Calling the experienced carb gurus...

Bike is running OK but I hope ya'll can steer me in the right direction with this.

'86 700, it sat for a long time. It would start but it would only run on full choke. I have rebuilt carbs before so I did not have any trouble finding the completely clogged idle passages.

I did a bench synch and thorough cleaning and put the carbs back on. It took a few minutes to cycle the crappy fuel still left in the fuel pump but the bike started on choke and idled steady. It starts on choke but doesn't idle high like it should on choke. Then it falters and dies. I can only get it to idle if I turn the idle adjuster higher. After a few miles, the idle is very high and I have to turn the screw again to lower it back to 1100 RPMs.

I think this means that the choke passages are not clear. Am I right?

Once warm the bike idles steady but power is jumpy and there is a little hesitation when I yank the throttle open. Could this be due to the aftermarket exhaust on it?
I don't know if it's just Supertrapp cans, or if it is a complete aftermarket system. I do know the main jets are the stock size and the EPA caps on the pilot screws were still in place.

Nobody would ever mistake me for a mechanic, I have no doubts that I have left something undone.
I can only guess the choke passages need to be gone through again. Or maybe since it runs pretty well I can cheat and put some SeaFoam through it.

Ideas much appreciated....overall these were easy carbs to get on and off and easy to work on, so I don't mind yanking them again if I only know what to look for....

Last time I had to do that little dance with the idle screw it was due to bad intake boots... as the bike warmed up the boots would expand and the vacuum leaks would decrease enough for it to idle better.

It sounds like a vacuum leak to me too... did you make sure the screws that you remove to connect vacuum lines are all in place and tight?

If the bike needs full choke to idle, and assuming you had the carbs all apart... did you change the clip position on the needles? You mentioned an exhaust was added... did you change the main jets? One thing to remember, On those constant velocity carbs, the engaging choke actually reduces airflow rather than adding fuel... Sounds like you may need to pull them off again, or at least drop the float bowls and make sure they didn't get pumped full of crud... "It took a few minutes to cycle the crappy fuel still left in the fuel pump"
Let us know what happens, and good luck.


Garry

first up.. you dont have "chokes" you have "enrichners" in any case.. i doubt its them..
you said you gave the carbs a good cleaning..
did you SEE through the PILOT/ idle jets??
did you blow out all the air ways with a air compressor?

make sure the holes for the cync tool are plugged up and the boots are tight..
next.. get a can of carb cleaner.. or if your like me and enjoy a good flash.. STARTING FLUID :lobby:

remove your gastank.. hook up a hang up a gas bottle.. or place your tank a few feet from the bike and run a long gas line to it.

once the bike is running.. spray some cleaner or starting fluid at the boot area.. if the bike stumbles or surges you know something wacky is going on.. try to get more direct and find whats leaking. :fing02:

If it turns out to be the carb boots, I have a set of 4, brand new in the bag.

Thanks for good information!

With less than 5k miles, the boots are in pretty good shape. But they ARE 25 years old. Nonetheless, I did a search here and the carbs seated right away with only a little hair dryer and lube. I figured that mean the boots were OK. maybe they aren't.

As for the exhuast, I just don't know. I didn't make whatever changes have been made from stock. I don't know what stock is supposed to be. Except for the main jet, I looked that up and mine is stock. I didn't change anything in the carbs, since the bike was supposed to have been running well with its current settings. I just cleaned (and cleaned, and cleaned). I cleaned until I could see light through the idle jets (used a teeny tiny string for my dulcimer, the guitar strings were too big). I cleaned the pilot screw holes till fluid poured out clean from either end. And so on with every passageway in the carbs.
Yes, there was still crappy fuel in the pump, I didn't think to hotwire it and cycle that stuff out. But of course I put the filter back on. And once it started it ran very well that first day, after about 2 miles of surging and bucking all that crap seemed to burn on through.

I think you guys are right and it's an intake leak. Next week when I put the bike on the lift and do the electrical mods, I will hook up the "gas tank in the sky" and run it, try to find that vacuum leak.
I hope it's that simple.

I did lose one of the clamps, the little square nut part. I used a regular hose clamp. maybe it didn't seal right.

Thanks for the information, if I don't have to pull the carbs again I'll be very happy about that....

[image: View Post]coffeebrake, on 15 October 2010 - 07:00 AM, said:

Thanks for good information!

With less than 5k miles, the boots are in pretty good shape. But they ARE 25 years old. Nonetheless, I did a search here and the carbs seated right away with only a little hair dryer and lube. I figured that mean the boots were OK. maybe they aren't.

