pilot jets and sync'ing ?

[59ndroy]

I've read lots of different threads about turning pilot jet screws from 1 3/4 turns out all the way to 3 turns.

 

So, how can you tell what "your happy number" of turns out is? What is the deciding factor? Will this effect gas mileage or is it something else?

 

Part 2 of this thread:

I'm trying to get the mileage up out of the 31 range. I've changed plugs, Seafoamed 7 tankfuls, tried sync'ing 3 times and have finally got her to idle and run decent. But it's still touchy with the choke in the cold mornings.

 

The other question is when sync'ing, at what rpm should it be? Idling or 2000 rpms? And when I think the sync is complete, (I do crack throttle during adjustments) my levels are constantly changing after that when I crack the throttle and let it settle back to idle. I mean everything gets wacky again. Never a consistant reading on any cylinders.

 

'86 Royale, 40,000 miles and homemade sync tool, board with tubing & trans fluid, 143 assorted bugs on windshield - 97.6% of those smashed flat allowing minimal wind resistance @60 mph.

[JohnMidnight]

Everything sealed right? Engine operates under vacuum. Cracks cause lots of problems, check your intake boots under the carbs, see if their OK.

[Pegasus1300]

If you can't maintain a setting start pulling your carb slides out and check for pinhole leaks in the rubber diaphrams.If they have never been changed they are over 25 years old.Just hold up to a light or sunlight and you will see the holes.

BTW for some reason my 86 got mileage in the mid 30's and nothing I ever did in 8 years would change that but you should get better then 31.

On the carbs you will need a torx with a post hole in it to take out the "tamper" proof screw.Harbor Freight has a whole set of them cheap.

[Snaggletooth]

If you can't maintain a setting start pulling your carb slides out and check for pinhole leaks in the rubber diaphrams.If they have never been changed they are over 25 years old.Just hold up to a light or sunlight and you will see the holes.

BTW for some reason my 86 got mileage in the mid 30's and nothing I ever did in 8 years would change that but you should get better then 31.

On the carbs you will need a torx with a post hole in it to take out the "tamper" proof screw.Harbor Freight has a whole set of them cheap.

 

 

Worth looking into. Since I rebuilt the carbs and got the bodies seated into the boots right I had issues like yours.

 

Once I replaced the diaphragms I was able to dial it in and things got better. Idle and starting were the biggest improvments. MPG went up from the 30's to. I average around 42 in town, if I behave, and have hit my personal best of 49 MPG on the back highways keeping speeds around 60 MPH. On one trip I pulled 242 miles out of one tank of fuel. It was almost vapors when I filled up but I was happy with the results.

 

I check the sync once a year every spring and it's never needs more than a tweek.

 

So take a look at them for sure.

 

Mike

[59ndroy]

Diaphragms make sense and I can check that out tonight after work.

 

But how about the pilot jets, how will I know that I've got that dialed in?

[joboo]

I am gonna post this and expect lots of flack but here is what I have done for the best pilot settings.. i have 4 exhausts so after it has warmed up, I hold my hand directly behind each exhaust, if it is warm, it is too rich, dial it in 1/4 turn, the exhaust should actually feel cool. If it is really rich it will "pop" against your hand as you move your hand closer. Dial it in some more. (For you 96 guys this cuts way down on the decel pop as well) If it is too lean it feels weak and is almost cold, dial it out 1/4 turn. - cool not cold. A little practice and you can dial it in pretty good. I know this is not very scientific but it sure works, after a minute or so the pipes cool pretty good close to the cylinders too if everything is dialed in. I also use the homemade manometer setup for sync and it is awesome. My bike runs better than it ever has.... I only wish I had learned some of this stuff a few years earlier. BTW I learned a LOT of this stuff from the guys here on this forum. Greatest resources on the planet!

[skydoc_17]

With out a doubt, if the Carb. Slider Diaphragms are leaking, this would be the first order of business to take care of. If you find that they are bad, Go to this web site.

http://www.siriusconinc.com/

 

You will need the SD-1 Diaphragms. Be sure to ask for the VR.ORG discount.

