HELP bike keeps dying on longer rides

I am sitting on the side of the high way, my bike keeps losing power. I will ride along and then it feels like no matter how hard I rev it I can’t get anything out of it and I slowly lose power. I pull off to the side of the road and as I coast the engine dies. Is it not getting fuel? The mechanic said he bypassed the vacuum petcock. Appreciate any input.

 

Is air getting into the fuel tank? That will make it splutter to a stop due to fuel starvation. Open the tank cap to see if it starts.

 

Ok on my way home, just died after about 20 miles, I have been opening the fuel cap after each time it dies on me, on the way to my destination it was able to restart but by the 4th and 5th time it was struggling to restart

 

Well it’s completely dead now, either the battery is too low from me trying to restart it or the solenoid went bad but it just flashes the oil sign and won’t turn over. Wife is on her way to pick me up and I will take the battery home

 

Thinking of replacing the pet cock and maki g it a vacuum based again and cleaning the gas cap. Put in an inline filter. Pull the carbs, I want to change the jet size and air filter type anyway.

 

Does it restart after it sits a while? Or did it before the solenoid went out? Maybe a restriction in the new petcock or fuel line. You can pull the fuel line and switch it ON...just see how freely the gas flows as a quick check.

 

How about the tank breather?

 

It did restart if it sat for a while but each consecutive time it got a little harder, I got frustrated and tried to hold the start button and rev it back to get it going and then it died. Battery is fully charged but now just emits a singular click so the solenoid is probably fried.

the vacuum petcock was bypassed so whenever I pull the fuel line it comes out. Might go through and see if I can switch it back to vacuum, I have a broken spare and perhaps I can mix and match

 

Not sure what this refers to? The gas cap or opening it after it dies?

 

Is your fuel routed correctly?

 

Fuel cap and filter are good suggestions. Have you checked valve clearances? If they are out of spec on the tight end the valves will not close all the way once everything warms up and expands, results in a loss of compression which equals loss of power nad a hard or no-start situation. Will act fine once cooled down but the cycle will repeat.

 

To my knowledge yes, petcock is on, and goes to the t tube of the carbs

 

Yes, I completed a valve clearance check and got them into spec. I am talking the valve cover off since oil is leaking from the donuts on the braking side of the bike and applying RVT so I will recheck them while in there.
How long does it take to warm up? I have been on 15 min rides in the hot sun and it wasn’t an issue.
Carbs were synched and unfortunately it runs rich. Couldn’t get to the Bunsen blue without the air fuel screws all the way in.

 

I meant does the pipe have any high points where air could be interfering with fuel flow? I should have explained this better. @Melnic had a high point in the fuel line but not sure if that was the problem on his machine.

 

You'd know within 15-30 minutes of riding.

This isn't right, it should die with the screws all the way in.

 

My thoughts exactly. So when I changed a couple I was unable to get the bike to start. My next action was to back them a half turn out. The bike was able to start maintain idle and ride well. I am super confident that the mechanic jetted it too rich. So next steps I’m planning are to go over the petcock and check what numbered jets are in my carbs replace the air filter and switch back to original jets

 

The petcock originally was a vacuum style. It would have 3 settings
ON, RES, PRI (On, Reserve, Prime).
There would be one thicker tube to the carb set and a smaller tube to one of the vacuum taps between carb and intake on the intake boots.
Common thing (my bike was like this) is they pull out the vacuum tap tube and plug the end, then put a nipple cap where they unplugged it from the vacuum tap (all 4 of the carb boots then have nipple plugs).
To run the bike you would then have to leave it on PRI which is pulling from the REserve level, To turn off, you turn it to ON or RES.

Some people replace with a manual petcock that will say ON, OFF, RES. Again, the carb nipples are all plugged but there is no vacuum line.

Figure out which you have.
That being said, If you have fuel flow but the bike dies 10,20,30 mins into the ride, and if letting it sit 10-15 minutes allows it to start and run, you have a fuel flow issue. If its not the petcock, its likely gunk in the little screens under the carb needle housing. Get some extra fuel line to troubleshoot.
You also can troubleshoot fuel flow issues by having clear tubing connected to the bowl drains and look at the bowl levels at the beginning and then when the trouble starts. I had this issue when the screens I had were clogging.

