hitachi carbs

hey guys, my journey down the carb highway has been beckoning me for a couple weeks now. Going to be taking the apart to see what size jets it has and all. But there's one thing i saw that i'm concerned about. The pilot screws are blocked off by a flush piece of machined brass! I'll get some pics up, but is this normal? don't i need to remove these if i'm going to be re-jetting, syncing, ect?

 

The brass plates cover 2 jets. Its normal, and needs to be there. You will need to remove the plates for jetting and cleaning.

All normal.

-Kaya

 

Also,

Be sure to keep track of which jet came out of which spot. There all labeled, but it can be tough if you dont pay attention to that.

Good luck!

-Kaya

 

Are you talking about the plate under the diaphragm that hides the main and pilot air jets?

Or do you mean the plugs covering the mixture screws on the top near the enrichment circuit valves?

Either way, yes they need to be removed for a proper cleaning and the mixture screw caps also need to come out if you are going to do a proper colortune or plug chops to get the carbs correct.

 

The mixture screw caps need to come out to get the mixture screws out to properly clean the passages and replace their o-rings.

You need to VERY CAREFULLY drill a small hole into the machined brass caps on the mixture screws; then run a tiny self-tapping screw into the hole and yank the cap out. You need to be very careful with the drill so as not to go down and damage the mixture screw.

 

Yes. Go by what BigFitz said. These are anti-tamper plugs installed at the factory for emissions purposes. They originally set the mixture screws pretty lean to satisfy the EPA, then put the plugs in to prevent us from enrichening the mixture. As Fitz said, be real careful when removing these, as to not damage the top of the mixture screws.

 

The Plug is only > 1/8" < thick.

There is VERY LITTLE space between the Bottom of the Plug and the TOP of the Delicate Soft Brass Mixture Screw below it.
The Drill will Damage the Mixture Screw if you run through the Plug.

USE Extreme Caution drilling the Plug.
Nip the Point off a Drywall Screw.
Screw the Drywall Screw into the Drilled Hole and get a good bite.

Grab the Screw with Vice Grips and remove it like pulling a tooth.

 

thanks guys, thats what i was looking for, glad you understood what i was saying. I figured thats what they are, since i see DO NOT ADJUST most often when the pilot screws are referred to.

I've takin a good look at the carbs, checking out the jets and all, float needle and it's (jet?/orifice?) has bee replaced at some point to a 4.0. And i got someone a little more, experienced with carbs and all from the old days (my old man) to take a look at the plugs for me. He's tellin me i'm nuts and they're fine. They were new plugs and the first thing they turned was white on the ground strap.

Now the ground strap is tan/brown and the .. not sure what to call it, base of the threads, where the ground strap is connected at, is blackish, and the insulator is white/gray. No signs of detonation.

to recap why i'm looking at this, bought the bike with pods and a 4-1 exhaust. just want to figure out what to do with it, if it hasn't been done already.

If it comes to me re-jetting, can the carbs be sync'ed without touching the pilot mixture screw? or is this one of those cases where i should ignore the book? With as much as I've read I still feel rather ignorant of carbs, and they still just scare me a bit.

 

As four of us have told you now; IGNORE THE BOOK, uncap the idle mixture screws and record where they're at to begin with, then pull them out so you can clean the passages and replace the o-rings.

Now that the bike has a different exhaust, different air filters and hopefully the valves have been brought into spec; the original factory setting mean nothing any more anyway.

 

Before you can get the Carbs to ::: respond ::: to efforts to tune them; the Rack needs to be functioning perfectly.

IF, ... you don't know when the last time the Rack was removed and given a thorough Cleaning; you should make having the Carbs Cleaned ::: and ::: "Clean-tuned" to insure they will deliver fuel at the peak of their performance.

Every single rack of Hitachi Carbs over 15 Years old needs to have:
Diaphragms Inspected for Holes and Leaks.
Diaphragm Piston Bores -- Scrubbed and Polished removing the film of "Aluminum Oxidation" that causes the Pistons to not move properly.

Jets and Tiny Metering Ports for Fuel and Air ALL free-flowing.
PASSAGES where Fuel and Air pass from the Fuel Bowl to Delivery Points Cleaned and Flushed for optimum Performance.

Just the passage of time, alone, will let Fuel Delivery Components to become contaminated to such an extent that Fine Tuning becomes impossible.

