carb issues

[Flynt]

Yes, there is interference with the shroud and the bottom of the (flat bottom) slide.

OK...  I'll check it when I'm in there next.  

Upped my mains to 120s yesterday and checked this out.  Flat bottom slide its 2mm above the top of the shrouded e-tubes...  no interference, at least on my bike.  This makes sense to me...  there are not special needles for the early carbs, so the point where the needle mounts to the slide must be the same height relative to the e-tube for either curved or flat.  Maybe Randy or Robert can check, but I bet the curved slides are the same length to the center as the flat bottom slides.

The 120s fixed my 3/4 to WOT lean condition (really mild, but bugging me more as is getting warmer).  Butt dyno registered more WOT grunt as well...  Happy Stormy! (now at 42.5/160 with 2.25 turns, 120 mains and needles out one notch, float level 1mm lower, and with 5 degrees ignition advance).  I'll check cold start behavior today and then make sure the carbs get a decent workout, maybe out on the coast.

Frank

[Pat Conlon]

Ok, thanks for the follow up Frank. I thought you went back to the non shrouded tubes...So you put back in the shrouded tubes?
Your '84 flat bottom slide carbs should be exactly like my old carbs, so I wonder what Randy's concerns were?
I'll let him chime in.

[Flynt]

I thought you went back to the non shrouded tubes...So you put back in the shrouded tubes?

Yep.  I was stepping the needles down also, so I put one of my old e-tubes back in to check it out.  Then swapped back my non-shroud stockers.

Frank

[racerrad8]

Randy,
Not picking on you, but if the fuel level is measured at the center of the float bowl then it doesn't matter what angle the carbs are sitting at.  The level pivots at the center of the bowl and is the same at all angles.

David, I think you are referring the external measurement of the fuel level in the float bowls.

I was referring to the angle recommended by Yamaha for measuring floats levels with the bowls off and a tool.

This photo here


I also am not sure if the external float levels will be the same regardless of carb angle. The float pivots at the rear of the carb near the needle. Since they are towards the rear, it would seem to me if you raised the rear at the pivot that will also raise the fuel level in the bowl.

I know I have read before that some guys who have jacked up the rear of their bike have lowered there fuel level to stop the fuel from leaking out of the now completely covered choke enrichment tube. The vacuum break hole at the top of the tube is covered and it will drain the bowls down until the hole is uncovered and the vacuum breaks.

That will have to be a future test someday to see for sure.

Randy - RPM

[Pat Conlon]

Re: Raised rear end vs. fuel level and vacuum break...I wonder if that is why this mod makes sense
http://www.fjowners.com/index.php?topic=7056.0

[racerrad8]

Re: Raised rear end vs. fuel level and vacuum break...I wonder if that is why this mod makes sense
http://www.fjowners.com/index.php?topic=7056.0

And that is why I stand by my statement then, as I do now about float height and ultimately carb angle.

Randy - RPM

[Pat Conlon]

Randy, so if the bike has the back end raised and because of this, the fuel level covers the hole in the tube, the additional (drilled) 1mm vent hole shown in the mod would help break the siphon action?

[racerrad8]

Randy, so if the bike has the back end raised and because of this, the fuel level covers the hole in the tube, the additional (drilled) 1mm vent hole shown in the mod would help break the siphon action?

I believe so, but I have never personally attempted. My concern is the additional venting source to draw air from. But, it might not matter as noted in the post, but again I have never attempted.

Randy - RPM

[FJ_Hooligan]

Randy,
Sorry, I must have misinterpreted your meaning.  You're correct, I was referring to the external FUEL level measurement.  I totally agree with you on the FLOAT height measurement.

[ergojack]

I've been on vacation & haven't fooled with the bike in a while.
I went to see the P.O. & he still all the OEM carb parts.  I am going to put
the OEM needles in. He had some 120 mains that I'm going to install also. They may
still be a little large, but are smaller than the 122.5s I have in now. I know they don't
have anything to do with my problem, but since the carbs are off, now is the time
to change them.  I just ordered some 155 air bleed jets from Randy. This engine is
bored to the 1200 specs. & 155s are what it is suppose to have. We will see how it runs
after this. 

[MarioR]

The question remains: If you have flat bottom slides (typical on early FJ's) and you have the shrouded type emulsion tubes, you will have rich running problems.
The shrouded tubes look like this:


These above emulsion tubes should be only used with the curved bottom slides.
Using these shrouded emulsion tubes on flat bottom slides, the shroud sticks up and holds the slide up (and thus the needle).
The shrouded tubes are designed for curved bottom slides.

Check this out and let us know.

I will apologise in advance for hijacking this thread but my question relates to the above information. The '85 FJ I'm currently working on, has choke issues.
It starts on the choke but after about 20-30 seconds running on it, stalls, it will re-start with a little throttle, choke off but will not idle until fully warmed. Any further use of the choke just stalls it. The carbs are the early model flat bottom slide version but have been fitted with new cut away slides. Who ever did the rebuild left the original flat top emulsion tubes in it. What effect, if any, would this have on tuning the carbs, especially the choke function? I suspect it won't be effecting it but am open to views from others with more experience than me.
  Regards, Pete.

Hi everyone,

Just doing my carbs first time for FJ. Bike came completely Frankenstein and did not even worked.  I was told carbs were re-built however when I took it apart, I noticed that all was BS. Broken float legs glued with epoxy! 0-rings under main jets!  broken vacuums etc.

Right now, carbs have curved bottom slides and flat emulsion tubes which i believe they call un-shrouded. Should I change emulsion to OEM shrouded and needles as well?

My set up as of right now:

112.5 main
40 pilot
160 air
3 1/4 turn out
needle clip 3 position from the top
KN filter in the box
F1 double slip on exhaust

Any recommendation will be much appreciated.
Thank you and have a good day guys.

[Flynt]

The question remains: If you have flat bottom slides (typical on early FJ's) and you have the shrouded type emulsion tubes, you will have rich running problems.
The shrouded tubes look like this:


These above emulsion tubes should be only used with the curved bottom slides.
Using these shrouded emulsion tubes on flat bottom slides, the shroud sticks up and holds the slide up (and thus the needle).
The shrouded tubes are designed for curved bottom slides.

Check this out and let us know.

I will apologise in advance for hijacking this thread but my question relates to the above information. The '85 FJ I'm currently working on, has choke issues.
It starts on the choke but after about 20-30 seconds running on it, stalls, it will re-start with a little throttle, choke off but will not idle until fully warmed. Any further use of the choke just stalls it. The carbs are the early model flat bottom slide version but have been fitted with new cut away slides. Who ever did the rebuild left the original flat top emulsion tubes in it. What effect, if any, would this have on tuning the carbs, especially the choke function? I suspect it won't be effecting it but am open to views from others with more experience than me.
  Regards, Pete.

Broken float legs glued with epoxy! 0-rings under main jets!  broken vacuums etc.

Right now, carbs have curved bottom slides and flat emulsion tubes which i believe they call un-shrouded. Should I change emulsion to OEM shrouded and needles as well?

My set up as of right now:

112.5 main
40 pilot
160 air
3 1/4 turn out
needle clip 3 position from the top
KN filter in the box
F1 double slip on exhaust

Any recommendation will be much appreciated.

I'd send the whole thing to RPM...  replace carb bodies that are shot, get all fueling circuits working properly, then tune to their recommendation...  the flat bottomed slides can be used and, at least I believe, will give you a more crisp response...  I think the curved slides are smoother (boring) in roll on...   

Frank

[MarioR]

The question remains: If you have flat bottom slides (typical on early FJ's) and you have the shrouded type emulsion tubes, you will have rich running problems.
The shrouded tubes look like this:


These above emulsion tubes should be only used with the curved bottom slides.
Using these shrouded emulsion tubes on flat bottom slides, the shroud sticks up and holds the slide up (and thus the needle).
The shrouded tubes are designed for curved bottom slides.

Check this out and let us know.

I will apologise in advance for hijacking this thread but my question relates to the above information. The '85 FJ I'm currently working on, has choke issues.
It starts on the choke but after about 20-30 seconds running on it, stalls, it will re-start with a little throttle, choke off but will not idle until fully warmed. Any further use of the choke just stalls it. The carbs are the early model flat bottom slide version but have been fitted with new cut away slides. Who ever did the rebuild left the original flat top emulsion tubes in it. What effect, if any, would this have on tuning the carbs, especially the choke function? I suspect it won't be effecting it but am open to views from others with more experience than me.
  Regards, Pete.

Broken float legs glued with epoxy! 0-rings under main jets!  broken vacuums etc.

Right now, carbs have curved bottom slides and flat emulsion tubes which i believe they call un-shrouded. Should I change emulsion to OEM shrouded and needles as well?

My set up as of right now:

112.5 main
40 pilot
160 air
3 1/4 turn out
needle clip 3 position from the top
KN filter in the box
F1 double slip on exhaust

Any recommendation will be much appreciated.

I'd send the whole thing to RPM...  replace carb bodies that are shot, get all fueling circuits working properly, then tune to their recommendation...  the flat bottomed slides can be used and, at least I believe, will give you a more crisp response...  I think the curved slides are smoother (boring) in roll on...   

Frank

Hi Frank,

Thanks for prompt responce and recomendation.

Since I am out of US, I would rather to work on it my self than sending it for unknown time to RPM.

Thank you