pilot screw

Sorry to ask where excatly is it located on the carb

 

The idle screw, which I believe goes by the term 'pilot screw' as well if I'm not mistaken (and I may be), is a knob visible between the #3 and #4 carbs on the airbox side.

 

These show you th bits n pieces
http://xjbikes.com/Forums/viewtopic/p=77032.html

http://xjbikes.com/Forums/viewtopic/t=8 ... ight=.html

Pilot screw and Idle adjust are not th same.

 

Cool thanks guys that clears up everything now I just have to figure out how to get my bike to stop idleing so high when I start it I have checked everything like the valves and cleaned the carbs it fires right up but wants to start idleing at like 4000 rpms any ideas about that I bench synched them the idle adjustment screw is all the way back and they don't catch on anything either so im kinda confused

 

Give us a bit of history. Did it start idleing high all of a sudden, or has there been work done on the carbs recently? It could be a if the carbs have been fiddled with that the idle screw is way off, but more than likely a vacuum leak. If it is a vacuum leak, it could come from a number of sources on the carbs. Look for the really obvious ones first...

Severly cracked carb intake boots. small surface cracks are ok, just make sure they are not cracked completely through. If they are cracked through, replace it.

Check the vacuum nipple caps on the carbs intake boots. If they are cracked,even a little bit, go ahead and replace them. They are very inexpensive and can be found at most autoparts stores. Just take one off and have them match it up for you.

Intake boot to head gaskets leaking. (Unlikely if the boots have not been removed, but if they have been removed by a PO and the original gaskets re-used, it could be leaking there)

If the above are not your culprit, then it is likely the throttle shaft seals, which can be remedied with a thorough carb rebuild. To test, with the bike running, use the gas from an unlit propane torch or carb cleaner or similar combustible fuel(not raw gas) and spray around carbs. If it revs higher (use a keen attention here, as it is already idle high) having subjected to the propane, voila.

 

This is the idle speed adjustment screw. Not the pilot screw.

 

Mook is probably 100% correct on the shaft seals.

This will help:

http://www.xj4ever.com/hitachi%20thrott ... 0seals.pdf

 

:? The issue with my bike at the moment, is that it only revs too high in idling, when it reaches operating temperature...I can manage a 1000+/- rpm idling until this point......then as it reaches operating temperature....up to 1400-1500 rpm, at idling?!!
Currently doing valve clearances/replacing shims to spec. (have had to change six clearances!!)- then see if still got symptoms........
My question is: if it is the throttle seals ONLY, would it race up to 1400+ immediately on start-up, not wait until operating temperature is arrived at? (i.e. throttle seals status of operation does not change with temperature)
The reason being, is it that my high idling at operating temperature, is only ocurring when the valves get warm and expand, because my valve clearances are out of spec.......???
Or could it be a combination of both...?
Any ideas.......
Regs.
Dale

 

If you've rebuild everything on the carbs, and adjusted the valve clearances, you still need to "tune" or basically, set up the carbs, to deliver the correct fuel mixture on a "per carb" basis, and to deliver it in a balanced way to your "specific" engine.

Again, this is assuming that all of the proper rebuilding/clean tuning has already been performed, otherwise, you're just wasting time. This is after the initial bench sync/pilot settings, as those have to be adjusted on a warmed up, running, engine.

1. Wet set the float levels - this affects fuel mixture in all ranges (although some more than others). Use Gasoline, build a test assembly to hold them level - this is done once
2. Set the pilot mixture screws. Colortune makes this much easier.
3. Running vacuum sync. Use YICS tool, or similar, if YICS engine.

You will repeat 2 and 3 several times before you get it right, as the two are interrelated. After each adjustment, set the idle, using the idle adjustment screw, to keep the idle in spec.

