean. I'm fairly knowledgeable about carbs and carb tuning so my > question is this, is it worth the effort to "un-lean" these carbs or > should I just swap the `86s out for an earlier set (or something else > altogether) and go from there? Any links/resources or known > procedures, etc. would be greatly appreciated. > > Thanx! > > JT --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en -~----------~----~----~----~------~----~------~--~---
