Idle won't come down below 2900!

I ride a 1987 VFR700F2 but recently picked up a 1986 VF500F as a project... Here is the scenario:

Got it in pieces, put it back together and it ran but very very rough. Would not run by itself, needed constant throttle. Changed all fluids, plugs and air filter. Completely disassembled, cleaned thoroughly and reassembled carburetors. All internal carburetor passageways cleared with gumout and compressed air. Now it runs smoothly and sounds great. I would like to synch the carbs. Problem is I can't get the idle below 2900rpm. If I adjust the main idle below 2900 the engine slows to nothing (takes about 3 secs). The choke is not stuck. There are no air leaks on the carb boots.

The idle jets looked fine and were free of any obstruction when inspected but maybe need replaced?

I attempted to adjust the idle screws (pilot screws, fuel/gas mixture screws) on each carburetor and found it had no effect on the idle whatsoever. Whether I closed them all completely or had them backed out 2 full turns past manufacturer recommended specs had no effect at all. She just kept on humming away at 2900. Could this be the cause?

Smokes lightly (white haze) on startup but goes away after it is warmed up.

Any ideas on how to get her down to proper idle rpm's would be greatly appreciated.

 

sounds like maybe a bad vacuum leak. carb mounting gaskets?

 

I ride a 1987 VFR700F2 but recently picked up a 1986 VF500F as a project... Here is the scenario:

Got it in pieces, put it back together and it ran but very very rough. Would not run by itself, needed constant throttle. Changed all fluids, plugs and air filter. Completely disassembled, cleaned thoroughly and reassembled carburetors. All internal carburetor passageways cleared with gumout and compressed air. Now it runs smoothly and sounds great. I would like to synch the carbs. Problem is I can't get the idle below 2900rpm. If I adjust the main idle below 2900 the engine slows to nothing (takes about 3 secs). The choke is not stuck. There are no air leaks on the carb boots.

The idle jets looked fine and were free of any obstruction when inspected but maybe need replaced?

I attempted to adjust the idle screws (pilot screws, fuel/gas mixture screws) on each carburetor and found it had no effect on the idle whatsoever. Whether I closed them all completely or had them backed out 2 full turns past manufacturer recommended specs had no effect at all. She just kept on humming away at 2900. Could this be the cause?

Smokes lightly (white haze) on startup but goes away after it is warmed up.

Any ideas on how to get her down to proper idle rpm's would be greatly appreciated.

 

Slack (lack of) in the throttle cable? Or throttle cable pinched?
If it's running that high of an RPM, it's probably on the verge of just coming off (or past) the pilot jets/air idle screws, so I don't think they'd make much difference...

 

Thank you both for the suggestions. I got lucky, the local motorcycle salvage yard has a vf500f. I bought the carb set off of it yesterday afternoon and will try swapping out the idle jets.

The carb mounting boots/gaskets seem to seal well but I have ordered a new set and will replace them to be sure of no vacuum leak.

The throttle cable is well lubed and slides freely (no pinches or kinks).

Any other suggestions are welcomed graciously. The sooner the better as I will have it in pieces again over the next few days. Thanks again.

 

this may be a little off base but have seen a throttle slide put in a$$ about and cause a similiar problem on a different bike

 

just posted on other thread is throtttle slide in the right way

 

Is there any chance the throttle cable isn't allowing the carbs to close all the way? Look down and see if theres a big gap in the carb throat. I've seen this happen on cars where they just needed the cable adjusted.

 

Dixlexus bangs head on computer monitor

:unsure:

Just ruled out the throttle cable as the possible culprit. Disconnected it completely and made sure the carbs were closed. Fired it up and no change. I will be taking the carbs off again on Saturday to replace the carb boots/gaskets, replace the idle jets and will also look into the possible throttle slide reversal issue. I'll drop the results on this thread by Monday. In the meantime I'm off for a short ride on the 700. eace:

I appreciate all the ideas.

 

Take a compression test.

 

Will do, thanks Dizzy

 

1 point 21 jigawatts!!!!

Found out the issue by accident. Checked the oil and the crank case had filled with fuel. I have a modified petcock as per instructions on Daugherty's Mod site (removes the vacuum line and makes it a basic on/off valve config).

My guess was that one or more of the carbs has a stuck, or cracked and sunken float causing a constant flow of fuel into the cylinders which then leaked around the rings into the crankcase. I removed the vacuum plugs on the sides of all 4 cylinders and opened the petcock. BINGO! Took about 2 mins and fuel began to flow out of the #3 cylinder vacuum plug hole. The cylinder had filled with fuel and overflowed out the vacuum hole. The carb on cylinder 3 is the culprit.

I will remove the carbs again this weekend for the third time, remedy the problem and report the results here on Monday.

:der:

 

Victory is Mine!!!!

Opened up the float bowls again Saturday morning. Stuck float on Carb 3 and 2 clogged idle jets. I guess I wasn't as careful as I thought the first time I cleaned them out. Regardless... She purrs like a kitten now. Hovers right at 1100 as she should.

Thank you all for your input and guidance.

:thumbsup: