backfiring/revving up to 5k rpm while idling

[crazy steve]

Ok, that's the original XJ ignition, so the 10M TCI is what you need. You have a XS cover over it though... I don't see a 'extra' wire; you should have a orange, gray, and black going to the ignition components.

These ignitions are not adjustable, so your timing is good as-installed. So the problem is in the carbs. So which carbs do you have? Are they the original XJ set, or did the '79 carbs come with the motor? You can identify them here: http://www.xs11.com/forum/showthread.php?t=35964

They probably need cleaning and adjusting/sync, a poor sync will cause your problem.

[pbaker27]

I know it says Mikuni on the side if that matters. I will look at them tomorrow, heading to bed.

[natemoen]

Check over those wires, there isn't a loom covering so you might even have some melted or scraped wire causing shorts. Follow them all the way under and across the back of the engine and check them.

[pbaker27]

Nate, the loom covering had melted a bit on the exhaust by the PO, but had already checked them to make sure they were ok.

Here are pictures of the carbs:
This is the right side of the bike.


This is the left side of the bike, with the choke.

[natemoen]

Looks like xs carbs or at least it has an XS choke setup.

Never trust a PO's work. If you didn't check them, check them yourself.

[pbaker27]

I was saying becuase of the PO the cover was melted, so I pulled it off and my Dad checked the wires/used a volt/ohm meter on them and they were fine.

Also, which carbs are better, the XS or the XJ carbs with the XS engine?

[crazy steve]

Also, which carbs are better, the XS or the XJ carbs with the XS engine?

It really doesn't matter which carbs you have, what is important is that the carbs be jetted correctly, i.e. to match the year of the carbs. Those look to be 1980 carbs, so the main jets should be between 110 and 115, a 42.5 pilot jet, and a 180 air jet. These may also be a set that require the rubber plug on the pilot jet, something to check...

[pbaker27]

I have no idea what to do with the carbs, I'll check with my buddy to see if that is something he can do, otherwise will have to take it to a shop

[crazy steve]

I have no idea what to do with the carbs, I'll check with my buddy to see if that is something he can do, otherwise will have to take it to a shop

NOOOOOOO!!!

Chances of you finding a competent shop to rebuild the carbs are slim and none... not to mention what they'll charge you. Here's a step-by-step rebuild... http://www.xs11.com/forum/showthread.php?t=36017

Still scared? Member 81xsproject offers carb rebuild services... http://xs1100carbs.blogspot.com/

[pbaker27]

Ok ok, I won't take them to a shop just kicking myself for not bringing my mechanic buddy with to begin with to see what was wrong with, but then I wouldn't be having these conversations with you lovely knowledgeable helpful people I just want to ride so bad, and have had the bike now over a month with not being able to ride

[pbaker27]

Where would I go about getting a rebuild kit for this? And how do I know for certain 100% what year my carbs are so I can get the right kits? I see ones for the 79 and ones for the 80 on ebay for sale.

[natemoen]

If none of the parts are damaged you probably don't need a kit. Only way to know for sure of the carbs is to open them up.

[pbaker27]

So an update on my bike, another buddy came over today and he started the bike up, and took each wire off, starting it back up after pulling a wire and killing it. He got to the left side and pulled the wire but the engine didn't kill, we pulled the plug, it was fouled so we cleaned it up and surprise surprise no more backfire! I will be replacing all of the plugs this week.

We pulled the carbs, cleaned them as best we could and put them back on with new carb boots. My friend drove it around the block without issue, though the engine idles at 2k RPM(vs 5k rpm before). It might just need some playing with the idle screw.