Trouble shooting nightmare check here!!!

[graybird78]

maybe take alook at vac advance unit. unhook vac supply to unit. see if problem gets better or worse. make sure vac hose is hooked up correct.it connects to carb nipple on #2 carb not to nipple on #2 carb boot. is battery and charging system working properly. no kinked fuel lines. just some more idea's.




graybird78

[thumperjsa]

Are you positive you are not getting any slipping on the timing chain? It sounds as if you are getting some pre/post ignition of the mixture of fuel/air. From what I recall, most of the issues you say you are having seem timing related. You mentioned as I recall that you changed out the coils and TCI as well as some other parts. Since you most likely did not change out the wiring and connectors to items like the TCI box, did you check that all those were good. Maybe pulling on some of the wires around it while running to see if there is any change. You might also try some wire tracing and pulling apart the connector from the TCI and doing some checks from that point and follow all the connectors. By pulling on the wires a little while you are tracing, you may find a bad wire or connector.


You may want to put some clear fuel filters in line to verify you are getting a steady flow of fuel to the carbs.

[Nastydude]

Ok folks i'm back sorry about the silence had much non bike related work to do. to answer some questions that were asked the tank was flushed multiple times with fresh gas before I even attemted to start the bike initially along with both petcock screens. I have checked and quadruple checked fuel delivery and the tank will supply more than adequate fuel to run the engine. as for water I have drained the float boals numerous times looking for moisture since i flushed the tank and have found no trace. Besides all of this although the bike runs like crap I have been driving it any way (short well planned trips 100 km or less) and have about 800km on the bike since I got it running in the hope that the bugs would work themselves out. I am running stock air box with a new filter. as for the fuse box the brass fuse holders were all corroded and have been replaced by aftermarket inline spade fuse holders which were soldered in. before i did this i stripped the wires and connected them directly with electrical grommets out of frustration but this produced no results. All plugs wires and connections between the tci pickups and coils have been cleaned and checked there was no change. however by brother pointed out a similar problem he had with a snowmobile which originated from inside his ignition switch and that is somthing I havn't even thought of checking so i'll get to that tommorrow and let U folks know how it turns out.

[Nastydude]

sorry forgot to mention the vacuume lines and intake boots. the vacume lines are new and routed correctly guarranteed and my intake boots had deep cracks so I checked them by running acetalene from my cutting torch over the boots and couln't find a leak but I still didn't trust those crackes so i removed the boots from the head and used a urathane primer and urathane sealant to all the boots reinstalled the boots carbs ect.. ran the bike and checked for leaks again and it once again tested good. and i'm gonna check my kill switch as well my plan is to hot wire rhe ignition and kill switch to see if that makes a differance.

[skids]

A couple of other things:

Remove the timing cover and plate and lube the mechanical advance.

Check the compression (did you already do that?)

Check the exhaust system integrity (did you already do that?)

Make sude that you are not using an older set of carbs with a newer airbox. The breather nipples in the newer airbox are filled with plastic and the older carbs have breather hoses that must not be plugged.

Make sure the choke circuit is linked correctly to the individual carbs and not staying open when you push it closed.

I am running out of ideas...

Let it run at the range where is starts running crappy and read a set of new plugs.

Originally posted by Nastydude
sorry forgot to mention the vacuume lines and intake boots. the vacume lines are new and routed correctly guarranteed and my intake boots had deep cracks so I checked them by running acetalene from my cutting torch over the boots and couln't find a leak but I still didn't trust those crackes so i removed the boots from the head and used a urathane primer and urathane sealant to all the boots reinstalled the boots carbs ect.. ran the bike and checked for leaks again and it once again tested good. and i'm gonna check my kill switch as well my plan is to hot wire rhe ignition and kill switch to see if that makes a differance.

