Jets or...? HELP!!!!

Need Carb help... I picked up what appeared to be a MINT 1982 Seca XJ550 with approx 3000K original miles on it back in June/July. It basically looks like it just came out of the factory crate. It's been sitting in storage as I was having a new home built with no time to play with it. Now I'm trying to get it tuned (since it ran like hell when it was delivered). Come to find out, it won't run at all without full choke and even then it wants to run at an approximate 4K+ RPM. I had a local mechanic go thru the carbs. He said they were all gummed up despite looking new on the outside. Now they are all spanky clean but the problem remains.

The bike appears to be stock with the exception of a MAC 4 into one exhaust. As the mechanic was going thru the carbs he noticed that it appears someone had previously gotten into the carbs as one airbox boot was not properly re-installed and some screw heads are a little boogered up. He suspects maybe the jets were changed. Does anyone know what the factory Mikuni jet #'s were/are for this bike? I know some exhausts need re-jetting but my understanding was that this MAC unit does not. I'll eventually be replacing the MAC with a NOS Kerker 4 into 1 I've been able to dig up.

Any other suggestions to get this gem running again properly?

Any and all help greatly appreciated!

 

Main jet is a 112.5 and pilot jet is a .35.

 

Cool! Thanks Much!

BTW.. where did you find that info?

 

On the XJCD. It is a CD containing the shop manuals with, (Yamaha's permission) and a compilation of info and how to's from the XJ gurus. Only costs $10 and is worth much more. There is a link on how to order it on this site.

 

The mechanic now tells me that if carb cleaner is sprayed on the choke portion of the carbs while the engine is running there is a surge. So it appears that there is a vacum leak from one or more of the rubber caps that seal the choke shaft (starter set?). A quick check with a local dealer tells me that those seals are discontinued. Are there any carb rebuild kits that would include all rubber parts such as these? (it wouldn't hurt if the jets were included also)

 

The rubber seals are to keep dust and grime out, they do not seal the choke circuit. The plungers that move up and down seal the choke circuit. However, there are intake boot seals in that area too! Make sure the clamps are tight on the carb side of the intake. Also check the intake boots for cracks.
Since the carbs have been cleaned it would have been good to know that the pilot mixture screws were set to 2.5 to 3 turns out. It sounds like your idle jets are either clogged or the pilots screws are set too lean. Not enough fuel getting in through the idle circuit so opening the choke lets fuel in through the starter circuit. But an air leak would keep even that fuel flow lean and cause a high idle, which is the most likely problem since the carb cleaner is getting into the intake tract.
There are no carb kits that include jets. The jets just don't wear out. They just need to be cleaned. But the jets are available from motorcyclecarbs.com.
So make sure the clamps are tight and even that the carbs are all the way into the intake boots. Then we can check the pilot mixture screws for proper setting.

 

The intake boots & gaskets were replaced as they were cracked (we assumed that was the root of the problem but like I've mentioned, despite new boots the problem remains). Agreed it seems that there may be a remaining air leak, the question is where?

At this point the carbs are being pulled again to verify the jet numbers and put that issue to rest. I'm confident that the carb internals, including jets, are clean. Are there any diagrams that show the location of the pilot mixture screws? I'd expect a lean air/fuel mix would show via the plugs but they actually appear to be very dark (sanity check... doesn't that indicate too rich a mixture?)

BTW... I will be running a K&N filter and a MAC 4 into 1 exhaust (later switching to a Kerker 4 into 1). Are the stock jets a good match for this setup or should I be looking for something different?

 

It doesn't matter how Clean the Carbs are if the Diaphragm Pistons are sticking.
You need to check that!

Search: "Clunk Test" in out archives.

The Diaphragm Pistons are housed in a finished aluminum bore.
The bore surrounding the Piston gets tight with aluma-oxidation.
A "Dust-like" substance similar to rust ... but, ultra fine.

The oxidation will cause the Piston to bind or hesitate or actually stick right in place.
That behavior needs to be eliminated by refinishing the bores.
(Outlined in my Post in our Archives)

I take the process a step further, these days, and actually polish the bores for maximum performance.

