81 xj550 trouble starting

Ok so once she's up and runing shes sound. I can turn her on and off again and will start first time however if left for a day or so she just doesn't wanna start even with full choke on . I've tried priming her for 30 seconds before starting but just won't go . It's as if I need a little bit more choke however it's opened up to the max. Any ideas

 

Your fuel enrichment circuit is plugged up. Try to give it a "HOT SHOT" , lift tank pull fuel line off petcock. Drain all 4 float bowls, and close drain screws, obtain a large syringe ( meat injector is best) squirt a mixture off Berrymans B12 carb cleaner and Acetone 50/50 mix into the fuel line will take several times . Let this set for 20 to 30 minutes, drain float bowls and reconnect fuel line to petcock . Set petcock to PRI and open fuel enrichment (ckoke) and crank see if this help on start up. Cheers

 

Craig

Did you ever check your valve clearances. I'm stubbornly of the opinion that incorrect settings lead to poor cold starting..

 

You are right I adjusted mine most of the exhaust clearances were too tight and after adjustment it starts all the time.

 

How do I do that a100man /Franz

 

Check out bigfitzs valve adjustment here.

https://www.xjbikes.com/forums/thre...valve-adjustment-with-pics-parts-i-ii.116006/


https://www.xjbikes.com/forums/thre...tment-part-2-the-tool-vs-ziptie-w-pics.29209/

 

Craig if using the tool to hold the valve bucket down keep the cam lobe away from the tool or you can crack your cylinder head. Turn the cam lobe away from the tool never towards the tool. You can also use the ziptie method which is outlined too.

 

Bloody hell that's not what I was hoping for lol. I'll have to have a good read up on that before I try it. The bikes only done 24 miles since 2012. I'm hoping a good run out on her may sort it out but if not I'll give this a go

 

Yes Craig the bikers on this forum know their XJ's alright. I have learned a lot since I joined, let us know how you get on.

 

check your battery drop voltage when starting after it sits for a day

or keep it on a battery tender

 

The battery is brand new however I did get it before I started doing the bike up and has been flattened a few time due to bike wouldn't start. I may take it back to Halfords have them check it

 

new batterys do go bad. if when cranking motor you are not above 10 volts tci will not fire

 

Yes it is a right royal PITA .. Checking is easy enough adjusting is what takes the time... No real harm in checking first and adjusting (if needed) when you have time. If they all come within spec it's something you've eliminated.

 

Checking and adjusting valve clearances is probably the starting point for anyone working on an XJ. They do go out of adjustment, and can damage the engine of let go too long, as unlike most engines they tighten, rather than loosen, as they wear. I would guess very few previous owners had valves adjusted/checked per the interval. I am an original owner, had them adjusted at 5K around 1987, then never did it again until 26k a few years ago. Yes, they were tight...and yes, it started better afterwards.

It isn't that hard to do. If I can do it (following the tutorial posted above), anyone can do it.

 

I think the shims are easier to do than the screw and locknuts on my old CB750K2.

 

Just a quick one. If I put a heater next to the engine for a bit the bike will fire up no probs first time . I've not touched the shims yet just thort I'd ask why people think that is

 

you are pre warming the bike.. the fuel would rather run through a warm motor than a cold one

 

My father was a mechanic and he used to throw an old coat over the engine on winter nights.

 

I found as it gets colder (like 50-65 out), I end up putting a lot more choke on to get the bike to fire up. Then, I can ease it off based on idle speed and let it warm up before turning it off entirely.

 

the fuel is feed to slide needle is asperated ,atomized to make it easier to ignight. the pilot jet is also mixed with air. when motor is cold and the enrichment circuit is used it allows raw fuel into the carb throat.
warmer motor allows enrichment fuel to vaporize.

the ignition coils on your xj produces a weak spark could be you need to upgrade the coils.
first step is to make sure your carbs are clean and properly adjusted. to properly adjust them valves must be adjusted properly and in spec.

first thing you need to do is check and adjust valves.
then you need to sync carbs and tune the pilot jets.
also make sure your enrichment tubes are clean and the wells for them in the carb bowls are clear.

make sure your ignition system is in spec and getting proper voltage by cleaning the connections. still using glass fuses?


did you do a voltage drop test yet? what are your numbers?