 

Check your alternator output at about 2000 rpms. You may be running on battery which drains it while you ride. I had a similiar problem and found low alternator output. Replaced the brushes and that solved the problem. But if you have an old weak battery it may not be taking a charge and is too weak to start the engine. I've had that problem also, and a new battery solved the problem.

 

And that’s the part where I am confused about what he did. He put a nipple cap on the carb boot and I do not see any caps on the vacuum tube of the petcock. Along with that he said not to change the setting and to leave it on the “on” position.

 

The battery has been on a trickle charger but that’s a great idea. I will have to look up how to do this, I did change some components of the alternator years ago, but easily could have messed something up or something went bad since then.

 

My bike is always stay on a trickle charger, but sooner or later the battery goes bad. To check the alternator output you need a cheap multimeter. Set it on 20 volts DC, start the engine, touch the negative post on the battery with the black lead from the meter, and the positive battery post with the red lead from the meter. At about 2000 rpm you should see a reading of 13.5 volts or higher. I'm told that the alternator doesn't really kick in until about 2000 rpm, but I don't know why.

 

@tabaka45 good point check this NicoRx.

https://xjbikes.com/forums/threads/testing-the-feild-coil.119720/

 

You don't "have" to plug the vacuum line actually, Only if the diaphragm leaks (rare) would that even really help. I just have seen people do it anyway.
Unless he hacked at the petcock guts , On would not make it flow gas, RES would. Maybe he hacked it. If you pull the tube off the petcock, you will find out.
If your ONLY running the bike with the petcock ON and its a vacuum type then he hacked it or it was leaking anyway.
If I were you, I'd pull the hose off the petcock output, then run a new hose to a gas can or container and find out which setting produces flow and which one does not.
Post pics if you can.
Once you know how its flowing, you can eliminate the petcock.

 

Well and now I replaced the solenoid and it is just clicking one time when I try to start. I will have to do a work up for this ugh

 

Battery reads 12.66 and solenoid 12.3 v

 

Is that with the engine running at 2000 rpm or better?
Also, the battery can read 12.66 but not have enough power (amps I think) to actually turn the engine and fire the plugs. Regardless of your fuel issue, I think you have a weak battery, or perhaps battery connections.

 

^^^^, yup, battery voltage will drop during start/load. More the drop, the worse the battery.
Battery tester will look at voltage when its starting and tell you if its good or not.
I have a cheap amazon one cause of all the vehicles I own and all the lead batteries I have.

 

So I attempted to short the solenoid and the bike did not turn over and I have no resistance from the negative terminal to the crank case. Would a weak battery still cause those symptoms?

 

That is with the bike completely off

 

Battery should show greater than 12.5 volts sitting there doing nothing, load it with a starter motor it should drop down to say 10.5 volts while cranking if it's fresh & strong. The resistance drop between the negative terminal of the battery and the engine itself should be a big-fat zero. Cranking the engine with the voltmeter between the negative terminal and the engine case should show less than a volt if the cable is good. This will also hold true for the positive battery cable between the battery terminal and the starter motor lug bolt while cranking, if the solenoid is bad it will show near the battery voltage.

 

I bought two back up solenoids and tried each one. The negative to the engine was near 0 and positive to solenoid was also near zero. Also zero when pressing in the ignition but all it did was cause the solenoid to click and continuity went up .002 for both. Bike voltage went down to 12 but after 5 mins of sitting was back above 12.6v

 

Battery ground/black to engine case, you using resistance setting (ohms) and not voltage correct? it should be from 0 ohms to maybe an ohm or two. Many meters may show an ohm or two when touching the meter terminals together. That is your offset.
Shorting the 2 big bolts of the solenoid should make starter run. One bolt should go direct to battery, other bolt goes to the + terminal of the starter motor. Shorting with a conductive metal would make starter move.

