Carb tuning help

[donimo]

I think I must be missing something easy, but my carbs seem to be rich AND lean?

At idle I have tuned the air screws as lean as they will go with out stalling, but it still smells rich (but idle is just idle so...)

if I rev the throttle in neutral I get black smoke, not a lot, but enough that it seems rich still

my new supertrapp is pretty black already, again rich.

the verry VERY end of the tip of the spark plug is a dark grey, which seems like it is a bit lean.

The bike is stock, valves were done last year, carbs synched too. Exhaust is a MAC 2-1 with a supertrapp with 5 discs in it.

I am extremely strapped for time right now so I was hoping someone had a similar situation and could shave a few hours off the procedure.

Bike seems to run fine otherwise though, nice idle, smooth power, no stumbles or dead spots...

I can ride it this way but i would rather have it tuned right (duh), I have always had trouble with carb tuning (on cars before), I must be missing something...

 

[Steve]

Which way are you turning the screws to "lean" the mixture?

How far out are they from lightly seated?

Yes, it's possible to be rich and lean, but it would have to be on different circuits. You could be running very rich on the idle circuit, but lean on the mains, or the other way around.

I see that you have a MAC and a 'Trapp. How about the air filter? Has the bike been re-jetted at all?

What you will have to do is "plug chops", where you hold a particular throttle setting for a set amount of time, hit the kill switch, pull in the clutch and coast to a stop in a safe place. Pull the plugs to see what the color is. You HAVE to use the kill switch to stop the engine. If you are doing a full-throttle run to check the main jets, idling for just a little bit as you come to a stop is enough to destroy the color that the main jets put on the plugs. You have to isolate it to operation on just one carb circuit to see where your problem lies.

Sorry if it takes some of your time, but that's the way it is.

.

 

[donimo]

Ergh I know, finishing reno's selling a house, inspecting a new house and a 1.5 year old are killing my free time thouroghly...

Jetting is untouched by me, bike came bone stock except for tires and some chinese mufflers strapped on the stock head pipes. Based on the shoddy muffler job I doubt anyone fixed the carbs.

I will check the air filter tonight but it was new last year.

I will try to get out and do some plug chops just seems odd that adding a 2-1 and a much freer flowing can would result in a rich and lean condition...

fuel injection has it's upsides...

 

[rapidray]

First thing, you don't turn the mixture screws as lean as they will go! You adjust each screw, one at a time, in or out till it idles as FAST as it will idle with that carb. If the idle jumps up a lot while adjusting one, turn it back down to idle speed & continue. After you have done one, move on to the next & continue down the line. After you finish that I would check carb sync next & then continue tuning. Ray.

 

[Steve]

After you have done one, move on to the next & continue down the line. ...

The nice part about his bike, once he does one, then the next, ... he's done.

There is no "down the line" with a twin-cylinder.

.

 

[donimo]

First thing, you don't turn the mixture screws as lean as they will go! You adjust each screw, one at a time, in or out till it idles as FAST as it will idle with that carb. If the idle jumps up a lot while adjusting one, turn it back down to idle speed & continue. After you have done one, move on to the next & continue down the line. After you finish that I would check carb sync next & then continue tuning. Ray.

Sorry, I said it wrong, I meant smoothest/fastest idle. I was meaning that I was fairly certain the mixture screws weren't set too rich.

I synched the carbs last summer.

 

[rapidray]

Domino, if you want some help, give me a call at 714-356-7845. Ray.

 

[donimo]

Domino, if you want some help, give me a call at 714-356-7845. Ray.

I am in the middle of buying/selling/moving right now, but I will take you up on that Ray (you may regret it ha).

One other thing, my choke seems to just chug out smoke, and not oil, like pig rich. Maybe a tiny bit blue. Is this common? Its really hard to get it in a place its happy too (the choke).

I took out the air filter and it did seem a bit over oiled. I wasnt at home when I did it (just killing time waiting for someone) but how oily should it be?

Plugs still hard to read, covered in black soot AND the tip is grey. rich/lean, rlean...lich?

I hope to spend some quality time with the bike in a few weeks when my wife doesnt have me doing EVERYTHING, just most of it...

 

[donimo]

anybody else have a choke that pukes out the stinky dark smoke?

 

[rustybronco]

Nope.......

Plugs still hard to read, covered in black soot...

if I rev the throttle in neutral I get black smoke, not a lot, but enough that it seems rich still

my new supertrapp is pretty black already, again rich.

Jetting is untouched by me... Based on the shoddy muffler job I doubt anyone fixed the carbs.

time to spend some "quality time" with those carbs.

