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Message started by JohnBoy on 08/06/10 at 11:58:54

Title: Wont pass emissions test!!!
Post by JohnBoy on 08/06/10 at 11:58:54
I need a little help...(the wife says “more than a little!”)
I changed the exhaust and the intake to let this big single breath a little better, and to climb out of the 25 horsepower hole it was in. But, it is no where close to passing emissions testing any more.
I had re jetted the carb to go up to a 155 main and a 55 pilot from 142 and 52.5.
I run a longshot straight pipe with Diamond Jim's baffle mounted at the end of the pipe.
It was actually fun to ride!
The emissions test said that Hydrocarbons were at half the allowable limit of 1800 with a reading of 513. Carbon Monoxide, on the other hand, was 10.13 with a limit of 5.5!!!
A local bike shop suggested that the straight pipe was not creating enough back pressure. They said that the failed CO reading was most likely due to raw gas being pumped through the system.
I reduced the main down to 150 and put the original pilot of 52.5 back in. With the original pilot back in the bike cracks and pops with every up shift and down shift. but feels strong through 85MPH.
I also plugged the baffle with Rock Wool to the point where it is hard to hold an idle. The baffle is a tight fit and designed so that all exhaust is forced through the baffle.
Absolute top speed (WOT) is 67mph!
The bike still failed with readings of 705 Hydrocarbons and 9.52 Carbon Monoxide.

I realize that it is a “Big Single” but I shouldn't have to choke it down to the point where your average 250cc will out run it, just to pass an emission test.
I hate the thought of doing an annual re-jet just to pass emissions ( in the only county in the country that still smog test bikes).

Any ideas or suggestions that don't include putting it back in stock condition?

Title: Re: Wont pass emissions test!!!
Post by CalisOsin on 08/06/10 at 12:15:43
i just had a problem passing emissions as well. i was at 10.5 Carbon Monoxide. All i did to pass was adjust the air/fuel mixture screw on the right hand side of the carb (remember how many turns you adjust). I tightened that screw all the way as lean as it would go and still run and lowered my idle as low as it would go as well. I passed the test under 1 Carbon Monoxide. Then i turned it all back to where it was.

Title: Re: Wont pass emissions test!!!
Post by Serowbot on 08/06/10 at 13:09:08
Turn up the idle speed... ;)... try to go up about 200 rpm...

Title: Re: Wont pass emissions test!!!
Post by JohnBoy on 08/06/10 at 13:51:40

44666B6E7448746E69070 wrote:
i just had a problem passing emissions as well. i was at 10.5 Carbon Monoxide. All i did to pass was adjust the air/fuel mixture screw on the right hand side of the carb (remember how many turns you adjust). I tightened that screw all the way as lean as it would go and still run and lowered my idle as low as it would go as well. I passed the test under 1 Carbon Monoxide. Then i turned it all back to where it was.


How close to stock is your machine? I believe this one would idle fine with the mixture screw turned all the way in. I would love to think it was that easy. "living in hope here"
Oh Yeah, I was told by several people that we were the only place in America still smog testing bikes...obviously that is not the case.

Title: Re: Wont pass emissions test!!!
Post by JohnBoy on 08/06/10 at 13:53:40

60424F4A506C504A4D230 wrote:
i just had a problem passing emissions as well....


Ha Ha Ha...I just noticed you are also from Maricopa...What are the odds!

Title: Re: Wont pass emissions test!!!
Post by Serowbot on 08/06/10 at 15:15:39
It sounds like reverse logic but,... raising the idle speed will usually lower emissions...  I used to do it in my car all the time, to get it to pass...

Notice on low speed tests, the emissions are always lower than the idle test...

Title: Re: Wont pass emissions test!!!
Post by Max_Morley on 08/06/10 at 15:50:47
From my emissions training days, HC are usually from ignition or misfire problems ie unburned fuel going out the exhaust.  CO is from mixture levels, your high numbers indicate too rich idle mixture, as suggested turn in the idle mixture screw until just before lean misfire. Won't be the smoothest idle but should pass. cruise (2500 RPM) will also benefit from this as there is no load so the needle is low in the jet. Also as suggested having the idle at the high end of the allowed range will helps. Max

Title: Re: Wont pass emissions test!!!
Post by JohnBoy on 08/06/10 at 19:24:20
OK, I have another question.
I turned the idle mixture completely in to the stop and took it for a ride. It never tried to backfire one time, on shut down it did a very weak "poof!" but nothing more. I never got it above 3000rpms and I was only out for about ten minutes but I expected it to run really rough with no fuel?
Would a high float level or a stuck needle cause the overly rich readings while allowing the bike to run smoothly with the idle mixture screw turned all the way in?
I didn't mention that I do have Diamond Jim's "Terbulator" installed and the purpose is to increase air speed and lower pressure through the carb, but I can't believe that it would make "that"much difference.
Any ideas? Thanks for the help.
JB

Title: Re: Wont pass emissions test!!!
Post by verslagen1 on 08/06/10 at 20:55:27

052027210D20364F0 wrote:
OK, I have another question.
I turned the idle mixture completely in to the stop and took it for a ride. It never tried to backfire one time, on shut down it did a very weak "poof!" but nothing more. I never got it above 3000rpms and I was only out for about ten minutes but I expected it to run really rough with no fuel?

sounds like your idle mixture jet is a size too big.

Title: Re: Wont pass emissions test!!!
Post by BuckHMCC on 08/07/10 at 16:26:43
Well done, the bike is slower, louder, and pollutes more than stock. To successfully modify an engine's breathing oft times requires the use of instrumentation and a dyno, and training on their use.

Title: Re: Wont pass emissions test!!!
Post by JohnBoy on 08/07/10 at 17:39:40

5D6A7C7457525C5C1F0 wrote:
Well done, the bike is slower, louder, and pollutes more than stock. To successfully modify an engine's breathing oft times requires the use of instrumentation and a dyno, and training on their use.

Buck, the bike after I worked on it, is definitely not slower than stock!
In stock form it cranks out about 26HP so does my 250 Honda. In the 1960's the 500 and 650 British bikes ruled the isle of Mann. All I want is to have it run at it's full potential. Is it louder...yes! Does it pollute more...yes! Does that bother me...not in the least. The day it passes emissions is the day I start putting it back the way I had it. Now If I had access to a dyno that would make life easier, in the mean time I will work with what I got.

Title: Re: Wont pass emissions test!!!
Post by CalisOsin on 08/17/10 at 19:08:39
@JohnBoy - sorry for the slow reply. I believe the bike is stock, but the cap over the air/ful mixture screw was already drilled so I'm not certain. This is my first bike and while I am fairly mechanically inclined, I've never done much with carbs. Took this one apart to clean it once but that was because of an unrelated issue. Can anyone tell me how can you tell the jet size? Do they have the sizes engraved on the side of the jet?

Title: Re: Wont pass emissions test!!!
Post by JohnBoy on 08/18/10 at 23:56:00
Yes the jet sizes are marked on the face or side of the jet.
Find a magnifying glass, you will need it.

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