Kawasaki VN750 Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
20 Posts
Discussion Starter #1
Just finished the Ear shave, looks freaking amazing. Bike starts up good, just got a new Glass Mat battery, now I want to sync the carbs. I build a manometer, not according to the versus but to this website instead:

http://www.obairlann.net/reaper/motorcycle/manometer.html

Looks good, easy enough to build. I tried it once, and the Rear cylinder carb sucked all the water through like a straw. Obviously they are way off.

I didn't have enough time to adjust them yet, but they are set to 2.5 turns on each side. Anyone have some advice to keep that from happening this next time?

Also, it takes a few seconds to decelerate at an idle. Obviously it's because I didn't connect the decel cable, but I don't understand why it's even necessary. The throttle snaps closed as soon as I let it go. Can someone explain this to me?

Last thing, I promise. While doing the ear shave, I deleted some emissions crap, and left some hoses unplugged, and it doesn't seem to change a thing. Firstly, the Red and Blue ports on the gas tank are just unplugged now, is that ok, plugging them in while running seems to have no change. And on the T shaped splitter, I left one of the vacuum lines open. I attached a hose to it and fed it to be accessible outside the bike, so I could play with it. Plugging that with my thumb makes the bike idle higher and die on acceleration.

Whew, sorry for the long post. I can take pictures if necessary.

Thanks
 

·
..have a vulcan good day!
Joined
·
4,508 Posts
Looks good, easy enough to build. I tried it once, and the Rear cylinder carb sucked all the water through like a straw. Obviously they are way off.

I didn't have enough time to adjust them yet, but they are set to 2.5 turns on each side. Anyone have some advice to keep that from happening this next time?
I did not view the Link, but use 15W or 20W oil....NOT water.

Also, it takes a few seconds to decelerate at an idle. Obviously it's because I didn't connect the decel cable, but I don't understand why it's even necessary. The throttle snaps closed as soon as I let it go. Can someone explain this to me?
I have similar issues...believe it to be deteriorated "Enrichners" / Decelerator Valves ...Air Valves in need of replacement.

:smiley_th
 

·
1986 VN750
Joined
·
3,255 Posts
If your throttle is closing but your idle is slow to return then it sounds like you have an air leak around your carb boots?

The 2.5 turns you are speaking about is the AF ratio screw, and it's not used for syncing.

I sent $30 on a sync tool off ebay that works without fluid etc.
 

·
Super Moderator
Joined
·
2,570 Posts
Rear cylinder carb sucked all the water through like a straw.
Thanks
another indication of an air leak somewhere.. front cylinder most likely by that statement.

that device will respond exactly like you described if you have good vacuum on one side, and piss poor on other (either very low, air leak, or not connected to proper vacuum port)
 

·
Registered
Joined
·
20 Posts
Discussion Starter #6
Thanks everyone. Yea, the air/fuel mix screws are what I was talking about. I feel like a fool for mistaking it.

The boots WERE leaking. I readjusted them, and idle drops right down. I never did re connect the decel cable. Tell me, is it even necessary?

Haven't done the manometer test yet, will do when I find a 7mm wrench >_>

Back to Air/Fuel. I tried adjusting it by setting idle to 1000 rpm, then rotating screw out on a carb, until idle drops, then back in a bit. Thing is, when I turn the screw in either direction, on either carb. There is no change!
 

·
2014 KLR 650!
Joined
·
3,365 Posts
Doing and having exactly the same thing

Ill write when i have time today. I am synching and my idle and throttle is all kinds of whacked
 

·
Registered
Joined
·
1,253 Posts
Thanks everyone. Yea, the air/fuel mix screws are what I was talking about. I feel like a fool for mistaking it.

The boots WERE leaking. I readjusted them, and idle drops right down. I never did re connect the decel cable. Tell me, is it even necessary?
It's a safety thing. You can run without it fine. But think about it like this...what if you are out on a back road in the middle of nowhere at dusk and the single throttle cable you have breaks? Uh oh. If you have both of them, you can swap that broken one with the other and keep on riding.

Haven't done the manometer test yet, will do when I find a 7mm wrench >_>
I got mine in a set from Harbor Freight. I think they were like $5 for 6 metric wrenches.

Back to Air/Fuel. I tried adjusting it by setting idle to 1000 rpm, then rotating screw out on a carb, until idle drops, then back in a bit. Thing is, when I turn the screw in either direction, on either carb. There is no change!
Are you turning the air/fuel mix screw on the carb or the big black knob on the left side? The knob is the idle adjustment.
 

·
2014 KLR 650!
Joined
·
3,365 Posts
Ok, at work so now I have time to type :-]

So my bike has an annoying buzz at 3500 RPM on up to at least 5k (haven't really been any faster because I'm afraid the thing will fall apart on me). It was suggested to do a carb synch. So I first started with the dual gauges. I just didn't get warm fuzzies from the dials. So I built my own manometer and I'll post some pics here soon. I used two stroke oil for my liquid.

