starts and only runs with choke?

[VaughanCustoms]

So the FJ starts and runs but only with the choke on. The throttle also seems to stick here and there, I get a popping out of the exhaust intermittently. I went through the carbs and cleaned them, drained the gas, added new fresh gas. The bike has a Vance and Hines exhaust, k&n drop in and has been rejetted around a year ago by the PO. This makes me really sad and I am not sure what to do. Unfortunately my girlfriend is not to happy about this and thinking I am wasting my money. So I am trying to get her going with little to no cost at all. I have some videos of me starting it and running if you want me to email them to get a better idea I can do that. Thanks so much guys and hopefully I can get her going so I will be able to keep my new FJ

[racerman_27410]

i would say you're probably gonna need to revisit the "cleaning the carbs" part again.

dont feel bad.... you're not the first one to have to do the job twice )or more).

is the inside of your gas tank rusty?

dont forget to sync the carbs after you get everything clean and back together.

checking the throttle cable for binding is pretty straightforward so..... good luck! 


KOokaloo!

[fj11.5]

I have a 1200 that sat 4 years untouched, would start but not with choke, and don't think about touching the throttle, emulsion tubes were mostly blocked, and after the second strip and clean,  david r suggested blocked choke tubes in the float bowels,  he was right,  id missed those

[VaughanCustoms]

Hmm I see, is there any tuning that can be done on these carbs or once the jets and things are in thats it? I unfortunatly dont have a vaccum guage to be able to sync the carbs so I am just not sure what to do at this point.

[andyb]

Float height might be off a bunch, pilot circuit is most likely not as clean as you'd think you got it, idle could be set to zero, vacuum leaks... etc.

See what the plugs tell you, but most likely your pilots are just still dirty.  You have to clean the little brass jet, but also the path that the fuel takes from where that jet is over to under the mix screws where it dumps into the airstream going into the motor.

A synch tool is invaluable but good ones are pricy.  Make your own from some cheap clear tubing and heavy gear oil/trans fluid.  Doesn't matter, you need the motor to be idling off choke before you really worry that part yet.

Do the usual stuff and see what's up.  If you can crank the motor over with a plug pulled, you should smell gas in the air puffing out, and smell more gas when the choke's on.  Most likely it's just not getting fuel through the pilot circuit.

[racerrad8]

I unfortunatly dont have a vaccum guage to be able to sync the carbs so I am just not sure what to do at this point.

It could have three completely closed throttle plates. When you activate the "choke" circuit you open a vacuum leak allow the engine to run.

The carb sync is just one of the things that could be causing the issue. Pilot jets plugged, float bowls plugged, & float levels are the most common issue.

Randy - RPM

[VaughanCustoms]

Ok thanks guys, so these motorcycle carbs are different than like automotive there is like no fuel air mixture sqrew or anything? It seems like to me that it is running lean. Also two other questions, the air box has two nipples on it one large one going to the crankcase I got that but there is a smaller one there and I can't remember if it was supposed to be plugged into anything. There is also about 6 hoses coming off the bottoms of the carbs one on each carb and one from the little tee inbetween the carbs are all of these supposed to just hang free or do some of these need to be connected to something? Thanks again.

[racerrad8]

Ok thanks guys, so these motorcycle carbs are different than like automotive there is like no fuel air mixture sqrew or anything?

There is a mixture screw located on each carb just behind the carb tops. That screw is different from a normal car fuel mixture screw. I differs because it does not only control fuel, but it regulate the pilot circuit mixture of fuel & air and regulate the quantity of mix air/fuel.

Also two other questions, the air box has two nipples on it one large one going to the crankcase I got that but there is a smaller one there and I can't remember if it was supposed to be plugged into anything.

The large one hooks to the crank case vent hose and the other is a moisture drain and should not hook to anything.

There is also about 6 hoses coming off the bottoms of the carbs one on each carb and one from the little tee inbetween the carbs are all of these supposed to just hang free or do some of these need to be connected to something?

Those six hoses, two larger than the other four are all vent point for the carb bowls and choke enrichment circuit.

Randy - RPM

[andyb]

The mixture screw controls only a portion of the mixture at idle, with the pilot jet doing the bulk of the work.  The screw is more for fine tuning than gross changes.

[VaughanCustoms]

Well the bike starts easy and runs pretty much perfect with just a tiny bit of choke then when you give it some revs it intermittently has a popping out of the exhaust. I honestly think its just down to tuning

[shortcut]

A simple very effective multi cyl manometer. 3 ft square piece of "peg board" and enough clear semi ridged 1/8" clear vinyl tubing to connect each cyl vacuum test port to peg board and allow a loop in the lower part of tubing of a foot or so. Attach each tube to board with safety wire thru holes in board so you end up with 4 identical loops side by side and adequate tube to reach engine. TIGHTLY PLUG the non eng end of each tube after putting equal amounts of ATF in each tube. The ATF should form 4 identical loops of red liquid that can't be sucked into the engine not matter what you do with the throttle. Seeing and comparing the levels of ATF while adjusting is easy and hanging the peg board up for tuning is a lot simpler than gages.   

[Goetz]

I have had this exact problem. My carbs were so dirty Randy had to put them thru the ultrasonic twice. Clean them, and then clean them again.

[fintip]

Where did you set your adjustment screws to? I normally put a bike like this at 3 turns out after a carb clean, and then adjust from there. Also, did you bench sync your carbs at least?

It might be down to tuning, but only if it is grossly off as is (no bench sync, closed up adjustment screws, or uneven bad compression from engine). If those things are in check, at least not grossly in error, then you probably need to clean the carbs again.

Motorcycle carbs are really finicky. 95% clean carbs can still run like crap and be untuneable.

A simple very effective multi cyl manometer. 3 ft square piece of "peg board" and enough clear semi ridged 1/8" clear vinyl tubing to connect each cyl vacuum test port to peg board and allow a loop in the lower part of tubing of a foot or so. Attach each tube to board with safety wire thru holes in board so you end up with 4 identical loops side by side and adequate tube to reach engine. TIGHTLY PLUG the non eng end of each tube after putting equal amounts of ATF in each tube. The ATF should form 4 identical loops of red liquid that can't be sucked into the engine not matter what you do with the throttle. Seeing and comparing the levels of ATF while adjusting is easy and hanging the peg board up for tuning is a lot simpler than gages.   

Nice shortcut, shortcut. Any pictures of this? I think I'm visualizing this right, but it'd be great to see a video of the process.