Jets or...? HELP!!!!

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.