1981 XJ 650 unable to set idle

Hi Guys, I have had the above bike for about five years, but have never been able to get it to idle smoothly. I have had the carbs ultrasonically cleaned and have fitted new parts, including new throttle shaft seals, diaphragms and gaskets. I have also set the float levels and have fitted new rubber intake manifolds, new coils and HT leads and plugs.

The engine starts easily hot or cold, but will not idle smoothly which makes the engine noisy and hard to ride. I can get the vacuum setting on all the cylinders almost right, but when the engine is revved up it goes all over the place and does not go back to the same vacuum readings.

Recently another problem has developed with number two cylinder not running at all, the exhaust pipe is cold and number four plug is black and sooty. I have checked that I have a spark on both cylinders and that was ok, and have done a compression test on all cylinders. The pressure were 155 psi on all cylinders, which apparently is good, So what the hell is going on, I have nearly pulled all my hair out, so your help would be most appreciated. Yours hopefully Mal.

 

No pin holes in the diaphragms ? have you fitted new caps to the vac' spigots ?

 

Have you color tuned your mixture settings?

 

Mal,
Welcome, your issues should get sorted out here in no time.

The things mentioned in your first paragraph; were they all done at once?

Was there something wrong with the old coils, leads and plugs?

 

did you try replacing the spark plug just because it fires outside the cylinder does not mean it is firing under compression.
How "new" are the coil packs and carb cleaning ?
are you running pods or stock airbox and filter

what does the #2 plug look like?

you say set the float levels do you mean you wet set fuel level or dry set float height?

 

Are the valves in spec?

Gary H.

 

I'd put a new plug in ......

 

Thanks for your reply, even with the vacuum gauge pipes on it is the same and the diaphragms are new. Or should I check them even they are new.

 

No I haven't, but I have set the mixture screws all the same at two and half turns out. Is the color tune good?

 

Thanks for trying to help, no I haven't fitted a new plug, but a spark tester showed this HT lead to be firing.

 

Thanks for helping Gary, I have checked the valve clearances are they are ok. But can you explain why this would matter, is it only a tight valve that would cause a problem?

 

Hi. yes the new parts were fitted all at the same time in an attempt to fix the problem. Don't know if the old coils and leads were faulty, just changed them to be sure.

 

Thanks for trying to help. I tested the plug by using a spark tester, which I think tests the plug and current to the plug. The Dynatek coils are new new, and I have cleaned the carbs many times, the last being this week.
I am running K&N pods. Number 2 plug looks slightly wet and black, but no soot.

 

This is a HUGE detail that you left out earlier.
Are you still running the stock jets?

 

Yes the jets are still stock, don't know where to get any others as this bike is quite rare and unloved in Western Australia. The dealers are only interested in the new stuff. As I said earlier I have K&N pods on the intake and a four in one exhaust with a 2006 R6 muffler. Any idea what size jets I need or can they be drilled out? Or will adjusting the mixture screws help. Thanks heaps Mal.

 

Do you have any of the original parts (airbox, muffler/ exhaust, coils, etc.)?

These bikes are a well thought out balanced system that is pert near perfection in a stock condition.
Doesn't mean that mods won't work but it does mean that we (the XJ community) can't tell you an exact jet size to use to fine tune your pod/ exhaust combination.

You may have a lot of experimentation ahead of you.

 

I am running K&N pods.

+1. This is a issue even with the valves in spec.

Gary H.

 

So what...... Is may SAY its firing, but if you have a cold pipe, it's either NOT FIRING, or you're not getting fuel..... Or both-----
Putting in a NEW plug helps narrow it down. Happen to notice if the plug is wet vs. dry? That's an indicator either way, too.

If you haven't:
-adjusted the valves
-thoroughly, totally cleaned carbs
-wet-set
-bench-synced
-new plugs
-correct jets
-correct airbox/clean filter
-colortuned
-running balanced

You're gonna have issues.

But, assuming that's done, we're looking at:
#2-pipe is cold. Therefore no fire. So, either it needs a plug or fuel. If plug is wet, there's fuel. If a new plug fires it.... Problem solved there. If it doesn't, then it's electrical. If there's no fuel, that needs to be addressed at the carb.

#4-black sooty.... It's running rich, you gotta adjust the mixture. Possibly make sure jets are not mixed up.

Still, after correcting those you'll need to do a running sync.

 

Aaaaagh-- I didn't even see the pods comment.....
I'm thinking i might make it a personal goal to not reply to anyone who has running issues unless they can prove that they are running an original airbox and filter with correct jets!!!

 

Ok, I guess I did cover that, though, in my list of things: airbox/filter/jets

 

Reminds me of another forum I used to be on--- guy was complaining that his brakes kept locking up on the from and nose-dived when braking..... After much discussion, Finally made the comment that his back brakes weren't hooked up yet........DOH--face palm.

 

it should be an automatic posted reply by the site computer when ever the words wont idle comes up
"Got Pods"?
he has answered 3 of 4 questions I asked so far.

question 4 would you answer it
You say set the float levels do you mean you wet set fuel level or dry set float height?

your getting fuel if plug is wet
1 replace the plug
2 if spark plug cap is a part separate from the wire cut back the lead to ensure that you have a good connection

3 read this thread it will guide you on jet replacment when you modify stuff. you will have to search for the info as it is packed with different info.

