Help!! Failed emissions test. - Sportbike Forum: Sportbike Motorcycle Forums
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post #1 of 5 (permalink) Old 10-17-2003, 02:26 PM Thread Starter
Join Date: Aug 2003
Posts: 4
Unhappy Help!! Failed emissions test.

Hi folks. Need some of that free advice I see posted here. After spending a good portion of the summer restoring my 91 ZX6, I finally got it insured and took it over for emissions testing today. Failed for high hydrocarbons. As a little background, during the rebuild this summer, I rebuilt the carbs. Everything looked OK in them apart from a few trashed o-rings which I replaced. All jets are factory stock sizes according to my manual. I adjusted the float heights per the manual, and set the idle screws to 2 1/4 turns out per the book. She started right up after the work, and I sync'ed the carbs up. It seems to run pretty darn good, but it does seem to "run on" a little when the throttle is blipped. I mean to say that it takes a few seconds for the idle to come back down to normal. In any case, my HC reading was 1924, and the standard (limit) is 1800. They also did a "preconditioning test" (2500 RPM) that read 1868, and the standard for it is 500. Based on those readings, am I too rich in my idle circuit? After reading the shop manual again, it looks like the settings for idle screws might be spec'ed at 1 3/4 (+/- 1/4) instead of the 2 1/4 I set them at. Kinda hard to tell the way the book is written.

Should I close them 1/2 turn and just get it retested, or do you think that will be enough to do the trick? Hate to waste a retest if that isn't going to be enough. I really don't want to pull the carbs again if I don't have to, but if that's what it takes I'll pull 'em. Needless to say, I was pretty bummed when the test tech handed me the failure notice. I was hoping to get in some "legal" riding this weekend.

What do you think given the test results above?

Thanks guys. I'm looking forward to meeting some of you if I ever get this thing on the road.

DRas is offline  
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post #2 of 5 (permalink) Old 10-17-2003, 02:42 PM
Join Date: Mar 2002
Posts: 866
adjust them like your going to, and see if your throttle still hangs, also are your sparkplugs clean still? oh and did you sync them?
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post #3 of 5 (permalink) Old 10-17-2003, 03:40 PM
Join Date: Jul 2003
Posts: 269

First check the valve clearances. It can drive you crazy trying to adjust pilot screws if your valves have insufficient clearance.

In re the pilot screws:

It can be that they're too lean, too. Taking a second or so to come back down to idle after a blip of the throttle is a sign of leanness, usually. Does the bike 'pop' under deceleration with the throttle closed and in gear? Does the bike keep a steady speed at 3-4000 RPM in second? If it surges it's lean.

Probably, though, if the bike is stock, it's slightly rich, like you note. Lean the screws 1/2 turn at a time until it just 'pops' on closed-throttle deceleration. Bring it back 1/4 turn to the rich, and you should be good to go.

Other things that will help: changing the oil, putting in a new set of (correctly gapped) plugs and a new battery can help.

Several local shops will help you tune your pilot screws with a sniffer for somewhere around $20. You'll pass emissions, then. Try Steve's Cycles on Main and Gilbert (thereabouts, anyway) in Mesa, if you live close to there.

For years my CBR would only pass at the elevated RPM. When I put my V&H and K&N on the bike, I changed my pilot jets to #38s (over the stock #35s), and when I did the idle-drop procedure (fourth paragraph above), it passed at 250 PPM HC.


Last edited by cdma2000; 10-17-2003 at 05:17 PM.
cdma2000 is offline  
post #4 of 5 (permalink) Old 10-17-2003, 10:20 PM Thread Starter
Join Date: Aug 2003
Posts: 4
Hmmm. I must admit I didn't check the valves. Believe it or not, the bike only has 5500 original miles on it, so I decided to skip the valve checks for awhile. Might have to rethink that one.

As far as the oil, coolant, plugs, battery -- all new in the last 30 miles!

I have no popping that I can tell. Sometimes harder to tell though with stock exhaust. I turned the mixture screws in 1/2 turn (now at 1 3/4 turns out). Got rid of the run on for the most part. Now have a noticable bog when the throttle is blipped open quickly. I took it for a quick ride around the neighborhood, and I can hold a real steady speed at 4000 revs -- no surging (didn't try this before closing the screws though). I also turned the idle speed down to 1000. It was closer to 1500 for some reason when I had it tested today. I might be good to go now since closing them some. Hate to take it all the way over there again just to fail though. I think you only get one free retest don't you? I'm new to all of this motorcycle emissions craziness here. I may try Steve's as suggested.

As a side note, I have a new V&H SS2R system and Dynojet stage 1 kit to install one of these days, but was hopng to put that off until it cools off in my garage some. I'm anxious to ride the darned thing after spending all summer rebuilding it!

Thanks for taking the time to reply.
DRas is offline  
post #5 of 5 (permalink) Old 10-18-2003, 02:13 AM
Join Date: Sep 2002
Posts: 184
while i don't have the knowledge about adjusting screws and shit like that messing with the carbs...i went through a similar situation trying to get my f2 registered a while back...after sitting for more than two years, the culprit was the old, stabilizer-additive fuel that was causing the prob(for some reason it just never crossed my mind)...a new fresh tank of fuel and a bottle of alcohol fixed me...hope your problem is solved as easily as mine...
dbo is offline  
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