 

For those whom are new to Hitachi carbs, the above picture is called an "emulsion tube" this is where fuel and air are mixed then metered by means of the "metering needle" which protrudes from the bottom of the slide.

 

When cleaning the carbs, it is imperative to make sure that all the tiny holes are free of obstruction in the "emulsion tube" as well as the other fuel and air galleries for there to be proper operation. But cleaning is just a small part of carb rehabilitation, there is also the replacement of gaskets, o-rings, and seals, to get the carbs operating as designed. Then there is the adjusting phase.
But all your efforts will be in vain if other parts of the bike are out of adjustment, such as valve clearances.

 

thanks guys, PO said he cleaned the jets, i don't know if he cleaned everything though, and i really don't trust his abilities due to many other overlooked issues on the bike specifically brakes. I want to get needed tools together before i start breaking them down.

So is a colortune highly advisable? Isn't it just more of a shortcut?

Whats my needed tools? just vacuum gauges and a good 'ol YICS stick?

If i rev the motor around 4k +, cut it and pull over and check the plugs, the insulators are a healthy brown/tan, but idling makes them white again, so my pilots def need some adjustment if i'm not mistaken.


I've seen this on the internet, can anyone here justify it's validity in the xj application?

 

Id wait for confirmation from someone a little more seasoned in tuning these, but its my understanding that many people tune without the YICS tool. I was talking with a guy yesterday who does a lot of motorcycle and small engine repair, and I mentioned the colortune and he said it wasnt needed. He was pretty sure he could get it tuned by the sound of the motor alone. I, however, am not that good. A $50 colortune, is a sound investment IMO.

Manometer is a cheap DIY thing. Ill see if i can dig up the post.

-Kaya

 

If the PO said he cleaned the jets...well even IF he did that right, that's not ALL the passages, emulsion tube, slide polishing, o-ring/gasket changing advice the guys are giving you. Blowing out the jets is a 15 minute step in a 2-20 hour process (depending on ability and how well things "come apart," take your time, you won't want to break anything).

Colortune is good if you don't already have an experienced "ear," it gives you a visual indication of the mixture, and is a substitute for the more expensive, and precise, exhuast gas analyzer, and give faster feedback than sparkplug readings. If you can't tune a lawn mower engine by ear, you won't be having much luck without the colortune, due to the effect of having 4 carbs to tune AND sync.

YICS tool is necessary to get your sync in the right ball park, but you CAN sync without it, it can just be more frustrating.

I think of it as the following linear algebra problem:
Vacuum1measured = A*VacCylinder1 + B*(sum(VacCylinder(2-4)))
Vacuum2measured = A*VacCylinder2 + B*(sum(VacCylinder(1,3,4)))
Vacuum3measured = A*VacCylinder3 + B*(sum(VacCylinder(1,2,4)))
Vacuum4measured = A*VacCylinder4 + B*(sum(VacCylinder(1-3)))

You need to solve for VacCylinder(1-4), but you don't have the coefficent matrix, where A>B. If they are all almost evenly balanced, the B*() factor is just a bias, but if they aren't, then there's probably an infinite number of solutions, unless we know A and B (and can assume it's linear). YICS tool zeros out B, so what you measure it what the cylinder pulls.

 

rgr that manbot, I'm seein the value in the YICS Tool. I'll stick to my plan to get one. and hey hey fellow marylander

 

alrright, finally got around to yanking these things apart, and cleaning them all up. Once i finally cracked them open, they're not as terrible as i once thought. from tidbits of information around, i pieced together all the questions i had about carbs, cleaning, tuning, ect.

had to call it quits last night after they were all back together and found a float needle wasn't seating on number 1, gonna have to play with it tonight after work.

I do have two questions about the float needles and their seats. first, my needle tips.. They're rubber, obviously new, (along with new seats). Is this the norm? anyone have any experience with these? I just imagine them not sealing as well as a piece of precision metal. The second question, the seats.. They each have a small filter at the top of the passage, where it meets the fuel line. however they are just loose between the seat and the bottom of the hole, and it appears there's enough play in there that they'd just kinda bob around. It just seems as if they should be attached to the bottom of the float pin seat, not just hangin around in that hole

someone did clean them before, just not very well.. the (emulsion tube?) was awfully dirty, air jets were neglected, and obviously pilot screw hole and parts where dirty. Other than that not to bad. clunk test was A-ok, diaphragms are good. now to order a manometer, color tune, and yics.. yuck, more money

 

No need to order an manometer. Make one. Costs about $4.

