Need some help

[jurob]

Got the bike last week. Running ok, horrible gas mileage. Just didn't feel right. Previous owner supposedly had the carbs rebuilt. Found that one of the carbs idle air screw was closed. Set all to 2 1/2 turns and gained substantial power, but sluggish at wot. Starts great idles fine, but something still seems off. Changed plugs and wires, no change.

 

Where I was at yesterday; gas mileage is horrendous, wot is fluttering, #3 cylinder exhaust temp 450ish and the rest 150-190ish. Starts easy, idles easy and runs down the road fine. Feels like I can drive it anywhere.

 

This morning I decided to pull the carbs. Boy it was a pita, throttle cables at the carb were a nightmare and reinstalling the cables and the vacuum line from engine to the air box was a royal pain.

 

Well, looks like I got half a rebuild. Looks like new diaphragms (or nice old ones), new air jets etc... The wet side was pretty nasty, but got it all cleaned out.

 

Put it back together and started it and it now idles at 3500+ without the choke. I can hold the throttle closed and will drop to 1500, let go back up. When I put my hand slamming the throttle it barely moves. Out side cable has slack, not sure about the inner cable.

 

Before I put the carbs on I tried to get all butterflies near closed and the same as best as my old eyes could so whatever sync that was on it is long gone.

 

Ideas on what I can do? I don't have a sync tool, but have a single vacuum gauge. I thinkmit might be an issue with the inner throttle cable.

 

I tried single gauge sync yesterday before I decided to pull the carbs and I had real bad flutter in the gauge so I limited flow and saw only about 1mm of vacuum in all carbs. Hopefully that changes tomorrow.

 

I'm real tight on money right now, so I won't have a sync tool for another couple of weeks.

[yamtom]

Hi,

Since I am a new Venture rider also, I wont offer any venture specific advice. Most of what I know about carb synch was learned on the xs11 list. Ive set up four bikes in the last year doing it in this manner, I am a little shy on starting on the venture. Thank goodness its running fine right now as I bought it.

 

A single gauge can be rigged to synch multiple carb setups or so I have read. I personally tried this method and found it didnt work so hot for me, but that could have been my lack of experience with rigging tubings in complicated configs., and the fact that I gave up before I glued the tubings in place. In any case, fish tank tubing can be bought and rigged in such a way that individual carbs vaccum can be turned on and off, thereby allowing one vac gauge to be used in sequence, to do all the carbs. To further elaborate on this, I went to a pet store and bought small tubings , elbows, shutoffs , and what I will call manifolds that multiple tubes can be connected to. I think I paid about ten bux for the works.

 

With imagination, the tubings are rigged such that the shutoffs isolate one carb to be set at a time , allowing the synch to take place in rotation, using one gauge. I personally didnt have much luck with this, I think due to vac leaks within the system. I would reccomend , gluing the tubings to the elbows and shutoffs and manifolds connections to stop leaks from interfering. Ive found seal all to be handy for jobs like that, found at most auto parts stores and hardwares.

 

Also, since you didnt mention it, a bench synch could be done to more accurately set your carbs . The guys on the xs11 list use a small wire found on bread bags to seal them as an appropriately sized wire for that purpose. The slides are adjusted such that the tiny wire can be barely removed from under the slide, you just adjust all the carbs to the same ,,,,wire slipping capability,,,,,, and you have a reasonably well running bench synch. I think that wire size is about one mm, but I think you could use other sizes, just adjust your overall idle screw setting to accomodate it. Since I dont think you mentioned it, is your idle speed screw on the carb set , can it be adjusted to lower the idle. Is it possible that your choke is in fact on, but not hooked to the cable or something?? Is it possible that your throttle cables are out of position and pulling inappropriately on the inner wire?? Is it possible that the forks are turned such that the throttle cable is putting tension on the inner wire??

 

If you were close by, I would have you bring it over and we could puzzle it all out together but VB is long honking way from midMichigan.

Edited August 13, 2011 by yamtom
didnt use all my words

[Yammer Dan]

Should be someone close with a Carb-Tune. Easy job if you have done a few.

[jurob]

Tks guys!

Ive tried to find a sync on here and local craigslist and have struck out.

 

Just got a big senior pictures bill to pay, vacation for me and the wife week after next and 25 hour endurance in Ohio in October....money is tight for toy stuff right now.

