First off , 97 evo ,40mm cv, 45/175 jets. BIke runs great but has always had a funky idle , does'nt change idle speed just rythem , if that makes sense. I had the carb off last night and noticed that the throttle plate is slightly open exsposing the transition ports, I backed the idle speed screw out til the plate closed and now it should idle using only the idle port . Put card back on the bike , again it will not idle fast enough until I run the Idle speed screw in enough to open the throttle plate , This also renders the idle mixture screw almost useless , very little effect at all because its running off the transition ports. I have a kit on the way , but I'm thinking its a clogged passage in the idle circuit , any thoughts from the carb experts ? Thanks

 

Clean and rebuild the carb, then let us know what happens. If you don't have any commercial carb cleaner to dunk the carb in use lacquer thinner in a clean one gallon paint can. You ca get this from Lowes, Home Depot, etc. Let it soak for 24 hours and blow it out with high pressure air. Besure to remove all rubber parts first. Oh and check the float level too. Hope this helps.
John

 

I've heard Pine-Sol works in lieu of carb dip as well. Or maybe......SeaFoam?.

 

Seafoam YES! made my carb shine like a new dime........

 

the exhaust is For me the reason its not working as well as maybe it should - and you may have too much low speed jet try a 44 or a 42 just to see if the carb responds

Now as far as the idle screw not being closed when its at idle - not enough air is able to pass the idle circuit with out the door being cracked just a bit - just my take - johnjzjz

 

Check VOES operation.

 

While I agree with the comments above about cleaning, this comment is not correct imho...

When you back the idle screw out until the plate is closed, that is the end of the idle adjustment and if it was supposed to run like that then why even have the idle speed screw. All the idle screw does is crack opwn that plate to change the ammount of air, which changes the vacumn in the venturi, which changes how much fuel is sucked in...

I have seen idle issues cause by the highspeed needle being too high but most common is a dirty carb... I do mine every 20K no matter how it's running...

Ds

 

Sounds like pretty much every Evo on the planet to me....this could also be caused by incorrect idle mixture setting, float height and jet size and even a dirty air filter element.

#45 or 48 idle jet is common in NZ but because your gas is different to ours a 42 is a better starting point as John pointed out.

 

Pine-Sol??? Seriously???

At least Mr. Clean (the old one) looks like a biker...


OP:
I gotta agree with the soak it and blow it crowd. Strip it down, and pull out all the rubber/plastic. Drop the CV into a can full of cleaner. Let it soak overnight and blow it out. Also a good time to check that rubber carb/manifold seal for cracks. Re-assemble with new gaskets, etc. Mine got the thorough cleaning this spring, and honestly it idles better than it has ever idled. Throttle response is excellent.

 

Jets would be what I looked at first, then air filter.