 

it was set to the continuity/diode test and was buzzing. I did not set it to ohms

thinking of attaching the + end of the battery to the starter connector and the negative end to the starter body while in neutral to see if it turns

 

This will bypass the solenoid and any other issues that may be lurking behind the scenes such as a bad starter which is not hard to rebuild, Amazon has the brush block for under $20.00 and I had mine done in half an hour... yes this proves a caveman like myself can do it. The extra cranking may have worn the brushes down to the nub causing it to turn slowly or not at all, the other alternative is to buy a rebuild outright and they're outrageously expensive for what they are. Either way you will need a starter motor to continue with the diagnostics and after going back to the start of this thread maybe another bike-nerd-tekky-guy to further assist you, another set of eyes never hurts. Unfortunately I'm about six maybe eight tanks of fuel away from Columbus depending on how hard I push it.

So here's the what I know about these fuel systems and all the related having put my XJ750 back together, it's the bike in my avatar that I got in several milkjug crates with the disclaimer of "Some Assembly (and much cleaning) Required" and the fuel system was no exception. Overall they're quite simple but they have a few quirks, my vacuum petcock leaked right away so it was replaced with a hand only shutoff piece and it works. I've always been in the habit of turning off my fuel since my dirtbike days so it's a no-brainer for me. Down the line are for super-small hat shaped screens over the fuel inlets of the float needle seats, they are the last stop for the crud that always manages to get past that Checkpoint-Charlie filter screen on the petcock. That being said brings up the question of super-fine "rust-dust" and other sediment in the tank that may be building up on the inlet screen and reducing the fuel and stopping the bike only to disperse a short time later when the flow stops. Think of a window screen with a fan blowing into the house at night, all the bugs accumulate and stick when the fan is running and eventually fall off when stopped. It only takes a little of that super fine crud to build after say 20 miles to reduce the fuel flow to a trickle or less and put you on the side of the road. Sure the fuel may flow like a fountain when checking it in the driveway but how about 30 minutes later?

Electrical... Battery might be going down during the ride, enough to stop the ignitor box from making a hot enough spark, I did a test with my ignition so time back to check the accuracy of the tachometer and also reduced the running voltage and found the cutoff to be just over 8 volts. 20 minutes is about the right amount of time to run a 12v battery down to that point with the electrical load of the XJ bike. I have the 750 SECA and with the stock headlight, two taillight bulbs and ignition the total demand is just over 10 amps of current once the battery has reached its 100% charge point. The alternator in these is only good for just shy of 20 amps and will not produce anything below about 2000 engine RPM, this is due to the threshold of the internal regulator transistor, a lengthy explanation for later. Weak brushes or corroded connections to the regulator box and the alternator is compromised. One of my brushes was broken when I got it so they were replaced, not difficult but a something that must be done. These use a special long length brush and our vendor Chacal has them. There are are also solder connections inside the alternator housing for the brushes that can go bad, something to consider.

While I don't know the specifics of the Maxim electrical the output of the alternator has to make its way to the battery and eventually the rest of the bike, have you checked the integrity of the fuses? How about the bond between the engine and the frame itself being these are rubber isolated engines? How about some of the other electrical connections? Those spade terminals do get crummy over time and the female side can lose its grip. I poked each and every one of mine out of their shells one at a time to sand the spade with a 320 wet & dry and carefully squeeze the female end to restore the grip, mating a 6 terminal connector now takes some effort but they're absolutely solid.

Since reassembly of the bike I have accumulated 7868 miles as of this post and will be adding more later today. I absolutely trust this bike to take me anywhere I want to go, it has been rock solid dependable and I ride it every day. The only major service so far has been a re-lining of the clutch and removal of the swingarm to address a side play issue. I have spanked S&S powered Harley Sportsters and a few "ninja" bikes on stoplight drags and done 500 miles interstate runs averaging 85 MPH with passing peaks in the triple digits. The only real bitching points I have are with the high-strung gearing and that ATARI game console speedometer that is so far off it's in another dimension... if anyone has a 0-120 speedometer I'd be interested. It runs Kenda Challenger rubber and handles well, there are no chicken strips on the back tire. Given the sheer simplicity of the Yamaha bikes I'm quite confidant the problems you're experiencing are lurking in plain sight, sometimes it takes another set of eyes to see what has blended into the background.

