cant get my idle

Ok so when i first came on to this web sight my main problem was for high idle/wouldn't idle right... everything pointed to rebuilding my carbs which it took a while to build my confidence since I never really messed with any carbs. Hours and hours of reading all of the great advice from this website. finally i went for it and everything went as smooth for the most part. 4 new rebuild kits new main and pilot jets new fuel supply o rings along with the fuel inlet fitting (fuel T that goes in between carbs 2 and 3) and new throttle shaft seals. I clean each carb one by one and after i cleaned each one i went back and completely did it again to all 4. Once i got them all back together clunk test passed perfect they dropped like a lead ball. Then i bench synched them. Then i check the fuel levels on all four carbs. The levels came right up to the float bowls just like they were supposed to. Then I check my valves. This whole time everyone is telling me get a new bike or take it to someone who know's what they are doing. F them all... right. No one will do as thorough as a job as I'm trying to do. the valves read from exhaust 1-4 .007,.006,.007,.006. Intake was 1-4 .004,.004,.005,.004. Is this a problem since they are not all the same but close??? Got the carbs back on the bike and still a high idle. I did a running sync. I got all 4 carbs very close and my idle to 1000 rpm's. even though i should be 1200 rpm's. So with all carb close to being perfectly in sync idle at 1000 rpm's once I give to gas the bike jumps to 2000 rpm's and won't come back down. clutch cable good as well as the throttle cable. New gas. Any advice would be most appreciated. And i hope i didn't ramble on to much. Thanks for reading. And the bike is a 1982 XJ550 Maxim with mikuni carbs.

 

First, it would help if you put your bike model and year in your signature.

Second, it sounds like you did a very good job cleaning your carbs, but some of your valves seem a bit tight (the intake valves at 0.004 and the exhaust valves at 0.006 inch). Specs are 0.0043 inch for intake and 0.0063 inch for exhaust. It would be a lot easier and more accurate if you use metric gauges.

This said, if your valves are tight, any attempt to sync your carbs will be useless.

You may have another issue, though (air leak at intake boots).

 

Your valves ARE tight, .004" = .10MM (.10160 to be exact) and .006" = .15MM which is out of spec.

It's not a matter of being the same, or close. Spec is .11mm ~ .15mm intake and .16mm ~ .20mm exhaust.

First step: Get your valves in spec. QB is right, a metric feeler set such as the widely available K-D Tools' #2274 makes the job much easier.

As for the fuel levels, they need to be at 2mm, +/-1mm, below the carb body-to-float bowl seam.

Step two: re-verify fuel levels not too high (or too low.)

Did you pull the pilot screws, clean those passages and replace the tiny o-rings on them?

Set your pilot screws at about 2 3/4 turns out to start.

Did you block the YICS when you did your vacuum sync?

What sort of manometer did you use for the vac sync?

The bike should idle at 1200RPM when you're done. It sounds like you're getting close, just not quite in sync yet or fuel levels off.

But none of that will matter until you get your valves IN SPEC and they're not. You won't get a truly good vac sync until they are.

From the factory manual:

 

Hey thanks qb and fitz for the reply's. tight valve's?? I understand not being in spec. but how do they get tight?? Over time I would thing that they would wear and thats why you need to put the shims in. But again I'm new at this and have no clue. The bike ran fine for years and never touched the valves. I do have a metric feeler gauge and will go back and recheck the valves. And i will go back and check the fuel levels correctly. I did pull out the pilot screw with a new o rings and set them all at 2 3/4 turns out to start. (?? i won't need to mess with the pilot screw until the colortune???) Blocking the YICS no clue. Any info would be great. I have four general auto vacuum gauges?? Is there a special vacuum gauge that i should be using? Back to qb ( air leak at intake boot) were you talking about from the air box or the engine side. The engine side is new they were old, hard, and cracked. Air box side never touched. They are very soft and flexible. Is this a bad thing?? Thanks again for helping me out everyone. Can't wait to go on a ride.

 

The valve seats wear, letting the valves move further into the head, closing the gap between the shim and the cam.

 

Correct. The valves pound themselves into their seats causing the clearances to tighten. The valve train itself wears much less than the valve seats which is why we're usually installing thinner shims when adjusting.

Get the valves in spec.

Get the float levels accurately wet-set.

Do a good accurate bench sync.

Leave the mixture screws at 2 3/4 out until the ColorTuning phase, yes.

You can use four separate vacuum gauges like you have; but you'll need to put restrictors in the lines to keep them from bouncing all over the place.

