I can't get my carb's tuned properly with exhaust and pods. ):

[Dylano*]

Well I'm off to get ready for bed.
Gotta wake up at 3:15 for work.
Back to the shop!

I've been checking on this forum on my breaks and lunch, if I have time and cell signal to reply I will..

Also in the morning when I get up I'll check and reply... Maybe even tonight on my phone when I get in bed..

You guys have all really been a huge help though, especially after that day of frustration! Getting my thoughts organised now, thanks a million for everythign so far!!

[motoman]

Totally 100% serious.
PLEASE TELL ME that is my only problem!!! haha

I honestly dont see why it would make a difference if the orifice is the same and all around the jet is sealed either way...

Tell me something else I don't know please. I'm begging for knowledge!!!

NATEMOEN appears to agree with me?
"The jets we use as air jets are call "Mikuni Small Round Main Jets". The jets we usr as main jets are called "Mikuni Large Round Main Jets". It just determines the size of the head of the jet I believe, I do not think it changes anything in the metering orifice"

OK.......put the large Mikunis in.......and yes that will affect ALL its running. The washer's precise THICKNESS indexes that jets location properly....can't just use 'any ole' washer that fits'. FWIW, Mikunis jet sizing is done by their particular flow rating technique. Aftermarket....who knows, but I can tell you the hole sizing, backside internal tapering is not even close to same as a Genuine Mikuni. Why..........cause Mikuni(subsidery of Yamaha, Kiehn(subsidery of Honda) has ongoing copy rights of those components.......can't be copied....least not identical, so in case of jets, internal taper and hole sizing HAS to be a bit different. Consequently, the results speak for themselves. BTW, whats the story on the mixture screws teeny washers and O-rings? No offense intended, but as you can see, I can be pretty blunt in oder to get to the bottom of someones issue. Least that way, if its out of my experience/expertise, definitely others here can fill the gaps. Not gonna pull any punches.......you got a mess, but listening and DOING what's suggested here WILL get you out of it sooner...than later.

[motoman]

Yes new ones are in and I believe I put them in the correct order!
It would sem strange for the o-ring to go BETWEEN the washer and the spring...

It is spring, then washer then o-ring correct?! haha

Yeppers....that be it.

[Dylano*]

OK.......put the large Mikunis in.......and yes that will affect ALL its running. The washer's precise THICKNESS indexes that jets location properly....can't just use 'any ole' washer that fits'. FWIW, Mikunis jet sizing is done by their particular flow rating technique. Aftermarket....who knows, but I can tell you the hole sizing, backside internal tapering is not even close to same as a Genuine Mikuni. Why..........cause Mikuni(subsidery of Yamaha, Kiehn(subsidery of Honda) has ongoing copy rights of those components.......can't be copied....least not identical, so in case of jets, internal taper and hole sizing HAS to be a bit different. Consequently, the results speak for themselves. BTW, whats the story on the mixture screws teeny washers and O-rings? No offense intended, but as you can see, I can be pretty blunt in oder to get to the bottom of someones issue. Least that way, if its out of my experience/expertise, definitely others here can fill the gaps. Not gonna pull any punches.......you got a mess, but listening and DOING what's suggested here WILL get you out of it sooner...than later.

Ok I see you see that I got the pilot screw and washers correct... as far as the small and big jet are concerned, you mention that the washer is critical, it seems as if that is more critical than the small or large mikuni jet so long as they are genuine? It is a genuine Main jet I have and I also have the correct washers installed. Will the fact that it is the small round type rather than the large still have a dramatic effect? I have zero problems with bluntness in this matter, straightforwardness is much easier when it comes to problem solving. I am trying to be straightforward as well. That Is why I keep asking specific "should I do this" questions...my goal is for multiple people to say "yes that sends like a good move" or something similar. A few posts ago I linked pilot jets and mains I'm considering purchasing. Those choices are based off the jet recommendation post. That is, moving DOWN in pilot size to one above stock and UP in main jet size to four above stock. No one seemed to respond to that. I've also been told that I could be running to rich rather that lean which would agree with those jet choices.

I'm falling asleep looking forward to more info tomorrow, thanks again everyone.

[natemoen]

Totally 100% serious.
PLEASE TELL ME that is my only problem!!! haha

I honestly dont see why it would make a difference if the orifice is the same and all around the jet is sealed either way...

Tell me something else I don't know please. I'm begging for knowledge!!!

NATEMOEN appears to agree with me?
"The jets we use as air jets are call "Mikuni Small Round Main Jets". The jets we usr as main jets are called "Mikuni Large Round Main Jets". It just determines the size of the head of the jet I believe, I do not think it changes anything in the metering orifice"
Yesterday 09:46 PM

Well, natemoen is not always correct!

