Carb jetting

[ws4transam]

Hello everyone, I have a question about my carbs.  My fj is an 84 with pods and a vance & hines 4 into 1 exhaust.  I put a dyno jet stage three kit in it last summer and could not get it dialed in.  The problem is I cant get it to except full throttle.  It bogs down with full throttle and if i let up  a little  it will go faster.  I started with the recommended 124 mains which made it a real dog.  Since then i have tried 120, 118, 116.  The 116s were to lean but there wasn't much of a difference between the 124, 120 or 118s.  My valves are within spec and I have synced the carbs recently.  I have had the carbs off at least 12 times over the last year trying to figure out whats wrong.  I am very frustrated with it now.  Its like i cant get enough air in it.  The bike starts and runs great except at full throttle.  Any help would be greatly appreciated.  Thanks

[ws4transam]

Come on.  Someone had to experience this before.  RPM Randy please help me.

[andyb]

Lack of fuel flow?
Air leak?
Throttles open fully?
Carb slides open fully?
Enough spark to light a full cylinder?
Are you actually getting enough air into it?


What do the plugs say after a WOT chop?  DJ118's should be pretty close to the mark.

[Antonn3]

ws4transam -
Im going through the assembly of my 85 carbs , I had a second 84 carb set. Do your carbs have a flat bottom on the needle slide or is it curved? This could be an issue, as Im sure Randy will fill in.
Did you use the 4105.003 kit in your bike? The 4109.002 is for the later  curved slide carbs (85). If Im correct.....
BTW Dynojet did not know the difference between the 84 and 85 carbs... but they have 2 kits for them!

Tony

[racerrad8]

Come on.  Someone had to experience this before.  RPM Randy please help me.

I'm. At work until Saturday, I can work on it then.

Randy - RPM

[ws4transam]

They are flat bottom and I did get the right jet kit

[ws4transam]

Come on.  Someone had to experience this before.  RPM Randy please help me.

I'm. At work until Saturday, I can work on it then.

Randy - RPM

[racerrad8]

So just confirming you have the flat bottom slides? If so do you still have the non-shroud emulsion tubes?

My only experience with the DJ parts is to remove them when they come through the door. I operate solely on the Mikuni parts as a "carb kit" made by another is a regional product. DJ is in Vegas, dry, hot & high (altitude) and if you are on the east coast in high humidity and sea level it is not going to work properly.

Then there is the fact that you have to drill out the slide, which drastically affects the slide function. If the slide speed is too fast, then the engine will see a flat spot at the upper range that it cannot overcome.

Finally, if the main jet needle or emulsion is the incorrect one (flat vs. curved) the needle could be either coming out too far or not far enough.

That is about all I can offer because if at anytime anyone change parts, installed the wrong incorrect version or drilled and/or modified other parts, you will never be able to get it running properly.

If you want me to take a look at them and try and resolve your issue, shoot me an email and we can try and get it worked out; randy@rpmracingca.com

Randy - RPM

[ws4transam]

Yes, the slides are flat bottom and the emulsion tubes are the correct non shrouded ones.  When I first got the bike, the carbs were all stock and had the stock air box.  I remember that it dogged off the line and took a second or two to clear up.  I also remember that on the highway, in top gear, If I wrapped it, it didn't pull as hard as it would with 80 or 90 % of throttle.  The bike came with the Vance & Hines ss2r exhaust, so I thought that re jetting it would fix all that.  That's why I put the jet kit in.  Turns out, the problem is still there.  With the 118 mains and the pods off, the bike is faster but, with the 116s, and the pods on, its too lean because it will jerk at high rpms.  I did notice that with the pods off, and the bike in neutral, when I rev it up, it sprays gas out of the backside of all 4 carbs.  Is that normal?  If not , what could be the reason for that?  Thanks again.

[racerrad8]

Turns out, the problem is still there.

If the problem existed prior to the kit, then there was something going prior to the install.

I did notice that with the pods off, and the bike in neutral, when I rev it up, it sprays gas out of the backside of all 4 carbs.  Is that normal?  If not , what could be the reason for that?  Thanks again.

Yes, that is the camshaft overlap putting that mist out. That is the reason the K&N filters are not a good choice for the FJ; the fuel spray washes out the oil rendering the filter useless.

Randy - RPM

[ws4transam]

So, do you think its carb related, or something else?