idle mixture

[armyofda12mnkeys]

sweet, Yamaha forums is back...

So i thought id give a shot at messing with my idle mixture screws a few days ago. The right cylinder seemed to be weak, Think i just rotated the right carb screw out a few turns as to see what would happen and it idled better than before ... so i was satisfied... but i went riding today and it seems to chug along (felt like bike was going 'up and down', like it was getting gas then less gas)...

so i was going to set the screws the right way. aka go all the way down on both screws till hit some resistance then pull it back out 3.5 turns as peeps recommend here...

I did that and i think it ran worse heh. like engine was not getting enough power at idle, and would turn off.

then i was thinking the springs underneith the idle screws might be making me think it has hit resistance when it hasnt...

so i took the springs off... and screwed it in to see how far i can go without the spring giving me extra resistance.... counted how many turns it took to get to the 'bottom' and then i would turn it out 3.5 turns... then count turns it takes to unscrew it off again... then put the spring back on and go that many turns down... doesnt even start up now heh.

EDIT:

i took out my spark plugs and saw were a lil wet from gas from one of the settings no doubt.

I must have made it too rich? before...

it starts up now and idles well. I took it out for a spin and when i give it throttle uphill in 3rd gear, it chugged along and bike turned off. Does that mean i need to enrich it, or maybe its too rich now and i should lean it?

Doesnt make much sense cause its at 1/4th-1/2 throttle which is not responsibility of idle mixture screw heh. I'll ride it a lil' more tomorrow in case needs to get some hiccups that the initial idle setting screwed up maybe.

I still had my original questions of

1. how many turns in theoretically should it take till it hits resistance.

Im asking as its hard to tell with the spring on as it gets a lil hard to turn at 8-9 turns in (but without the spring it'll go 11-12 turns in easily i think)... I kinda got scared and just turned both screws in 9 turns, versus going all the way down and pulling back 3.5 turns...

2. what happens if you go too far...

will the screw break off as it gets close to a flat metal part inside ... or is the tapered sharp end going inside a hole and eventually hits resistance of the outside edge of the hole its going into (and hence shaving off the screw/tapering it more at some point)

Here are my screws, the left one seems a lil more tapered, yes no?:

Here is my bike at idle if anyone is interested, Im not sure if its normal for the bike to sound like it does (esp sounds coming out of the contact points area) so thought Id ask peeps to listen (this is unrelated to idle mixture problem above, it has always sounded like this):

[HoughMade]

That doesn't sound bad at all. There seems to be a little valve noise when you had the mic right up by the valves, but nothing too serious. It may be worth checking the clearances if you have not done that lately.

As to you questions, I don't know how many turns in it should take to bottom the screws- I just go by feel. Your screws look fine. If they are forced in to far, the tips can be flattened or even broken off. Y'know, I'm so dense that when I first adjusted the idle mixture (at least the first time I did it right), I has to put a dot with a Sharpie on one side of the screw so I could keep track of the turns out accurately. I use about 3.25-3.5. The first time I tried it at all, I was used to servicing a different kind of engine where carb adjustments were described in terms of how many "flats" the screws were turned out- this means every time the screw slot is turned so it is oriented in the same way is a flat...which means only a turn of 180 degrees instead of 360...but I soon learned the error of my ways...but I digress.

When the throttle is open, I wouldn't thing the idle mixture would effect much. Have you ever modified the main jet or needle? If not, it's probably not that either. Have you balanced the carbs? The idle sounds pretty good, but if you have not, give that a shot. If your plugs look carbon fouled, it may be time to lean it a bit, I guess, but again, if the problem is when the throttle is open....how are your air filters?

[drewpy]

if you scerw in too far you will seat the tips and they will grip the sides and snap off.

aircooled engines are noisy beasts, oil level ok?

check valve clearances (tappets are for OHV engines )

cam chain can slacken and you can get piston slap if bore is worn, but it don't sound like that.

you can get a long screw driver and hold the handle to your ear and touch the other end against the engine, this cam pin point any dodgy noises.

drewps

[Noah]

clean the fouled plugs or replace them, check the oil level aswell as your valve tolerances since it does seem to be some valve clattering, I know it's hard to hear everything in a vid that was heard in person, you could also try to use some stuff that I forget the name of but you spray it into the carb with the engine running and at a medium rpm and the stuff foams up inside the engine and stalls it out let it sit for the time the can says then start it back up and you'll see this huge black cloud come out the pipes as you rev the bike close to redline and all the carbon build up in the cylinders comes blowing out

[armyofda12mnkeys]

if you scerw in too far you will seat the tips and they will grip the sides and snap off.

Cool, I kinda get the jist but its hard to imagine without a drawing or pic of the parts it is going against (not really sure what ya mean by 'seat the tips').

Getting an extra carb tomorrow to play around and rebuild. Maybe I'll open it up and understand better.

aircooled engines are noisy beasts, oil level ok?

Yeh, oil level is at upper end. It has a little head gasket leak but thats a fix in the future.

check valve clearances (tappets are for OHV engines )

k, I'll check the valves at some point soon since you both seem to agree it may be valve noise.

You could also try to use some stuff that I forget the name of but you spray it into the carb

I wonder if Noah means the product Sea'Foam' (i guess he means something else though as SeaFoam seems to be a more longterm liquid treatment you do via fuel coming into engine and treating it... or put in the crankcase as some peeps say it cleans up junk)? Where would you spray it 'into the carbs' (like should you spray it into the airbox or fuel intake?).

Have you ever modified the main jet or needle? If not, it's probably not that either. Have you balanced the carbs?

Nah, just messed with the clutch adjustment and idle mixture adjustment that day. Maybe the plugs are still not clean enough. I'll clean them off and see whats up (can i just use solvent or rubbing alcohol on a paper towel to take off some of the black, so i can diagnose mixture better?).

[Noah]

I don't believe it's seafoam, the stuff I used in the past was made specificlly for a certain jeep engine that has notorious issues with carbon build up, it was my buddies jeep and he got the stuff, I just helped him, he had me spray it directlly into the carb.

what is ment by seating the tips is where the jets screw into is basiclly the same size and shape as the jet it's self so when you bottom out the jet the tip of it is "seated" in the hole making a really tight fit, the problem with bottoming out jets is that the tip is very small and fine and can be bent or worse it can be so over tightened "happens very easily" that the tip snaps off in the hole. think of seating as the same with valves you have to grind the bevel just right so it seats proper without any gaps.

[armyofda12mnkeys]

hmmm so i may know why it started chugging along... one of the spark plugs wasn't getting a white/blue spark like the other one was. i tried it in different sides and same result. however it did start working alright after a while. Both are gapped to .030. Still couldnt get her to start. Im just going to buy new plugs tomorrow and try them out. otherwise it may be the coils or something but i doubt it. Think the gas/carbon from the bad idle mixture setting fouled up one of the plugs.

[Noah]

it's possible one of the plugs got fouled, try taking a small, soft wire brush and cleaning the plugs up or just go ahead and get new ones since they are cheap insurance.

[armyofda12mnkeys]

it's possible one of the plugs got fouled, try taking a small, soft wire brush and cleaning the plugs up or just go ahead and get new ones since they are cheap insurance.

Cool I shall...

Someone passed me some nice pics to show where the idle mixture screws generally sit against in the carb.

The 2nd picture he said someone broke off the tip on left side (as its just stuck in the hole), (and the right side, he did some major damage and tried fixing with JB Weld)