But we don't really have a definite answer to the question yet, so I may still be right, we shall see.

[Dylano*]

Well, natemoen is not always correct!

But we don't really have a definite answer to the question yet, so I may still be right, we shall see.

Ha, no one can ALWAYS be right!
Luckily, something like this actually has a factual answer,
rather than, -well other people agree with me, it must be true-!

Now I just have to keep searching,
Also lickily, this place seems to be full of answers on the relative subject!

[TADracer]

All I can say is WOW !

With due respect to everyone, after reading six pages of post in this thread my head is spinning. But what occurs to me, Dylano, is that you have a hodge-podge of jets and parts and carbs and filters and pipes and absolutely no baseline from which to start tuning. Add to that the fact you probably started out with some wrong stuff when you got the bike from the PO and everything is compounded.

So IMHO, in spite of the pod filters and open pipes, it is time to go back to stock settings. First, get a manual! Then clean those carbs again and install real Mikuni jets all around. They will have a little M stamped on them if they are real Mikuni parts. Forget about all the other places to get jets and go to Jets-R-Us. They have the real thing, are not expensive, their service is quick and yes, the jet style and manufacture do make a difference. Check out those pickup coils and your ignition coils, put in some new or at least cleaned and gapped NGK BP-6ES spark plugs (or whatever is stock for your year if not that), do a full tune-up including timing, cam clearance check and then start adjusting from there....ONE THING AND ONLY ONE THING AT A TIME...and note your changes as you go. Try tuning your carbys from the top down like Factory-Pro says (www.factorypro.com/tech/carbtun.html). It is a bit of a PIA to do but works. Once you get the performance you like, that becomes your new baseline to tune from as long as you do not change anything. Write it all down.

I know I have not given and exact detail like jet size or float measurement or stuff like that but really, Dylano, unless you go back to a known place and start from there you might chase this forever and never hit on the combination.

Off of the soapbox

[MPittma100]

Carb Tuning

AMEN TADracer! "Start From Stock" or stay lost.

Mike

[Dylano*]

With due respect to everyone, after reading six pages of post in this thread my head is spinning. But what occurs to me, Dylano, is that you have a hodge-podge of jets and parts and carbs and filters and pipes and absolutely no baseline from which to start tuning. Add to that the fact you probably started out with some wrong stuff when you got the bike from the PO and everything is compounded.

So IMHO, in spite of the pod filters and open pipes, it is time to go back to stock settings. First, get a manual! Then clean those carbs again and install real Mikuni jets all around. They will have a little M stamped on them if they are real Mikuni parts. Forget about all the other places to get jets and go to Jets-R-Us. They have the real thing, are not expensive, their service is quick and yes, the jet style and manufacture do make a difference. Check out those pickup coils and your ignition coils, put in some new or at least cleaned and gapped NGK BP-6ES spark plugs (or whatever is stock for your year if not that), do a full tune-up including timing, cam clearance check and then start adjusting from there....ONE THING AND ONLY ONE THING AT A TIME...and note your changes as you go. Try tuning your carbys from the top down like Factory-Pro says (www.factorypro.com/tech/carbtun.html). It is a bit of a PIA to do but works. Once you get the performance you like, that becomes your new baseline to tune from as long as you do not change anything. Write it all down.

I know I have not given and exact detail like jet size or float measurement or stuff like that but really, Dylano, unless you go back to a known place and start from there you might chase this forever and never hit on the combination.

Off of the soapbox

Fair enough, I will purchase, real and stock sized gets tonight. With them I will also purchase the one overt pilots and for over mains ads suggested per the jet suggestion post. I will start with the stock ones and go from there. I will as well re clean my carbs when they are out againnn. sounds like a solid idea to me.

I believe the jets that were in the bike when last running were the correct size, but the pilots were non bleed and maybe not genuine. However those stock jets were, as I mentioned striped when taking apart the carbs on round one and I never tried running with those stockish jets with these pods and open exhaust, so it seems like a good starting place, thanks!!!

[MPittma100]

Carb Tuning

Now you have it!

After cleaning and installing new parts, fill carbs with gas via remote fuel source and check for leaks prior to installing on bike. Lot easier to fix a leak while off. Pay close attention to adjusting the floats exactly by the OEM spec. Take your time doing this as it is a critical adjustment.

After installing and running bike to operating temperature, it is time to sync them.

After they are synced and bike is running properly, you want to ride it and check fuel mileage and plug coloring - white is too lean and black is too rich. A rusty brownish to tan color is on the money.



