Won't idle.

I just got a 1981(82?) Xj650 (5N8).
I would like to note that I am familiar with carbs, but I am no master.
So, I can run on the enrichment circuit, but as soon as i turn it off the bike dies. Idling is not happening. I CAN use the enrichment and get moving, then turn it off down the road. It wont have much power, and it feels like it surges, but it'll run, and that's how I got it home. It looks like the carbs have been rebuilt, the gaskets seem new, and the Jets look suspiciously new. If someone has changed the Jets, I don't think they used the right ones. Any thoughts?

View attachment 34702

 

So maybe the so called “rebuild “ was not complete.
“Church of clean” is an involved undertaking. Jets, gaskets, o rings, seals etc etc. Most bike shops will not do this because of the cost involved that many people won’t buck up to have it done.
There are a few of us that do this work.
Out west me , east is @hogfiddles.
In most cases an idle adjustment and syncing is all that is required after you have checked the valve clearance.

 

I should still be able to get SOME idle. But I still got nothing. I'll be taking pictures tonight

 

Pardox, we need a little back ground on the bike. Did the bike just come out of a storage shed, back of someones house, out in the back yard for yrs under some tree? Many of the folks that will help you out here will need to know how you cleaned or if you cleaned the carbs. The most common fact is, if they have not been cleaned as stated above, you will have issues. When the carbs are fully stripped down and cleaned as in the "Church of Clean" the bike will start and run well. Other issues could be some air leaks from cracks carb boots front or back.

When you get a chance fill us in a little more and we will be able to help you out more.

 

first thing you should do is check valve clearances
then warm up bike with enrichment circuit. then try adjusting the idle knob as you back off enrichment circuit. you should be able to set idle at 1050 or 1100 rpm.
if you cannot adjust the idle with the knob it is indicative that your pilot jets circuit is dirty. that's the pilot jets and mixture screws.
check your jet size numbers and check the air jets for proper location.

are all the headers getting hot?

 

The p.o. rebuilt the motor/carbs and added a 4-1 exhaust. The boots and seals all look new It was stored in a dry barn over the winter. I suspect he had no idea how to tune these....clearly neither do i

 

How long are you letting it warm up before shutting off the enrichment?

 

Probably 3 min. At one point i drove it on the enrichment to see if it wasn't getting warm enough. No dice.

 

So I just found the set screw by the enrichment plungers. None of them were even close to the same setting. I've put them at 2 1/2 turn, I will update soon.

 

My jet sizes were;

40
110

 

Those are the idle mixture screws. 2 1/2 turns is a good baseline, but you will likely need to bump them closer to 2 3/4.

 

Well, now it isn't starting at all...... I can get it to run on starting fluid, but it won't even put with the enrichment.

 

did you set the floats at all? #1 and 4 look high so the wet set would be low. maybe it's just the picture

 

I can't find definitive sources. What are these? Mikuni, or hitachi?

 

Can't find definitive sources?
We must have missed pointing you to: The Information Overload Hour
You have Hitachi carbs.
Set the fuel levels wet: Setting the fuel levels

Given the state of the idle mixture screws I would not trust that the PO knew anything at all about what he was doing.
Assume that he did everything wrong.
Just go through and double-check his work for now.
IN THE CHURCH OF CLEAN

You can sort-of test the throttle shaft seas for newness by removing the E clip from the outer two carbs, removing the plastic washer, and using a drop or three of automatic transmision fluid on them (one end at a time, set the carbs with the shaft end pointing up) and see if any of it leaks onto the throttle plate after a few minutes.

 

What are the butterfly shaft seals made of? I have the tools to make my own, I just need a material list.

 

you can use a couple of o rings I think it is #10 buna orings. there are a few threads on the use of orings

 

The good replacements have an X profile. Buna-N.
They are inexpensive enough that making them isn't worth the wage you would pay yourself to do it.

 

Just an observation did you try turning idle adjustment screw in , if it is set to low then bike might only run with enrichment on. Idle should be 1095 to 1100 rpm is ideal.

 

Ok, progress has been made. after taking It to church, It will now run without choke. But it revs up to 6k at startup and wont idle down passed 2500 rpm. The idle set screw is mostly for looks. I do have vacuume leaks according to the propane test. BUT it's a step in the right direction, I'm going to have to change my shaft seals and find boot fittings that aren't bottomed out and bent.
For giggles I took it for a mile long stretch down the road, and it does not like the low end. But dam is it happy passed 4.5k. Then it also has trouble reving down, no doubt a symptom of vacuume leaks.

 

You need to a running synch , if one carb opens more than another this will cause what you describe, and if butterfly plates are not centered right is another symptom.

 

Tomorrow I'm going to be looking at affordable vacuume gauges. I'm not too fond of the two bottle thing. I'm also curious about that clear spark plug whos name escapes me.

 

The clear sparkplug is a Gunson Colortune.

Cheap gauges are just that. Invest a bit more for a MorganCarbtune, or a set of MotionPro stick guages. If you can find a used Morgan Carbtune set all the better; those don't ever need to be calibrated.

