Seems I have a problem with idle.

So, the 750 that got me here.

Braks rebuilt front and rear, carbs rebuilt, floats set, valves clearanced. Should need a sync and be good to go, right?

So I build a synchronizer and go at it. Synched 1-2, then 3-4, then 1-2-3-4.

And then it revs to 3000 all on it's own. And when it doesn't and runs at 100 or so, there is this clattering sound from the engine.

The only thing I can think of is that the timing chain guide gave up the ghost and the chain is loose.

What else could it be?

This is disappointing enough to think about dumping this bike...

 

Re: Seems I have a problem.

probably just the cam chain slapping around with poor running/jerky engine. Your description of the problem was quite vague. Can you hit us again with a more detailled description of how its running/starting etc?

 

Re: Seems I have a problem.

what do you mean runs at 100 or so? Do you mean 1000rpms?

Are your vacuum rubber caps new? They can seem good but still leak and after getting pried off and on that might crop up. Drink a brew, sit it out for a bit. Whatever it is can't be that hard and can be solved.

Also just to be clear, how was it running before the synch? Or do you just now have it back running after all the maintenance?

 

Re: Seems I have a problem.

Probably a vacuum leak, either between an intake manifold and the head, or throttle shaft seals (unless you already replaced them.)

Or you missed on either the sync or float levels.

 

Re: Seems I have a problem.

Dont worry,
The xj sound notoriously crappy and jerky when its running at a low rpm
Im not sure if it has to do with the starter clutch or the transmission.

try spraying starter fluid or better yet an unlit propane torch around the intake boots to check for a leak.

Did you use the YICS tool when you synced and colortuned?

 

Re: Seems I have a problem.

Huh? :? are your carbs synced up properly?

 

Re: Seems I have a problem.

Only time my Maxim-X ran crappy and jerky at idle was when the carbs were out of balance (out of synch).

 

Re: Seems I have a problem.

I agree. My 550 when I first got it was noisy at idle-but after a valve adjustment, full carb clean, synch, once through the maintenance schedule and several oil changes with Q moto oil it now sounds like a well oiled machine even at idle. Of course it's not as quiet as a modern water cooled bike, but that would be scary if it was.

In short the XJ's may produce more decibels of sound at idle than some other similar bikes, but they should sound rhythmic and healthy all the same.

 

Re: Seems I have a problem.

Sonofa...

One of the rubber sections of the YICS tool was ripped up. I guess this makes the sync completely wrong.

 

Re: Seems I have a problem.

Yeah, would mean the valves were more than fag-paper tight :?

And yep afraid it's true JPaganel, sync is likely out if the YICS tool wasn't sealing correctly. At least it's an easier fix than a timing chain

 

Re: Seems I have a problem.

Time to use the YICS rag doll! lol!

 

Re: Seems I have a problem.

^^ +1

Or shopping for silicone hose of the right size that doesn't come from a pothead shop lol

 

Re: Seems I have a problem.

I don't use a YICS tool......yes, I have one--it's in the plastic sleeve that it came in. It's the fancy one, too. I like it--it looks neat and I can show people one at carb clinics.

dave fox

 

Re: Seems I have a problem.

YICS tool use is stressful, i always wind up destroying the little rubbers on the tool. I just stuff oiled up rags in and can leave it there the whole time, not worrying if it burns or gets a little warm .

Good luck with the sync!

 

Re: Seems I have a problem.

don't use the tool and live happily ever after

 

Re: Seems I have a problem.

Aaaand...

@#$%^&*()_)(*&^%$#$%^&*()_)_+_+_&$$#@@$%^&*&*&^#@#!#@#!!!!!!!!

Redid the sync with the tool sealing correctly. It idled at 1000.

Let it cool down, pulled the tool. Put the plugs back in. Put the tank on.

With enrichment completely shut off it promptly started and idled at a nice 6000 RPM. Fdisk me sideways.

I guess what upsets me is that I had such high expectations...


BTw, to answer some of the questions, vacuum caps are new, throttle seals are new, MNMaxims helped me with float levels. Intake boots are not cracked or weathered in any way and are bolted up tightly.

I wonder if YICS tool making a difference means that there is something wrong with the head.

 

Re: Seems I have a problem.

Are your copper sealing washers on the YICS plugs in good shape? (are they missing even?)

Sounds like you have a HUGE leak somewhere... or your throttle cable is hanging up somehow & pulling your leg...

 

Re: Seems I have a problem.

Washers are OK.

The leak has to be truly something. Pulling off a vacuum cap doesn't make any difference...

 

Re: Seems I have a problem.

you're sure the throttle is closing properly too? Many people have been fooled by either a frayed cable or bad routing under the tank before now, myself included.

EDIT-: and I trust your carb pistons clunk test nicely too?