YICS can be blocked using a YICS blocking tool as shown in the manuals; either buy a replica or you can make one. Or you can use an oil-soaked cotton rag twisted into a rope and pulled into the passage.

 

Also, make sure your enrichener ("choke") circuit is adjusted correctly and that the enrichener valves are not partially extended. Many times the actuator rod or valve(s) will stick causing a super-rich condition at idle.

 

Thanks for the replies I'm going go back and do the valves. I'll get them in specs and go from there. Any tips or advice special tools that I might need would be very much appreciated. it might take a few days since i'm going to be busy with work but I'm sure I have question and i'll post them. thanks again.

 

Valve Clearances: http://xjbikes.com/Forums/viewtopic/t=14827.html

Part Deux, alternatives to "the tool" http://xjbikes.com/Forums/viewtopic/t=29209.html

 

thanks fitz.

 

An alternative to the Motion Pro tool is to pull the cams. I tried the tool on both my XS11 and the XJ650 and never got it to work right. If all your shims are tight, pulling the cams will allow you to swap them all at once.

After messing with it for half a day the MP tool ended up in the garbage.

As far as measuring the gap, if you dont have them yet, I highly recommend a set of go/no-go gauges. They make the measuring very easy. If you havent used them before it has a small step on the feeler so you get a fer solid measurement. I picked up mine at a local parts store for I think $8.

 

Ok I got the tool and after three tries I got it to work. Now I can't read the numbers on the back of the shim. I tried a magnify glass w/ a light nothing in the sun and in the shade nothing. Can I go on to the next valve WITH THE SHIM STILL OUT??? Or do i have to put it back in to go to the next valve?? I was thinking of using a micrometer to compare the shim to another one that hopefully has a number on the back of it. any advise would be great thanks again everyone for the help.

 

You absolutely can not turn the cam without all of the shims in place. What you can do is buy an inexpensive set of dial calipers so you can measure the unreadable shims.

 

thanks for the reply!! Didn't touch anything after i got the first one out. thank god. I was having a little trouble with the first exhaust valve so i went to the first intake valve. my clearance reading intake on the first intake valve was .10 mm. When i took the shim out I couldn't read it but i thought it said y270. when i took the dial caliper to the shim the reading was 2.6924mm. I'm not a math major or any good at it but is this basically the same as the 270 reading that i thought i saw of the shim or is my math way off and need to try again?? If i was correct with my reading would I go with the new shim at 265?? or the 260. This is kinda above and beyond my knowledge with this stuff but I'm trying and really appreciate all the help. Thanks again

 

http://www.harborfreight.com/4-inch-dig ... 47256.html

On Sale!

 

You will need a shim one size thinner than your 270, so a 265, it will bring your clearance at 0.15 mm, right in specs.

 

Youre gettin it!
The 270 shim is yes, 2.7mm
As with all the shims. The one you cant read? Measure it. It'll tell you what shim it is.
Do you have a manual? That has a quick reference guide that will certainly tell you what shim to replace with, with the right clearances.
Valves
(Id do a carb cleaner test on the boots around the carb and check for air leaks just to be sure. Spray cleaner. If the RPMS rise, you have an air leak)
Sync
Colortune
And should run like a champ!
-Chris

 

Hey so I got all of the shims out and recorded there sizes except one. It is the 2nd valve on the exhaust side. All of the other valves i was able to spin them to access the little openening where you put the screw driver to pop the shim out. This one will not spin. I still goes up and down as I turn the motor but wont spin. Any adives. How much of a problem is this. Thanks for the help.

 

Ok got my valves in spec. The exhaust all .18. Intake (1-4) .13 .15 .13 .13. Next off to the wet set. So on to the wet set i measured 2mm just below the carb body to float bowl seam and marked on each bowl. They all came right to the line. Sounds like things are to easy right. Now on to the bench sync. Using a business got them all just about the same. Is there something else I should use?? Got it all back together and were still idling at 5000 rpms no choke and won't come down???? I sprayed WD40 on both sides of the carb boots. Nothing. I'm going to do a compression test a little later today making sure there isn't a blown head. Do another bench sync just because I was messing with the idle screw and to double check the bench sync. As far as blocking the yics I don't have the block tool so i was going to use a cloth does anyone have a write on it. Soak a rag slide it in?? Can I take both bolts out and fish it through then put one of the bolts back in?? Should I go on to try and sync them?? Trying not to rush anything but I really want to get it running. CORRECTLY!!!! Sorry for typing so much. Thanks for listening. Any advise is alway very appreciated!!!!!!!!

