Throttle adjustment

[Scudrunner]

I'm trying to get my 84 Venture running properly but so far I can only get a slow idle out of it after it warms up. I have been following the other threads re diaphragms, etc but my question relates to the closed throttle position. When the bike is idling I can retard the throttle or push down on the front carb lever and it closes a little more and the rpm will rise a little. Basically, I run out of idle screw adjustment before it contacts the first carb lever. I loosened the throttle cable adjustment housing and put slack in the cable but the throttle still doesn't seem to close all the way. I would think the throttle plates should close tight when there is no tension on them.

I also notice that my full cold choke setting is not complete as I can take a pair of plies and pull on the choke linkage and it will snap further about another 1/16 on an inch but it will still start with the partial choke.

I know I have to tune the carbs together but I'm not at that point yet until I get this linkage figured out. I had it running last spring when I went to a "meat and eat" in Jacksonville and one of the guys brought his carbtune but even though it ran fairly well but the vacumn was barely registering. I got home and messed with the carbs and that's where it sat until I started working on it again. I would appreciate any suggestions.

[MiCarl]

1) your low vacuum was probably due to at least one, but probably 2 or even 3 cylinders not firing at idle.

 

2) "messed with the carbs" doesn't tell us what you did to it, but opens up the possibility of the sync being way off.

 

3) your condition is probably the result of being WAY out of sync and multiple cylinders not running.

 

I'd suggest you check for spark on all four cylinders. Then check for good compression on all four. If that's all good the carbs need to come off and be properly cleaned and bench set.

 

Then you can fine tune the motorcycle.

[Condor]

A possibility might be that your sync screws on 4 and 3 are set too tight, and they are controlling your idle.....

[Scudrunner]

I have tried to accomplish the suggestion provided but what I am running into is that with slack in both throttle cables and all carb screws backed out, the front carb is not fully closing. Something seems to be keeping it cracked open as viewed through the airbox with the slide pulled back. Or, is that just the normal position for that carb?

[bkuhr]

I would suggest you will need to pull the carb rack and inspect for bent linkage.

 

Also while it is out on the table you can play with the sync screws and seeing how they work with each other will help greatly when you are ready to do the actual sync.

 

If you suspect you may have issues with the carbs, it would also be a great time for teardown and cleaning, but some gaskets will be required new.

 

I had a simular problem, and notice in my pic how the 'L' shaped link is 'twisted' and not a square 90deg. This was my problem.

 

edit: here is the thread where I tracked down the bent link holding throttle plates open

http://www.venturerider.org/forum/showthread.php?t=47349

Edited June 23, 2012 by bkuhr
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[Venturous Randy]

I would like to make some suggestions, but the way you are describing things seem to be somewhat backwards. You say it will barely idle then you say you can not get the plates to close, or if you try to close them, the idle will go up.

My first suggestion would be to try to find vacuum leaks. You can do this by spraying some starter fluid around the base of the carbs. You will need to fix the vacuum leaks before you can sync the carbs. I am curious if you are even adjusting on the idle adjustment, It is the star shaped knob under the carbs on the left side of the bike.

RandyA

[Marcarl]

You'll have a hard time with any syncing unless the diaphrams are in good shape and seated properly, so check and maybe fix that first. Then you can look for more vacuum leaks. You should also somehow make sure the carbs are clean and workable so that all cylinders are firing, then finally you'll have something you can work with to use the sync tool. If you try to short cut the process you'll not get anywhere, but totally frustrated.

[Scudrunner]

Thanks for the tips. I have previously taken the carbs off and cleaned them after reading all the warnings. I have also sprayed around the carbs and boots for vac. leaks finding none. Diaphragms are fine. I will check the "L" brackets for any misalignment issues. Put all new plugs and disconnected one at a time when running to prove they are firing, all ok. I recently bought a AGM Scorpion battery for $78.00 and highly recommend one.

I feel my main problem is that the first carb does not close enough at idle as it will start fine with full choke but dies at the opening of throttle or reduction of choke but I am trying to get it to run off choke on just that one carb. With the idle screw under the throttle stop backed all the way out I can still push down on the first carb lever which tells me it is not closing all the way. I work on it a little at a time but I'm traveling a bit and try to work on it in my spare time. As I said before it was running fairly well a year ago and I can't say enough about the bike regardless being 28 years old. I'll keep at it and work it out with all the help from the members eventually. You folks are a great resource and I appreciate all your help.

[Venturous Randy]

but I am trying to get it to run off choke on just that one carb.

 

OK, now I am really confused.

RandyA

[Scudrunner]

Randy, The reason I say one carb is that I have all the screws backed off so the other 3 are closed. I had the three adjusted to just touching the stops with the first carb but I noticed that the adjustments on the 2nd and 3rd screw seem to move the first off of the somewhat closed position and again it would die with any throttle.

[MiCarl]

Randy, The reason I say one carb is that I have all the screws backed off so the other 3 are closed.

 

This is your (current) problem. The sync screws should be adjusted so all four are the same. You are grossly out of sync.

 

As soon as one closes they all stop and the idle stop screw (the knurled knob pointing down on LH side) has no effect.

 

You've got to get it to where all four butterflies are the same and almost closed. Then you have a chance of getting it to run.

[Venturous Randy]

This is your (current) problem. The sync screws should be adjusted so all four are the same. You are grossly out of sync.

 

As soon as one closes they all stop and the idle stop screw (the knurled knob pointing down on LH side) has no effect.

 

You've got to get it to where all four butterflies are the same and almost closed. Then you have a chance of getting it to run.

 

I think you are right. Normally it increases idle when the choke is engaged, but I have no idea what his is doing. I want to help him, but I don't know where to start.

RandyA