 

I upped my main jets from a 120 to a 122 just for the K&N filter. With a header I would assume at least another jet size. There should be some info and advice that comes with the header so go with what Kerker says.
Rick has a good point so check that the carb pistons move smoothly and drop free with a clunk. I would also make sure the choke is all the way off. Open it could let in the carb cleaner as the mechanic found out. It is also possible that the carbs are just enough out of sync to cause this. Since you are pulling the carbs off check them with a static or bench sync. Simply put this is checking that the butterflies are open the same amount at the bottom when the throttle or butterflies are closed.

 

Both MAC and Kerker say no re-jetting "should be" necessary. I wish I could remember what I did with my original bike I had setup this way 25 yrs ago.

 

After 20 Years, you need to know the Diaphragm Pistons are rising and falling with no drag on them. I can't imagine anyone with our style of Carbs not needing to check Diaphragm Piston movement.

The close tolerances get even closer when the Bore gets oxidized and the Piston cannot rise and fall with the slight changes of pressure that occur during open and closed throttles.

In the same manner ... the Bores of the Enrichment Valves will shrink due to oxidation. Enough to make the so-called Choke Valves stick open and cause for a Rich running condition.

At the very least, some ScotchBrite Pad should be used to burnish the Bores clean and get the oxidation off the Inside Diameters and allow the Pistons or Valves to have NO Problem moving up and down.

 

Since the carbs are being pulled out again, I'll make sure everything moves freely. I'm pretty sure the guy working them has already done this but it won't hurt. The whole bike looks like new but we've already caught some rubber rot. I can't imagine there is any oxidation from what I've seen but I know what you're talking about and we'll take a look.

 

khornet, it seem you biggest problem is letting someone who claims to be a mechanic work on the carbs while you relay info back and forth. It's best to do all the work on your bike yourself so you know it's done correctly rather than depending on some high school drop out to do it.

 

You've got that right! But believe me, if I thought I had a clue as to what I was doing with a set of carbs, I would do it myself. It's been much too long since I've tinkered with a bike. I've still got an ounce of confidence this guy will figure it out. When that is gone, I'll dive in if nececssary and hope I really don't screw it up.

If only I still lived in Phoenix/Glendale, I'd let you help me!

 

We are about to that point in time where the Dealerships might NOT be the best place to bring your Bike for a Carb Cleaning.

Why?

Because it takes too much time for the job to be done RIGHT!
Taking them off.
Tearing them down.
Cleaning the whole deal right
Putting them back together
Getting them back-on the Bike
Doing the Syncs and Mixture settings ...

This is NOT what a Dealership Tech wants to do with his Money Making Day.

The Technician can complete Work-Orders on several Bikes in the time it takes to get them off and take them down.

Several more completed Work Orders (at full rate) in the time it takes to really clean the carbs quite thoroughly.

He's losing money on your Old XJ Bike.
Combine the factors that make the Job even more difficult:
Soft steel fasteners
Stuck Jets
Mangled Pilot Mixture Screws ...

The sight of your Bike to a Latter-Day Service Tech sends shivvers down his spine.

That's why they don't want to mess with your Bike at the Dealership.
The Owner is pee-owed you are hanging on to the old bike and not doing business for a new one.
The have to order whatever you need and keep your bike "In the way" of progress.
The Techs get pee-owed having an antique mess their schedule up and begrudge the guy working two bikes at a time while he's pulling your carbs.

And so the story goes ...

Your bike means a frustrating day of getting backed-up on his weekly gross.

You need to be able to do your own Carb Cleaning and Tuning.
A little practice and expenditure for what you need to make the job easy
will get your bike tuned-up better if you take the time and do it yourself!

 

Long story... but the guy working this comes highly recommended by local bikers & the local dealer. He is an ex-dealer mechanic who is disabled and still does bike work at his residence to make some extra cash. I'm confident that he has the know how and ability to get this done and that he is being meticulous about the work. I ended up working this with him since there's not a single local dealer within driving range that will touch ANY make bike over 10 yrs old (supposedly for liability reasons) and since I don't have the time myself to get to this anytime in the near future.

He just called me with news that he confirmed that the carbs still have the factory jets. He's going over the whole set once again to make sure he didn't miss anything. The current game plan is to take the carbs off my other (running) Seca and put them on the bike currently having issues just to be certain that the issue is not something else. Conversly we may put the problem set on the running bike to make sure the problem moves with them.