This is a picture of a plug out of my 1979SF Special that gets 35 MPG. All jets, exhaust, and air filter housing are stock.

Not stock are the ignition coils, spark plugs, and air filter. Coils are the Dyna Coil brand, plugs are NGK Iridium (stock heat range), and the air filter is K&N. This plug appears to be a little on the lean side, but not too lean.

Theoretically, I could have increased jet size since I have aftermarket coils and air filter, but I chose not to before I tried it out. I like the 35 MPG. You need all the MPG you can get on a Special (small tank). So I made no modifications to the carburetors. The bike does run very well.

Another way to enrich or lean the fuel mixture is to move the needle clip (needle jet) down or up respectively. Don't know for sure if this is the same on the XJ carbs, but if it is, this is a change you can make without replacing any parts. On the XS carbs, the center clip position is the standard location.

You can use this picture (coloring) as a reference for your tuning.

Good Luck.

Mike

[Dylano*]

Now you have it!

After cleaning and installing new parts, fill carbs with gas via remote fuel source and check for leaks prior to installing on bike. Lot easier to fix a leak while off. Pay close attention to adjusting the floats exactly by the OEM spec. Take your time doing this as it is a critical adjustment.

After installing and running bike to operating temperature, it is time to sync them.

After they are synced and bike is running properly, you want to ride it and check fuel mileage and plug coloring - white is too lean and black is too rich. A rusty brownish to tan color is on the money.



This is a picture of a plug out of my 1979SF Special that gets 35 MPG. All jets, exhaust, and air filter housing are stock.

Not stock are the ignition coils, spark plugs, and air filter. Coils are the Dyna Coil brand, plugs are NGK Iridium (stock heat range), and the air filter is K&N. This plug appears to be a little on the lean side, but not too lean.

Theoretically, I could have increased jet size since I have aftermarket coils and air filter, but I chose not to before I tried it out. I like the 35 MPG. You need all the MPG you can get on a Special (small tank). So I made no modifications to the carburetors. The bike does run very well.

Another way to enrich or lean the fuel mixture is to move the needle clip (needle jet) down or up respectively. Don't know for sure if this is the same on the XJ carbs, but if it is, this is a change you can make without replacing any parts. On the XS carbs, the center clip position is the standard location.

You can use this picture (coloring) as a reference for your tuning.

Good Luck.

Mike

GREAT! I'm glad I finally have multiple people agreeing with what my next step should be.

Unfortunately the needles on the xjs are fixed position.. at least mine are!

I'll order those jets tonight!
Hooray I'm excited now.

[3Phase]

I've been under the impression that the mains only matter when under HEAVY throttle, like 2/3 or more.

I can't even make it to 1/2 throttle it seems like!

Dylano,

Welcome to the site!


The carburetor slide needles never completely seat in and block the main jets so there is always at least some minuscule amount of fuel flowing through the main jets even at idle.

The main jets start to flow more fuel the instant the needles start to rise along with the slides and the length/taper of the needles determines when and how much fuel the main jets can flow until the needles lift completely clear of the main jets.


Note: The carburetor slide needles are called "Jet Needles" in Mikuni-speak and the mixture/emulsion tubes are called "Needle Jets".

.

[BA80]

Dylano,

Welcome to the site!


The carburetor slide needles never completely seat in and block the main jets so there is always at least some minuscule amount of fuel flowing through the main jets even at idle.

.

I have to disagree with you on that Scott. The fuel flow from the needle jets is dependent on air flowing over the opening to create a vacuum to pull the fuel up and out of the bowl. The butterfly valves are all but closed letting just enough air through to mix with what little fuel is coming through the idle system. There isn't enough air flow there to create a vacuum in the needle jet.

[3Phase]

That's why I said, "miniscule."

In a nutshell: I did some main jet swapping to find out which ones my wallet likes and which ones Columbo likes -- fuel economy vs power and acceleration.

Changing the main jets made a very slight difference in the idle speed and I had to readjust the mixture screws. Looking in the carburetor inlets with the engine idling I could see the occasional micro-trace of fuel wafting from the needle/jet opening.


P.S. Never blip the throttle with the airbox off while you're looking into the carb inlets. DAMHIK!

.

[motoman]

Not to hijack, but FWIW to some, the early 78-79 carbies draw fuel from both idle and main circuit thru ALL the rpm ranges since having the cross-over casting(that got plugged on the early 80 "bastardized" carbs. IMO, this is what seems to make them a bit easier to to tune with intake and exhaust modifications.

Aside from that, previous suggestions to start stock as a baseline(assuming there are no SECONDARY ignition voltage issues) is spot-on for a baseline to decifer what direction jetting needs to go, where AND how much.