Very hard to start below 60 degrees.

My 1982 XJ550 26Kmiles runs excellently after it turns over and starts. It starts easily above 65 degrees. It's choke is working perfectly, I overhauled and synched the carbs and performed a valve job. It purrs like a kitten and idles very smoothly at 1100 rpm. I keep it well maintained.

But when the temperature gets below 60 degrees, it just doesn't turn over without a lot of cranking. What factors could cause this? I believe the fuel system/choke is working fine, but maybe the air/fuel amixture adjustment? Could the electrical system be a cause? Would a weak spark cause sensitivity to temperature? I'm searching for working hypotheses but I got nothing, I'm stumped. Thanks for your advice!

 

They are cold natured. I just went up 1 size on the pilots and shimmed the needles .010 on my 750. Fires right up can turn off the choke as soon as its running and it will idle.

 

Cold natured yes, but not at 60ºF. My 750 is bone stock and starts with a press of the button at 40ºF.

Check for vacuum leaks (use propane or spray carb cleaner).

I have to ask: are the carbs Church of Clean clean?

Are the float levels in spec?

What are the pilot screws set at?

 

read the thread about vacuum and compression you both seem to be talking about the same problem and symptoms

 

A weak battery would be sensitive to cooler temperatures.

How old is your battery?

+1 to starting at 40F, for an XJ650 Maxim.

 

All i was saying is on either bike yea the will start at 40 degrees but soon as they fire can you shut off the choke and drive off. I can just like with a older bikes from the 70s. Gas mileage did not change. These bikes came very lean from the factory on the idle circuit back then for emission testing on motorcycles was at idle. Their could be other problems and a 550 is completely different then the 650s and 750s the cam profiles are much more aggressive for the size of the motor and they have mikuni carbs. Not to mention they have a much less vacuum signal and need larger idle jets then their bigger brothers just to get a sip of fuel.

 

Yes, by 55 degrees, I am scared to go riding because I might get stranded because I can't start my bike.

I didn't know about vacuum problems, I will check it out. I will also read up on vaccum. My spark plugs are a tiny bit rich but other wise nice looking according to the manual. So it's prob not electrical.

Thanks everyone!

 

It could still be your battery. My plugs looked great but I had the same problem. The battery would spin the engine well but if it didn't fire off immediately it wouldn't start. I discovered that if I charged the battery it started almost immediately. Let it sit a day or so and it had problems again. I replaced the battery with a good AGM and it fires off almost as soon as I touch the starter. So the next time you have a problem you might try to jump it with a car battery--car not running I'm told-- and see if that works. If so, replace the battery. Apparently the TCI ignition relies more heavily on the battery to provide a hot spark needed for starting than the CDI system that has a condenser or capacitor.

 

If you were to ride, say 10 miles, and stop.
would it be hard to start again.

 

No, once it gets up to operating temperature, it starts without any problem whatsoever... and runs perfectly.

 

I will definitely try this tomorrow, it is going to be a cold day in Chicago, thank you very much.

 

your not giving it any throttle at all, right?
same routine as if were 80

 

mine is hard to start below 50 as well
I know I need a new battery, it will be a next year thing
over 50 it is a lot easier

 

Alas, no luck. This morning, I jumped the XJ550's battery with my car and it did not turn over, but it did crank more enthusiastically. It was 50 degrees exactly.

I was really hoping that would be it.

This extreme dependence and sensitivity to temperature is amazing. It will warm up this week to 70 and I guarantee it will start without much problem.

 

Cranking more enthusiastically is a clue. Have you inspected the starter brushes?

 

I just replaced the entire starter with a rebuilt one from Len. Bad wording - by enthusiastic, I mean that a nice big car battery is better than a little m/c battery, and that the cable connection was solid.

Are there vacuum hoses that might have leaks that I need to check? If there are any other quick checks that I should do, let me know please. Thanks to all!

 

There is a vacuum line on the #3 carb boot that goes to the petcock, and vacuum caps on the other intake boots. They are inexpensive, so just replace them all. If they are not cracked now, they will be eventually due to age. You should also check the intake boots for cracks. Propane is your friend here, but it will not always find a crack that only opens up at high rpm or when the boots get up to engine operating temperature.

 

I have a similar problem with my XJ 650 Maxim, when temperature outside is: lets say 45 f its hard to start.
Battery is new and up to spec, new plugs. I rode the bike during winter, with the exception of February, its Chicago and there was a lot of snow and salt.
when cold outside I used starting fluid, starts just fine, without it, pushing the bike did the trick or sometimes i just crank it on intervals it eventually starts.
No air leaks from the carb boots. bike is 90% stock, the exhaust is a slip on form what I can guess XJ 750 ( not sure about this) also I don't know if it was jetted properly or at all.
Also i replaced the petcock with a generic, since the original vacuum petcock was leaking. I plugged the vacuum line on boot #3

 

I also have this issue! 33-45 degrees it can be a real pain to start. Bomb starts no issue, BRAND NEW battery, newish plugs, carbs cleaned. at 3 after work the bike fires up no choke required. only in the cold mornings. I can get it to start by standing there and taking my time with the start button. is it just too cold for the fuel?

 

How does one use starting fluid with these bikes? Where do I squirt the fluid? How much? Anybody have a youtube? Also, if it start (or doesn't start) easier with the starting fluid, what does that imply in terms of diagnostic information?

 

I will also check out whether pushing it to start works at lower temperatures. Maybe if this works it can tell me something.

