1982 Yamaha Xj1100 maxim will not start

I recently acquired a 1982 XJ1100 Maxim, which required extensive carburetor refurbishment due to disassembly. I meticulously cleaned all components using both an ultrasonic cleaner and carburetor cleaner. I bought missing float needles and O-rings from a local shop, I reassembled the carburetor and had it professionally inspected, confirming correct assembly.

Despite this, upon installation, the motorcycle fails to start autonomously, although the engine turns over smoothly and spark integrity is confirmed with new plugs. When aided by starting fluid, the engine runs temporarily. I've also cleaned the octopus diaphragm and attempted to bypass it to no avail.

It appears that the engine's reliance on starting fluid suggests a fuel delivery issue. Notably, on manifold #2, a nipple is present, which I connected to the octopus vacuum port. Additionally, carb #2 features a nipple, advised to be capped due to the absence of a hose from behind the left advancer cover.

I seek guidance on rectifying this issue to enable the engine to run independently, facilitating carburetor tuning. Any insights or recommendations would be immensely appreciated. Thank you for your assistance in advance.

 

Hi, when starting is your gas tank on the bike? The vacuum line to the pet cock must be hooked up (or pintch off) to start.
I was in the same boat a month ago thinking it was a fuel issue. Please cap off the port to the intake boot and try again.

 

So my tank has 2 petcock's with 2 Nipples each. Which one is the vacuum? To my understanding they are both (4 total ) are for fuel, and the vacuum port is on the octopus diaphragm. I have the nipple on carb 2 capped off and the intake nipple on the rubber manifold ran to the octopus vacuum port. The tank is. Currently off and I am using a IV style portable gas tank to make tuning easier without the gas tank in the way.

 

I just did a quick search, your carbs are simular to my 650 but theres a bit more going on. I can't upload a link to another thread but there is one titled New to me XJ 1100 talking more about your specific carbs
If you really want to hear it run I would suggest trying with the tank on

 

You are correct that both nipples on the petcocks are fuel, and the vacuum valve for fuel is the octopus diaphragm.

The nipple on #2 connects to a spark advance module, a small black box that looks like a relay mounted under the tank. "Left advancer cover" sounds like you are referring to the vacuum advance on the XS1100 which was not used on the XJ.

Have you read through this link?

https://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/

In particular, the emphasis on the jets in the bottom of the bowl for the enrichment (choke) circuit? They are difficult to clean and often missed, and if plugged, they can not be opened just with carb cleaner or ultrasonic. They require a fine wire or drill bit.

 

I bypassed all the fuel and vacuum lines when I had one of these. The Octopus was just too much tubing to be under the tank and above them carbs IMHO. I made a "T" fuel line that ran from one petcock to the other, with "T" to each side of the carb rack. If you have a AUX tank and a way to feed both sides of the carbs start there. This will get the bike running and give you more confidence that you cleaned the carbs and the bike runs. Once the bike is running, then you can decide what to do with that Octopus of lines under the tank.

As mentioned above, the XS models had a vacuum advance on the left-hand side of the bike. The wires they used were some type of tin and would break from the constant movement from ever-changing vacuum. Easy to find when you apply pressure to the wire you can see the break in the wire as the insulation will get thin at the brake. XS would just stop or run poorly as one of more of those wires were damaged.

 

Any update on the bike?