XJ650RJ bogs down and dies when warm

Hi guys,

I have this weird issue that been killing my riding season.. After trying a bunch of stuff myself from spring into summer I finally brought the bike to a mechanic who said he couldn't figure out the issue.. He has a good reputation around here but I don't know how good he is with older carburated bikes..

Now my issue is the bike seems to run absolutely perfectly and starts great but after some time riding, I seem to get a loss of power and the bike will bog down, stall and won't turn back on.. I can ride it for about 15-20 minutes on the highway before it starts to seem starved and won't take in gas anymore (seems like the issue, could be something else). At that point it seems like its not firing on all cylinders.. prior to stalling it will run a little bit on low power while not firing on all 4. Plugs seem a bit oily/sooty black after a while. Often I'll let it cool or clean the plugs thoroughly and it'll fire right back up like it's new. I've been on a few rides where these symptoms happened much quicker, after like 2-300 meters and the thing has no power, full throttle will keep it going but struggling for a bit until it dies.

I've reverted everything back to stock airbox, new filter, new oil, new carb boots to airbox + engine. I have a brand new battery, new coils + wires + caps + plugs. I checked the valves last season, maybe they're due now. I did a whole church of clean cleaning on my carbs other than throttle shaft seals. When I cleaned the carbs I did a dry set of the fuel levels. I also did new fuel lines DOT approved stuff, swapped out my vacuum lines to carb to see if that would make a difference.. New in-line fuel filter as well. The mecahnic did some obvious checks like electrical system, compression and said everything seemed really good.

I want this thing to be running consistently on long rides.. Anyone have any ideas? What would cause it to die after a 20km ride.. Usually when I get higher up in revs/speed.

This weekend I was going to check:
-Try to wet set the fuel levels
-Gas cap air flow, do a thorough cleaning
-Petcock cleaning(although it seems to work fine, doesn't leak and runs freely while on prime)
-Clean the interior of the tank for any surface rust
-Recheck the valve clearance

Sorry for the wall of text..Anything I'm missing here?

 

If the plugs are sooty that would not seem to indicate starvation, but rather an overly rich condition that is fouling the plugs. If the plugs are oily then there may be a problem with the rings, or maybe valve stem seals, both of which could foul the plugs. If it is over rich a proper wet setting of the floats and a proper setting of the pilot screws will probably fix the problem. I set my floats about 1mm below the target but still within the allowed range. A colortune plug will really help in setting the pilot screws. Now, all of this assumes you have the proper jets and they are installed properly.

 

Is your new fuel filter the paper type? It must be the brass type to allow enough fuel to flow. When you changed back to spec airbox, did you ensure that the jets were the stock? The wrong ones wouldn't cause the symptoms you describe (the 15 minute delay), but that's what jumped to my mind.

 

Stock paper filter? Any oil in bottom of airbox? Gas cap vent? Coils getting hot and breaking down? Have the jets in carbs been replaced , stock Canadian seca has 112 mains. Have seen "stock" jets drilled out making it impossible to get running correctly . Plug caps new?

 

Stock paper filter? Any oil in bottom of airbox? Gas cap vent? Coils getting hot and breaking down? Have the jets in carbs been replaced , stock Canadian seca has 112 mains. Have seen "stock" jets drilled out making it impossible to get running correctly . Plug caps new?

 

ohm out your pick up coils before you ride and then if it stalls out on you

 

Im betting on a pinched/collapsing vacuum line, or a plugged gas cap vent.

 

here is how to clean your cap. you can test this as the problem by opening the cap just unlock it to let the air flow as you ride.
Your Gas Cap and You

and vac line is 4mm is the size . you could switch to prime to see if this is your problem. Just good to replace it anyways

 

I've started to wet set the carbs this weekend.. very long and frustrating process..

I also noticed that the mixture screws were way out of wack, I set them back to 2.5 turns.. It's a full 2.5 360 degree rotation out from fully closed, correct?

I'll buy a new gas cap and do a full tank cleaning with vinegar/distilled water to make sure there's no loose debris in there. I took apart the gas cap real quick and everything seemed nice and clean in there.. The jets I'm running are #112 and #43 air jets are #205 pilot air jet and #50 main air jet. Would having a #43 rather than #40 make a big difference? I have a 4-1 exhaust with the stock airbox.

