Interstate Speeds and (interminttently) Bike Dies

[Shifty2932]

So recently as far back as 3-4 weeks ago I have been starting to have problems with riding my bike on the interstate (cruising about 65-70, thats a guess as I don't ride with a speedo or tach). But every now and again I get on the interstate to go to work and the bike starts to stall out around 5 min of high speed riding. I am still in the process of trying to tune my carbs. I have 1977 xs650 w/ UNI 4" Pods, straight pipes, and BS38's. As of Sunday the carbs are now setup as follows. Pilot - 35, main - 142.5, needle clip is in the second slot, and mixture screw is 2.75 turns out. Before Sunday the only thing that was different was the pilot jet was a 32.5. But in this setup I was hitting a flat spot around 1/8 throttle and getting lots of break up. And still in that setup I was having intermittent issues on the interstate. And before that setup I was running 30 pilot 142.5 main and needle clip in the 3 slot, but again still intermittent issue on the highway and this setup was just sluggish all around and that is why have leaned the needle and increased my pilot to what it is now. The current setup seems to work really well. Much better throttle response when the bike is wanting to run. Now when this happens I pull over let the bike sit for a bit and start it back up and allow it to idle. Bike will run okay for a little bit 10 min and start to stall out again. It will sit all day work and I ride it home with little to no issues. Any thoughts? There has also been a few times were gas wants to piss out the left air pod (this morning, as it died a few miles done the road from my house house), but this as only happened a few times. I orginally replaced the left float needle, maybe I need to replace the right one has well. The floats are set at 24mm and this seemed to have worked really well for me as before they were set at 22mm and I was running really lean. I intend to rebuild the carbs this fall. I have checked the voltage of the battery before and the volts climb as R's increase.I feel like I am just banging my head against the wall. and i want to be doing more of this - .

 

[JP50515]

Check your regulator specifically the ground. I have the same bike same setup and had the same issue. Ended up being a bad ground on the regulator. However I was frying out completely. Describe "stalling out" for us. Does it just flat out die? Sputter? any info is helpful in diagnosing the situation.

 

[Shifty2932]

JP,

Stalling out: cruising along and all of a sudden things go flat and then sputter and then flat and then sputter (i feather the throttle a bit to try to keep it running) if I push the clutch in it dies and then if I let it back out it will try to kick itself back on and then when I stop it usually dies. Hope this helps. I have noticed that the wiring job the PO did on this bike is not up to par and the wires from the regulator and the regulator itself are not in the best of shape. Rewiring the bike is another thing I intend to do this winter.

 

[jasonslackisrad]

How is the battery? Check if it is charging at like 2-3K

Iv'e had this happen now a few times. I can get the bike running by kicking it and if i am on throttle it will keep running. But if i stop it dies. if i clutch in too long it dies.

If the battery isn't properly charged to begin with it just doesn't seem to charge itself.

 

[Shifty2932]

Jason,

thanks for the reply. I've checked the battery voltage before and after rides recently. As this issue happened last week as well and from reading other thread the battery was the first thing I checked. With the bike off the battery is at 12v. When reving the bike up the volts climb. The issue i have described is very specific to the interstate. I have been riding this bike now for about 2 months and these symptoms only happen on the interstate and it happens so randomly I am just trying to figure out why. Thanks for info and I will check again when I get home, but from what JP wrote earlier in this thread I am leaning more towards an electrical probelm with something coming loose or having a bad conection due to the excessive viabrations at high speeds.

 

[jayel]

when it starts to sputter open the gas cap might be vapor locking (running out of gas) if cap vent is blocked

 

[Shifty2932]

Jayel,

Noted. Previos to Sunday I believe I was getting some major vapor lock. Full tank, much quicker and more frequent issues. I bought a new vented gas gap on Monday and it seems to have helped a bit. I have an inline fuel filter I can see and watch if fuel is being able to leave the tank and fill the filter so when the filter gets low i crack the cap and it will slowly begin to build back up. I was cracking the gas gap this morning and it did seem to help. But did not fully solve my problem. Any thoughts or ideas on how to prevent the vapor lock? Becaues obviously the vented gas cap is not working properly.

 

[jayel]

stock cap or after market? atmospheric vents to the carb bowls clear?

 

[Shifty2932]

Jayel,

I have a pre 1975 HD sportster tank. So the cap is an OEM/Aftermarket cap from Drag Specialties. Not sure if that is a problem or not. The cap is the exact same cap that came with the bike. My buddy has a Flyrite chopper with the same sportster tank. He ended up drilling like a 1/32 inch hole on the top of the tank just in front of the gas cap bung. He said that worked for him. Remind me again were these vents are at? This past weekend I chem dipped/cleaned the carb bowls and jets and sparyed carb cleaner through the carbs.

