Starting problems

Hi Guys,
Some of you may already know my bike but I do an intro in any case here:

1984 xj900rl Seca



I´ve done a clean of the carbs but no syncing or adjusting of any kind. Just a pretty thorough clean.
The bike runs great when it is warmed up but the starting is always a risk

What happens at start?
The bike usually kicks over the first go, but it takes some skill to keep it running for the first 10 sec or so.
It is usually running very lumpy and rough for the first 30 sec or so. Work with the choke is required.
If it survives this then all OK.

If not then trouble ensues!
If she stalls in the first seconds, then it is pretty certain I will not get it running.
The starter motor will turn her over without so much as a sigh of life till the battery can´t do it any more!
Usually leaving it for a few hours will "reset" this effect. I have got her going by clutch starting in an emergency case!

Other symptoms:
The spark plugs are kind of dark and wet indicating a rich setting in the carbs. Don´t know what to do about this at the moment.
Flicking opening the throttle when she is warm sometimes results in a short stall of the engine before it reacts.
Starting with the choke already open or opening it after she is running for a few seconds seems to make no difference to a successfull start.
Battery seems OK
Have not looked very carefully into the electricals at all.

Anyone has any ideas on the cause?

 

I am no expert by any stretch, but it sounds like you need to sync and tune the carbs. A lot of folks recommend purchasing a Colortune to make setting the mixture easier. You also need to use a manometer, such as a carbtune, to ensure carbs 1,2,and 4 are in sync with 3. There are some great tutorials on the process here on the site.

Edit : another thought is you might also check the fuel level in the bowls. However, you should still tune the carbs.

 

After cleaning you really must do a bench synch at the very least, along with a baseline idle mixture setting of 2 1/2 turns out from a soft-seat.

When you cleaned the carbs did you go to church?
Did you wet-set the fuel levels?

You are quite rich, but the question is why. There can be a few causes and all of them require you revisiting the work that you have already done.

 

Hi K-moe
I am not a church guy so most probably I have not lived up to any minimum measure of sanctity as yet. (the story of my life in fact)
I did not bench sync or and check of fuel levels in the bowls. I gather that is what you are getting at with your comment "wet-set the fuel levels"

Yes from what I can tell she is running rich. Dunno what to practically do about this at the moment.
The bike runs most of the time and the riding season is upon us. I am loathed to rip into the only running bike I got!

I do have an interesting opportunity though.
Since this thread started, I have acquired another XJ900RL!
As you can see here she´s being stripped for a rebuild

I have decided to do a major mod on this bike and keep the first one stock.

(for those that read the other thread of mine about the air box, notice that this one is still in the frame. Despite this level of dismantling, the air box is still not comming out. WTF!
I know K-moe suggested a hot air gun and deforming it to get it out, but this sounds easier that it really is! Pity anyone who has to replace an airbox in this model)

The carbs are off this bike and I am in the process of rebuilding them.
So with the experience of the first carb rebuild, I am taking on, with more confidence, this second carb rebuild.

So I plan to do the bench sync and wet-set the fuel levels (what ever that exactly is)
And then mount this second carb rack onto the first bike thats running at the moment


Then start with the third carb rebuild which will be the one that is origianlly the subject of this thread.

Just as a little more about this second carb rebuild:
I had to break the rack open because I do not have a degreasing station or access to one and have to do it all in a kitchen bowl.
Also seems that to get the choke parts out of the carbs breaking the rack is necessary.

So K-moe
I am getting more religious with this rebuild.
I also have access to compressed air now which I did not have in the first rebuild, so I could not blow clear all the various holes and cavities.

So to end this post K-moe, could you give me a little more clarity on what wet-set the fuel levels means.

many thanks

 

If you go to http://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/ and then look for Float HEIGHT sets the Fuel LEVEL: about 1/2 way through, you will find an explanation of wet setting. Also, the service manual has instructions an illustrations.
Check out this link for a video of wet setting:

 

OK
all clear now with the wet-set the fuel levels.
I half suspected that this is what you were meaning but the vid and the diagram make it much clearer for those that follow.
Again great support guys and thanks heaps.

A

 

Yep. High fuel levels will cause the bike to run rich (or worse).

 

I came across this vid on utub which was very informative as to how exaclty the different channels in the carb work together



enjoy

A

 

That is a good overview. Just keep in mind that the actual circuits vary in location depending on which CV carb you're working on.

 

Also the part of the vid where he adjusts the fuel air mixutre is greatly simplified when working on a single carb engine.
Still yet to come across a vid or explaination on how to do this on the 4x carb engines.

A