 

Gimme a minute, too much to type right now. You didn't "blow the head."

CHILL.

stay tuned

 

5,000 rpm's is NOT Idle.
5-Grand means your Throttles are open.

Getting the Linkage Connection to the Cable stuck behind the Head is commonplace.

Manifold Clamps interfering with Linkage, another.

Mis-alignment of the Bodies will bind Throttles open.

"Something" is opening the Throttles.
Try touching the Sync Screws with a Tuning Screwdriver and see if the Linkage is binding.

 

So before I did my valves the idle was like 4000 rpms. And my neighbor said the same thing so I disconnected my throttle cable and gave it gas by hand the carbs come back down but not the rmps. They were level after I cleaned them. Took them off again today to bench sync an put a level back on top just to see cause i read that it was very important to have them level and they were. Tomorrow when I get them back together I will try touching the sync screws but I think i already tried that. Had the same problem since the start. I must be missing something. I could take some pics of the springs and post them but not one is criss crossed or stuck.

 

Mine has a throttle adjustment that I can turn by hand. I had to turn it down so the butterflies were basically closed in order to get it down to 1000.

 

I have one too and turned it down all the way same idle. Something has to be opened still like rick said. Its gotta be something stupid. Hopefully! Just don't no what. FYI Checked my compression and averaged 130. All pretty close. Thank you everyone for the responses keep them coming.

 

Took the carbs off again. Did a good bench sync. Double checked everything again. All good. Put the carbs back on and... I got it to idle at 1200 rmps ran it for about ten minutes or so. There was a slight hesitation when I gave it gas before it came back down. Maybe a second or two. Is this do to out of sync carbs. Haven't synced them yet I was looking for a write up on the home made yics blocking tool. I saw a write up about one and it said it was 3 or 4 dollars. Haven't been able to find it again. Anyone have it??? Or the oil soaked rag way. Is it as simple as soaking a rag and stuffing it in there??? Does anyone have a write up for that one??? Thanks everyone for all the help. It looks like this bike might be getting close!!!

 

Cut the Hem off a T-shirt.
Then, ... cut the Body in a continuous Strip about 3/4 of an Inch wide.

Wet the Strip with Marvel Mystery Oil.
Use a narrow Dowel or Brazing Rod to pack the YICS Channel tightly with the Cotton Strip.

http://xjbikes.com/Forums/viewtopic/t=4 ... +yics.html

 

Thanks rick

 

Here are some pics of my carbs. Can anyone tell me if something doesn't look right. Keep in mind 30yr old springs. Not sure what to do. My next thought would to go back and realign the carbs.

 

The studs that hold the spring on the opsosit side of your adjustment screws.To me it looks like its (They) are missing the pic is small I might be wrong

 

I got a pic. of a brand new set of carbs. And everything looked the same. Except that mine are 30 yrs old. Went to sync the carbs and got them all close. But when I took the vacuum gauges off I saw that 2 of them were not even close to zero where they should be when they are not in use. So I'm taking them back. (harbor freight fuel and vacuum gauge testers 15$ each times 4) Does anyone no of a good set that works good with these bike or should I make a homemade one??? Thanks again everybody!!!

 

Have you WET-SET the float levels yet? I didn't see it anywhere above.

Bench sync is more accurate if you key off the tiny holes in the top of the carb throats in relation to the edges of the butterflies than use any sort of feeler gauge.

A genuine Morgan Carbtune (4-stick manometer) only runs around $100; and there are less expensive equivalents by Motion Pro and other aftermarket companies for what you paid.

Did you block the YICS for your sync attempts?

 

Thanks Fitz.
Wet set twice. Almost did it again today. Fuel levels need to be at 2mm +/-1mm below the carb body-to-float bowl seam. Marked the carb body and all were perfect.

Not sure if I follow the "key off the tiny holes in the top of the carb throats in relation to the edges of the butterflies". I have bench synced them at least 6 times using a business cards. The tiny hole that your talking about is where the pilot screw if all the way down pokes through??? Every time all very close and I open and close them with each adjustment to make sure they all go back into place.

Will look for the Morgan Carbtune manometer.

Blocked the yics with 3/4 inch strips of a shirt soaked with Marvel Mystery Oil like rick said. (should I get the blocking tool)?

Today I backed off the pilot screws a 1/4 turn and a very small change for the better but still not sure but i THINK its running lean????????????????