When I first hooked it up, the rear carb was just about sucking the stuck up the hose immediately so I started loosening the bolt - counter clockwise. It's a bitch getting to the thing with any sort of normal tool. I go at it from the right side although others have said the left. So the result was that I did in fact get the two columns of liquid pretty close to even at idle but after the first ride the idle is at about 1500-2000rpm and will not go down unless I put pressure on the throttle to PUSH it down.

Part of the carb synch was to loosen your throttle so that the carbs are totally shut off by the throttle- for lack of a better way of saying it. I can only guess that I screwed something up. So my idle screw no longer does anything -it does not LOOK broken. I have looosened that up pretty much all the way trying to get the idle down. I think the problem is that now I have to adjust the throttle cables at the carbs. I have no idea how to do this.

I am also going to check the carb boots and I am assuming that it is the rubber that connects the carbs to the cylinder head.

As for the new bike owner Alien guy - I had lots of engine cutting off problems until I cleaned as many electrical connections and grounds using a dremel as I could get my hands on. Cleaning the switch UNDER the key fixed ALL of my shutting off problems - it's black and two screws gets it off after you remove the headlight bucket.

So anyway, that's where I am with this carb synch business. It's fun but the girlfriend is getting really annoyed that I spend so much time on the bike but the maybe I should get a new girlfriend :pepper:
 

·
..have a vulcan good day!
Joined
·
4,508 Posts
So anyway, that's where I am with this carb synch business. It's fun but the girlfriend is getting really annoyed that I spend so much time on the bike but the maybe I should get a new girlfriend :pepper:
She'll live with it..... then make up for it (spend a lot of time) during the winter (off season).
.

.

.

...or I forgot, that is season we perform a tear-down & repaint on our bikes !

LOL

LOL

:smiley_th
 

·
Registered
Joined
·
20 Posts
Discussion Starter #11
Are you turning the air/fuel mix screw on the carb or the big black knob on the left side? The knob is the idle adjustment.
Yea, I set the idle to 1000 rpm. Then using the air/fuel screws, I try to adjust the ratio.

But no matter how far in I go, or how far out I go, on either carb, the idle doesn't change at all.
 

·
Registered
Joined
·
1,253 Posts
After setting the idle to about 1100-1200 on mine, I've adjusted the A/F screws numerous times without it affecting the idle. I basically adjusted the screws to eliminate the popping once I coastered and to make sure I wasn't running lean once I put my V&H cruzers on. But I never noticed the idle changing as a result of that. Granted, I have only adjusted them a 1/4 turn at a time. But I never expected that to change the idle either.
 

·
2014 KLR 650!
Joined
·
3,365 Posts
Idle

The air mix screws don't change the idle because the idle screw is really just pushing the throttle out and in. My problem is there is nothing left to let off the throttle so either I have my throttle decel cable wrong or vacuum leak I guess.
 

·
Premium Member
Joined
·
3,027 Posts
I have my pilot air screws both exactly 2 1/2 turns out. That's over a full turn more than stock. The engine idles a lot smoother, and doesn't have that misfire at idle like it did with the screws set to the stock position. The misfire is caused by a lean A/F mixture at idle. I also have my idle set at 1000 rpm (when warm) I don't like a really high idle.

As for the "decel" cable, I got rid of mine (30,000 miles ago) That is a controversial subject, just like the clutch and sidestand safety switches, which I also got rid of. So I am not recommending it. First of all I like simplicity, and there was no need I cared about for 2 cables. I also didn't like the idea of the extra friction caused by 2 cables. I have read about a couple of cases of the throttle sticking because the cables were corroded. That is an obvious lack of maintenance, but having 2 cables doubled the chances of one of the cables binding. I had already removed the second cable from a couple of other bikes, so I knew it worked fine. I found the throttle was noticeably lighter and easier to turn, and snapped back easier with one well lubricated cable. If that cable breaks, the carb spring should close the throttle. If not, the kill switch is right there under your left thumb. You can always carry a spare cable if you want. A lot of Japanese bikes came with only one cable. I haven't had a broken cable since getting rid of my '66 Triumph. But, if you decide to get rid of that cable, at least put some thought into it first, and have a good understanding of how everything works.
 

·
R/R = Relocated *******
Joined
·
628 Posts
Part of the carb synch was to loosen your throttle so that the carbs are totally shut off by the throttle- for lack of a better way of saying it. I can only guess that I screwed something up. So my idle screw no longer does anything -it does not LOOK broken. I have looosened that up pretty much all the way trying to get the idle down. I think the problem is that now I have to adjust the throttle cables at the carbs. I have no idea how to do this.
:pepper:
You shouldn't really have to adjust them at the carbs, but it's simple enough. The adjustment is at the cable bracket. Loosen lock nut towards the front push the cable towards the carb and loosen the back nut to add tension to the cable, tighten the nut to remove it. There should be a little slack in the cables and you need to try and get them as close to each other as you can.

It sounds to me like you may have over tightened the cable. It also helps to lube the cables. I used zoom spout turbine oil to do mine, but others swear by WD40.

Sent from Motorcycle.com Free App
 

Attachments

1 - 15 of 15 Posts
Top