As for vacuum line pinching, is it usually the one going from carb to the petcock that is the culprit? I had one come with the carb>engine boots I bought and put it on and it was doing the same thing.. problem is it's just as old as the previous one so might just be the same problem.

I am running a brand new stock paper filter in the airbox.. I'll check for fuel in there. I'll also post a picture of the plus once I run it a little bit. I have to put it all back together see if everything runs well. Fuel filter is brass, it's a straight one tho, no angle.. is it possible that the fuel line orientation is causing bubbles or something?

 

2 1/2 full 360 turns from lightly closed is what most folks recommend as a starting point. However, the 4 - 1 exhaust and a non-stock jet could have a big influence on the final setting. There are other folks on here that know a lot more about that. I keep everything stock to make tuning much easier.

The vacuum line going from the carb intake boot to the petcock is the one that controls the petcock. Just make sure it's a good vacuum line and you should be fine. I found that there is a lot more vacuum pressure than I expected when I made a two bottle manometer and used plactic baby bottles--which collapse almost immediately.

Once you get the wet set complete and the carbs back on, a colortune plug will really be helpful in getting the pilot screws (you called mixture screws) set correctly. With a colortune plug you can set the screws so that you get a white flame (lean) and then open them until the white goes away and you get a blue flame. Then install new plugs and take a ride. Read the plugs and adjust the screws, about the width of a dime, and ride and read again. Repeat until you get the nice tan or light brown color on the plugs. You might find the screw settings to be more or less than 2 1/2 turns. Mine are all less than two.

My fuel filter is a straight one also, and I installed it so that it is straight up and down--i.e., closer to the fuel rail than the petcock--somewhat of a pain to change. However, I have a 90 degree filter on my Honda Rebel located near the petcock and it always has air in it but doesn't seem to be an issue.

 

My 1980 xj650 was running 118 mains with 42 pilots and I have pods but could not get it to run right until I changed out my pilots to 41 then it runs great full throttle no bad spots also it has a four into one exhaust, but every bikes different so they say, good luck the wet setting is a pain

 

One item that was not mentioned ..was the fuel line ,is it new and not kninked when tank is down? ( This happened to me once on my Honda CB750 had just replaced it ,but didn't check it after tank was put down , took off went to filling station and left rode 1 mile from home headed to work and bike died . I got it to start after many tries rode a few hundred feet and died again ,fuel was dripping into float bowls after I got it home That was when I figured it out.)

 

Fuel line is brand new, no kinks.

I am going to pick up a piece of vacuum line to connect to the petcock. I'll clean up the tank and make sure the petcock is nice and clean as well.

I was also going to fabricate one of these with an old sparkplug. This is saying that you can use an old spark plug body and some clear epoxy to fabricate one of these things.. would be pretty cool to save myself 100$.
http://www.theflyingbanana.com/tfbtechtips.htm

I'll report back once I get more done.

 

I made one of those for someone it is a bitch to remove the porcelin from spark plug body. you need to use slow settng epoxy for strongest results
just do not forget to wear a good face shield when looking at the flame

 

Have someone video tape it.

 

Alright so I'll keep in the same thread because the problem still persists.. I finished wet setting each carb to the right specs. I rebuilt petcock and gas cap and thoroughly cleaned the gas tank. Last night I put everything back together and it started it up as usual. I went for a quick ride but the problem keeps coming back. There seems to be some oil leaking from the crank case cover on the right side.. I have a loss of power and responsiveness.. The problem mostly happens during high reving but remains once it's started.. sometimes it'll just kind of pick up and act normal again for a short period of time and then start sounding weird again.. check out these two videos of how it sounds when it's running weird.. I'm at my whits end I can't seem to find out whats going on, could these be engine internal issues? TCI issues with firing timing or something?

 

I really don't hear anything out of the ordinary.
Although I can't tell when you are twisting the throttle and if there is a delay to the engine response.

When you put the factory airbox back in did you re-jet the carbs?