 

Thanks Fitz.
Wet set twice. Almost did it again today. Fuel levels need to be at 2mm +/-1mm below the carb body-to-float bowl seam. Marked the carb body and all were perfect.

Not sure if I follow the "key off the tiny holes in the top of the carb throats in relation to the edges of the butterflies". I have bench synced them at least 6 times using a business cards. The tiny hole that your talking about is where the pilot screw if all the way down pokes through??? Every time all very close and I open and close them with each adjustment to make sure they all go back into place.

Will look for the Morgan Carbtune manometer.

Blocked the yics with 3/4 inch strips of a shirt soaked with Marvel Mystery Oil like rick said. (should I get the blocking tool)?

Today I backed off the pilot screws a 1/4 turn and a very small change for the better but still not sure but i THINK its running lean????????????????

 

Look in the top of the carb throats. Look CLOSELY and you'll see three tiny tiny TINY holes. As the butterflies open, they uncover these holes.

Use the relationship between the first tiny hole and the edge of the butterfly to compare the positions of the butterflies in the carbs rather than trying to "feel a gap" to set them. Open the throttles slightly, and see where #3's butterfly is in relation to its first tiny hole; then compare the others and adjust so they all match. You can get much closer this way than you can with feelers. Just always be sure that when you're done, all 4 butterflies will close fully with the main knob backed off.

Mikuni apart: http://xjbikes.com/Forums/viewtopic/t=31061.html

 

Thanks again Fitz. I was able to locate to the tiny holes and match them all up to the very first one. Put it all back together and same thing Idle will either hang up around 3000 rpm and slowly come back down and die. Once in a while it will idle around 1100 rpms give it gas and it will still just hang up there. When the idle is low I turn it up and when I even touch it a little it just shoots up to 3000 rpm and if its high turn it down it just dies. Just replaced the throttle cable. Nothing interfering with it or anything else. Tried with and without the cable.

For fun I took them off again and adjusted the butterflies closed. It would idle with the choke on and my throttle response was great. No hanging up or anything. turn off the choke and for course it will die unless I give it gas. And the throttle response is still great no hang up. Why would this be??? Still trying to figure it out. Thanks

 

One more thing. I got under my bike and was inspecting the exhaust and found 2 tiny pin holes on my muffler. (1 on each) They seem to be in the same place but I haven't measured yet and they don't look like its from rust. But there is some condensation now coming from them. Air temp 70. Stock exhaust. Anyone have them as well or should they be welded up??

 

That's what the holes are for; helps to keep the mufflers from rusting out (as quickly). Water vapor is one of the products of the combustion of hydrocarbons. When the exhaust is cold (technically when it's at, or below, the dewpoint) condensation will form. Once the system heats up sufficiently the vapor will go along it's merry way, continuing it's journey to become one with the sea.

 

And the story goes on. I got a little mad ripped the carbs off again and... complete tear down of the carbs. Instead of boiling them I went with chem-dip. (Which I don't think made that big of a difference) Ok so I cleaned the gas tank out. (Which if your gonna clean the carbs might as well do that too and get a inline fuel filter) Still kicking myself in the a$$ for not doing this first. Everything cleaned now again. Putting the rack back together. STOP!!!!!!!!!! Flush, level, and Plumb...

Are there any how too's??

Carb alignment... Don't want to put them back together until 100% sure.

I use a level on all sides to make sure there are no gaps and that everything matched up properly. Is this sufficient? Or should i be doing something else?? Wouldn't the support brackets align them though??? (Couldn't be that ez just curious why they don't)

The 2nd carb... ???return string???? not sure the name of it. (On the outside that closes the buttfly valve.) Seems to not what to snap closed as all the other carbs. Will the other carbs assist or Do I need an new one or can i wrap it around one more time to get a little more tension???

And we'll go from there.

Thanks again everyone.

 

check the write up for realignment of carb rack...see page 27 & 28

Throttle Shaft Seals

 

carb #2 - this is off my 1982 XJ750J Maxim.....

note spring placement.....included shot of other side

 

Fiveofakind thanks for the right up... What up SD.

Got everything back together. Still can't get a good consistent idle. Should I just go ahead and try to sync them or am I just gonna be fighting a loosing battle? With a good bench sync I shouldn't be that far off. Right? I can go ride around the block to warm it up enough. Just not sure what to do.

Thanks again.

 

Valves in spec, float levels wet set to spec and as good of a bench sync as you can get?

Block the YICS and vacuum sync it. Then if it still won't behave you'll need to revisit the carbs and check very carefully for vacuum leaks.