 

Tom,

 

Inner wire tension is a possibility, but ran out of daylight yesterday.

 

Really not in the mood to pull the carbs in the afternoon. Thinking I will look from the top and set all butterflies completely closed and go from there.

 

Choke is definitely off. Idle screw has no effect. Might have set the butterflies too open, I hope.

[asigetic]

I have a set of cable from a 1983 without cruise if you need them. I live in Cleveland Oh PM me if your interested and also have a set of sync gauges to use.

[Squidley]

I agree with the sync, the carb will do funny things if they aren't done right. Give this thread a day or 2 and I'm sure there will be a member close by that would hook up with you to do a sync on your bike.

[frankd]

Is there any chance that the main idle speed had been set way too high when the thing was gunked up? On the left side, look and see which carb. does NOT have a syncronizing screw (I think it's the rear one). Underneath of that carb, there will be a little (a little bigger than a dime) wheel with notches all around it. This is the master idle speed adjustment screw---it moves all 4 carbs. Take a long flat bladed screwdriver and turn the screw counter-clockwise. As soon as you move it, you SHOULD hear the motor slow down.

 

Another posibility-----you said that your idle vacuum was low? Could you have a vacuum leak? Make sure the carbs are in the boots properly, and that the vacuum advance hose is on the left front cylinder (I think you said you have a MkII). Crimp the hose near the port with a pair of pliers to verify that you don't have a leak downstream.

 

Frank D.

[mlew]

You can get a real good bench sync by using a piece of paper instead of the bread wrap wire. I use a 1/4" wide piece and adjust each carb so it just pulls through. If you set each one so the pulling tension is the same you won't be very far off with the sync or idle speed.

Check those float levels while you have them off. High levels will cause bad mileage.

[muffinman]

Just talked to Rob and he is bringing the bike down this afternoon so I can work on it.

Sounds like the cables are out of spec and a carb tune might get it right.

Jeff

[Venturous Randy]

Just talked to Rob and he is bringing the bike down this afternoon so I can work on it.

 

Sounds like the cables are out of spec and a carb tune might get it right.

 

 

Jeff

 

Good for you Jeff.

I wonder if he had one of the cables not slide back up into the housing where the cables come together under the fairing. That almost always happens to me when I am trying to put carbs back on,

RandyA

[muffinman]

Well Rob made it down around 4 or so and we worked on his Blonde she now runs great the cables were in need of lube we removed the left fairing so I could play with the cables and then we did the carb sinc they were way out but not any longer.

I think that Rob was surprised at how his bike felt when it runs properly.He is a great guy and has a nice looking 84 with 13k on the odometer.

he is in need of a trunk for it though the second owner didnt have it when he picked up the bike 8 days ago so if you know of one let him know.

Jeff

[jurob]

Tks again Jeff!

 

I cleaned the carbs yesterday and reinstalled them. I tried to "bench sync" my carbs before I installed them. In hindsight, I now realize what I did wrong. I should have rebuilt them and not messed with any screws!

 

I woke up this morning and realized my high idle was caused by the cables but more so that I set the blades just a tad open on all 4 then reconnected the linkage to carbs 1&2 to carbs 3 and 4 which caused two butterflies to open substantially more than the other two.

 

I completely loosened the idle screw and backed out the front front sync screw on the right side then tightened to just take up the slack which I felt would get the butterflies similar on all 4 and let it warm and used the idle screw to set the idle. Took it for a ride and knew I was on the right track! With clean carbs it ran much better, but still needed more work. My throttle was so tight I really had no more use for cruise control.

 

While I was fiddling with the carbs in my driveway I got call from Jeff who volunteered his services to me. I rode 75 miles to Jeff's house and could tell I was getting better mpg. At Jeff's house he worked his magic on my cables, showed me a ton of tricks and did a carb sync.

 

My carbs were way off and he turned it into a finely tuned machine in minutes. I never had the privilege to ride a new 1st gen, but I would have been completely happy to leave the showroom and have it run like mine. These bikes are strong runners!

 

I refueled about 15 miles from home with only one bar showing. I rode 131 miles and filled up at the identical level and put in 3.5 gallons netting me 37.4 mpg! A full tank with Jeff's tune should easily get me 40+ mpg.

 

Jeff, you are the man!