You can bet that while both sets are off everything will be closely inspected for drag, etc per the recommendations y'all have provided so far.

All comments continue to be greatly appreciated.

 

pilot screws are located under the plug in the pic. If this has not been removed then the carbs are not clean. Under the plug there is a small screw. Turn the screw all the way in and count the number of turns it takes to bottom it out. This should be about 2.5 turns in. Be careful not to overtighten it. Then back it out all the way and remove it. There should a spring rubber o-ring and a small washer on it. Make sure all these parts come out. Then spray some carb cleaner in the hole with the straw installed and see if any cleaner comes out of the small ports in the carbs by the butterflies and the stem that goes into the bowl. If none comes out, then they are clogged. To unclog these small holes just keep spraying some carb cleaned down the holes until all the crud comes out. You may have to let the carbs sit for some time to get these ports to unclog. Kind of a soaking. Good luck. Read Ric-o-matics cleaning you carbs the whole nine yards post. It is a great post full of great information.

 

Sorry... where do I find that post?

 

http://www.xjbikes.com/Forums/viewtopic/t=2908.html
Right here. Great reading.

 

I see all this mention of Hitachi being the most widely used carb on these bikes but of the 3 Seca's and one Maxim I've owned, they ALL came with Mikuni's. ?????

 

OK, so here's where this currently stands... my "recommended" mechanic has thrown in the towel as he can't figure it out, so I guess I'm now forced to learn about carbs whether I'm ready or not. No biggie, bring em on!

First thing I've done is yank the brass plugs over the mixture screws (I only lightly messed up one screwhead), removed the screws and cleaned those passages out really good. I also pulled each "starter assembly" and made sure those were clean. I re-installed the mixture screws to the 2.5 turn recommendation. I then re-installed the carbs sans the airbox & filter and tested. It did now seem to idle down as I reduced the choke and as it warmed up. It would not do this previously. It will now run at a constant idle (with choke @1200rpm) but when you hit the throttle it revs high (4K+rpm) and takes 10 seconds or more to drop back down (again previously, it would not drop back down). I've also verified that the throttle cable is free moving and not sticking.

Is not having the airbox and filter connected going to cause me issues with troubleshooting this?

So I yanked the carbs again and did the CLUNK test and each bore is shiny, each slide is golden, and they definately go CLUNK without any stickage. The diaphragms look like new. Next, I plan to take a look at the floats and make sure they are good. What else should I look at?

I ordered a Stage1 jet kit, since I'm going to have a K&N filter and 4 into 1 pipe on this bike. Is it worth continued testing without these new jets or should I just wait?

also... never got any comments on my observation that all my XJ550's have had Mikunis, not Hitachi carbs. Anyone else seen this?

 

The 550 runs Mikuni.

You are going to have to solve the age-old riddle of how to Jet for NO Airbox.
The Carbs are engineered to have the Total Intake Air Supply come from the Intake Opening in the Airbox and get shared by the four Carbs.

The Intake Air leaving the Airbox rushes through the four Boots which are the Racks "Velocity Stacks"

Without the Velocity Stack effect on the Intake Air ... getting the right amount of Intake Air across the top of the Emulsion Tube in each Carb is difficult ... at best!

 

OK, so I guess my next step is check floats then reinstall with airbox and filter and test. Then go from there.

thanks for the confirmation on the Mikunis.

 

Hornet.....all XJ550 Maxim and Seca models used Mikuni carbs from the factory. Only the XJ650 (except Turbo), XJ750 (all), and XJ700 non-X models used Hitachi carbs. So although many more models used Mikuni carbs (all 550's, 650 Turbos, 700-X, 900, and 1100), all of the higher production models used Hitachis.

The lack of airbox boots can cause alot of difficulty in diagnosing problems. As much of a pain as they are to install, I would suggest putting them on so you can have a baseline situation from which to evaluate from.

The idling-only-with-choke-engaged and the high revs could be manifestations of two separate problems. The first one, could be clogged starter jets. The second one sounds very much like a piston that is hanging, even though you have checked that issue. Rick can give more insights.