 

[TheCafeKid]

Nope.......





time to spend some "quality time" with those carbs.

Indeed, I agree with Dale. For starters You need to make ABSOLUTELY SURE your float levels are correctly set. As little as a tenth of a millimeter or two can make a vast difference (I know, I learned the hard way a long time ago) Also, turning the screws OUT will richen the mixture. It sounds, by your own explaination of your plugs and the soot on your 'Trapp..(i had the same issue on my 1100) that you're definately rich on the pilot circuit. The CHOKE circuit isnt really that, its more of an enrichener, unlike a car choke. It will dump quite a bit of gas into the system, and opening the throttle will cancel its effectiveness. What it sounds like to me though, honestly, and its hard to tell just over the web here, is that either your floats are set much to low (allowing more gas into the bowls before the float hits the shut off) or your pilots are just way too far out. Or both. With that exhaust, you'll likely need to fiddle with the main and needle settings to get it running perfectly, but one step at a time.

My 1100ES came to me with a 'Trapp and pods on it, and seemed to run OK except it was rediculously rich down low. Tossed soot all over the place...and i was constantly smelling gas. I found that whomever had 'jetted' the carbs for the pods and pipe had simply gone huge on the main jet, and had the float settings all screwed up so the bike got enough gas to perform even adequately. After installing a Dynojet kit, fixing the float level, and some tuning and testing, it revealed to me a WHOLE NEW LEVEL of power.

I recently installed some larger carbs, and again, another level of power..
At any rate, check on those float heights, and once you have them set as per the manual (they have to be EXACT to have a good baseline to tune from) Shut your pilot screws down to lightly seated, back them out to 2.5 turns out, and then see how she feels/runs.... Let us know!!

 

[donimo]

OK, fair enough, it would be the ONE thing I forgot to do when I tore apart the carbs for a complete rebuild last year.

I did everything but bench sync and float level check. I always seem to forget something when I do stuff like this, and it usually turns out to be that one thing that messes up. The carbs were spotless and all the o-rings looked new, I replaced them all anyways and it turns out the one thing that was wrong is the thing that is "free", sounds about right

I have checked the pilot screws probably 10 times now, reseating and tuning to best idle.

The choke/smog issue was there before the rebuild too, choke seems to do what it supposed to (can be finicky) but just eye wateringly smoky (wife loves that)

I agree with the pipe I should be a touch lean up top (and that explains the juuust lean tip on the plug) but I think I have something else to sort out first before I tackle that one.

Floats sounds right now that you say it, now to find the time to pull the carbs and check (why not design them to be checked installed? )

 

[donimo]

So, found some time so here is an update:

- Took off the carbs and gave them a once over, turns out the floats WERE off by about 2mm, but they were too low, I set them up to spec (22.4mm) anyways.

- While I was in there and it was staring me in the face I swapped the 120 jets out for 125's, I think I should have gone up more, but this is what they had in stock at the local store and I needed the bike workinmg for today, next size up was 137.5 and that is too much.

- Squirted some carb cleaner in the holes and blew them out, general once over and shoehorned those puppies back in (man I can't imagine the PITA a rack of 4 would be, ecch)

- found out airbox "tubes" were installed backwards, which is nuts because they have locator tabs to show you how to install them, plus the snorkels on the other side of the airbox were not in right either, PO's eh? Explains why they never fit over the carbs right before.

- reset pilot screws to 1.5 turns.

- fired it up, had to turn up the idle a bit, may have accidentaly tweaked it I guess when I pulled them out.

- runs way smoother, MUCH better off idle throttle response, no more "lag", all around runs better, strangely the top end seems the same as before, but the plugs have tan on them now so maybe it was close already.

- choke still pukes out smoke in the morning, I think it is actually oil? Seems to start clean, then after about 10 seconds it starts getting smokey, then really smokey. Runs fine, choke does what its supposed too, but its rank (embarassingly so).

In conclusion, I found the opposite of what I was expecting (floats were too low, had to raise them), but acheived positive results anyways. The bike runs MUCH smoother and idles better and the rich bursts when I rev it are gone, so I guess I will just not look this horse in the mouth.

now if I could just figure out why it is burning oil with the choke on...

thanks guys!

 

[Guest]

The smoke is probably bad valve stem oil seals.

 

[gs road racer]

The smoke is probably bad valve stem oil seals.

and cold motor.....

 

[donimo]

and cold motor.....

I figured, but only on choke? Without choke on a warm morning (today) I can get it to start without choke and there is no smoke at all...

I have new seals, just not enough time or desire to install them (or how the heck to get a spring compressor on them...)

Sure does run nice right now...