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Re:Bike runs tad rough at constant speed on level or
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TOPIC: Re:Bike runs tad rough at constant speed on level or
#493847
shacky (User)
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Bike runs tad rough at constant speed on level or 12 Months ago  
I have Maxair and Speedstar long drag pits. Curt ported my intake.

Runs pretty good but I notice when I'm cruising and trying to hold throttle at steady state (no acceleration) it seems to be misfiring and sounding shity. Only on level ground or going down hil. If I'm going uphill holding throttle steady it's fine. WOT fine.

Haven't checked plugs but does this sound rich or lean?

37.5 pilot, 175 main, needle on 3rd clip and PMS out 3.25 turns. Elevation 550 in Rochester NY.
 
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Last Edit: 2012/05/21 18:13 By shacky. Reason: correct
 
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#493897
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Re:Bike runs tad rough at constant speed on level or 12 Months ago  
If you have a 172.5 main put it in and put a second silver washer under the needle so you have two on it. I'd also put a 35 pilot in and set the PMS to two turns and ride. You can tweak the PMS a little but you should end up with it around two or 2 1/2 when it runs smooth.
 
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#493906
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Re:Bike runs tad rough at constant speed on level or 12 Months ago  
Here is a blurp from the Mikuni HSR manual.

RICH CONDITION:
If acceleration is crisp but the
engine hesitates or staggers as the
throttle is quickly closed from 3/4 to
1/2 throttle, the mixture is too rich.
Lower the needle one notch and
repeat the test. The needle will be
correct when acceleration is crisp at
mid-rpm yet the engine does not load
up during throttle shut down.

This is the link to The Mikuni HSR Manual and the Tuning manual. http://www.mikuni.com/fs-carburetor.html
Read them and learn from them because what they sau hold true for most all carbs including the CV40.
 
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#494362
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Re:Bike runs tad rough at constant speed on level or 12 Months ago  
Thanks Curt. Went for ride tonight and tried closing PMS a 1/2 turn. Ran better. I'll play with PMS some more till I get up nerve to pop open the carb again.
 
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#497260
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
Curt,

Looked through my Maxair jet kit and do not have 172.5. Smallest I have is a 180.

I was looking at the Maxair lit again and they say 37.5 pilot and 190 main!!!

I trust you more than them. If I need to purchase a 172.5 where can I get them?

I had backed down on accel pump too.

Bike sounds like shit unless I'm pulling. It runs very rough on choke and warm up. Wondering if I should try another direction - up?
 
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#497267
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
Your 180, is probably a DJ jet. Curts 172.5, is a mikuni. The 180(DJ), is smaller then the mikuni 172.5. Do you have a 185(dj) in your kit?
The 37.5 for the pilot, is fine, it will allow you to turn your PMS in further. The PMS will limit the flow of fuel thru the pilot/primary circuit.

Edit,...

If the 180, is actually a mikuni jet, then you should see about getting the 172.5(mikuni) Curt suggested. A 180 mikuni is "Big".

If you still haven't added the second washer under the clip, your still lean in the overlap. 3 is just on the lean side.
 
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Last Edit: 2012/05/30 15:43 By SKWEARpeg.
 
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#497282
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
They came in the Maxxair kit. Did they use DJ?

As I recall bike ran worse with 35 pilot.
 
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#497319
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
After my first comment...before the edit I went and checked, and I think that the maxair uses mikuni's. The 180 mikuni is overkill in my opinion. However, the size of the main, is really only an issue when your at WOT(unless its to small). If you aren't always racing around at WOT, you could have a jet the size of a water hose and it probably wouldn't matter.
I think whats causing you trouble, is the clip in the 3rd groove. Its making the transition between the pilot circuit, and the main circuit to lean. That's why Curt was suggesting the extra washer under the white plastic spacer. That'll give you more fuel in the midrange(what I called the overlap). The 37.5 pilot, is helping to ease the lean in the midrange, but the clip in the 3rd, is retarding the main circuit.
The reason the bike runs better at WOT, is because the slide has lifted the needle, and the fuel is flowing freer. Your out of the midrange at that point. When your just driving along, and the bike is at 1/4 throttle, the needle isn't letting enough fuel past, because the clip is in the third.
Just my thought on this,...it seems like Maxair realizes that the bike will need more fuel in the pilot and midrange, so they put the 37.5 pilot in to cover that, but then they choke off the overlap by putting the clip in the 3rd groove . This is causing a lean lag, crappy running in the midrange(cruising in 5th, at 55 to 65 mph).
I have the 37.5 in mine, and am happy with it, and I'm running the poormans BAK. You really should be fine, because you can use the PMS to lean it out if needed.

Here is a link I think Curt posted before for mikuni's..
http://www.pjmotorsports.com/mikuni-jets.html

If the kit didn't have an extra washer, you can put the clip in the 4th and see what happens. You may have to turn the PMS in just a bit more if you try that. You can do it with the carb on the bike, just pull the tank, and the top of the carb is right there, Remove the two screws, take off the cap, and lift out the diapragm and slide, and move the clip.
 
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Last Edit: 2012/05/30 18:13 By SKWEARpeg.
 
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#497329
shacky (User)
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
Thanks! I was reading the link you suggested in another post and was coming to same conclusion about the needle clip. It runs great WOT. And I like that I don't have to pull carb - though Curt taught me to drop the bowl for jets
 
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#497379
shacky (User)
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Re:Bike runs tad rough at constant speed on level or 11 Months, 3 Weeks ago  
Skwearpeg you get a Gold Star !!!!

Put the needle on 4th clip with one washer. Zipped her up and took the misses for a ride. Never ran smoother!!! B$%^ is smooth.

Mama said wow it's riding real nice.

When Mama's happy...

Thanks Skwearpeg!!!
 
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