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bmannon

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I got my charging problem fixed and moved on to figure out why the front left cylinder wasnt always running. While I was tearing into things I noticed the cable from the servo motor to the butterflys was cut. Also the plug to the boost module (the one with the vacuum line) was unplugged. So I guess the previous owner had been having boost problems and just unhooked everything.

I opened the butterfly by hand and it is not seized, so that is good I suppose.

Here is my questions. I dont really have the money to start replacing parts to fix the boost, I know for sure I will need the cable, I havent tested the other parts yet but I am suspecting problems ( I have no real reason to suspect other problems, just a gut feeling). Would I gain anything by just pulling the butterfly open and holding it open with a wire tie? or should I just leave it alone until I can afford to replace the cable. Honestly my riding style will rarely put me past the 6krpm range where the boost works, but on the occasion I need it I dont want the bike to fall flat on its face either.

What do the people that are familiar with this beast think? :confused2:
 
You're going to get a lot of opinions. Some like the low end stumble of the boost held open. Some like the T boost. Others like it stock.

If it were mine. I would replace the cable, plug it up, and see what happens. I prefer a functional system that can be modified to the way you like it, rather than a completely inoperable one.

Mine had problems when I brought it home. After I replaced the servo, it still wouldn't cycle correctly and I didn't want to put the money out on a new controller. I promptly cracked that baby open and found that the problem was that the controller had some cold solder joints on the board.
Cost: Two hours, a six pack of Fosters, and thirty cents worth of solder. Way cheaper than a new controller.

Good luck.
 
Get that vacuum line back on.It has to be running bad sucking air.The vboost cable can't cost very much.Is it the short one on the butterfly or the longer one to the servo?I would bet less than $10.
 
eatatjoz said:
You're going to get a lot of opinions. Some like the low end stumble of the boost held open. Some like the T boost. Others like it stock.

If it were mine. I would replace the cable, plug it up, and see what happens. I prefer a functional system that can be modified to the way you like it, rather than a completely inoperable one.

Mine had problems when I brought it home. After I replaced the servo, it still wouldn't cycle correctly and I didn't want to put the money out on a new controller. I promptly cracked that baby open and found that the problem was that the controller had some cold solder joints on the board.
Cost: Two hours, a six pack of Fosters, and thirty cents worth of solder. Way cheaper than a new controller.

Good luck.
Click to expand...

I have repaired them also by resoldering some bad joints.
 
shawn kloker said:
Get that vacuum line back on.It has to be running bad sucking air.The vboost cable can't cost very much.Is it the short one on the butterfly or the longer one to the servo?I would bet less than $10.
Click to expand...

It is the long cable. The vacuum line wasnt loose, it was the electrical connection that was loose.
 
bmannon said:
It is the long cable. The vacuum line wasnt loose, it was the electrical connection that was loose.
Click to expand...

I'm sure someone on the forum has a used one that they can either give you or sell to you cheap. Post a new thread with your request in the title of the thread.
 
Before I do that I should verify everything else is operating properly.

If I turn on the key the servo motor should turn if everything is working, correct?
 
disconnect the butterfly cable (it's already cut, it could be jammed or rusted). plug the controller back up, and turn the key on. You should hear it cycle twice.

I'll dig out the test for the servo. If it's that, I've got one on my parts shelf. It's twenty years old, but it's free for a fellow biker in a hard spot.
 
If it doesn't cycle open then closed then a short open again the controller or servo could be bad.If you can not tear into and resolder the controller I can for you if you ship it here to western pa.
The cable is $27 for the long one and $3 for the short one from university.
 
I just plugged it all up and turned the key on, Nothing happend. I didnt unhook what was left of the cable, but it made no sounds like it was even trying, and I had my hand on it and it didnt feel like it was trying to move.

I need to see if it is getting a signal to operate. Guess I will read the manual tonight and check it tomorrow after work. Anything I should give a quick look at?



eatatjoz said:
disconnect the butterfly cable (it's already cut, it could be jammed or rusted). plug the controller back up, and turn the key on. You should hear it cycle twice.

I'll dig out the test for the servo. If it's that, I've got one on my parts shelf. It's twenty years old, but it's free for a fellow biker in a hard spot.
Click to expand...
 
