Running Problem?

My bike, 86 VFR 700, runs pretty good. I just had a few last problems to fix up to make it perfect, that will be the next post however!

I have a problem with the bike running. It will run great for about 10 minutes, then totally crap out. after I turn the run switch to off, and restart I have no problem the rest of the ride, does anyone have any suggestions? I am totally perplexed with this one!

could it be the coil?

The battery and R/R are working properly, carb has been cleaned, and new spark plugs with new wires. any ideas?

 

Check the contacts in the switch itself for corrosion as well as the connector to the main harness.

 

well, the problem is that the bike usually starts running really bad, like there is no power, I can kill it with the switch and restart and runs great. I can usually do this while driving. strange part is that the bike wont do it on the freeway usually. what other electronic parts would have this effect?

 

The vent in the tank cap plugged maybe? It sounds like the likely culprit to me.

 

In terms of electrical I think the first possibility to eliminate is the kill switch. I would get a diagram and determine which two wires the switch 'shorts' , follow the kill switch harness to its coupler, and short the wires manually (maybe paper clip and electrical tape?...be creative). If your problem goes away that's it.

You could verify the fuel tank vent pretty easily by opening the gas cap while it's running crappy and if that makes it come out of it...then that's the problem

 

Yes, you need to determine if it's starving for fuel or loosing spark. Just because the fuel filter has fuel in it dosen't mean it's good. Take it off and blow through it. Replace if any resistance. My 86 would crap out on me and then with in a few minutes fire right up and run fine for a while and do the same thing all over again. I'd replace it every 10,000 miles. Any rust or sediment in the fuel tank?

 

Wiggle your ignition key while it is running and see if it affects the bike.

 

Guys, sorry it has taken me so long to reply. I have been really busy with work, and school.

I have tired all of the suggestions and here is what I found:

my gas cap is keyed, so I drained the tank to a very small amount of gas, and left the lid unlatched. ghetto, really ghetto, and scary, but the bike still ran really bad.

I wired in a bypass for the stop switch, still ran bad.

I tired wiggling the key, no dice.

on my way home from work the other day, it ran so bad and died right on the spot. I could not get it started for a minute or two and was a bit nervous. I am pretty sure the bike is loosing spark. unfortunately it only runs bad under load, so trying to replicate the situation for knowledgeable people has been tough.

I talked to my neighbor ( head mechanic at honda shop) about this and we figured it must be one of the electronic pieces that make this bike run.

considering the bike has 100,000 miles on it, i think this is totally feasible. Now I guess I need to dig out the FSM and start testing. What would be a good way of testing the electronics? should I use my heat gun to warm it up if i cant find a fault anywhere?

this is not a constant problem, and happens intermittently, it drives me crazy!

I dunno, any other ideas?

By the way, Ill probably post tonight, but I am going to be doing a pretty big rebuild on this bike, ill start a new thread for that tonight with pics.

 

needless to say, I wont be riding this till I get all my work done and get my bike running right!

I learned my lesson the hard way, 60 miles from home with a bad r/r. glad I have good friends!

 

dang good idea, i will look at this tonight. should you be able to blow through it with no resistance at all??

this is a factor I did not consider at all....

sorry for the multiple posts. Just had a heat transfer midterm, my mind isnt all there right now! haha

 

It sure sounds like the pulse generators to me. They will typically fail only when hot and progressively get worse to the point that they don't work at all. You would seem to be right in the middle of that process. It's a real pain, but you can check the resistance of the pulse generators immedately after the bike stalls and see if that's the problem. I'll bet that's the culprit.

 

great! thanks for the advice! now i just need to find some! haha. but seriously, a place to start is great.

do you think I would be able to replicate the condition if I heat them up to about 100 deg or so with my heat gun? and maybe just maybe get a failure?

I looked at pulse generators, ignition coils and pick up coils on ebay. is this usually a bad route, or is it hit and miss?

Jamie, I have checked out your site, and really like it! you know your stuff quite well! I will be upgrading my rear shock soon.

 

I'd probably avoid doing this. If you tried it and your pulse generator(s) are the not the problem then you will likely ruin them in the process. You need to check the resistance of them with the bike bone-cold and then compare it to when the engine is hot, preferably when the problem starts to occur.