One thing though: I would do everything possible to make SURE that the carbs perform FLAWLESSLY in their stock configuration before you start installing jet kits, etc.......the "re-tuning" aspect of these carbs is a huge enough of a finicky chore in and of itself, and if there are also any carb-related issues to deal with, then it becomes something beyond a nightmare situation to try and sort out. Just my (unhappy) 2-cents....!

 

Exactly true! If you don't have your Carbs right on-the-money in a Stock configuration ... Modifying them will be a long nightmare because you won't know what needs to be changed to re-adjust the Mixtures for correct Air~Fuel Ratio.

I say "Correct" ... but, ... it's not going to be correct after any Mods.
Something has to give!

You may be happy with the Mid-range and top-end while the Low-end is a little strange ... or, have a hole in the Mid-range while the Idle and Top-end are OK.

It depends on what Kit and how much you are willing to fool-around trying to get the square peg into the round hole.

On some bikes ... it fits and they say it runs fine.
I don't know about that ... it seems like a sales pitch for misery.

I have not seen a XJ-Bike run well enough with Carb Mods to make me happy if I had to ride it!

 

ok, thanks. where do I find the starter jets?

 

You don't! The starter jets are pressed into the bowl passage, and non-removable. Only choice is to clean them! I offer a special sized drill bit that is the correct size and long enough to allow you to get down into that well and gently clean out the jet:

z7) Aftermarket wire gauge Drill Bit for Bowl Starter Jet. As you will quickly discover if you ever try to clean or rebuild your Hitachi carbs, the tiny, non-removable starter jet that is stuck wa-a-a-y down at the bottom of a drilled passage in the carb bowl is next to impossible to clean. For one, did we mention that the jet opening is TINY? And did I also mention that it's stuck way down at the bottom of a small passageway, and basically unreachable? AND THEREFORE, NO ONE EVER REALLY EVEN ATTEMPTS TO CLEAN IT OUT? And that a clogged starter jet not only means trouble starting and idling, but that starter circuit is actually also involved in idle and off-idle performance? Well, how do you actually clean it? Even the tiniest cleaning rod in our HCP950 and HCP953 carb passage cleaning sets (above) aren't small enough to fit through this starter jet (it is THE smallest jet-passage in the entire carb)...

Well, here's how you clean it: with this tiny drill bit. Just big enough to get through the jet, but not big enough to ENLARGE the jet (that's a huge no-no), this high-speed steel bit can be gently rotated (but never "pushed", as it will break) through the toughest of crud. This is the only way to properly clean these starter jets.

NOTE: this is a TINY drill bit, and will not chuck into a standard drill chuck. You have to use a mini pin-vise attachment or do it carefully by hand...... ALSO: this drill bit is a mere 1-1/2" long, and as such, will disappear below the top "plane" of the bowl as it goes down into the jet. You will have to use a pair of very slim needle-nose pliers to grip the tip of this drill bit and rotate it!

HCP2296 Starter Jet Clean-Out Drill Bit, for all Hitachi carbs:
$ 11.95

HCP2293 Starter Jet Clean-Out Drill Bit, for Mikuni carbs used on all XJ550 and XJ700-X models:
$ 11.95


http://www.xjbikes.com/Forums/viewtopic ... t=180.html

 

Yeah Rick is right on the dealership. They asked me what kind of bike i had and said no right away and didn't know what the problem even was.

 

OK, I'm willing to give that a shot but still doesn't tell me where to use the drill bit. You say "carb bowl", you mean float bowl? Happen to have any pics so I know exactly what I'm doing?

Is there a phone number I can reach you at since we've got a few other items on my list to get from you also?

 

Khornet....you've got a privae mail awaiting you!

 

Khornet....you've got a private mail awaiting you!

 

gotcha Thanks Len!

I just went thru them all. I picked up a $.40 medical syringe at walmart that fits nicely in that brass tube and allowed me to inject carb cleaner down thru that tube/jet. I pulled all the "starter sets" and I saw the cleaner freely flowing thru each. I put it all back together, reinstalled the carbs and it appears I've now made some great progress. It's still not perfect but the bike mostly idles now without the choke and is much more responsive to the throttle.

I still haven't connected up the airbox yet, but this is very encouraging. I'm now trying to figure out how I'm going to get those airbox connectors in there. so I've got a "real world " test. I think a good long soak in some hot water is the start, so they will at least be more pliable to work in that cramp space.