Shawn I can resolder the connections, not a problem. The big box with the round plug is the controller, correct? That controls the servo? What is the little box with the vacuum line?

shawn kloker said:
If it doesn't cycle open then closed then a short open again the controller or servo could be bad.If you can not tear into and resolder the controller I can for you if you ship it here to western pa.
The cable is $27 for the long one and $3 for the short one from university.
Click to expand...
 
I can't think of anything obvious right off the top of my head. It sounds like you're going to have to get the multimeter out.
 
The box with the round plug under the left scoop is the servo controller.The small box with the hose is the vacuum advance.
 
shawn kloker said:
The box with the round plug under the left scoop is the servo controller.The small box with the hose is the vacuum advance.
Click to expand...

I actually just saw the other day a way to modify the vacuum advance circut to get more advance by adding some resistors into the circut.It was either on outlaw or yahoo list.I did save it but I do not know if my dyna still uses the stock box or not.I am going to call them and see.
 
Ahhhh so my vacuum advance is what was unplugged!
So its either the controller or the sevo, nothing else in the circuit?

shawn kloker said:
The box with the round plug under the left scoop is the servo controller.The small box with the hose is the vacuum advance.
Click to expand...
 
bmannon said:
I got my charging problem fixed and moved on to figure out why the front left cylinder wasnt always running. While I was tearing into things I noticed the cable from the servo motor to the butterflys was cut. Also the plug to the boost module (the one with the vacuum line) was unplugged. So I guess the previous owner had been having boost problems and just unhooked everything.

I opened the butterfly by hand and it is not seized, so that is good I suppose.

Here is my questions. I dont really have the money to start replacing parts to fix the boost, I know for sure I will need the cable, I havent tested the other parts yet but I am suspecting problems ( I have no real reason to suspect other problems, just a gut feeling). Would I gain anything by just pulling the butterfly open and holding it open with a wire tie? or should I just leave it alone until I can afford to replace the cable. Honestly my riding style will rarely put me past the 6krpm range where the boost works, but on the occasion I need it I dont want the bike to fall flat on its face either.

What do the people that are familiar with this beast think? :confused2:
Click to expand...

The module with the vaccum line is not the boost module. It is the manifold air pressure sensor (actually vaccum) and it controls the timing advance. If the electriclal plug wasn't hooked up it is not going to run to good.

Now for my opinion and that's all it is.

I haven't had Vboost for over a year and love the way it runs. The servo is gone and the cable is wired open, it runs great!
If i didn't have Vboost I would bother getting it I would just want the crossover tubes in order to leave it open all the time.
Originally I lost some bottom end response but it hasn't hurt my 1/4 mile times and actually improved the midrange alot.
You'l have to turn the idle up a little with the Vboost open all the time but it will still idle fine at 1100rpm

If you really want the Vboost functional and are sure the servo and signal to it are good let me know and I can mail you my servo cables.
 
Last edited:
I run with the vboost eliminator tubes.My servo and butterflies are removed.I also run stage 7.The only downfall is that I had to buy a weber synchrometer to syncronize the carbs.My mercury sticks can only do 1&2 to 3&4 now since they are wide open between 1&2 and 3&4 now.They can be bought new pretty cheap on ebay though.

I tore out my complete vboost and sold it to someone over in singapore or one of those countries over there.
 
Spent another afternoon tinkering with the max and here is what I found....

1- The servo works if I apply 12 vdc to it, however when I checked the resistance on the potentiometer I found that it was correct unless it was all the way back to the stop, then it abruptly dropped to 0. I could adjust the stop somehow I suppose.

2- As far as I can tell the control module for the servo doesnt work. I couldnt find in the manual how to test and see if the module was getting control voltage to it however, so thats still up in the air.

3- My idle mixture screws were all at 1 turn, I turned them out to 2-1/2 and things seem better.

4- I hooked a wire tie to my butterfly valve and ran it behing the left scoop so that I can open the valves manually. Doing that makes a big difference in the sound of the idle, sounds like a small block with a monster cam with them open! I will have to wait for better weather to try it out. I will most likely repair the system though.
 
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