 

ok! perfect! I will do that instead. thanks for the tip!

 

I'm on boat with Jamie. If a bike runs,... starts and runs, then you dont have an issue with your CDI or your ISU's. Your battery has enough amp to crank, so its not likely to have a bad cell and you not know about it. Start solenoid is working, no complaints from you about hard to start, fuse box wouldnt be a problem, nor the start switch, cause as you have worked them over and over, they are performing their function... I have RARELY seen a pulse generator go bad, only two to be exact. But your problem is that you have either a AMP load drop (Pulse Generator / battery / R/R), or you have a loose ground wire somewhere. (That ones a fear, cause it could be anywhere in the ignition circuit).

My suggestion is to side with Jamie. Get out your prints, and a meter, and start checking at the Generator. start your bike, plug up your meter, and watch your Volts, you should have ~ 14.4 V while running. and your Battery should have ~ 12.2 to 12.7 to crank.

Possible questions: Have you re-wired your connection from the pulse gen to the R/R? some people have this plug to melt, and they rewire them wrong. Try a known new battery? you stil(tho not likely), could have a bad cell thats shorting out.

 

I tried last night to get the bike started. I got it started, ran great. Then I could not get it to start after I shut it off, crank crank crank! I am not sure if this is another problem? or maybe this is the same one just a bit worse? I dunno.

I did check the fuel filter, but not the pump. as I was doing some reading on here last night and thinking that might be a good thing to look at tonight.

I really don't think its a dead cell the battery is pretty new. about 7 moths ago I had the R/R go out. I replaced it with an R1 R/R and rewired it all. I checked this out when I first had the problem. and the wiring is good! not a short, and I traced all the connections back, they all work!

is the best way to test the fuel pump to unplug the connection to the carbs, and see if fuel pulses out?

 

I was just this past weekend with a friend of mine who had a bad battery. he had it only 3 months. all meters showed it at 12.6V... I.e. it was good. we put one of those special $400.00 battery cell testers on it, and it told us it was bad. took it to a shop and they agreed the battery was giving a false reading due to only one cell being bad.

also, if you wired your RR, you can still wire it, and have it work, but be over charging your battery... that will make your battery operate eratically. (spelled that right?). Since you said you re-wired this new R/R... I'm more convinced that your problem is in this area. if you get no fuel, then your problem would be more like, the bike runs, then slowly dies... very slowly. hell, take the fuel line completely off, and pour fuel in a glass jar, then gravity feed it to your carbs. Same problem? then its not your fuel system.

This sounds electrical. When did all this start? about the same time or within 3 or 4 months of your new R/R?

 

Hi,
if this can help : the same occurred to my VFR 750 ('87). I don't know how I arrived to find the solution. I can say what I did :
Check battery connections (mainly the ground wire); ELECTRICAL SPRAY cleaner in the ignition lock, in the kill switch, on the electrical contacts of the fuel pump.
Check tank vent cap ; last : I refill with a 98 octane gasoline and a little amount of "green treatment" for gasoline.
I do not know which of these actions was the right one but now my VFR runs very good and does not "die".
Maybe there was a valve that in a randomic way stalled and the green treatment (lead substitutive) helped to lubricate the valves that are the "dry" parts of the engine. It happens to old bikes.
Ciao and let me know if this helps you.
Lamps.
Carmine

 

right after I got the bike running, with a new R/R. My R/R could be over-charging. I highly doubt it, but it might be. Every time I check it, at 1,200 RPM, lights on, normal running etc, its 13 volts. would that be over charging? I will try to get my battery tested tonight, I have it out of the bike already.


what If the fuel pump does not run when this problem happens? it would make sense. it only fills the float bowls a few times, then dies a bit down the road. I dunno. I am really trying to think about this, and because it is intermittent it makes it much more tough to test. sometimes it wont do it at all, but for now it may be that part bit the dust. I will try filling the float bowls manually. it doesn't run currently.

I will get the battery tested, and see if that is the problem. it cranks great though, does it plenty of times, I know I tested it last night

I will also try the fuel pump tonight.

 

If the float bowls run from full to dry - you will get about 5-10 miles.