 

Took it to get tested and the guy said it was at 200 cranking amps and it was good despite being 2 years old

 

Well that's a start.. pun intended. So you've bypassed the solenoid, checked the wiring from the battery terminals to the engine and starter lug and still no crank? My money is on worn down brushes in the starter or the clock springs that push the brushes have lost tension, either way you're looking at either another starter motor or repairing it. Again they're not difficult to work with if you have some mechanical experience, the thing you have to be careful of is getting everything "clocked" or positioned correctly inside as they index into slots which are not always obvious being covered in slimy grease. I worked at a rebuilder in my youth and screwed a few up along the way. They're quite expensive on the evil-bay used, I don't know what the rebuild price is but the brush block is just under $20 from Amazon and not difficult to replace. They used to be $45.00 when I was rebuilding them in the late-80's with a $20.00 core... times have changed.
So until you address the cranking issue everything else is on hold, 200 cranking amps is about right for these batteries so while it has the juice to turn it over that doesn't mean it can run a marathon, you will need to get the engine running and back to the diagnostics of why it has a limited running range be it electrical, fuel or mechanical.

 

As Brhatweed said they are quite expensive.

https://xjbikes.com/forums/threads/how-to-test-your-starter-circuit.7828/

https://xjbikes.com/forums/threads/replacing-your-starter-motor-brushes-w-pics.45727/

 

It’s frustrating, I replaced the starter brushes I think a couple of years ago and this bike has only gone 300 miles since Ryan and only had 5k to begin with. I will open up the starter and take some pics for sure. Lots of work to do but excited to fix these problems on the bike

 

I get where you're coming from, it's very frustrating but an unfortunate fact of our throw-away world of chinese made junk. I do my own work and have never taken my car to a shop once in 235K miles so I spend just as much time looking for quality as I do the work itself. The cool thing about the XJ is they're quite simple and easy to work on, a 10MM gets most everything done, the brushes in the starter are short & thin to begin with and pass a lot of current for a short time, the added cranking of the problems & diagnostics all adds up to more wear. To me a $20.00 brush block is a half hour opportunity to clean things up and make it right so it's reliable, I live in a very small town do put on a lot of rural miles with Minneapolis just over 90 miles to the south so reliability is paramount and I'm not known to compromise. 300 miles in a couple of years? Dude you gotta get out and ride man.
Bikes are a lot of work but I take things as challenges and learn things hands-on, don't take it as a frustration as you will figure things out. That big sh!t-eatin' grin on your face going down the road comes from knowing you did it yourself, sure better than some store bought ninja bike or potato mashin' Harley cruiser covered in yards of chrome... only one grinnin' there is the cleaning products companies.

I will say those are great tutorials that Franz pointed out.

 

Hard to believe it would be the brushes again....... but never know.

 

From what I gathered he's gone thru the solenoid, cables and the battery itself so either the brushes have burned down or the armature has an open.

 

Finally started disassembling the bike into all of the problem pieces. I had half a tank of gas and with clear tubing reserve was the fastest to drain but it still took close to 45 minutes to drain. Prime and ON both drained but were slower.

 

That is a long time! Your problem may simply be a bad petcock, or clogged screen in the tank.

 

Answers that question, a new or rebuilt petcock from Chacal and you're riding into the sunset.

 

A cap on the petcock vac nip is not a necessity to disable the vacuum operation of the automatic type petcocks.......since you've disabled the vacuum source (at the intake manifold nipple, by removing the vac hose running to the petcock), there is no longer any "(vacuum) signal" to the petcock to turn it on or off (when hooked up as originally designed, the engine vacuum sucks on a diaphram inside the petcock body which pulls open a normally-closed passageway inside the petcock which then allows fuel to flow when the petcock selector lever/handle is set into the ON or RES positions).

So a vac cap on the PETCOCK vac port isn't a "must do", but would certainly be recommended to keep "stuff" from getting in there.......

