Randomly dying at operating temp

[vladthedog]

I know this same type of post has shown up a thousand times, but I've been reading through many of them, and don't seem to fit my same circumstances. Been having nothing but issues on my bike these last few months. The problem is intermittent enough that I think I got it fixed, only to come back again. It will seem to run fine for a while, but then randomly start sputtering at throttle (turning on the choke sometimes helps, but doesn't seem to "fix" it, and it can still die).

A month ago it started happening more, and I noticed that after it died, the fuel pump kept clicking even after turning the key on 7 or 8 times. I pulled out the carbs and cleaned them all up, swapped out the fuel pump and fuel filter, and put it all together again. Seemed to be running fine until yesterday, I rode about 60 miles (most highway) with nary an issue, and when i was about a mile from my stopping point (last 5 miles or so were city riding), it died on me while giving it some throttle. I turned on/off the key to see if the pump would keep clicking, and it did not. I ended up having to wait a couple minutes, turn on the choke, and limped it to my destination. After being parked for an hour I thought it would have no issues, but right away it was doing the same thing. I thought it might be a low gas issue (was close to when the fuel light would come on, but when I first had issues an hour or so prior I flipped on the "reserve" switch to rule that out as an issue. I got it to a gas station and put about 3 gallons in.

It does feel like it's running out of fuel when it does it, which is why i replaced the fuel pump at first. It seems to happen more when it's been running for a while at operating temps, but it has happened a couple times right when i started it up. I've run seafoam through it, and looking in the gas tank it looks surprisingly clean. In the old fuel filter no buildup or anything on it. When I drained the bowls nothing came out except gas.

My bike has a stage 7, and these problems started after I installed the vboost butterfly valves (but not right after; just stating the last "big" thing I did to the bike). I was wanting the valves on there for tuning, as well as I was going to experiment having them open at a lower RPM. I've tried leaving them open completely (and disconnecting so they don't even operate) and problems still happen, so don't think it's related. I also did the "crimp fix" a little while ago. It doesn't seem to have a charging issue, but was in the mood to tinker so thought I'd go ahead and do it. It seems to hold a charge as well, since I had it parked for a couple months and it started right up.

 

[jdeitz1979]

Did you check battery voltages running and not running? I'd look into electrical. My bike acted funny last year, so I tested a bunch of stuff and found my r/r was fried. I tested my stator as well as the battery. Did the battery mod along with the r/r mod, and new ground cables. Check it all lol. Be a great rainy day project. Preventative maintenance is good maintenance


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[Eugene Brad]

My 85 has some similar issues I had a bad connection at the plug from stator to r/r. It would run fine cold and would charge too but after getting hot I figure that connection stopped passing current through. After I jockied the plug around to expose it the next time I started the bike smoke came rolling out of it. You might check that plug.

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[D-Max2012]

If you have the time, read thru the posts.
Check out my original question when I 1st got my 91..
See if this problem sounds familiar. Maybe it can help you out..

http://www.starvmax.com/kunena/28-help-desk/173491-91-vmx12-question?limitstart=0

 

[vladthedog]

Thanks guys. I left it at my parents last weekend, but this weekend when I get it back home I'll run through some electrical stuff. Kept focusing on fuel-related stuff since thats how it felt.

 

[sdt354]

My 85 has some similar issues I had a bad connection at the plug from stator to r/r. It would run fine cold and would charge too but after getting hot I figure that connection stopped passing current through. After I jockied the plug around to expose it the next time I started the bike smoke came rolling out of it. You might check that plug.

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+1, that plug is a major cause of Vmax aggravation. Mine is long gone. Cut out and wires soldered. Nice charging is nice running.

 

[kalbo]

I had an almost identical problem. It would run fine for a while and then die as if running out of fuel. I was also going to change the fuel pump, but someone on the board suggested I swap out the fuel pump relay first, as its cheaper than a new pump! I changed the relay and the problem was solved and it has run fine ever since. The fuel pump relay is the first at the front under the left side air scoop.

 

[kalbo]

I will also add. When i had this problem, my fuel pump would click for a few seconds when I turned on the ignition, but the fuel pump should also 'click' about once every 3 seconds when the engine is running. Usually, you don't hear this as it is dampened by the seat and the noise of the engine. If you remove the seat, and put your finger on the pump, with the engine running you should hear and feel the pump click every few seconds. If it isn't it is likely to be a faulty relay.
On start up, the pump was supplying fuel, but usually just sufficient for the bike to reach working temperature. I had assumed that the temperature had something to do with the bike dying, when in fact it was fuel starvation. The lower the speed I was riding, would determine how far I could ride before it died. A minimal amount of fuel was being supplied, but not at the correct rate.
I'm no expert, this is just my own personal experience.

 

[wildweasel_pt]

Vacuum lock in tank?

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[vladthedog]

So voltages were definitely lower in comparison to what i'm reading in the electrical forum. I should have written it down, but without running or key, I was at 12.8v (good so far), but on idling at 1k, it was around the same, and then at 2.5k it was only at 13.1v. I ended up wiring the R/R directly to the battery, and now at 2.5k I'm around 14.2v. I haven't been able to take it out and really push it so won't know if it's fixed the issue for a bit, but at least I know it's charging like it should now. Thanks everyone so far for all your help.

 

[Bill Seward]

Ya might want to have a look at the 3 wire connector between the stator and regulator. These burn sometimes, and mess up charging. Yours is prolly ok, but a look at it to check for signs of melting or other defect wouldn't hurt.