Or depending on where you are in Maryland give me shout and come use mine. I can most likely even borrow a YICS tool. My bike missed out on that fun so I don't have one.

I'm in Essex.

 

well, a little late on the manometer. ha. i was thinking about making one, and just thought for a second, knowing my luck i'de suck some water right on into my intake manifold or something, water lock the engine, ha. you know where to get a yics tool though? i haven't ordered one yet. just got my carbs all sticky float free here. changed the oil for good measure. but did notice something disheartening when i had my air filters off, a knocking noise. took the ol screw driver handle to my ear and it's from cylinder 2. not sure what this is gonna do to me, or what i should do period.

 

Some New "Aftermarket" Carb Kits need some Finishing Touches before buttoning-up the Fuel Bowl.

I roll-up a tight roll of 2000 Finishing Paper and "Dress" the I-D's of the Float Valve Seat.
I hang the Pin on the Float and closely inspect the Geometry of the Pin rising and falling inn the Seat.
If the Pin gets tilted, ... I change things around to get a perfectly-centered motion.
• Flip the Wire Clip 180 sometimes helps
• Bend the Wire Clip
• Eliminate side-to-side movement of the Float
>Bent the Alignment Tab
>>Add miniature Thrust Washers on Hinges.

Be sure to do an accurate Float Height setting.
If you have done a comprehensive cleaning; don't leave one detail unchecked.
You'll see the fruits of your labor when you get-on to Fine Tuning.

 

Use ATF in your home built. Then if you did suck some it just burns off and the only harm is some smoke. And it's red and easy to see.

I do. I'll see if I can get it touch with him and borrow it.

Have you check your valve clearance? Compression check?

 

Well you need to find out what that knocking is before you go any further. Could be serious, bearing maybe?
As for the manometer I bought one from Len to do all four carbs at once. I don't believe in toying with settings that need to be precise.

 

I didn't see any parts that needed replacement in the carbs, so it's all what was in there already. someone has replaced the float seats and needles. They seemed alright, and float heights were good. like i said after a little tapping, (after taking them back apart to ensure cleanliness) they function just as they should. It's actually amazing to be able to set to PRI and not have fuel gush out, ha. been doing that since i got it a few months ago.

compression was one of the first things i did. it's all within 10psi 123-130 across the board if i remember right. little low, but not terrible.

valve shims are all done, did all that before i put the engine back in.

a knocking can be caused by a bad spark right? i noticed on number 2 there's been a few times that the plug was wet when i pulled it out to check color. never thought much of it. I don't really know why, i just kinda dismissed it. maybe trying to avoid the problem

 

switch the #2 and #3 plug wire and see if the sound moves.

 

If you want to save the cost of the YICS tool, one of the resident Guru's, Rick Massey, swears by a strip of T-shirt soaked in Mystery Oil as more than adequate to the task ...

 

2 and 3 dont fire at the same time i thought though. Couldnt this damage the engine? I thought no cyclinder fired the same time as another. Am i wrong?

 

Should be 1 & 4 on one coil. 2&3 on the other so 1 & 4 fire on compression & exhaust strokes & so do 2 & 3. So as to switching coil wires 2 & 3 you will be alright.

 

To clarify a bit on what Kwiski said, they do fire at the same time: 1&4, 2&3.

 

i'm just confused now, ha. I did as suggested. not difference in sound. basically... there is a sound from the left side of the engine, around 1 & 2, but very well could be a large shim gap from when i swapped those out. I can't say it's def one cylinder or another, can't distinguish whatsoever. thought it might be an exhaust leak, but bolts are to spec. def sounds like it could be one though. exhaust is new, new studs, ect. only thing i could suspect is that the studs are barely large enough (threads not being long enough) , had a hard time finding ones that would fit. maybe they're too small now that the new exhaust gaskets have collapsed? If i had to guess where the sound is coming from, it's the exhaust, thats where i hear it loudest.

but, this second thing may change that theory.

there's another tap, the one i noticed when i had the filters off, and thats actually coming from the carbs. I'm not sure what parts are called what, but you can feel the tap/knock in the rod that the (throttle plates?) pivot on. When i say you can feel it, i mean it's no doubt. what could cause this? is this because the carbs are actually clean now? or dirty? or because the mixture isn't set yet? or carbs aren't synced yet? thanks for your help so far. I knew once i started on the carbs i'de end up having a lot of question, and have to address problems i've been avoiding. Non the less, time to get this thing to where i'm actually confident in it's mechanical dependability.

