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%.