Couple noob questions

So after having my carbs rebuilt/synced by a local shop and replacing the spark plugs, the bike I bought a few months ago started up for the first time (very excited). So excited, in fact, that I forgot to hook up the throttle/choke cables. After disassembling and reattaching the cables, the bike wouldn't start back up. Any idea why? I'm recharging the battery in case that could be the problem.

Second question: When i got the bike, the plugs were black and sooty. Should the bench sync I got when I got my carbs rebuilt stop the rich mixture, or do I need to mess with the air/fuel screw?

 

If your throttle wasn't adjusted just right it may have affected the mixture when you hooked it up. Not positive on that matter tho.

There are a number of factors that could affect the color of your plugs. One of which being your valve clearance (if you hadn't done this yet, you wasted your money on the carb work.). The color of your plugs is affected by the mixture of your gas and air. So yes the mixture screw would affect the color of your plugs. Some of the other guys will have some more input on this matter.

Also you need to check your brakes before you ride it. There are a few good how to's on the site on checking your brakes (and your valves for that matter).

Bob

 

It is possible to hook up the enrichment & the throttle the wrong way round.

 

So when you got the carbs back it started without the cables attached at all? Pull your plugs now and look at them, they might be fouled. You should need at least a little enrichment(choke) to start from cold.

-Battery charged (12.2-12.5v at least)
-Cables check orientation like Wiz said
-Fuel going to carbs? Check petcock.
-Got good spark?

Valve clearance being off won't negate your clean carbs or the bench synch, but they must be in spec or you won't get it tuned right. Did your mech wet set your floats? You'll need a running synch to get it all-the-way right. Your mixtures could be off as well.

Without knowing what caused your too rich in the first place or what else the shop did or didn't do to your carbs there is no way to answer that. You can't dial in the mixtures until you have it running, but you can put them at the factory spec and start from there. You need to put your bike in your signature so we know what it is. You could start with the mixture screws 2.5 turns out from bottomed-be careful when you turn them and bottom them very easy to prevent damage. And take notes on where they were (turns out) so you can always put them back if need be.

The bench synch just sets each carb at the exact same point. The variances in compression etc. in each cylinder is why you need to do a running synch. Typically too rich is caused by mixture setting, float settings, fuel jets too large, or restricted air flow.

 

Thank you so much for taking the time to help. I'm sorry, but i'm very new, and this is my first bike. I know nothing about carburetted motors, and am not even sure where the mixture screw is on the bike. The air filter appears to be clean. I can call the shop and ask them if they wet set my floats.

 

IF, ... It ran without the *Choke* and Throttle Cables hooked-up and won't with the Cables attached, ...

It sure sounds like:

The Pilot Mixtures are Rich enough to Cold Start and Idle.
The *Choke* Cable getting attached has caused the Enrichment Valves to become unseated and not the Bike is All-together too Rich now.

Before you can take a step off of "Square-one" to begin doing the proper adjustments and tuning necessary to make your Bike run right; you must acquire a Reference Manual to guide you in identifying parts and illustrating procedures.

a) The GENUINE Yamaha Factory Workshop Manual -- specific to your Bike -- is BEST!
b) A Haynes or Clymer Manual is better than nothing.

 

Another thing too is that most places do not go deep enough into the the cleaning of these 30 year old carbs. Plus you have to have your valves set. This is a must!
Then you need to sync and color tune your bike.
I bet after you do these things you will fire up.

 

Please put your bike info in your signature so we can give you more specific advice.

Understand something: Old motorcycles are not old cars. There is a whole litany of things that you need to attend to BEFORE you try to trust a 30 year old bike as transportation, and more importantly, not present a DANGER to you when riding it.

Let's back up and start with the brakes; specifically the rear brake. The original rear brake shoes on these bikes are known to delaminate with alarming frequency. You cannot detect this condition without VISUALLY INSPECTING the rear brake shoes. THIS MUST BE DONE or you stand a good chance of getting wrecked, seriously. Read this: http://xjbikes.com/Forums/viewtopic/t=15874.html

As alluded to above, the "bench sync" is only one step in the middle of the process of properly tuning an XJ. Most shops don't really have the skillset to properly care for these bikes; if you plan to keep and ride this one, you're going to need to learn to work on it yourself, or go broke in the process.

VALVE CLEARANCE ADJUSTMENT is critical to not only setting up the carbs, but to the long-term health of the motor, and needs to be done every 5000 miles. Might want to ask the shop how much that's gonna set you back every 5K. If they even know how to do it. If they tell you it's not necessary, then you know their skills are SADLY lacking, be very afraid.

If you really want the bike to run 100%, the following needs to be done, in order, and no shortcuts:
-VALVES IN SPEC.
-Carbs clean, slides go "clunk" (do a forum search on "clunk test.")
-Float levels "wet" set using fuel and clear tubing.
-Bench sync.
Once back on the bike:
-Running vacuum sync (with YICS blocked, if applicable.)
-Final mixture adjustment by ColorTune, or by ear, with plug reading.

Leave anything out, and you'll fight with it until you actually DO the steps in order. I'm willing to bet the shop DID NOT do everything on the list.

But fix the brakes first. Once you're sure the rear isn't about to bite you, the front system will need to be overhauled. You can't ignore them because they "seem to work fine" trust me, that won't last and the results can be disastrous.