Runs great, then loses all power and dies

[Grimace]

Just like the title says. I have been having carb problems for about 3 years. Finally bought another set of carb bodies and a bunch of extra parts (thanks a ton cokeman ) and got the carbs all together. Bike ran GREAT! Rode to work this morning, and it felt really strong on the highway, and ran great in town. Got on to go home, and it died once leaving work. Hit the starter and it fired right up, went on home.

Almost home, I got a gap in traffic, and pinned the throttle, expecting to have to hold on for dear life, but instead I just sat there on the bike with it stuttering like it was bogging down, but not slowing down. It was like 2 cylinders dropped out when I nailed it. Let off the throttle, and it ran fine. As long as I didn't crawl off in it, bike seemed to run fine.

This evening, I put another 20 mile highway trip on her. Got to the exit ramp, and bike died. Hit the starter button, nada. All lights were off also. At the bottom of the ramp, I got power back and drove on to my destination. Going home (3 hours later) bike would hardly stay running. Was on the highway and it bucked twice, lost all power (pitch black now) then fired back up and ran really well. Same problem when I went WFO, but at normal highway cruise speed it ran excellent. Now it is doing it more often. Ride down the road, and it loses all power, winds down and dies (if I pull the clutch it dies instantly).
After a couple of seconds I get all power back and it runs good again.

I have new air filters, new petcocks, freshly rebuilt carbs (for the 30th time) brand new coils, wires, and plug caps from mikesxs.

Getting frustrated.

Thanks, Grimace.

[oseaghdha]

My xs would lose electrics occasionally until I replaced the fuse box.
Sounds like loose/corroded connections.

[red bandit]

Check your main fuse and connection. Might want to check all of your fuses and connections. Check and dielectric grease all your electical plugs/connections.

[Toolmaker Tim]

Fuse box

Hey Grimace, had something like that happen to me. Turned out to be the fuse box. Got one of the ones TopCat sells. It works great and I haven't had any electrical problems since. It's a bargin at twice the price. Highly recommend it!

[Grimace]

Thanks guys, sounds like I need a fuse box. I will get ahold of T.C. and get one. Thanks again!

[oseaghdha]

Almost home, I got a gap in traffic, and pinned the throttle, expecting to have to hold on for dear life, but instead I just sat there on the bike with it stuttering like it was bogging down, but not slowing down. It was like 2 cylinders dropped out when I nailed it. Let off the throttle, and it ran fine. As long as I didn't crawl off in it, bike seemed to run fine.

You may also want to check the tips on the pickup coils.
My SF was getting sloppy around 4KRPM, that was the problem there.

If you have not already found them, check these out:

Modifications

Repairs

[trbig]

I don't have one on my bike, but does this not sound like a vent tube being clogged? Sounds like a fuel starvation issue to me. When this happens, open your tank filler cap and see if you can hear air sucking in.


Tod

[81xsproject]

Yeah I too would say pickup coils, vent tubes, or gas cap vent.

[dbeardslee]

Grimace - When I first got Betsy she had the annoying habit of dying for no good reason. Everything would just shut off - lights, starter - everything. I found that by moving the wires around by the fusebox she would start again. Started looking more closely around the fusebox and found the wire sheathing burned off of a heavy-gauge wire. Every now and then it would make contact with the frame, and everything would go dark. Also had some burned wires inside the headlight bucket. Yours kind of sounds similar. I would take a good look at the connectors and also the wires themselves where you can get at them. My $.02

[Grimace]

Originally posted by trbig
I don't have one on my bike, but does this not sound like a vent tube being clogged? Sounds like a fuel starvation issue to me. When this happens, open your tank filler cap and see if you can hear air sucking in.


Tod

It would be a clogged vent tube if it did it all the time, but half of the time I can pin the throttle and it picks up and runs like it should. Other times it sputters and acts like one coil dropped out. I forgot to mention I had just gone through the carbs again, and replaced the throttle shaft seals, and cleaned the fuel supply and vent tee fittings.


I just got finished with the pickup coil wire replacement. Used the old leads from a multimeter I have. I did find one wire that was questionable, but not broken completely. I will ride it here in a bit after a short nap (up last night late reading posts here looking for ideas).

As far as the fuse box goes, I did find the ignition fuse holder cracked, and when I pulled the ignition fuse out, the holder fell apart. I spliced in a spade fuse holder until I get my new fuse block from TC.

One other thing, would the needle height affect the 4k-5500 rpm range that much? I have them set on the middle groove, but was thinking it might be starving/flooding then the engine catches up. Just thinking outside the box.

Thanks for the replies, and keep em comin,
Justin

[Grimace]

Ok, just got back after a ride. I synced the carbs, and tinkered with the idle air adjustment like the tech section says. Bike idles fine, but driving around town at 40 mph in 4th gear, it has a gurgle in the exhaust. Kind of a stutter, but if I barely crack the throttle more, it goes away (as long as it is under a load). The problem I had with going WOT is still there. When I pin the throttle, it stutters like at least one if not 2 cylinders dropped out. Let off the gas a little and the problem goes away. Gently roll into the throttle, and it will go wide open no problem.

I am stumped.

[oldyam80sg]

It seems to me that the carbs might be dirty even after you synced them.If i crack my throttle open at any time the bike instantly responds.When you cleaned the carbs did you remove the float valves and clean the screen thing at the bottom?Mine was plugged up with crap in 2 carbs.After a cleaning you could feel the difference.Did you remove the screw at the bottom of the carbs and make sure that fuel comes out?Better yet remove the float bowls and see if all fuel levels are the same in each one.Also what color are the spark plugs?

[Grimace]

Good questions oldyam, let me clarify. I tore the carbs down to bare housings, soaked the housings in carb cleaner in the gallon can, then hosed down the carbs inside and out with spray cans. Then re-assembled the carbs with new throttle shaft seals, and cleaned all internal components. Then I set the float levels like Mr Talbot did in the tech section. Then pre-synced the way TopCat described (looking at the top of the throttle bore at the three little machined holes and syncing that way) and then ran the bike around a square mile section (4 miles total) and then did an actual sync with a motion pro mercury carb stick.


Here are my latest findings as of an hour ago. Pulled all 4 plugs after a mild romp down a side street.
#1 black and fairly sooty=rich
#2 very little color, looked almost brand new=lean
#3 a little more color, with only one dark spot right under the ground strap=lean but closer
#4 just a touch lighter than #3=lean

I found if I am cruising in 4th or 5th at about 4K and pin it, she bucks and stutters and gets tourettes pretty bad. If I am in 4th at 4K and drop a gear to 3rd and pin it, she hickups once and goes straight to full boogie and it is Katie bar the door.

With this new round of data, could that point to the diaphrams not pulling up fast enough to meet the engines demands, causing a lean condition?

[Grimace]

CRAP!!

I just remembered why #1 is black. I used a different style of pilot jet in that carb. It has 8 side holes in it instead of 6. Even though it is still a 45, it must be making that cylinder lean.

Guess I will be changing the other three to that style. Better to be a tad rich than lean.

[dbeardslee]

Grimace - How did you adjust your mixture screws?