 

My guess on the carbs is that one of the diaphragms is not sealed properly.

Did you measure the valve shims/gap after you did whatever you did?

A mechanic friend of mine has a trick for getting at noises: Take a screwdriver and press it against the metal in one area to test and put the handle against your ear. The screw driver conducts the sound to your ear. As you move the tip around, you should be able to isolate the sound that way.

 

i'll double check the diaphragms.

yes i measured the gap after new shims,

and yes i used the screwdriver to the ear trick

 

If you remeasured it shouldn't be a large gap in the valves. They should all be in spec or you're not done there.

Some valve noise is normal at idle.

 

Troubleshoot the Noise:
If the Noise is a KNOCK.

If you have Probed and "Hear" the Noise on No.-2, ...

Run the Bike.
With the Engine running, ... remove the Spark Plug Cap for No.-2.
If the Noise diminishes ::: SIGNIFICANTLY ::: you suspect a problem with the Connecting Rod Bearing.

If the Noise DOES NOT diminish, ... It could be a Main Bearing.

The Rod Bearing will be a distinct "Knock".
Rhythmic and pronounced.

A Main Bearing is LESS pronounced.
Dull sounding.

Because you probed it near 2, ...
Remove the Cam Cover and make two observations.
1. Look for "Scratching" on the inside of the cover, ... possibly made by the Timing Chain.

2. LIFT the Cam Chain straight-up ... Off from the Center of the Guide Bridge.
The Chain should be TIGHT.

If there is excessive slack:
Adjust the Cam Chain Tensioner.

Search: Cam Chain Tension Adjust

 

valves are all in spec, at least were a month ago, with plenty of room to shrink up.

i really just don't know what i'm hearing anymore. lemme try and get the carbs quiet and check the diaphragms, get that out of the way

then get new exhaust studs just to be sure, so i can rule that out.
anyone know where i can get the proper ones at not astronomical prices?

the more i listen to it the more unsure i get

 

Len (Chacal) @ xj4ever his banner is in the top right.

You may be able to feel the air from an exhaust leak with your hand.

 

thanks rick, when i get a day to sit down with this thing, i'll do that stuff. just haven't had much time to devote to it. There is a faint rail road track noise i've noticed. rhythmic three dunks, a pause, then the same three dunks/knocks whatever you want to call it. but it's very very faint. I checked all my diaphragms, put it back together, everything looks fine, but it is quieter now. still that little tap tap tap coming from the carbs. You start listening to this stuff to much and it just gets to the point you don't know what you're hearing and from where it is. all the sounds are kinda quiet today, but when i was so focused on it yesterday, they sounded so damned loud. gonna try and find a third party mechanics smart person to take a listen.

did get my color tune in, and went ahead and did that up in the last hour. but i have a question about that...

i followed instructions, brought it to yellow, and backed off just till the yellow went away, couldn't really see that dark blue they talk about. but now my plugs are black! lol. i did a better job just tweekin it by hand. had them nice and brown. it's almost a full turn more out now with the color tune route. have i done something wrong?

 

yeah i've ordered stuff from him, it just seems like a lot of money for some nuts and bolts. i'll probably try washers/spacers before i spend all that on some new studs and nuts

 

I can see if the studs will come out of my parts bike. If they do you're welcome to them.

 

alright, got a little time on it, not much, but some. had a stethoscope. All the noise is coming from the valve shim area. Rick has me wanting to check my chain though. was listening to it, I have nothing to compare to so i can't tell if it's noisy, but i just want to double check it. Had a qualified mechanic listen to it, he says it sounds pretty good. i'm just hearing the shims and valves

on the down note i finally got around to taking my riding test today, the pressure got to me and i failed :/ off the charts in braking, (in the good way) dropped a foot in the u turns, that i've done over and over again fine at, and took a turn going way to fast, to worried about them timing me

 

If you think the noise is coming from the Carbs, ... you have to check that the LIP of each Diaphragm Rubber is SEATED in the Groove.

It sometimes helps to SMEAR some Synthetic Grease along the Loacting Channel to act as an "Adhesive" holding the Diaphragm Rubber securely in place while the Carbs Hat is attached.

 

yeah i went through all my diaphragms rick, re-seated them all, much better now. put washers on my exhaust stud nuts too, i know thats terribly wrong to do

now i can sit down and try and see where the railroad track thumps are comin from