 

Not sure how your clutch cable is routed, but on my 650 it is almost impossible to get the intake boot for #3 in from the right side because the clutch cable blocks access. Much easier to do it from the left.

I do them 3, 2, 1 from the left then #4 from the right.

 

shouldn't be an issue, the cable isn't even close.

 

Hook-up the two inside ones first.
Do the two outside ones last.

Make a tool that you can use to "Shoe Horn" the Boots over the Intake necks if they don't just fold-back and flop right into place.

Use the locating tab on the outside diameter of the Boot to line it up right to get them on the way they came off.

Make sure the tool you make doesn't have a sharp edge that will slice the Boot.

 

Already Done! took about 15 minutes of Mr Circus Rubber hands to get all those airbox boots installed.

Now it runs even a bit better but still revving high and not coming down immediately (but least it does eventually come down now). still idles at @1200rpm nicely which it never would do before.

I'll give it a fresh tank of new premium gas, some Seafoam, and then I'm going to ride it a bit to see if it gets better. If not I'll take yet ANOTHER look at those slides and break out the polish.

 

12-Hundred isn't Idle.
12-Hundred is just off-idle and you are probably bringing-in some Main Jet Fuel.
Try adjusting the Idle Adjustment Rod, below and between the 2 & 3 Carb to reduce RPM's to below 11-Hundred.
1,050 should be the High-side of Idle. 900 being really good and dependent on Pilot Mixture Air~Fuel alone.

If the Idle Adjustment Rod will not adjust-out the High revving Idle, you may have to undo the Throttle Cable Slack adjuster at the Throttle Perch to slack-0ff the Cable slightly. There should be a little slack in the Cable to allow the Throttle Butterfly's to close.

It sounds like you are close to being where the Bike needs to be. Bear in mind that the Final adjustments are determined by actually looking at individual Plugs after the Bike has been run some.

When you get ready to make >Tweak< adjustments ... the Tweaking is a VERY SLIGHT movement of the Pilot Mixture Screw.
Since the P-M-Screws are ultra fine threaded ... you may only need to Enrich or Lean-out an individual Screw with a slight movement.

This SLIGHT Movement is measured in degrees. Not anything in fractions.
You should inspect the Plug.
Determine if that Plug's color is too Dark or Light and make the adjustment accordingly.

When determining if the Mixture is too Lean, you have to take a close look at the Ceramic Tip surrounding the Plug's Base Electrode.
The Ceramic will be colored from the Combustion.
If the Plug is looking CLEAN ... a Lean condition is happening.

Too Lean will overheat that Ceramic and cause it to deteriorate.
The Ceramic will also begin to show hairline fractures from the stress of the hole being too Lean.

Too Rich is obvious. The Plug will be dark with unburned Fuel stain.

You should Tweak the Pilot Mixture Screw of that Cylinder until the Plug is Tanned or a light Brown.

Don't be persuaded by how well the Bike will run in a slightly LEAN configuration to leave it Lean.
Too lean is a HOT Mixture that will soon take its toll on the Engine; causing the gases to be too hot and subjecting the Valves, Seats, Piston Crown, Cylinder Hole and Cylinder Head to higher temperatures than Normal.

You look to achieve a coloration of the Plugs that is Light Brown.

Within this window of find tuning is a narrow window of differing performance.
Lean: Faster acceleration, crisp throttle and engine braking.

Rich: Smooth application of power, smooth acceleration and engine coasting when the throttles are closed.

 

WOO HOOOO!!!!! IT's ALIVE!!!!!!

Started her up today and let it run to operating tempeture. I noticed I now had good throttle response, although running at 4K rpm. Made me think the idle speed was just way out of whack so I cranked it down and it's now running great! Idling normally at 1K with no choke.

Time for fine tuning. I'll pickup one of those colortune plugs and a Carbtune for sycn'ing them all. Between the two bikes I'll get my money out of both. (I've already got my YICS tool). Probably need the valve adjustment tool while I'm at it.

I can't thank you guys here on this forum enough for your comments and giving me the confidence to jump in on this and resolving the issue!

Len I still owe you a call and you'll be hearing from me in the next few days.

 

Idle spec for the 550 is 1200rpm.

This is according to the Clymer's manual.

 

I've got her idling comfortably at 1K without any further tuning.