 

Yea.. I know it's a bit hard to tell ,specially without comparing the regular noise, but it's a whole different pitch. Normal proper function isn't that throaty and deep.. I'll try to take a video when it's running properly for comparison. While I'm driving and it's going smoothly the sound is normal, then I can hear the bike going throaty and I know that it will start to bog once I slow down - at that point I get a loss of power and responsiveness. It will run like this for a while, I never go far, but it has no acceleration - it will eventually build up speed as I hold the throttle open.

I did not rejet when I put the factory airbox back on. I'll try to temporarily put the pods on to see.

 

if you have oil dripping out of the right crank cover remove the cover and confirm the seal is leaking
this is not a good thing. easy to replace.
I can not tell from diagram if it is under pressure from oil.

 

All four or is it isolated to 1,4 or 2,3?

This is a good suggestion, particularly if you see wet plugs isolated to one coil group, either 1,4 or 2,3. Since you seem to be able to get it back to the garage and running poorly just pull the connector at the TCI to do a quick check on the pick-up coils. The resistance of the pick-ups will go up when hot about 20%.

 

I am not super familiar with testing the pickup coils. Doing something like this?

 

That would work, except for the part about "jam it in there". You don't want to open up that spade terminal, so if the probe does not fit and you don't have a spade connector adapter for your DMM, you can usually back probe the connectors. Do it cold first so you have a reference and know just where to go when it is misbehaving.

And what about the plugs, was it all four or just two that were wet/sooty?

 

Ok so I ended up checking the pickup coils and they don't seem to have an issue.. other than they might be the devil. I did this cold, although when I started the bike today I was getting the same throaty noise from the beginning, it didn't have to warm up. Just for good measure I did a quick test after the fact and they were both reading ~690.


Now as for the spark plugs. #1 is really dry sooty.. I need to figure out why.. I put in brand new spark plugs right after and still had the same problem. Once I fix the problem I'll need to get a hold of a colortune.. with CAD$ conversion and shipping they are all over 100$...

I also tried putting on boots temporarily to see if the air box was causing and issue and it was doing the same thing. I can't wait to solve this!

 

gap looks off on #2

why are you using resistor plugs??

 

All Canadian models use resistor plugs and 5k ohm caps but shouldn't need 42 or 43 pilot jet even with pods and 4-1 pipes and stock mains in Canada are 112 on the xj650rjc.
Pull up beside some old 50's or 60's car with stock radio and bike with non resistor plugs can make the car radio crackle

 

I remember watching TV as a kid, whenever a snowmobile rode down our street it would scramble the signal.

 

are the plugs mandated by Canadain Gvt?

 

I have both resistor plugs and regular plugs.. those R ones I just happen to have in the garage, they're a bit easier to source in a hurry around here. I put in non resistor fresh new plugs and problem is the exact same.

This is what I get from the wiki for Canadian RJ models:
Main FUEL Jet Size: #110 (running 112)
Pilot FUEL Jet Size: #40 (running 43)
Main AIR Jet Size: #50 (running 50)
Pilot AIR Jet Size: #195 (running 205)

would a few size differences make that big of a difference on performance? Even with pods on at the moment it's acting up and it's kind of intermittent.. I figure if it was a jetting issue it would be a constant running problem, no?

 

I looked at the Wiki site and found it a bit confusing, but had concluded from that and the Hayne's manual that the 1982 YICS Canadian used the 43 pilot and 112 main. I also looked back at your earlier post and although there was some confusion it was determined that you had a 1982 RJC.

Plus per Len:

#43: all 1982-84 XJ650 Canadian models, 1982-84 XJ650 UK/European (11N and 14R) models, 1981-83 XJ750 Maxim, Midnight Maxim Canadian models, 1981-84 XJ750 UK/European (11M) models, and XJ750 Police (24L and 37H) models.

#112: all 1982-84 XJ650 UK/European (11N and 14R) models and 1982-84 XJ650 Canadian models.

Yea that plug could even be fouled and not sparking, and the other plug for that coil is not looking much better. Since 2,3 look OK is it safe to assume this is a plug reading where the bike had warmed up and there was no enrichment?