 

Valves in spec
Floats wets set and in spec
Bench sync I'm sure its close is just think it should run better.

Vacuum leaks? First thought the boots. Engine side new. Sprayed wd40 and carb cleaner on the air box side. Nothing. New hose from the petcock to the boot. The caps old a little hard but I think that there still good and don't leak. But I will change them tomorrow. Any other places I should be looking at.

Thinking about going with the homemade manometer. Yics blocked with a t shirt. Any thoughts?

 

It is more money to be spent......but I would suggest buying a Morgan Carbtune Pro manometer ( $114) , a YICS sync tool ($40), & a Gunson colortune plug ($58) from Chacal.....that way you will always have it.....

Did you change your throttle shaft seals & fuel O-rings ???????

I am in the La Mesa aea......92117 seems to be in the Clairemont or Kearny Mesa area.....

I will PM you...we can exchange phone numbers if you want

 

Went to sync my carbs... Pull off the vacuum cap on the carb boots and the hole valve came out with it. Just another problem. They are pretty much brand new. What type of glue or epoxy should i use to get it back in there?

After I let the bike idle for 10-15 min the bike starts to idle higher without any throttle. I dont no if its cause the bike is now fully warmed up and out of sync.

Rick said a while ago to. "Something" is opening the Throttles.
Try touching the Sync Screws with a Tuning Screwdriver and see if the Linkage is binding.

When i touch that sync screw with some pressure applied the idle will go down. Why???? If they were binding why would it do it with no throttle given and only when its warm. Its fine when its cold. This is making my head spin. Any help is very appreciated.

 

If applying a bit of pressure to the linkages brings-down the Idle, ... something is hindering the Throttles to close.

The alignment may be askew.
There might a swollen seal.
The Handlebar Control might be tugging the Cable.
The Wire Cable might be frayed.
The Shafts might need lube.

Before I remount Carbs, I stand them on-end and lube the Shafts with Marvel Mystery Oil.
Then, I flip them over and do the other side.

I make sure there isn't anything keeping the Butterfly's from unrestricted movement.

Detach the Throttle Cable and see if that's your problem.
There's a Cable Slack Knurl on the Elbow where the Cable enters the Grip Housing.

The Grip Housing might be too tilted.
The Cable might be tight.
The Carbs might not be fully seated in the Manifolds.
The Manifold Clamps sometimes foul the Linkage from moving all the way shut.

There is also the possibility of an "Occult Air Leak"
A leak that does not reveal itself during routine troubleshooting.

The Manifolds have untreated Paper Gaskets; but rely upon Rubber O-type Rings to make the Manifold to Head mate air-tight.
Time renders those O-rings capacity to seal the joint ineffective when they become old, pressed, brittle and hardened.

You might have Air getting-by one moment and not the next.

Be careful!!!

Most people try tightening the Manifold Cap Bolts.
Those Cap Bolts are dirt-cheap soft-steel. Crap.
Installed during the build without treatment, they commonly seize.
BUT, ... they ACT like they are turning.
They are NOT turning.
They're TWISTING!!!

Without warning they SNAP.

A snapped Manifold Cap Bolt is a NIGHTMARE of the first magnitude!
A genuine Twilight-Zone Summer Buzz-killer.

 

I suggest you replace the caps that you say are hard but still LOOK good. Mine looked good too but I was having a H*ll of a time doing my vacuum sync. Couldn't get it right. Finally someone, on the forum, suggested I replace them. I did and after that EVERYTHING worked out. They where leaking and everything I did to detect a leak did NOT show that they where leaking. Get new ones and new clamps and replace them. This is one of those little things that should be replaced when someone buys one of these old bikes. And don't use automotive caps they do not stand up to the heat from the engine. I know I tried them don't last more then a few hours of riding.

 

Thanks for the reply Rick. I'll check all that stuff.

Ground-Hugger thank you as well. Yes i did replace them... And yes I did get them from a auto parts store and i did notice them being a little thin. I will get some from Chacal.

Does anyone no what the torque specs on the manifolds (carb holders/boots...) should be. Can't find anything in my manual or here.

Thanks again.

 

Which manual?

7.2 ft/lb. You really need an inch-pound torque wrench for the small stuff; so in in/lbs that would be 86.4 in/lb. (I just go with 86.)

If you're bumping along with the Clymer, PM me with an email address and I'll send you the relevant pages from the factory Max supplement.

 

I go with "Hand-tight"

I rather have to re-tighten them a dozen times, ...

Than have one strip or break ... once!