 

Well I figured I would give you guys an update on my journey. The bike is currently torn down in the garage with all of the known demons excised from the body and sequestered on the work bench or garage floor. Photo #2 is all the problem children I plan to fix and am excited to get those done right.

-Replace gas cap o rings and clean the innards.
-Petcock rebuild so that it works as originally intended.
-Collectors box holes will be welded over.
-Carbs will be inspected and possibly new jets put in depending on what is currently lurking within.
-Chucking the KN filter into the trash and ordering a paper filter.
-Adding RTV ultra red to the half moon sections on the valve cover head to prevent the minor leaking of oil (Anyone know how to get oil out of jeans? lol)
-Go through and fix/replace the starter

And a fun lil bit of luck and terror in photo #3. I had a bolt snap off in the valve head. I was able to eventually extract it after some elbow grease and a left handed drill bit. The bit had snapped apart twice but was still usable after each break. During one of those I was unable to find a small section and hoped and prayed it flew somewhere in the garage and not the bike. Well after taking off the valve cover to recheck clearances and fix the gasket my eye caught a golden twinkle too bright to be just light reflecting on oil. Grabbed my wife’s tweezers and pulled that little guy from the corner. Thankful I found it now and not after a he bike had been ridden for hundreds of miles!

 

Yeah there's a wonderful product from ZEP that's called 505 degreaser in a yellow gallon jug for about $10 at ACE Hardware. Spray it on full strength to the oil stains and allow it to soak for at least 6 hours and wash with HOT-HOT-HOT water I mean coffee hot. This stuff also works great on engine grease/oil not to mention concrete garage floors & driveways. Another is ZEP Industrial Purple Degreaser that is basically the base cleaning solution of the old Formula 409 and will take most anything out but do be aware this stuff is very tough on skin so do wear PPE. I use this to clean the shop rags in an antique Maytag washer, scalding hot water and a 5-gallon bucket of rags followed by a quart of the Purple stuff and leave it run for the afternoon and they come out just as clean as Cintas.

Now don't kid yourself into thinking all the demons have been excised... they multiply like jack-rabbits and become harder to stomp with each successive generation. The only way to truly kill them all is to love them a little and look at this as an adventure. Now you can use some RTV for the half-moons or completly clean out the grooves & channels and go with the correct cover gasket using a little and I mean little bit of Hi-Tack sealer to hold everything in place. I'm using no RTV or any other sealer on my top cover gasket and have no issues with weep or leaking at the half-moons or any other place for that matter. I'm not saying it's a perfect world but they were never intended to used RTV in the first place. Every time I've used a sealer it's always weeped a little right at those locations. To keep the gasket in place while installing the top cover I used a little Scotch tape to hold it up and wet the rubber with a little oil where the tape went across so it didn't stick to the gasket then before torquing pulled all the tape out so the gasket was true on the surface then worked the bolts from the inside out in a criss-cross pattern using new grommets. This was done after I drilled, tapped and heli-coiled all my top cover holes including the internal ones doubling up the coils inside to make a full length thread. I know it's frustrating BUT the fact they have the wear & tear on them tells me the previous owner did something under the cover... take that as you may. The PO of my bike did shim & set the valves as req'd but instead of replacing the OE shims as needed used what appears to be a surface grinder on the back sides to set the clearances, not the best in my book but shims are cheaper than valves.

Don't can the K&N filter just yet. Reason being it may not be the detriment that everyone believes them to be. I'm still working on the 6000 sag with my SECA 750 and will be adding a wideband O2 sensor and mixture meter to get a better sense of what's going on in this transition period. Some have problems with going lean, I've seen it go rich during my tests and actually stuffed a camera into my airbox to observe what the slides are doing in realtime going across the RPM's. They're posted on YouTube under my member name here so maybe check them out.

Anyway enuff for the moment.

 

You've "seen them going rich"? How then, would be a good trick if you could do that..
Maybe you're assuming slides lifting is giving you richer mixture? Never assume, ever...

 

That's easy if you have something to check AFR with

 

The plugs tell all