You can check for a fouled plug with a standard meter. It is not as good as a HV meter, but can tell you if the plug is fouled. You should get a reading of at least 10meg and preferably open with the meter set to its highest scale. Here is an example of a fouled plug (from fuel) that read in the kohms.



So, looking at your plugs you need to determine why the 1,4 are so sooty. If you are confident in the carburetors - correct jets, jets not drilled, enrichment circuit plungers working and sealing properly, air jets in the proper location, then a poor spark condition could be the culprit, although an overly rich mixture is still highly suspect.

Electrical - you have done just about all, new coils, new wires, caps, pickups ohming OK leaving only the TCI. Unless you have a scope where you can evaluate the TCI primary waveform for proper dwell and current sinking your only option is to try a known good one or have another member test yours. I guess I might add that since it is the 1,4 plugs that look so bad and those are common to one channel of the ignition system I would be inclined to go that route.

I would also suggest that even though you have replaced the ignition coils a resistance check on both the primary and secondary side of the ignition coils would be in order just to verify workmanship and possible defective new components.

 

No, my understanding is that these types of carbs (CV - Constant Velocity) require a stable air intake to perform best. The stability is best garnered from an air box.

With pods they are drawing air from any direction and can even be influenced by the wind as the bike is standing still, then you start riding and the air swirls around/ between your legs and what not... now your constant, stable air velocity has turned into a tumultuous, turbulent, un-metered mess. Even though the jets are saying "I shall only allow this much air/ fuel to pass", the venturi effect from the unstable velocity is making everything chaotic.

 

Yes I get that but the fact is I've been running the air box for weeks and am still getting the same issue. I just put pods on for 15-20 minutes last night to see how it would react but it's still doing the same thing, it's sounding almost exactly the same. I was just double checking if it could be a problem where the newly installed airbox was restricting too much air flow.

@Rooster - I put in some new spark plugs, I'll run in for a while and see if they react the same. I had checked the primary and secondary coils after I had installed them and everything was fine. I will double check tonight. Could a poor connection or short somewhere be causing this particular coil to misbehave? The PO had replaced the original fuse box with a new blade style one but the connections weren't super clean, a little half-assed for my taste although I never got around to changing this because all the other electrical things on the bike such as ignition, lights, etc.. all seem to work perfectly fine.

 

A poor connection in the ignition circuit can cause problems, just like low battery voltage when the starter is cranking can reduce the available voltage to the coils and cause a weak spark. If it is at the fuse box it would likely affect both coils as the output of the ignition fuse goes directly to the kill switch, and then through splices in the main harness goes to the individual coils and other components in the ignition circuit. The best way to check the integrity of the circuit using a DMM is to monitor the voltage at the output of the kill switch (TCI or ignition coil) and check it when the ignition key is first turned on. The reason for doing it at power up is that when the TCI powers up it sinks a fair amount of current usually through one coil so any resistance along the line would result in a voltage drop.

 

Alright.. good news is that the bike seems to be running fine, great even.. for now? I did a bunch of testing on the coils this weekend, tweeked the pilot screws a bit for #1 and #4 to make them a bit leaner and she fired up perfectly. I drove her to work this morning and had no issues at all. Wondering if just plugging everything back in and making sure everything was tight helped something. She was a bit low on oil too so I topped it off.

However.. while testing the coils I had some weird numbers.. primary seemed a bit high, 3.0-3.1 ohms.. These are new aftermarket coils from a CB750 recommended from someone on the forum here. However, my stock ones I had laying around were showing similar numbers. What I'm concerned if the secondary.. I might be doing something wrong because the numbers seem way off. I was pulling like 25,000 ~ohms (with caps on) ? Is that possible?



Still have oil leaking from the right crankcase cover. You can see a drop of oil building up on that big allen head. Where could oil be coming out of? The gasket being held in by those 4 philips screws? Those 2 down facing hex bolts or the big allen head facing the camera? Before opening these up, are these holding large amounts of oil or is these things I can replace without draining the oil? I did an oil change not long ago so it would be a shame to have to waste it!

 

Yes with the caps on you need to add that to the number. So with 5k caps x2 and approximately 11K for the secondary the nominal reading would be 21 K ohms.

