Senior Members Please Help Troubleshoot!!

[Mack]

Wish I could post this in the main forum. Sorry to post again but I am really in a bind. Here it goes again.

Hey guys,

Have an 84'R that seems to run fine until nice and warm. Once warmed up, whenever I bring it down to an idle it wants to rev really high. I was thinking it may be running lean so I took the carb apart only to find the guy I bought it from had a 120 main jet in it when the spec calls for a 130. I changed it and now have the 1/2 to wot power I was missing but it still wants to rev way higher than it should when I idle down. I have good compression maybe even a little high considering my gauge is 100% accurate 180psi consistently. All intake boots are tightened snug, exhaust flange to pipe is sealed with rtv, new plug ( with great spark) , fresh 32:1 mix, clean filter and carb, and idle and air fuel mix dialed in after a couple minutes of warming up. This problem doesn't happen til I've ran it for 5 or 10 minutes but stays consistent. any insight would be greatly appreciated. wanna get it dialed in before I go balls to the wall. also, there is no oil in the dry side of the case so at least that crank seal is good.

[jb2wheels]

What's your plug look like when this happens?

[yaegerb]

if he changed the main, are you sure he didn't mess with the pilot as well? If it is idling erratically that's what I would look for. General rule of thumb: On idle to 1/4 throttle you run on pilot, 1/4 to 3/4 on needle and 3/4 on its running on the main. Also sounds like a potential air leak, so ensure that your vacuum is good and gaskets are solid. I would check is a sticking slide. Sometimes the slides varnish up with age and either the slide or the carb throat makes the action stick. Last, ensure that your throttle cable/return springs (both in carb and in thumb/twist housing) are operating properly. If all that checks out let us know.

[Mack]

Pilot jet is stock #50, Slide is functioning properly but I'm beginning to suspect an air leak as well. I just picked up the parts for a homemade leak down tester for 14 bucks. Does this seem like the next thing you all would test? Ill post pics in a separate thread since I can't add to the the existing leak down thread. Im a new member.

[Mack]

Plug is white but I'm running 93 oct pump gas and I heard pump gas is known to give inaccurate plug readings. plus I didn't check it after wot, just after idling. I'll check that tomorrow too.

[yaegerb]

White indicates a lean condition....I would perform a thorough plug chop when you have time.

[yaegerb]

Yes, I would perform a leak down test asap. Could also be the reason your plug is white....excess air getting in somewhere.

[Mack]

Thanks guys. Plan on testimg it first thing in the morning. Will post results

[RIDE-RED 250r]

You are on the right track with your doing a leakdown test. White plug is definitely lean. Now to find out why... Keep us posted.

[Mack]

Hey guys just did a leak down test. Pumped it up to 7 pounds and it lost 1 pound in ten minutes. Let me know how these results sound to you. I'll probably go run the test a couple more times just to get an average result and maybe break out a spray bottle of soapy water. Thanks, Mack

[v30Magna]

Not a senior member, but if it idles high after goosing it, it's possibly an air leak, which the white plug might be indicating. It often means a surplus of fuel, like if your slide is getting stuck, or if the carb has been improperly tuned to run better with an underlying problem (like a carb that has had the needle raised too much or too much fuel from the idle adjustment screw to compensate for the wrong jets). A carburetor with too large a venturi for your engine may do it too, and be impossible to tune.

[Mack]

I did the leak down test twice more with the same results. At 7psi it will lose 1 pound in 10 minutes and barely any more after 20 minutes (maybe an 1/8 of a pound more). I put it all back together with a new exhaust gasket and lightly greased the air box where it fits into the intake boot of the carb. Fired up on the second kick. After 15 to 20 minutes of riding some wheelies and hauling ass around the backyard I did not notice this high revving thing when i brought it down to idle. not once. I think i was taking in air between the air box and the carb and greasing it sealed it up. Let me know if this sounds inaccurate.

However, my idle screw is now pretty much all the way in and I had to back my air/fuel screw out to 2 full turns to achieve good idle. this doesn't seem right with stock carb, keihin stock size jets, stock exhaust etc. I have a new filter but its just a foam oem looking pro design filter. I don't see that letting enough air in to justify jetting larger. and btw its like 65 degrees and sunny at sea level

Any advice or info would be appreciated. idle all the way in and air/fuel setting just doesn't seem right

Thanks, Mack

[Alberta250r]

I just put a carb kit in my 84 and idel screw 8 full turns in from all the way out and air/fuel screw is 5 1/2 turns from all the way out, it starts and runs nice, brown plug, and like eveyone said it sounds like a leak somewhere, check the aluminum plate between your carb and reed cage, ive had one crack on me before and do the same thing you describe, eventually i blew it up

[Mack]

I'll definitely pull out the reed cage and have a look at all that.. The thing is, I sprayed carb cleaner around all the intake boots and the reed cage as suggested above and it didn't cause any revving and once i greased the air box/boot seal, it stopped revving high when I idled down and would idle properly. I just can't figure out why the idle screw is all the way in and I had to back out the mixture screw to get proper idle. I also did a plug chop and it came out dark brown. Thanks for all the good info and suggestions.

[badass350x]

Thats like taking air in from your filter, basically you just sealed off dust from getting in the carb!

[Mack]

I just put a carb kit in my 84 and idel screw 8 full turns in from all the way out and air/fuel screw is 5 1/2 turns from all the way out, it starts and runs nice, brown plug, and like eveyone said it sounds like a leak somewhere, check the aluminum plate between your carb and reed cage, ive had one crack on me before and do the same thing you describe, eventually i blew it up

By the way, what kind of carb did you put in it? PJ34 by chance?

[badass350x]

Check out your reeds, but it sounds like a carb problem!

[Mack]

Thats like taking air in from your filter, basically you just sealed off dust from getting in the carb!

So you're saying an air leak that would cause high revving would only take place after the carb?
I guess now that I think about it lol my bad. It doesn't matter how much air is getting in the carb as long as your mixing enough fuel with it.

[Mack]

Any suggestions on what kind of carb problems I could be facing? I've rebuilt the damn thing 4 times this week. cleaned every hole I can see with carb cleaner and compressed air. factory recommended jets installed.

[badass350x]

Correct!!!

[badass350x]

Thats the round slide carb correct? Factory carb?

[Mack]

yep, keihin PE30.