 

Do you HAVE to remove the carbs, to do a carb synchronisation on a bench, or whatever, or can you use (after youve checked the float levels, while still installed on the bike, and they are ok) vaccum guages, to synch (or colortune, which seems you have to install, in no.1 plug socket, and then the rest alternatively while you adjust the screws to get a bunsen burner blue colour - do you get two colortune plugs, cos you only have one screw to synch two carbs with two plugs at same time, and if you only have one colortune plug, you can presumably only look at one plug, whilst adjusting one screw which is responsible for two......, the other plug (no. 2 for example, you cannot see the status of firing....!!!!) So when youve set the colour on no 1. plug by the screw responsible, for nos 1 AND 2, you might have to readjust it for No. 2, plug, and so consequently No 1 plug becomes out of spec again....!???
Vacuum guages, you can see either status of one, two at a time, or three or four simultaneously - do you get my point, or am I talking confused nonsense...please enlighten me as regards how colortune operation is performed.....moreover, is it absolutely necessary to bench synch, when float levels have been measured to be ok??
Regs.

 

A few things here...
1) If the idle only hangs when it is cold, then that is still indicative of poor seals. Rubber expands when it heats up, thereby making a better seal when the engine is warm. If the idle races when cold, and settles down when warm...you still have a seal/vacuum leak to address.

2) A bench sync of the carbs is done on a bench after cleaning/rebuilding the carbs, but before they are installed on the bike for fine tuning. Your goal is to get the buttery valve as close to equal as possible before installing them on the bike for fine tuning using vacuum gauges.

3) It sounds to me you are confusing syncing the carbs (and there corresponding adjustment screws) with colortuning.

There are only 3 sync screws. They are on the throttle shaft and only control the opening of the butterfly valves in the throat of the carbs. The 4th is actually the big idle screw that is between carb #2 & #3.

The idle mixture screws are in the carb bodies and are what you adjust when colortuning...and there are 4.

When doing the fine tuning, you will sync, then color tune, then sync, then colortune, and keep repeating until it is fine tuned appropriately.

Just as Manbot stated, if you are attempting to do this tuning without first fully servicing the carbs, then you are pi$$ing into a fan...

 

When TUNING the Carbs, ... you have to do ONE thing at a time.

Once you are prepared to address Carb Tuning, ... after Checking Valve Clearances and making necessary adjustments:

1. Observe and Set Float Heights
2. BENCH Sync (3X5 Card ~ Resume' Paper ~ Strips of 35mm Film)
Begin with the Throttles Closed.
3. Install Carbs (Protect Cable Attachment from being pinched under Head.
Assure Manifold Clamps are tight. Check Manifold Clamps do not interfere with Linkage Closing.)
4. Preset Mixture Screws. (To depths recorded before disassembling. To 5/32nds below Top of Screw Hole. Or to: 2.8 Turns Out.)

5. ColorTune -or- Otherwise set IDLE.
6. Adjust Sync Screws for Vacuum Idle.

 

Ok so do all the mixture screws need to be adjusted

 

When I got the bike and got the carbs off it all the jets and everthing where tightened all the way down so im not sure where to adjust them to

 

Mine are right at 5/32nds "Deep"
Top of Carb -to- Top of Screw.

They are at this depth after;
Cleaning and Installing NEW Pilot O-rings.
Color-Tuning
Plugs inspected after several weekly adjustments.

 

Thanks mook

All understood and noted, in case I have to undertake any of these tasks, should I still have poor consumption and high idling in operating temperature, when I have completed valve clearances.....
Ps. one thing: when doing a float level test, whilst VERTICAL square, and carbs still on bike, do you disengage the vacuum pipe from tank or not.......or I'll put it plainer...do you leave both fuel supply and vacuum pipes connected, whilst carrying out float level test with clear plastic pipe up side of carbs......or do you disconnect one.....?
:? Regs.
Dale

 

The jets should be tighten all the way down. Jets are not adjustable and not accessible unless the float bowls are off. Are you referring to the idle mixture screw on top of the carb?

Do the float level test with the carbs off the bike. These need to be level, not close to level, but level.

 

I feel a little retarded I got it figured out throttle cable was to tight just got the actual synch to do now

 

For checking the float levels (on the bike) it has nothing to do with disconnecting the vacuum line. The vacuum line can only "operate" the petcock when the motor is running ("vacuum" and all that.) Put the petcock on PRI (so it flows all the time) to check the floats. The vacuum line will then have nothing to do with it.

And you DO have to "undertake these tasks." Valve clearances and float levels are probably the two most critical adjustments to how an XJ runs; for without them being right, you cannot sync the carbs.