You could clean that area up really well and maybe isolate if the oil is coming from the hex screw or from inside the cover. You can remove the cover and check for oil, as it should be dry in there just like the opposite side with the pickup coils. Oil inside that area indicates a faulty oil seal on the crankshaft. I am not sure if the OEM can be pulled in situation as sometimes they have a lip on them making it difficult to remove. Hopefully, someone else will chime in on how to replace it if needed.

If leaking from the hex screw (plug) they do utilize an o-ring, but don't go there unless you are sure it is leaking there as they are know to break when removing.

A colortune would normally be suggested, but checking the plugs for color can assure correct mixture also.

 

That big hex screw is the main oil gallery plug. Don't mess with it unless you absolutely have to, and be prepared to have it break on you. Extracting the remnant can be a PITA.

It looks to have taken a hit at some point, and unless the leak is more than a slow weep I'd just leave it alone until Winter (and maybe leave it alone forever).

 

That's an easy solution!

I'll clean everything up and see exactly where it's coming from, that will give me a better idea.

 

Bad news.. the bike started having the same issues after about a week of perfect riding. I wasn't doing very long rides as I was trying to rebuild confidence that the bike wouldn't die on me every second. I rode it to work about 20-25 minutes back and forth for a week with no issues.

All of a sudden, same issue at speed is that I can feel the bike losing power, almost slipping sometimes firing properly, sometimes throttle goes no where.. sometimes power kicks in as I'm almost full throttle so that the lower powered bike goes somewhere.

Got home checked the plugs and they are back to dry black - hearing a bit of back firing now. Plus one plug's porcelain was actually broken? Brand new plug.. how the f? Thermal shock maybe from cold water?

PIC: (#1 at the top #4 bottom)





Could it be a jetting issues? Seems to be fine at idle when the plugs are clean but they are getting really black at high revs. Or could it be something with the compression of the engine? Some sort of piston ring issue thats holding compression at times but slipping at high revs?

 

It's nothing to do with the piston rings. If it were you'd see oil on the plugs.

I've seen plugs break like that before. It got dropped at some point during production or shipping. Not an engine issue.

Refresh us on what's been done to the carbs.

Cleaned how?
Parts replaced?
What jets?
Air jets in the proper positions (not what the manuals show)?

 

I had exactly the same issue .
bike gets warm ,engine starts to die , gradually grind to a halt. let it cool down 15 mins , starts right up runs a few miles, and dies again.
but problem was not consistent depending, on how hot it got ,or the weather temp.
eventually traced fault to a kinked fuel line, which looked perfectly round whilst cool ,but kinked up when hot, due to rubber becoming more flexible.
re-routed fuel line, and bingo, not had the problem again.
could the plugs be sooting up because theres not quite enough fuel to fire them.?
stu

 

Air jets:
Main FUEL Jet Size: (running 112)
Pilot FUEL Jet Size: (running 43)
Main AIR Jet Size: (running 50)
Pilot AIR Jet Size: (running 205)

Carbs have been thoroughly cleaned multiple times. All passages were cleaned even the pilot jet in the carb bowls could shoot carb cleaner. Everything was moving freely and smoothly. Carbs were wet set on carb rack to spec. Parts weren't replaced as everything seemed in good shape - just needed to be cleaned. I am planning on separating the carbs and doing throttle shaft seals in the off season. I was just hoping to get it running well enough that I could ride around for another month or two.. it's so unreliable now that I fear going on any ride.

Does anyone have a picture of the proper routed fuel with that has a straight 180* inline fuel filter? I was checking my line and was wondering if maybe the way it's set could cause it to kink under heat.

 

That could be something....
I have the 90* filter from XJ4Ever, even still it seems there isn't a lot of room for fuel line, filter, fuel line.

Curious to see if anyone responds with a straight filter.

 

A little hard to tell on two of the plugs, but it appears as all of them are running rich, and since it ran well for a while and likely fouled the new plugs another indication of running way rich. Did you ever do a gas mileage check?

How much on the pilot screws?

If they have not been drilled by the PO. The bike did come with PODS, so a strong possibility.

Also, did you check the main jet needles to be sure they were not shimmed to richen the mixture - another POD modification?

I use the 90 degree filter also from Len so no help on that.