@chacal sells all of that (except for the possability of getting one used).

 

Just ordered one of these. Can't believe it's taken me this long. I've got a suzuki gt750, Honda cb750, a katana, a goldwing, and a couple vws. I can only imagine the kind of difference I'm going to have after everything is tuned properly.

 

You will not believe how easy it is to use and tune, I have the 4 vacuum gauge manifold , finally ordered the Morgan tune , I was close with the vacuum gauges but now spot on .

 

Well, this is the reading I got......

My #4 has no vacuume, at least not enough for my guage to pick up... I moved the tubes around in different ways, but every time, the result was the same.

I suppose that points to valves....

 

nipple could be plugged. shims out of spec.

move hose to another cylinder see if it is the tool

 

i think the only way to have no vacuum is to have no compression

 

Pretty much. Unless it's not.

Compression test is order, in addition to the things XJ550H mentioned.

Valves being out of spec would still draw vacuum, and if they were so far off that there was no vacuum then that would mean they aren't opening at all. That is unllikely to happen on just one cylinder.

 

Bout had a heart attack, it was a plugged nipple.

 

The easy things.....

 

Does anyone have the exact measurements of the yics blicking tool? I would like to see if I can make them.

Also, are the passages the same on every bike?

 

I think somewhere here are the measurements to make one but it's not needed IMHO. I've sync'd mine with and without, cant tell a difference

 

Well, I've cleaned my carbs with the intensity of a thousand suns. My throttle shaft seals are still soft, and look fairly new. I have the Carbs synched, and the pilot jets opened to 2 turns. But I can't get the dam thing to idle. It barley even responds to tuning but it will run with enrichment.. I've tried a lean mixture, and a rich mixture. Everything is where it should be, I've checked 4x. The only thing I can think of messing it up is the 4-1 exhaust that came on the bike.

 

don't need exact measurements, don't need the tool at all really. all it takes is to isolate each port, and keep the ends sealed.
the ports are in line with the carbs so somewhere between the carbs works

 

two turns isn't enough try 3
turn the idle up till it will run and take it from there
4/1 pipes isn't the problem as far as idle goes

 

3 turns... Dayum. I'll try it when I get off work. I think I read somewhere that you can jam a strip of ATF soaked tee-shirt in the port and block it off with that.

 

ATF, what a mess. then are you sure their all blocked? 1 and 4 are close to the ends, is there a vacuum leak there?

 

I work in a diesel shop so I have plenty of crush washers, I'm going to try changing them. But the boots aren't leaking.

 

What size are they?

 

don't know, haven't taken one out for many years

 

I was going to make one myself but found a guy on Ebay that makes a nice aluminum one with o-rings for $33.

 

If you're not idling now, then blocking the YICS ports isn't going to fix that. [EDIT} Unless there is a vacuum leak at the YICS mainfold.

A 4-1 will make it a tad lean (not much though), and since the baseline for the idle mixture screws is for the stock exhaust, and most of the time we end up at 2 3/4 turns out you might need 3, or to go up one size for the pilot jet.


If you really want to mess with the tool:
home-made-yics-tool-diagrams.72713
@chacal also sells them, including OEM quality seals.

Keep in mind that hardly any of us use the thing, and the one member that I'd trust to rebuild my carbs has his sitting on a shelf still in the wrapper.



Merged so we can keep track of what's going on.

 

Ok.....im getting really good at pulling and replacing these carbs. A skill I hope to carry on to my other bikes. I was doing some reading and I found that there are o rings in the pilot jet bores. I never even saw them. So I got them out and found 2 that were flat, and one that was flat broke. I went ahead and purchased a full rebuild kit complete with o-rings and new jets. I'm tired of fixing someone else's f***up. I wanna fix my own f***ups damit.
I've got a colortune on the way, and a few other parts, and tools.
Now, I also read another post where the o.p. was having basically the same issue as me. Then, dudes neighbor pops in and tells him to adjust his timing chain and switch to a higher octane. As far as I know, the choice in octane won't keep these bikes from idling. But I was curious aboyt the chain adjustment. And how I would check it.

 

The camchain on yours adjusts automatically.
The machine was engineered to run on low-test pump gas. Increasing the octane is just a waste of your money.

The idle mixture screw o-rings are often ignored, and will cause no end of trouble unless they are in good condition. Vacuum operated carbs are intolerant of vacuum leaks.

 

your motor will not benefit from high test fuel.



it is located under the carbs. you will see a bolt with a lock nut on it pointing 90 degrees out of the adjuster if it is adjustable.

if it is an automatic adjuster it may need to be removed and cleaned and reinstalled.

 

this link shows how to adjust if it were adjustable
http://www.xjcd.org/650H_engine_maintenance

 

My new rebuild kit came in today. I'm going to tinker with that tonight. My colortune also came, so it's going to be an interesting 24hrs.

 

With my MAC 4-1 I have to run almost 5 turns out. If you're at 3, that's prolly why it won't idle.

I bet it you raise the idle screw in enough it will, but if you touch the throttle it will never come back down.