 

Re: Seems I have a problem.

Is that possible one or two YICS passages are plugged up?

 

Re: Seems I have a problem.

Been there, done that, fixed it.

Yes, they did. The carbs were torn apart to the last screw and seal and cleaned ten different ways. I actually took the bodies to a shop to get them into an ultrasonic washer.

 

Re: Seems I have a problem.

Hm. Dunno. Perhaps one of the big guns will chime in.

 

Re: Seems I have a problem.

Check all your Boots. Then you can also do the paperclip sync. Remove carbs, open up idle speed till you can fit the clip in between wall & butterfly on I believe#3 carb. set all the rest of the carbs using clip under each one starting with #4,then #2, then#1. This should get you in the ballpark. After I did this I also used my vacuum sync tool I used on my multi carbed cars. It worked for me & this bike is gotten me lots of miles with no issues. also make sure that the floats are also not rubbing the sidewalls of the float bowl

 

Re: Seems I have a problem.

6,000 rpm's!

For the Plant to make 6,000 rpm's ... the THROTTLES have to be OPEN.
Have to be.

Not a small Air Leak.

BIG Air getting in!!!
Main Jet supplied Fuel.

I would suspect Cable-related or Linkage-related issues.

Handlebar Control loose.
Cable not anchored and pulling.
Choke and Throttle Cables errantly swapped.
Throttles stuck open.
Linkage problem.
"Something" keeping the Throttles wide-open.

P.S. You DID put the Plug for the YICS Passage back-in, ... right???

 

Re: Seems I have a problem.

And the amount of resting rpms is twice what you started with that should be a clue to you. It was running up to 3k now 6k-that is about 70% throttle averaged across your carbs. So back up and realize what must for sure be happening. The cause is yet TBD but the result is your butterfly's are opening and your CV pistons are lifting, or most of them are at the very least.

Maybe chasing a dead end but when you say 'cleaned 10 different ways' what do you mean?

 

Re: Seems I have a problem.

When Carbs are taken off, cleaned and put-back on, ... it is not uncommon to wedge the Linkage Cable Attachment under the back-side of he Head.

 

Re: Seems I have a problem.

Sounds like you havent really tried much of anything
Throttle shaft seals
Especially since you broke the rack.
Bench sync.
Set air fuel mixture screws to 2 1/2
Install
Spray carb cleaner on intake boots, listen for higher revving.
Spray on Throttle shaft seals, listen for revving
Spray on Intake boots, listen for revving.
Youve got an air leak
-Chris

 

Re: Seems I have a problem.

Good point Rick.
I've done that once before.
Only once though. Caught the mistake when I went to install the throttle cable though. "Oh. You shouldnt be here"

 

Re: Seems I have a problem.

6-Thousand Revs!

Ain't no Throttle Shaft Seals or some-other minor Air Leak!

The Throttles are OPEN
MAIN Jet Fuel entering Combustion Chambers.

You're closer to the Red Line than you are Idle.

 

Re: Seems I have a problem.

As above. You have a cable hang up or similar. This is not a cleaning/leak exercise.

 

Re: Seems I have a problem.

You sure you didn't simply mix up the throttle and choke cables, or the throttle cable has maybe jumped loose from its perch at either end? The motor cannot run at 6K without the butterflies being open, and that is a mechanical function.

 

Re: Seems I have a problem.

Big guns or small peashooters, the answer seems to be the same either way. Maybe I'm not so daft

And no YICS blockage would INCREASE revs any way shape or form :?

 

Re: Seems I have a problem.

FWIW .. have had the same problem with torn up yics tool seals..went back to stuffed with oily rags and the last time i synched the carbs ended up with a high idle when at running temp' , about 500rpm high so i did it again and it was right. Either you got th sync' wrong or it's a mechanical fault, for that many revs I'll go with mechanical fault as well.

When putting th carbs together after cleaning / seals etc did you make sure they were all lined up on a flat surface as you tightened the rail? that they mount together on and that the springs on the adjustment screws were all sitting properly. When i did mine i got a spring sitting wrong somehow but noticed before putting them back on, luckily.

 

Re: Seems I have a problem.

Throttle moves properly. Although, this did happen after I put the tank back on. Sigh... I'll pull it off again and see if it pinches anything.

Well, I'm sure I tightened SOMETHING on both sides of the engine... Yeah, I'm confident I did.

Taken apart to the last screw, dipped in chemical cleaner, brush bristles inserted into passages, ultrasonic cleaned at a shop. Jets cleaned separately in Chemtool. Verified light through them.

Look further up this thread.

Brand spanking new.

Done.

Done.

I'm sure they are not mixed up. The choke cable moves the valves, not the throttle.

As for the throttle cable, it seems to be moving properly, but since this happened after I put the tank back on, it's worth a look.