 

[redneksoldier]

I had a similar set of symptoms with my first Vmax took me forever to find it. I had so much trouble with it that I nearly sold the bike. I had rebuilt the carbs, replaced the fuel pump and filter, troubleshot and corrected the charging and ignition system, etc, etc, etc. I was really getting frustrated! Turned out that the fuel tank vent was plugged up with rust in the top of the tank. Since it was on the top of the tank, you couldn't see it. When looking through the fill hole, it all looked clean and shiny. I can't remember what made me pull the tank and check it, but I wad really shocked at how much rust was actually built up inside the top of the tank.

 

[Fire-medic]

I forget if you posted about this before. Did you have a problem with reduced/non-existent gas flow thru the fuel pump because the tank vent was clogged?

I had a similar set of symptoms with my first Vmax took me forever to find it. I had so much trouble with it that I nearly sold the bike. I had rebuilt the carbs, replaced the fuel pump and filter, troubleshot and corrected the charging and ignition system, etc, etc, etc. I was really getting frustrated! Turned out that the fuel tank vent was plugged up with rust in the top of the tank. Since it was on the top of the tank, you couldn't see it. When looking through the fill hole, it all looked clean and shiny. I can't remember what made me pull the tank and check it, but I wad really shocked at how much rust was actually built up inside the top of the tank.

 

[redneksoldier]

Yeah, i had a thread on here about it, but i cant seem to find it. Now that you mention it, that was how I discovered the problem. While I was using the fuel pump to drain the tank into a fuel can, I noticed that after a while the flow would stop. I would stop the pump and start it again and have good flow again for a few minutes.

This would be a good test for you if you are willing to try it. Disconnect the fuel lune from the carbs. Use a couple of jumpers from the battery to power the fuel pump directly. Extend the fuel line into a container and let it pump. Make sure the fuel cap is on. If the flow peters out and the pump is still running, take the fuel cap off and see if the flow returns.

 

[Fire-medic]

Yes, that's the 'side of the road' troubleshooting tip, pop tbe gas cap to see if flow returns.

Sometimes the vehicle manual will specify a volume pumped per time specified. Another way to check.

Coating the inside of the tank plugs the vent port.

 

[vladthedog]

So, after spending a few weeks trying to get this fixed, I'm still struggling to get this thing to run right. I wired up a cheap volt meter to the battery so I could watch voltage as I was riding around. I wired the R/R directly to the batter with its own fuse, and started riding around. At cruising speeds, it was consistently around 14.3v. Riding around for about 45 minutes, I had no issues, but then on my way home, it suddenly died on me. It seems to feel like it happens when I give it a little gas after going slow for a bit. Looking at the voltage as it was happening I did not see any huge dips in voltage. Obviously when it died it dropped down to about 12.7v but before that I didn't see anything (doesn't mean it didn't happen though). I got it to the side of the road and let it sit for 5 minutes or so. Then I had to use the choke to get it started, but thats when I noticed that voltage wouldn't go above about 13.3v even when I revved it, which led me to believe it's *still* something electrical. I only rode it for about 5 minutes to get it home, but I didn't see it get back to the higher voltage it was at before having this issue.

I don't want to just start throwing money at it, but was thinking of getting a replacement R/R. It's odd that I didn't notice any voltage issues until after it died on me, but I may have missed it, or it's possibly a cheap enough volt meter that it doesn't read fine enough detail to capture fast fluctuations.

Looking at the wires coming from the stator, they are not melted or damaged at all. I'm not 100% confident I tested it correctly, but I remember thinking that the results on my stator were well within tolerances.

The problems are intermittent enough I don't think it would have to do with gas ventilation. Some days I can ride it for an hour or two without any issues, and then other days I can put 10-15 miles on it when it dies. I went through a lot of the gas troubleshooting a year or two ago when I was having problems (because I didn't use a gasket on the stator cover after I patched an oil leak coming from the grommet of the wires that feed the R/R).

Thanks again.

 

[Orion]

Have you tried testing the stator resistances before and after it dies and compared the results?

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[Orion]

Stator and pickup/pulsar coil*

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[Hinterwaldler]

Any updates? My 95 is doing something similar. Running great then earlier this summer cruising along the highway and it was like the fuelpump shut off, started dying out then quit. Pulled over let it sit for a minute or two then turned on the key and pump ran for a couple of seconds like it had lst its prime or something then it started and ran for about 6 or 7 miles and did it again. I pulled everything apart in the fuel system and bought a fuel pump but could never get it to reproduce the issue so never replaced the pump. Then yesterday it did it again except this time the fuel pump only clicked a few times and quit like it had built pressure but I had to do it several times before it finally started...almost ran the battery down, though the battery didn't last as long as I thought it would turning it over.

In the 6 miles home, it would run enough to go thru the gears then die out like the pump was only barely filling the bowl then losing prime or quitting or something. I had to accel hard to high speed and when it quit coast to a stop and repeat once I finally would get it to start. I got home and put the battery on a charger since it was nearly dead after all the starting and turning over but on the charger it didn't seem to do it again.

Not sure if it is a fuel pump relay issue or a charging issue, though everything else electrical works or doesn't give any sign of the battery having a low charge.....

I am going to to the crimp mod and have ordered an SH775 regulator/rectifier and will check the output before I do anything but before I sink money into what seems to be an expensive fuel pump relay, I thought I'd see if you ever found your issue??

 

[MaxMidnight]

Have you checked that the tank breather is clear and of pinched?