VintageVmax.com

I have an '86 with a low end bog so I took the carbs off to clean them.

Can anybody tell me if these ports look modified?

The bridge has been knifed but that looks to be about it.

opsled

Thanks for the help.

How about these enrichener plungers- are they the right ones? I've see two different kinds- ones with the needles on the ends and ones without. When I bought the sled it had one of each installed so I bought this replacement cable.

Here is a short video of the hestitation or bog I'm trying to fix. Once I get the rpms up it runs great but I have to feather the throttle to get it going.

This was taken at the end of last year and I have since cleaned the carbs but havn't started it yet until I find out if the enrichener plungers are correct.

http://s151.photobucket.com/albums/s152 ... H03823.mp4

yeah those enrichener plugs or "chokes" should be fine. some have those needles, some don't. i think the needles just keep the plugs centered better, but sometimes they get corroded and make the plugs stick even worse.

run what you have. For a little bit of comfort, check to make sure both carbs have a small hole for the needle to go into. i dont have sound on this computer so ill try to remember to check out your video when i get home.

thanks for the reply. The carbs do have holes for the needles.

I will put it together tonight and fire her up and hopefully the bog is gone after cleaning the carbs although they looked clean to begin with.

Those plungers could be your problem. The original didn't have the pin like the ones you are using. I listened to the vid and it sounds fat and blubbery down low just like a choke not sealing right. All the round slide 38 Mics Yamaha used on the 540 and even the Exciter 570 used an 8U9 choke plunger. It didn't have the pin. The carbs that had the pin type plunger were flatslides. The plunger goes in sideways on a flatslide and the pin probably helps keep things centered (not sure).

If it still runs like crap try changing the plungers to the non pin style.

opsled

could I just remove the pin from the plunger or are the correct plungers different on the ends?

nice port job. phil is right on, wrong plungers/ choke cable. key here is look at the smoke in your video. sled dose not clean out. 3:16 (yammie tony)

I have had my Vmax sence new and they did have the needles on the choke plungers. I have two other sets of carbs, 84's and 85's and they also have those needles. My 88 Exciter also had them as well. Not trying to confuse you, just saying what I have seen.

yeah its been awhile since i have had my 84 carbs apart but im pretty sure i have the needles and it runs just fine. The chokes might need adjusted. i have mine adjusted so that the spring just barely has compression on it when they are put together.

tyler440 wrote:yeah its been awhile since i have had my 84 carbs apart but im pretty sure i have the needles and it runs just fine. The chokes might need adjusted. i have mine adjusted so that the sprint just barely has compression on it when they are put together.

I tried to adjust them according to manual but I'm wondering if there wasnt enough slack to let the plungers close completly.

I will install them with the springs lightly loaded as you mentioned.

How do these plungers work- does the gas come up through the center hole in the plunger bore or are there little ports on the side of the bore?

I found the answer to my question about plunger operation with a little internet research.

http://wiki.bssd.org/index.php/Starter_enrichment_valve

In the bell of the carb, at about the 3 oclock position is a small hole that runs all the way back to the plunger. If you look in there carefully with a light, you can see as the plunger moves up and down as you move the lever

After Vmax-540's post I checked three sets of 540 carbs I have on the shelf today and all three have the needles on the plungers so I was wrong (thanks for the correction). They do have them so you should be good there.

It still sounded real fat down low and as Tony said never seemed to clean up. Until you get it to idle (clean) the rest won't matter. Choke adjustment, pilot jet and/or pilot air passages need to be all clean and functioning.

Also check the pipes/silencer for possible obstruction. Fuel pumps could also have a bad diaphram and leaking through the pulse lines (one or both). These things are also known to to load up the cases with fuel when sitting. Especially if the tail is elevated.

I'd pull the pipes and run it a bit to see if both sides are giving issues or just one.

opsled

PS, just listened to it again and it sounds like one side is dropping off when it comes down. Pull the pipes and watch/listen to what is is doing. If one side is smoking and one isn't you've narrowed things down buy 50%. Switch the plug wires from side to side and run it again. If no changed you have eliminated a plug or cap. Look in the exhaust ports at the piston/cylinders too. If there are mechanical issues you should see them. If a piston is scored or going down it could miss at low rpm and no amount of carb work will cure it.