Running rough suddenly....

[XJ1100]

82 XJ1100..ran like a finely tuned Swiss clock when I got it. It sat for about 2 weeks due to 2 full weeks of rain and fog...

Started it up the yesterday to take it for a spin. Choked it, hit the starter, and it ran perfect. Sounded great! At idle and reving the engine in neutral, it sounds great. I let it warm up a bit and took it for a spin. Found out at the first stop sign that if I didn't stay on the throttle, it would die. If I just cruise with no real load on the engine, it sounds perfect. If I push it at all, it starts to sputter like it's only running on two cylinders, it's out of gas, or the choke is stuck.

What would suddenly cause it to run so rough after only sitting for two weeks?

HELP!

[Czekus21]

sounds like mabee a carb cleaning is in order. Mabee something like rust, or dirt is clogging a jet or two.

[Dennyz]

It sounds like you have a cylinder or two not firing. First thing to do is find out which one(s). I like to use a candle or crayon. While the engine is running draw a short line on each of the exhaust tubes near the head. It will be real obvious which ones are running and which are not.

general rules.

- if it is only one cylinder, first conclusion is fuel (carb)
- if 1-4 or 2-3, suspect electrical (coils and/or pickups)
- if 1-2 or 3-4, suspect fuel delivery (petcocks, fuel lines, ...)

Keep an open mind, there are always those exceptions that drive us nuts.

[XJ1100]

I can't believe the carbs would need any cleaning. They were just completely rebuilt by a Yamaha mechanic. It was running perfect until it sat for 2 weeks. The tank is spotless on the inside. No rust, corrosion, or sediment. Good clean gas.

What would cause one or more cylinders to just suddenly quit firing? Also, it seems to run perfect if I stay on the throttle in neutral. It's in gear and when it's under load that it starts to act goofy.

Help! The sun is out and I want to ride!!

[TopCatGr58]

Hey Dave,

I can't believe the carbs would need any cleaning. They were just completely rebuilt by a Yamaha mechanic.

Well, there's your problem!! Naw, seriously, what John said, YOU need to do some diagnostic work! The TCI-black box has been known to develop bad solder joints, and can drop out a pair of cylinders. Without load, it doesn't take much to spin the crank, but under load, you need all four to push these behemoths!

A recent Xjer had same thing happen, was cold solder joints in the TCI, resoldered and problem solved. Do your diagnostics, and then report back!
T.C.

[trbig]

The way he talked about moisture for 2 full weeks, makes me wonder if moisture got into the tank or in the electronics. (Like moisture under a distributer cap) Did you run the bike long enough to get everything good and hot and dried out?

Tod

[trbig]

I just re-read that. I didn't mean to say that these have a distributer cap.... was just meaning like when it happens to a car.



Tod

[turbopete]

Re: Running rough suddenly....

Originally posted by XJ1100
82 XJ1100..ran like a finely tuned Swiss clock when I got it. It sat for about 2 weeks due to 2 full weeks of rain and fog...

Started it up the yesterday to take it for a spin. Choked it, hit the starter, and it ran perfect. Sounded great! At idle and reving the engine in neutral, it sounds great. I let it warm up a bit and took it for a spin. Found out at the first stop sign that if I didn't stay on the throttle, it would die. If I just cruise with no real load on the engine, it sounds perfect. If I push it at all, it starts to sputter like it's only running on two cylinders, it's out of gas, or the choke is stuck.

What would suddenly cause it to run so rough after only sitting for two weeks?

HELP!

Exact symtopms mine had when a coil went bad. You'll find it's missing on 1 and 4 or 2 and 3. Figure out which it is, then close up the spark plug gaps on those two. if it runs better, you have a soon-to-be-dead coil.

P.S. mine was cause by my running it with a loose plug cap.

[XJ1100]

That's actually kinda funny you should mention that Pete...

Dave says in a very meek voice....

It was a loose plug wire that I didn't even check before I freaked out and posted this problem please don't yell at me I'm new to XJ's and I just wanted to go on a nice little ride because it's so sunny and nice today!! Very rare for Northern Minnesota...

Thanks!

[trbig]

LOL.. Dave, glad to hear you got it running good again. It's great that it was something simple... my elec. problems NEVER are!

Don't feel too bad.... here's a link to some of the things some have actually "Fessed up" to. I am sure there's worse... just too embarrassed to say.... lol. Some of these guys have been at the bike thing for years, and still screw up, so don't feel too bad...


LINK


Tod

[XJ1100]

That's some funny stuff! Thanks for sharing Tod. I don't mind sharing the stupid things I do...but it happens so damn often!

I've had a couple of real doozies in my time....

[LoHo]

Dave, I think I can top that:

Bike ran rough, no power, gawd-awful mileage. Saw the posts about the vacuum advance, checked the wires, and saw that they were parted. When I clipped them, the interior was basically copper powder. Did the wire fix.

Still runs the same. Do a valve adjustment. No change.

Rebuild the carbs. Buy a four dial synchronizer and get her in synch. No change.

Replace all of the vacuum hoses and fuel lines. No change.

I basically stared at my bike for all of 2005, unable to fathom its mysteries.

Then I went back through what I'd done. Okay, check the vacuum advance wires again. Solder joints look okay...pink to pink...brown to brown...blue to GREEN?! WTF! Okay, match up the wires again, now it runs like a champ. And I learned sooooo much about her inner workings [grumble grumble].

[Meatloaf]

I'm kind of in the same boat but haven't had a chance to start wrenching yet. Bought bike cheap, took it to Yamaha mechanic to get if tuned-up and safetied because I want it done fast. I can do the wrenching myself but figure I'll lose 3 weeks of summer weather riding time while I get it done at my non-professional pace.

Ironically, 3 weeks and $1500 in parts and labour later the shop calls me to say they're done.

I'm driving it home from the shop, my first ride in almost 20 years, bike runs like a top for a few miles and then starts sputtering like mad. The only way I can get it to run properly is to keep revs between 3000 and 4000 RPM in the lower gears. 50 MPH tops all the way home with tractor trailers on my butt the whole way. I barely make it home and call dealership who launch into a very defensive posture and complain that they couldn't properly test bike because it wasn't plated. "But you're a Yamaha dealership", I respond "why didn't you just stick a dealer plate in it asnd take it out on the highway?"

The conversation went downhill from there. I'm going to wrap this up myself. I haven't pulled it apart yet but a flashlight check shows an awful lot of wetness around the #2 carb boot. So I'm assuming it's the culprit.

The smoothness from 3000-4000 rpm is interesting though. Assuming I hadn't spotted the wetness around #2, would smooth operation only in this specific rpm range typically signify anything?

Thanks

[DiverRay]

I would check your local laws, ans see about a partial refund. You need the carbs rebuilt, as the shop probably didn't do it correctly.
The '78 has the screw in seat and needle, and that SHOLD be new. I would check the "Tech Tips", and plan on pulling the carbs, flipping the set upside down, and pulling the float bowls. Check that ALL floats are set the same, and then hook up a "spare" gas source. with the carbs upside down, turn the fuel on to one pair of carbs at a time. Let them sit for about 5 minutes, and check for leaks. You should NOT have any gas come out of the needle with the float upside down.
The other running problem can be that one of the vacume lines could have "poped off" a fitting. If this happens, you have no fuel going to that pair of carbs.
Ray

[Meatloaf]

Here's a killer. They just called and offered to rebuild my carbs for free if I pulled them and brought them in. I just took another look at my two page bill and there are no charges for any carb parts and labour says "cleaned carbs as well as possible". I don't think anything was malicious just maybe the guy wasn't the best at working on old bikes.