As for the exhuast, I just don't know. I didn't make whatever changes have been made from stock. I don't know what stock is supposed to be. Except for the main jet, I looked that up and mine is stock. I didn't change anything in the carbs, since the bike was supposed to have been running well with its current settings. I just cleaned (and cleaned, and cleaned). I cleaned until I could see light through the idle jets (used a teeny tiny string for my dulcimer, the guitar strings were too big). I cleaned the pilot screw holes till fluid poured out clean from either end. And so on with every passageway in the carbs.
Yes, there was still crappy fuel in the pump, I didn't think to hotwire it and cycle that stuff out. But of course I put the filter back on. And once it started it ran very well that first day, after about 2 miles of surging and bucking all that crap seemed to burn on through.

I think you guys are right and it's an intake leak. Next week when I put the bike on the lift and do the electrical mods, I will hook up the "gas tank in the sky" and run it, try to find that vacuum leak.
I hope it's that simple.

I did lose one of the clamps, the little square nut part. I used a regular hose clamp. maybe it didn't seal right.

Thanks for the information, if I don't have to pull the carbs again I'll be very happy about that....


unless the boots are fairly pliable (unlikely after 25 years) the hose clamp may not do it. spray ether around and see if your speed goes up. did you pull the epa caps? they should have a spring, washer and critical o-ring.

Many old fuel systems spit out crap after work is done on them, look at the filters under the needle seat. There are brass tubes that stick in the bowls that look plugged but have small orifices in them, are they clear?
I'm assuming you did a full dis-assembly and soak, then sprayed through all the passages?
if not, you may have washed down crap back into the smaller passages.

How are your air and fuel filter?

Going with boots, or some vac. leak, also.

[image: View Post]Rivcyko, on 15 October 2010 - 03:53 PM, said:

Going with boots, or some vac. leak, also.

Check the carb diaphragm. Make sure it is not ripped or perforated. You may want to replace anyway due to age.

What PLCGuy said about the EPA caps on the pilot screws. If you did not remove the caps then you didn't do a good enough job cleaning the carbs. Spray cleaner and compressed air back and forth through them. Just take a drill and drill just far enough to break through caps and use a screw to pull them out. You will have a small washer and and spring and oring in there, dont lose them. Get the right clamp for that carb and make sure clean gas comes out of that tank. My .02 good luck :beer:

Partial thread hyjack in progress :491:

I just finished restoring my 85 VF1000R this past weekend and got her on the road... I am also having a carb problem that I'm hoping to correct.

My problem is idle speed. In order to sync the carbs, I need to get the idle corrected. After warm up withthe choke ("enrichners") the bike will idle around 1500 RPM (should be closer to 1100). After riding the bike and letting the engine heat up, the bike will idle between 2500 - 2900 ???? The idle adjustment knob does not appear to be working (spins freely with no changes).

Does this also sound like a carb boot/vacuum leak?

Thanks

Write up & pics coming soon)

[image: View Post]VFRDYLAN, on 18 October 2010 - 10:46 AM, said:

Partial thread hyjack in progress :491:

I just finished restoring my 85 VF1000R this past weekend and got her on the road... I am also having a carb problem that I'm hoping to correct.

My problem is idle speed. In order to sync the carbs, I need to get the idle corrected. After warm up withthe choke ("enrichners") the bike will idle around 1500 RPM (should be closer to 1100). After riding the bike and letting the engine heat up, the bike will idle between 2500 - 2900 ???? The idle adjustment knob does not appear to be working (spins freely with no changes).

Does this also sound like a carb boot/vacuum leak?

Thanks

Write up & pics coming soon)


yes. and a possible idle screw way to high.. or cables to tight

Hey thanks for more information. I was in Daytona for Biketoberfest. On the Kawasaki, which overheated, evidently the three month old thermostat is bad. I pulled it out, purged the system, hotwired the fan motor to a switch, and no more overheating. All in the campground with a dime store wrench and a length of extension cord for wire. Sheesh.

Anyway, I hear what you're saying about the carbs, I did remove the EPA cap, fully expecting and finding a tiny washer and o-ring, the o-rings were in great shape but the passageway was completely clogged. When I was done it was very clear, with carb cleaner shooting through all the little holes in the throat equally. I am not a carb guru but I think I got that part right.

Diaphragms are great, looked new with no damage at all.

I think the vacuum theories are spot on, and hey it's free and easy to check, right?
Thanks, I should get to it very soon.

Boy was there ever a vacuum leak!!!

One of the screws that is in the manifold was missing. These are the screws that allow you to hook up to the carb synch tool that measures the vacuum.
One of 'em...just gone.

I found something with the same threads and stuck in there, bike is on the lift warming up to see if I have to turn the idle screw.

I sprayed WD-40 on each boot in turn and got no change. I hope that means no vacuum leaks at the boots.

I don't know how the thing was running with that screw missing. May as well go do a carb synch while I'm in there with a warm bike....