How to Start an XJ750?

In my car, the manual says to turn the key without any gas. I think in the winter or cold, give it slight gas.

Since I don't have a manual for my 83 XJ750, I was wondering what the manual says as how to start it?
Do I give it a little gas as I push the START Button? None? Half?
Is it different in cold weather then hot summer?

I always used the choke in the mornings. My friend (1100 Honda Saber) told me he never used the choke, so I tried to start mine this morning without it. It didn't start and when I put the choke on, it still didn't start. I had to push start it. I will always use the choke when cold from now on.

I know it may be different with different bikes, but I wanted to start with how the XJ is supposed to be started?

Thank you,
Chris.

 

A properly tuned XJ shouldn't need any throttle for a cold start. Only the enrichment circuit (choke) is normally used.

 

Mine idles a little higher when it's been running and warn then when it's cold.

Chris.

 

Things that will make your XJ harder to start.
1. Weak electrical system (loose or corroded connections, old or burnt wiring, bad plugs and plug wires, fuse block and fuses).
2. Weak charging system (alternator, regulator/rectifier and bad battery).
3. Dirty or improperly adjusted carbs.
4. Air leaks in carb boots, too much air intake or improper carb jetting.
5. Improper valve specs, burnt valves or low compression.
And few other things I didn't think of. Then there's the temperamental XJ that doesn't like to sit long or cold mornings. Make sure everything is right and safe, and your bike will start easier. I have to give mine a shot of starting fluid (50% ether) if it sits long or it's cold out.
Make sure the battery is charged all the way up, give it a shot of starting fluid and hit the start button. Continual attempts will drain the battery quick, adding to the starting problem.

 

As far as the proper way to start your bike is concerned, all depends on your bike and what works best: choke or no choke, throttle or no throttle. You'll just have to figure out what works best for your bike.
Mine: above 70 degrees, turn key- give throttle 2 quick twists- hit starter button. Under 70 degrees, choke. Under 50 degrees, starting fluid.

 

Just out of curiosity, what do you think "giving the throttle 2 quick twists" does besides just open and close the butterflies?

Starting regimen for a properly tuned XJ is to put the "choke" (enrichment lever) to full on, and hit the button without giving it any throttle. Once it fires, you give it a quick 'blip' and then control the RPMs by turning the choke down a bit at a time as the bike warms up.

Since these are CV carbs, using the throttle can prove counterproductive; the closed butterflies are the closest thing to a REAL "choke" in there.

 

Maybe two "Quick Twists" gives the accelerator pumps a chance to squirt a few shots of gas into the intake manifold?????????

I know better but I just had to say it. :lol:

 

Gee my 83 XJ750 must be properly tuned!! It starts exactly the way Fitz described!

 

I concur!

 

I was in the "hold the throttle open a crack" group...but I hope my new battery will change that (if so I'd fall into camp #2, first start this morning with it in). A new AGM battery, to replace the walmart special I bought two years ago, made a heck of a difference.

Sometimes though, I do think giving it a little throttle can help when you over enrich the mixture (since the amount of enrichment you give it depends on temperature).

Also remember, you carbs bowls are open to atmosphere, and don't hold all that much gas. If you let your bike sit too long (for more than a week in some climates), and have a functioning petcock, the gas in the bowls evaporates to a low level. It will only refill with the engine is turning over, providing a vacuum and opening the valve in the "vacuum operated" petcock. So those first few times turning over the engine, you are just refilling the bowls. Flip it to PRI for a minute and let the bowls refill, then try to start.

 

Giving the throttle 2 quick twists doesn't just move the butterflies, it also makes the slide pistons move which draws fuel from the bowls into the carb which PRIMES the carb, does it not?
Also, after 2 twists, the butterflies would be closed and not be counterproductive to "choke". Wide open throttle would keep the butterflies open.

 

Not on these CV carbs. Only a pressure difference between the venturi and atmosphere, sufficient to overcome the spring force behind the slide, will cause them to lift. And you only get a pressure drop in the venturi when there is air flowing through it.

Throttle cable only actuates the butterflies. On "slide" carbs, it lifts the slides, but not on CV (or constant velocity) carbs.

 

The slide pistons are vacuum operated not mechanically operated.

MN

 

Thanks Manbot, I was thinking along the lines of my round slides and not the CV's.

 

Does anyone have a 83 750 manual they can quote to see how it's supposed to be started?
I wanted to start out with how it's supposed to be started, to see what happens.

Chris.

 

My owners manual says just what Fitz told you,and no enrichement when motor is warmed up.

 

I went out in the morning after a couple days of sitting. I found if I put on the choke, without any throttle at all, it's hard to start. All I have to do is, when I hit the start button, barley flick the throttle, I mean just a very slight flick, it starts right up. Not sure what it means.
Next, I will try and flick the throttle before I hit the start button, with no throttle.

Chris.

 

You shouldn't need any throttle when starting from cold, your enrichment passages are clogged.

 

You might also check that your enrichment cable is adjusted properly. watch the plungers when you move the enrichment lever to verify they are lifting.

 

When I first got my 83 XJ750K running properly and on the road I had similar problem.
First how are the plugs are they running rich/black or lean/white?
Second I had to play with the throttle stop screw, big nob under carbs, to get it set to the sweet spot so it would start as per Fitz's description.
Third I put Stabil in the gas ran it and let it sit. Stabil will and does help get rid of any residue varnish left in the carb passages. Some old-timers run it in the tanks all the time. Especially if the bike is not run all the time. If the bike sits for more then a week put it in. Wont hurt anything.
Also how are the vacuum ports on the boots? If they are the originals get rid of them and replace with new ones, also new clamp springs.
These carbs are very touchy but once you have them set and adjusted properly they just work great. Only real threat is varnish from the gas. So like I said run some Stabil through her now and then.