 

[jayel]

Jayel,

I have a pre 1975 HD sportster tank. So the cap is an OEM/Aftermarket cap from Drag Specialties. Not sure if that is a problem or not. The cap is the exact same cap that came with the bike. My buddy has a Flyrite chopper with the same sportster tank. He ended up drilling like a 1/32 inch hole on the top of the tank just in front of the gas cap bung. He said that worked for him. Remind me again were these vents are at? This past weekend I chem dipped/cleaned the carb bowls and jets and sparyed carb cleaner through the carbs.

sportsters tanks have used both a vented and a non-vented cap, depends on year and model, some tanks will have a vent tube that runs from the inside of the bung down to the front of the tank (if the tube is open you use the non-vent cap(and they can be opened if plugged at the bottom)) no tube you need a vented cap

the carb air vents are the small upper brass fittings, need to be open to air with short 4 -5 inch hoses... your carbs may be slightly different (no fuel crossover or no choke crossover) but the air vent are the upper small tubes on the inside of the carbs... there are better pics in the carb tech section

 

[Shifty2932]

Jayel,

I don't believe that I have the tank you have described. It has no vent tube and that is why I have a vented gas cap. The BS 38's I have are a 78-79 carb set.

 

[jayel]

well carb/fuel problems can appear electrical and electrical problems can appear to be carbs, all you can do is check and eliminate one thing at a time

 

[Shifty2932]

Jayel,

True. The vent cap that I have is similar to the style that is shown in the top right picture. Mine though as a hole in the middle of the cap where the vent diaphram moves up and down. I will check and make sure the air vent holes are free and clear.

 

[Shifty2932]

Jayel,

Went out side quick to take a peak at the air vent. Without taking it off I cannot really tell. But if the carb in your last pic is a BS38 the air vent looks different than mine. My carbs do not have that brass fitting/piece in the air vent.

 

[5twins]

The air vent on the side in Jayel's pic was made sort of internal on the '78-'79 carbs, drawing it's air through the air filter. The vents can be seen here at 3 and 9 o'clock .....

I don't think it's a carb venting problem. As you can see, there's 2 vents and they're very big, rarely if ever clogging. It could still be a vapor lock problem relating to the tank though. Have you opened the gas cap just after the bike stalls and listened for the tell-tale "whoosh" sound of air rushing in, of you relieving the vacuum build-up?

 

[gggGary]

Have you tried a new fuel filter or run without it for a bit?
Specifically freeway or specifically sustained high speed running? What ignition do you have?

 

[Shifty2932]

Gary,

As far as i can tell just the standard points ignition. I have not tried running with a new filter yet, but I did do a flow test the on Saturday when I was working in the bike and fuel was flowing out rather well.

 

[Shifty2932]

5twins,

Yes with the old cap lots of pressure would build up and when I would release the cap I would get that sound of the pressure being released. Now with the new cap the sound or venting was not as forceful.

 

[Shifty2932]

Update. Thanks to all who have responded to my thread. I appreciate your input. So after work today I got on the bike it started and was idling a bit rough. I made it down the road about .5 miles and it started to sputter and stall out again. This time I was only doing about 20-30 mph in 2 and 3 gear. Bike died when I stopped and for about 5 min would not start or idle. Once I got the bike started the bike would idle, but when I introduced a little throttle it would immediately die. After a bit of doing this I was able to get it going and again made less than a mile and repeated the process all over. Got on the interstate and was just limping along (sputter, die, sputter, die, sputter, die....you get the picture.) pulled over agin bike dies. Now when it dies it really feels like a loss of power. But not total power as the headlight and taillight are still lit and on. I'm thinking loss of ignition power. So once again bike sits for a few minutes and go through the same process, won't start, finally starts, idles rough, throttle and die, until it wants to except some throttle and go. The happened for about another mile with two more stops and I finally threw in the towel. Called the wife and she came and picked me up. Luckily I had a guy from work with me who had is bike parked behind mine with his flashers on as we were sitting on the side of I90 and then another guy from work saw us and pulled over and he had a tow strap so he towed me to the next exit and gas station ( about 1.5 miles) were I waited for the wife with the truck and trailer. Got home unloaded the bike and haven't touched it. I think the vapor lock can be a valid issue here but as I was trying to rule that out with a slightly loose gas cap and the problem was still occurring. plus while cruising down the highway I lost it when the bike started to act up again and lost focus on the gas cap and it rattled off. So far now I have the old on the tank.

Any thoughts? Where do you all think I should start? I have two full months of riding left here in south western South Dakota and really want to get this thing fixed ASAP. While I was on the side of the road I wanted to check for spark so when the bike was running I pulled each plug wire off individually. Every time I pulled the right wire the bike died. The left side however was abnormal as sometimes it died and sometimes it kept running. So I don't know. As mentioned before the wiring on the bike is shady. The regulator and the wires going out of it are in rough shape. I was planning on waiting to rewrite the bike this winter when everything was refreshed and done. But i can do this in an afternoon if that truly is the best option. Just need to get a new regulator. The only question I have is the plan was to upgrade the ignition to a pamco plus and get rid of the points. Are the regulators different for these two systems?

Again, thanks for the input and please keep the wisdom and opinions flowing. Help me troubleshoot this figure out what's going on.

Thanks Again,
Shifty

 

[nj1639]

Almost sounds like a carb issue as you were basically doing the dead cylinder method except for increasing the idle. Might look into doing that for synching but if your wiring is sketchy......
Won't cost you anything but time to check and then you may sort it out.
I went TCI and bs34's....f them points.....