The second time around with new rubber seals I oiled the tool before inserting (that sounds seriously dirty ), made things much easier.

 

Re: Seems I have a problem.

 

Re: Seems I have a problem.

I have the exact same issue with my bike.
Bike runs buttery smooth until it reaches operating temperature. Then it will either spontaneously rev to 5k or if you blip the throttle it will stay at 5k.

I pulled the carbs off and rechecked EVERYTHING twice and it still has the problem. Ive recently pulled them off again and done every check for the umpteenth time, though I havent gotten around to reinstalling them and trying again.
Carbs ultrasonically cleaned. Pistons passed the clunk test on 3 seperate rebuild sessions, I even polished theis last time. All manifolds meticulously checked for vacuum leaks. Throttle shaft seals replaced, floats set, carbs synced with a manometer, shims done but I may change them around again.


The throttle does not need to be open to rev to 5k rpm at idle, and none of the vacuum piston are opened up when the problem is occuring(i ran it without the airbox last time to check this). We are talking about a totally unloaded engine not a motor in 5th gear crusing down the freeway. 5krpm only takes a few % throttle when in neutral.
Having the YICS tool in doesnt effect the problem.

 

Re: Seems I have a problem.

for whatever reason your only running on 2 or 3 cylinders,your idle speed is adjusted to 1K with missing cylinders. then when it gets warm the rest kick in and away go the RPM's.
your bad cylinders are probably lean when it's cold and close enough as it warms up.
when it's cold, start it up, and see which pipe stays cooler the longest.
look into the enrichment circuit maybe
maybe turn that mixture screw out,see if that brings up RPM's, evenness across the carbs doesn't matter
get some new plugs.
sync doesn't really care if the cylinders are firing or not

 

Re: Seems I have a problem.

Pulled off the tank, verified throttle cable is OK, verified spark on all cylinders.


And then it wouldn't start. Just cranked till the battery started dying.

I'm starting to think this bike is haunted.

 

Re: Seems I have a problem.

Alright so run us through the symptoms again. Hard to start, then idles at 6k? Anything else? How are those plugs? If you get it started see if one or more pipes runs cool.

 

Re: Seems I have a problem.

Good point, I'd have to say this is a distinct possibility if nothing mechanical is opening the throttle on you. It can be hard to detect even a 2 cylinder misfire on these engines (ask me how I know!)

 

Re: Seems I have a problem.

To restate the latest sequence:

Synched with YICS blocked, idled at 1000
Pulled YICS tool, put plugs back in, put the tank back on
Started and immediately revved to 6000
Pulled the tank, put the gas bottle on
Checked throttle linkage
Checked spark on all cylinders.
No start

 

Re: Seems I have a problem.

if you used a paper clip to do a bench sync and never turned the idle knob down to lower the idle, there's a chance that 6K is what the idle is set for.
it might be set high enough to defeat the enrichment circuit.
try backing off the idle screw till it's off the linkage then go in till it touches and then in 3/4 to 1 turn.(that's a guess), no yics tool.
if you pull a vacuum cap and nothing happens, could be because that cylinder isn't firing.
sometimes a plug will fire outside the engine but not when it's under compression

 

Re: Seems I have a problem.

So, I turned out the idle knob.

Got it to start and idle at 1000.

And then it jumped to 3000. At least it's not 6K...

 

Re: Seems I have a problem.

Still misfiring on a couple of pots at cold startup, idle is adjusted to 1000 on the firing cylinders & then as the engine warms, the other 1 or 2 start firing and the revs shoot up would be my educated guess...

 

Re: Seems I have a problem.

Sounds logical.

What would be the next step from here? New coils?

 

Re: Seems I have a problem.

New plugs not coils!!! (unless you know something we don't, have you checked the resistances?)

I've found bad plugs can cause hard starting & on multi cylinder bikes can cause a miss until they warm slightly, plus they're a cheap option. What code number is on the plugs that are fitted?

 

Re: Seems I have a problem.

We're still waiting for you to tell us if one or more pipes are cooler. At least that will narrow it down to a particular cylinder(s)

 

Re: Seems I have a problem.

All the pipes run hot, as far as I can tell. #4 seems to be hotter than the rest, but that's about it.

 

Re: Seems I have a problem.

you can't wait till their hot, check the pipes as soon as you start it, while it's still at 1K.
don't even sit on it to start it, kneel down by the pipes and feel for heat as soon as it starts.
go get some new plugs.
then let the bike warm up real good,(3K idle, choke off) set the idle to about 1500, and start the sync again and try to keep that 1500 while you sync.
then go to 1200 and start on the mixture screws

 

Re: Seems I have a problem.

So, the plugs I have in it are B7ES. The parts catalog says they should be BP7ES.

Do I not have the right plug?