[DEmily]

Nasty,

Sounds like everyone has thrown everything at this deal. The two thjings that I have experienced that caused similar issues with my XS and my wifes KAW: The BIGDOG ( XS11) had very speratic misses and back fires similar to what you have discribed. For the XS it was the solder joints in the TCI. Sometimes it would run great and then suddenly it would get weird. Resoldered all the joints, problem solved. I recqall you swapped out TCI units so I guess that is not an issue for you. My Wife was having very similar issues about a year ago with her KAW. While checking the bike, I used a vacume gauge off her intake manifold. When I reved the motor full trottle, the vacum did not drop to zero momentarily as it should. When you first open the trottle all the way, the vacume gauge should hit 0 for a second or two. This is usually an indication of plugged exhaust. I pulled the mufflers and the bike ran great. It was load as hell but ran great.

My gut feeling would be electrical, but I am not one of the experts here. Maybe pickup coil clearence, coil jumping fire to frame, something odd like that. When I dig in to these kind of things I always consider the three major areas and then break each of those down until I find it. The three areas I look at are Fire (Electrical), Fuel and Compression.

Wish I had an answer to help you Nasty. Don't give up! You will find it.

Goodluck!

[DEmily]

Nasty,

One other thing I wanted to bring up. I would be sure your ground strap is in good condition and making good contact.

[pgg]

The sticking carb slide idea would be worth checking out closer. I had that problem once also. One slide kept sticking wide open and the motor ran like crap until reaching high revs.

[DEmily]

I think the slide can be checked by pushing the slide up and holding your finger over the air hole. The slide should slowly come down while your finger or thumb is over the air hole. If it is sticking up, and you pull your thumb off the hole the slide should drop quickly. That is how I tested mine. This will also test the diaphrames, which could be the issue for you.

[DEmily]

I should clarify. The air hole I am speaking of is at the top of the carb mouth. At least it is on my 79 XS.

[pgg]

If it's sticking, it stays up (wide open). Fixed mine by polishing with smooth emery paper.

[scalded dog]

I just remembered, I had a similar problem prior to the cdi box problem I mentioned before. I found a wire broken, and barely touching, right where it connects to the ignition switch. Just one more thing to check. Later 'Dog

[shutchis]

'80 XS11 Surges at 4500 RPM

Team, I'm having the same surging problem at 4500 RPMs. I know this is an old post but I'm stuck. Anyone know of a fix?

Background: This bike is fuel injected. It's not a carb issue. The tank is clean, and the fuel pump is putting at 40 psig. I have replaced the yamaha ignition system with a GM DIS unit. The timing is electrically controlled by the EFI controller, so it's NOT the TCI system or the vacuum advance circuit. The air filter is clean.

I could sure use some help. It runs great from 1200 to 4500 rpms, it idles smooth, but when you hit 4500 rpms, it's bucks and surges. It also surges while in neutral and sitting in the driveway, so it's not a slipping clutch or drive train issue.

[ViperRon]

Check the wiring going to the kill switch and ignition and measure your battery and charge circuit make sure it has a good 12 volts and goes up to better than 13v when above 2000 rpm. A dead cell in a battery or bad voltage regulator or ground could possibly cause the problem. A bad kill switch or the tip over switch could have rust in them shorting out. These are other things that come to mind. Any shorting wires to these could cause problems also. aint right

If you check all this then it ain't fixed I'd definately go to church on sunday cause something just is not going your way.

[James England]

Team, I'm having the same surging problem at 4500 RPMs. I know this is an old post but I'm stuck. Anyone know of a fix?

Background: This bike is fuel injected. It's not a carb issue. The tank is clean, and the fuel pump is putting at 40 psig. I have replaced the yamaha ignition system with a GM DIS unit. The timing is electrically controlled by the EFI controller, so it's NOT the TCI system or the vacuum advance circuit. The air filter is clean.

I could sure use some help. It runs great from 1200 to 4500 rpms, it idles smooth, but when you hit 4500 rpms, it's bucks and surges. It also surges while in neutral and sitting in the driveway, so it's not a slipping clutch or drive train issue.

YOu really ought to start a new thread, rather than hijack thisone. Otherwise things are going to get very complicated......