The Information Overload Hour


http://xjbikes.wikidot.com/carb-specs
is this your bike???
Years & Models: 1980-1 XJ650 4K0 and 4K1 models (UK/Europe)
Carb Manufacturer: Hitachi
Carb Series: HSC32
Carb Model ID: 4K000
Main FUEL Jet Size: #110
Pilot FUEL Jet Size: #40
Main AIR Jet Size: #50
Pilot AIR Jet Size: #195
AIR COMPENSATOR Jet Size: unknown
Starter FUEL Jet Size: #40 (non-replaceable, in float bowl)
Main jet NEEDLE ID: #Y-11
Main needle JET Size: #3.2mm (the main needle JET is also known as the "power valve" or "emulsion tube").
Fuel Level in float bowls: 3mm +/- 1mm (.118" +/- .039")
Idle RPM's: 1,050 rpms

Although not part of your carbs, your valve clearances should be considered as part of your "intake system", so here are those specs, too. Note that valve clearances should be measured with the engine "cold", meaning 70-degrees Fahrenheit or less:

Valve Clearance Intake: 0.11 - 0.15mm ( = 0.004 - 0.006")
Valve Clearance Exhaust: 0.16 - 0.20mm (= 0.006 - 0.008")

 

DR my arm keeps hurting when i do this..............
sounds like an episode from the 3 stooges

 

I wouldn't worry about being 70 less. It's more important that it is 'sat-overnight cold'. I've never had issues with shims on an 85 degree day, etc.... But don't check clearances on the same day that the bike was running.

If any bikes need clearances check at a carb clinic, I insist that the bike be dropped off at least a day in advance. That way I KNOW the bike has sat overnight.

 

Yes the jets are stock, but can the mixture screws be adjusted to compensate? Or what sizes do I need?

 

Thanks for the advice. The carbs are as clean as when they left the factory, and have been wet set and bench synced. The rest of the items you have mentioned I will check again. I told one of the other guys that the bike has K&N pods on it and he seemed to think this would make it very difficult to sort. But I noticed several of the members have bikes with after market exhausts and pods, so what did they do?

 

Constantly fiddle and fart around with him and trying get them to where it's the Most acceptable performance. Some are lucky enough to have it dialed in fairly well. Some Keep at it it by trial and error. Some give up and put the airbox and filter back in, go back To the original jetting, Re-tune their bike.... Then go enjoy riding

 

Then, of course there are those that, If a plug is not firing properly, will try putting a new spark plug and first…

 

just think of it this way, you can look cool with pods or pull up aside of someone who looks cool with the pod set up , rev your bike on leave him behind in your dust because you will not have that flat spot in the throttle response. your bike will just pull hard through out the throttle , giving you that edge

 

Mostly they put-up with a bike that doesn't perform well.
Your idle issue (not the faulty plug that you should replace) is directly attributable to the pods. You're running too lean.

 

I think I will put new plugs in and get a colortune, then see where I am at. If the pods will not work I still have the original air box and a new filter, I took them off for two reasons, one I think the pods look better, second it makes taking off the carbs a lot easier.
Don't know if this is relevant, but when I was checking out the ignition system I found the grey and orange wires that go from the TCI unit to the coils have a resistance of 0.2 ohms. But the red and white wires that go from the TCI to the coils has a resistance of 3.4 ohms. Should there be a difference or do the red and white wires got through a switch or something? Everything else checks out ok.

If the TCI were faulty what options are there, are there any aftermarket units available in the US, certainly none over here.

 

I think I will put new plugs in and get a colortune, then see where I am at. If the pods will not work I still have the original air box and a new filter, I took them off for two reasons, one I think the pods look better, second it makes taking off the carbs a lot easier.
Don't know if this is relevant, but when I was checking out the ignition system I found the grey and orange wires that go from the TCI unit to the coils have a resistance of 0.2 ohms. But the red and white wires that go from the TCI to the coils has a resistance of 3.4 ohms. Should there be a difference or do the red and white wires got through a switch or something? Everything else checks out ok.

If the TCI were faulty what options are there, are there any aftermarket units available in the US, certainly none over here.

 

How are you testing? This really won't tell you anything. You have spark on all cylinders, so you shouldn't have a TCI or pickup issue. You can test the coils by getting an Ohm reading across red/white and gray and red/white and orange (unplugged from the TCI of course).

 

I am using a multimeter set on 200 ohms scale. I checked the wires from the connectors on the TCI box to the connector onto the coil disconnected at both ends, just in case there was a break or short, I know the coils are ok because they are new not sure about the TCI box. Just wondering why there is such a difference between the two wires that go to and from the same place.

 

Becasue they don't go to and from exactly the same place. You have spark on both coils. Your TCI can be assumed to be fine at this point. Work one problem at a time or you'll go crazy and never make any progress.

 

For rejetting just for future info "jets r us" has our jets

 

So does Chacal.

 

He has NEW PLUGS available, too----

Have you thought of trying new plugs yet? It could be as simple as that.....

 

Good starting point with pods is up 2 on the mains & up 1 on the pilots.