 

After xj's are ridden for a spell at operating temp the mill has a tendency to suck vacuum and burn whatever fuel is in each chamber after they have been shut off. In my experience open the er, turn the petcock to prime, wait 30 seconds then hit the start button. If all is good it should start.

Gary H.

 

What grade of oil are you using?

 

they have summer and winter mixes for gas. has something to do with vapor pressure, whatever that means. maybe your bike doesn't like whatever their selling at that temperature. do you always get the same kind of gas

 

Perhaps Polock is on to something... My car always gives me a "Check engine" light when the station switches from winter gas to summer gas and vice versa. These bikes may feel the same way, but have no onboard diagnostic system with which to express their discontent.

 

P.S. how do you know when your starter jet is really, truly, zestfully clean? One of two ways:

a) shine a strong penlight or mini flashlight into the bottom of the bowl, where this jet passage "intake" is located. Look through the top of the bowl down into the jet passage "outflow" passage (this is the passage that the brass suction tube in the bottom of the carb body actually fits down into). Focus your eye carefully on the jet opening and make sure it's clean. P.S. it helps to do all this while in a darkened area.........see the picture "starter-jet.jpg" on page 2 of this forum thread topic for a great image of what you want to see!:

http://xjbikes.com/forums/index.php?threads/4050


b) put the spray tip (you may have to gently shape the end of it to a fine point) of a can of carb or brake cleaner into the intake opening of the starter jet and let rip a spray. A STEADY, FINE, POWERFUL STREAM OF FLUID WILL COME OUT OF THE OUTFLOW PASSAGE ON THE TOP OF THE CARB BOWL IF THE JET IS PERFECTLY CLEAN AND OPEN. I mean this stream will absolutely spit out a good 5-10 feet. If the stream isn't powerful and laser-like precise coming out of the jet, then the jet isn't zestfully clean.....

By the way, when using the spray-stream method of checking the jet, don't even THINK of putting your eye or face anywhere even NEAR the jet outflow path, unless you like a painful and potentially serious trip to the emergency room.

 

It's been a few years since I performed this performed this procedure while synching my carbs. Looks like I get the pleasure of taking the carbs back off since the starter jets they probably plugged back up!

 

You just need to take the bowls off, all the starter jet issues reside entirely within the bowls. If you huff and puff and hold your tongue just right, you can get all the bowls off while the rack is still mounted. I would start with the outer carbs (they're the easiest bowls to get off/out) and see if that is the problem. A cold no-start situation usually means that ALL of the bowls are plugged, as even having just one or two clear starter jets will allow the bike to (reluctantly) start even in the cold (and certainly at 60F).

 

Yes I clearly remember doing this a few years ago. There is a very fine and thin channel that runs up along the side of the bowl that needs to get checked. It is super easy to miss.

It will be easy to check the outer bowls and the results might definitively diagnose the problem since they are probably all clogged or none clogged.

Thank you! I am a man on a carbbowl mission.

 

I tried, but it looks like I am going to have to remove the carbs to remove the bowls, so this will take a little work.

One quick question before I do that however. I observe that the choke really does have a strong effect on the idle (after I get it to start at warmer temperatures). Does that not mean that the starter jets are already clear then? Or does activating the choke open up other jets than the starter jets? In other words, if the choke has an effect, does that necessarily mean that the starter jets are clear?

For general reference, how likely are the starter jets to become clogged? I drain the fuel each winter before hibernating the bike. How can I prevent them from clogging again?

 

The choke isn't a choke. It is a seperate enrichment circuit with its own fuel passages.

 

Aha. Thank you.

 

Data point: Pushing it at 51 deg F to start it was not successful.

 

FOR ALL OF YOU doing this yourself, check out this deja vu thread: http://xjbikes.com/forums/threads/colortune-question.16515/#post-141264

 

remove the seat, under the tool box holder there is a square opening (the air box) , 2 second spray of starting fluid should do it in there, try to not over do it ,
that worked for me when was super cold (20f Chicago)

 

rear top of air box is an inlet across the top just spray it in there its about 1/2 inch wide

 

I pulled the carbs and cleaned the starter jets! Hurray. While the carbs are off, I am looking at the intake air port rubber boots (if that is the correct name). They are the ones between the carbs and the aluminum heads. Their condition may suggest that they are leaking there, and from what I understand, could cause the behavior of bad cold starting.

First, the gaskets are very old and may not seal. When I remove them and look at the interface between the aluminum and rubber, there looks to be an O-ring on the rubber boot that has been flattened since 1982. But I cannot remove the O-ring, suggesting it might be normal or perhaps built-in to the boot. Or maybe it is an O-ring that became fused. What is the structure here supposed to look like? Is there supposed to be an O-ring there that needs to get replaced? It would make sense that there would be something like and O-ring to make the seal.

The reason I ask is because I am trying to figure if I should get just new gaskets or gaskets + new boots. They are not cracked and are supple otherwise, and I'm on a budget, so I don't want to buy parts that I don't need.

Let me know if photos would help and I will take some.

 

The o-rings are replaceable. You will have to dig them out since they are age hardened.

 

The o-rings are NOT replacable on his model (they are on 650 Turbo, 700's and 900's, but not only any other models). they are molded into the "skin" of the boot/tube. Although the crushed versions don't produce as good as seal as young, fresh, firm, tight manifolds with perky, upright O-rings, you may be able to get away with some new, supple, might I say "virgin" gaskets and button her up nice-and-snug and call it a......day, or something like that.