Now, about those "Magic" Idle Mixture Screws. Because you said that your bike is slow to warm up, and runs rough at start up, I suggest you set all 4 Idle Mixture Screws to 21/2 turns from bottom out. *CAUTION* If you bottom these screws out too hard, you will damage the Carb. Body, and it will need to be replaced! I use WD-40 on the screw threads EVERY TIME I make an adjustment. Because your bike spends very little time at Idle, it would be better to have that circuit run a bit rich for better start up.

Now, about that Carb. Sync. Set the Carbs. at 1000 RPM's. When you finish the Sync. Hold the bike at 2000 RPM's, then 3000 RPM's. If the Sync. is off at the higher RPM's, then this is a sign that you have other issues. I have been known to "split the difference" between idle, and 3500RPM's because I spend a lot more time at 3500 than I do at 1000.

If you get to the point where you are splitting hairs on the Carb. Sync. you are doing better than most, I assure you. Work on the "Big Problems" first, then you can "Fine Tune" at your leisure. Here is a link to a thread in the First Gen. Tech Library on a Carb. Sync. with the Carbtune Manometer. The idea is the same no matter what Manometer you use.

http://www.venturerider.org/forum/showthread.php?t=56723

 

This is an example of a Carb. Sync. on a First Gen. Motorcycle. It is not the only way, just one way. The pics will give you an Idea where the screws are, and what to mess with.

Good Luck on getting your VR Road Worthy.

Earl

[Trader]

BUT......the question that has not been answered is, as 59ndroy asked.....

 

How do you know if 2 1/2 turns is better than 2 3/4 or 3 or 3 1/2???

 

"feel the exhaust" won't work so well with collectors.

[Venturous Randy]

On adjusting the air/fuel ratio on cars, I used to have a set idle speed and when adjusting the air/fuel screws, I would stop at the highest idle, then I would reset the idle with the idle screw. I am not sure how well we can do this on our four carburated bikes.

RandyA

[Snaggletooth]

I gonna say I was taught long ago by an experienced old wrench bender to do it this way. We were doing it on twin carbs but I've had problems with my idle circuits on this set so I'm hoping it work when I get the set I'm going through now finished up.

 

I'm sure the carb guys will let me know if it's right or not on the four carb rack.

 

Set the air screws to the suggested setting, in our case 2.5 turns out from bottom.

 

Find a smooth idle point with adjustor screw to start.

 

Hook up a manometer and balance the carbs as per instruction to as close as possible.

 

Start with first carb turning IN the air screw slowly until it starts to stumble and back it out until smooth idle again. Adjust idle as needed.

 

Second carb the same.

 

And so on and so on for the number of carbs.

 

Then check sync again and make final adjustment and reset idle to spec.

 

 

But for this to work the idle circuits have to be clean and functional and ALL leaks have to be taken care of first.

 

The 2.5 turns is only a recommended starting point. The final setting for each carb could be all over the place at the end.

 

Like I said I have problems with my low circuits so I can't say this is the right way. But it has worked for me in the past on other setups.

 

 

So opinions?.........Thoughts?........ High fives? ...... Stick to the back of the head?

 

Mike

[GaryZ]

All of the answers here are excellent. I will add that the low speed circuit (you are calling it the idle circuit) is important for maximum MPG because this circuit is contributing at 1/8th throttle. It turns out that 1/8th throttle is where we find ourselves cruising down the highway . . .

 

[MiCarl]

I do a lot of carburetors. Sometimes I use a colortune plug, but that's not very practical where the spark plugs are buried like the Venture.

 

What I do to set low speed mixture is attach a digital tachometer and set the idle speed (1000 in the case of the Venture). I start with one carburetor and back the mixture screw out watching for an RPM increase. If it only goes down you started too far out and need to screw in until the RPM rises then begins to fall - then start backing it out again.

 

As I back the screw out I watch for the idle to fall, then turn it back in so the idle is at its peak.

 

Reset the idle stop screw to 1000 RPM and repeat for the remaining carburetors.

 

If you had to back the idle stop screw off a lot as you worked it is probably worth going 'round a second time.

 

By the way, a well running synced Venture will pull about 10" vacuum. If you're seeing less then it's not running right.