Moody XJ 750

My 1982 XJ 750 has mood swings when it will start and when it wont; yep defo a female lol

When I park the bike up for a few days and try and start the bike it fires a few times and wont start.

If I leave the bike for a few hours the bike will then start straight away?

The next day the whole cycle begins again and don't have any confidence in taking the bike out.

I have e a spark at the plugs but seemingly no smell of fuel?

I took off the fuel line from the fuel tap and turned the fuel tap to reserve; no fuel comes out?

If i turn the fuel tap to prime, fuel comes out but the bike will still not fire up.

I have taken the carb tops off and cleaned injectors, all seems to be ok.

I have to mention the bike was previously stored for 19 years and I have just got the bike back on the road. Could the problem be dirt from the tank clogging up the fuel tap?

Has anyone one else had the same issue and could some kind soul provide a possible solution to this issue.

 

Does the bike fire up on choke only and when the choke is then turned off the bike dies?

 

Thanks for responding; No the bike fires a couple of times or tries to fire up then just turns over and wont start.

Really weird how sometimes it starts straight away then other times it wont start for love nor money.

Should petrol pour from the fuel tap if i turn the tap to reserve when i remove the fuel line?

 

Yes, petrol should pour out of the reserve tap.
Another problem if the bike has been stood 19 years is that rust and paint flakes from the inside of the tank could have blocked the taps filter.
I think you need to give the taps and the carbs a good cleaning.

 

I have cleaned out the carbs, done a full service, the only thing I have not done is the fuel tap will try that tomorrow. But when I turn the fuel tap onto prime the petrol flows but still the bike wont start up?

 

In the first post you said no smell of fuel. Sounds like no fuel to the cylinders. Are the plugs wet or dry when taken out?
Have you only taken the carb tops off? Is there fuel to the float bowls? When you unscrew the bowl drain screws does fuel come out?
Forgive me on this one but what are the injectors?
I don't want to seem like i'm teaching you to suck eggs so to speak, but something ain't right.

 

To be honest your correct I have little knowledge of carbs. I took the tops off and took the diaphragms out and assumed the intake holes below were the injectors?
I used some carb cleaner and put the tops back on. OOPS feel rather stupid now lol.

When i take the plugs out they are dry so no fuel is getting to the plugs but i do get a spark.

 

Those intake holes below the diaphragm are the needle jets. They are probably clogged with chrystalized fuel, or whatever it's called, and other crap, dirt, rust, etc.
Carb cleaner is good but I think you're going to have to take the carbs off and take them apart and really clean them properly.
19 years of standing is really far too long to expect a bike to run properly.
Good to hear there's a spark at the plugs, halfway there mate.

 

Sorry to say you need to take your carbs to Church of Clean...spray cleaner will not get into the tiny passages of the carb , and while you are at it do a full tear down of the carbs and replace butterfly seals and idle mixture O ring and fuel rail O rings . Then do a full Soak I prefer Berrymans Carb dip (1 gallon bucket) ( I'm sure there is similar product in the UK) After cleaning soak in hot water with Dawn dish soap( or Fairy liquid UK) dry fully and reassemble , Yes this involves "Breaking the Rack" cheers

 

1. No, fuel should NOT pour out of the petcock when turned to Reserve. That should only happen when it is set to Prime.

2. The float bowls are vented to atmosphere and fuel will evaporate from them. If the bike sets for a few days you have to refill the float bowls by setting the petcock to Prime for a few seconds before attempting to start.

3. You should not have to do that for just an overnight sit, so something is amiss. Please take the advice that was given above about servicing your carbs.

IN THE CHURCH OF CLEAN

Why you should replace butterfly (throttle shaft) seals.

Replacing your Hitachi throttle shaft seals

Setting the fuel levels

I would also suggest cleaning the fuel tank of any loose rust, and fitting an inline fuel filter between the petcock and the carbs.

 

Was this issue ever resolved?
idle-speed-on-my-xj750-increases-when-warm.124169

From this point on, please keep everything about your bike in this thread (not the above thread) so we can keep track and help you better.

 

I second this, I bought some acid cleaner on Amazon which came from Germany in 2-3 days (delivery to UK) and it worked a treat. Empty the bottle into the tank, fill with almost boiling water, insulate in sheets/blankets etc to keep warm and leave for a few hours or over night depending on the severity.

Rinsed with cold clean water and sealed with the included sealant. Has been fine since.

Rostio Tank rust remover 1 Liter plus Tank-protection Emulsion Tank Sealing Set, Tank Rust Removal https://www.amazon.co.uk/dp/B019U5T9K2/ref=cm_sw_r_cp_apa_i_AbncDbAMRCZD5

 

Given that they are not forthcoming about what's actually in their product, I suspect that you grossly overpaid for some commonly available chemicals.
But if you're happy with the results then that probably doesn't matter so much.

 

For £25 I wasn't going to go out of my way looking for other products

 

Put in NEW plugs.
My bike would do this every spring. No amount of fiddling with carb adjustments, spark, grounds, and even cleaning the old plugs - worked.
I put in NEW plugs every spring for the last 25 years... and have never had starting issues.

 

Shouldn't need to do that every year. Plugs do fail from time to time, but not every year. Heck, not even every decade for the most part.

Besides, he said the original coils solved the problem. The coils he bought were cheap knockoff junk.