XJ550R Dies after 5 minutes at 110kph

So I just bought a 1983 XJ550 Seca a few weeks ago. It works great at speeds below 100 or so, but if I take it onto a freeway and go about 110 it will die after a few minutes. It's actually so consistent with when it dies that I pull onto the highway just outside my town and it'll die exactly at the same road about 8km down the freeway every time. Then when I get it started up again and head home it'll die exactly at the point where I turned onto the highway. What happens is I start to lose power, then it surges a few times and then the engine cuts out. Then I have to wait a few minutes before it will start again (regardless of what I do with the petcock, fuel cap, or choke)

I've read some other threads on similar issues which got me pointed in the direction of fuel delivery. The in-line (paper element) filter that came on the bike looked dirty so I replaced it with an identical one. Then I noticed the line was kinked behind the filter, and also I read that you shouldn't use paper, so I got rid of the filter and now there are no kinks, but the issue is identical. I checked the gas gap, but it seems to vent air nicely and the bike won't start (in the few minutes after it dies) even if you open it up. I know there's another filter attached to the petcock but if I take the line off and put it to prime it flows out pretty strong so I'm inclined to rule that out.

Today it actually wouldn't start at all after it died the second time. I pushed the bike the rest of the way home (about 2km, checking to see if it would start occasionally) then when I got it home it fired right up like it usually does. I looked at all the plugs and they don't look black, which I was surprised by. I thought I'd be running quite rich. I'm pretty stumped at this point.

 

What are you using for vacuum line to the petcock? Could it be collapsing?

 

I'm not too sure about the vacuum line. It seems to be pretty similar to the fuel line. I've experimented with switching the petcock to prime when I feel the loss in power, but it'll just die anyway. Does that rule out the vacuum line collapsing? Also it will refuse to start for the few minutes after it dies even on prime.

 

Fuel flow? like clogged petcock screen inside tank or if you have a clogged inline filter?

Sounds like the bowls are slowly emptying out....

 

Others have stated that paper fuel filters may not give sufficient fuel flow, esp. since the XJ550 has no fuel pump. My XJ550 Maxim had not fuel filter from the factory. Try getting a bronze sintered fuel filter. I added one from XJ4ever and have never had a problem.

If I understand you, you tried straight fuel line with no filter, and the problem is still there?

Perhaps when it happens, quickly open a carb bowl drain screw with a screwdriver and see if the bowls still have fuel?

 

That's a really good idea, thank you! I'll try that next time I go out. And yes currently I have no in line fuel filter and the problem is exactly the same as with the filter (8km driving at 110-115, then stops)

 

Don't know about the 550, but the 700 carbs have an internal screen over each needle valve that can get gummed up and restrict fuel flow. Try setting the petcock to Prime and open the bowl drain screws and see if you get a strong flow from each bowl. What you describe sure sounds like starvation.

 

do you have original spark plug caps? resistors could be failing when they heat up or pickup coils are failing.
your story is similar to what i went through bike would die at same spot in test runs.
vacuum line is cheap buy some 4mm line and replace it . do you still have the original molded vac line and wire clamps? if you were to disconnect the vac line bike would be hard to start even on prime
this is how to clean your gas cap worth doing it does not take long
Your Gas Cap and You

check your wet set fuel levels too

Setting the fuel levels

still have the original molded fuel line? 6mm

 

Guys, thank you so much for the responses. I'm feeling much more optimistic about this now! You really know how to make a new guy feel welcome to the forum.

 

Agreed. If it isn't a flow issue, the floats may be set to low... It really does sound like fuel starvation, ie it takes exactly x kms to burn what's in the bowl, and if the float was higher, you wouldn't run dry.

 

fuel starvation does not explain the time it takes to restart bike but he needs to make sure his fuel system is in proper order .
maybe try a different test loop . different speeds

 

Welcome aboard....was thinking maybe you were in the bermuda triangle if bike quits in same spot? But seriously make sure your battery is fully charged.... if it dies on you and you are cranking engine over alot battery can get drained quick . Keep us informed of any updates. Cheers

 

did you ever check the valves?

 

you may want to replace the fuse holders also you may be loosing contact after it heats up

inline blade holders would be a quick fix on the ignition fuse

 

Set the petcock to prime, go for a ride, and see if the problem will repeat.

 

So it's been a while since i've had the opportunity for motorcycle rides that potentially end in me being stranded but I have some updates.

1. my parents were over for thanksgiving, (my dad used to own a fj600 which he rode for over 100,000km) so we did the valve clearances together. 2 were .002in too tight, fixed now.
2. I replaced the vacuum line
3. I checked out ignition system. Pickups, coil primaries and secondaries were all to spec, but my caps are way out of whack

caps:
1: 75k
2: 20k
3: 9k
4: 12k​

XJ550H, I'm not sure if the caps are original, they say on them "TD T-131" and "TD T-135". Obviously, i'll be replacing them and going out for a drive tomorrow to see if that fixes it (I have NGK "R" plugs installed, which apparently have 5k resistors built in, so should I get 5k plug caps or 10k?)

4. I put the petcock on prime and opened up the bowl drain screws to see if fuel flowed out well, and it seemed like a good amount to me (a pretty steady trickle, i'd say)

 

A”trickle” doesn’t seem right. Mine will pour out. Could be a fuel issue.

 

I too had an open plug cap on my 83 XJ550. I replaced them all with the 5K NGK plug caps, and 5K resistor plugs, for a total of 10k ohms per spec. Works fine.

I wrote on the back of the caps with a silver sharpie to remember to use resistor plugs in the future, since manuals call for non resistor plugs with 10k caps.

If you want stock 10k caps, I think Xj4ever has the correct ones to use non resistor sparkplugs.

 

What about the gas cap vent ? If it's clogged you will get fuel starvation. And plug caps at your local Lordco. For Canadian bikes resistor plugs and 5k ohm caps