Clue to poor gas mileage problem?

[Dragonslayer]

I'm wondering what effect this condition has on my poor gas mileage problem, and what it means.

 

 

I took the diaphram covers off the carbs.

 

 

All of the diaphrams had 2 to 5 pin holes in them, plus

 

Carb 1 (left front), 2 (Left rear) and 3 (Right front) as your sitting on the bike,

all had a film of dry dirty, greasy coating the inside surface of the covers, and the carb surface behind the diaphrams.

 

The diaphram had a sticky feel to it like wet paint. ( probably partially disengrating rubber coating from previouse pin hole fixes with liquid rubber)

 

 

[ATTACH]71649[/ATTACH]

 

[ATTACH]71650[/ATTACH]

 

[ATTACH]71651[/ATTACH]

 

[ATTACH]71652[/ATTACH]

 

#4 (right rear) was cleaner and wet with gas:confused24:

[frankd]

Any chance those diaphragms were repaired with RTV or something that won't hold up in gasoline?? Mine had holes in them also, but were still reasonably clean. Now I've heard that replacing bad diaphragms would increase gas mileage, but I'm not certain that it did on mine. I'll have more to say about that after I finish the next tank of gas. Before I fixed mine, the gas mileage was about 42 normal riding and 40 MPG @72mph (cruise on 75). Good diaphrams made it sound a lot different (quieter) and also smoothed it out a lot. It also made it faster.

 

 

Frank D.

[Keemez]

I've had my diaphragms out several times and discovered this same or at least a similar condition. I just make sure I clean everything up real good when I put it back together- doesn't seem to hurt the runnin of it any.

93 with 83325 on the clock.... still can pull 44-45mpg out of it sometimes. Dips into the 30s during extended interstate running (73-74). I should put new diaphragms in mine- they all have the telltale pinholes.

[Dragonslayer]

Any chance those diaphragms were repaired with RTV or something that won't hold up in gasoline?? Mine had holes in them also, but were still reasonably clean. Now I've heard that replacing bad diaphragms would increase gas mileage, but I'm not certain that it did on mine. I'll have more to say about that after I finish the next tank of gas. Before I fixed mine, the gas mileage was about 42 normal riding and 40 MPG @72mph (cruise on 75). Good diaphrams made it sound a lot different (quieter) and also smoothed it out a lot. It also made it faster.

 

 

Frank D.

Not RTV, the last time I repaired the pin holes I used the aerosol PLASTI Dip spray on product on both side of the diaphram. With that product you get a much more even coat but it is a much thinner coat of rubber. I just believe in time the gasoline must break it down. On this repair I believe i'll go back to the brush on liquid rubber product.

 

I was getting more like 28 MPG, and trying to figure out why.

Edited September 17, 2012 by Dragonslayer

[frankd]

28MPG is pretty low, and it's not the diaphragms causing that. It almost sounds like you're missing a cylinder, and it's not the carb. causing it. Are you 100% sure it's running on all 4?

 

If it is, are you leaking gas somewhere? Do you have a dragging brake (that'd get real hot!)? When you get 28 MPG, how are you riding?

 

A vacuum leak in the hose to the boost sensor causes the mileage to go down 4-5 MPG. To check this, hook up a vacuum testor (a Mighty-vac or equiv.) to the hose, start the bike and have somebody hold the engine speed @ 3000 RPM. Then pump up the vacuum....the engine should speed up, and the vacuum reading should hold. If you have a leak, check the first section of hose (between the engine port and the restrictor) first.

 

Another thought.....how do your plugs look? If it's that rich, you will have dark plugs.

 

Frank D.

[Peder_y2k]

The oily sludge is from the crankcase breather system. Is yours routed the original way, or re-routed to open air like many of us have done?

-Pete, in Tacoma Wa USA

'83, 88 Venture

[Dragonslayer]

The oily sludge is from the crankcase breather system. Is yours routed the original way, or re-routed to open air like many of us have done?

-Pete, in Tacoma Wa USA

'83, 88 Venture

I took the banana twinkie tube off and put on one of those after market breather filter things.

[Peder_y2k]

Poor fuel economy can be the result of low compression, bad valves, carb problems like high fuel level, worn main jet and needle, leaking jet block o-ring. Ignition system problems, worn spark plugs. Just a thought.

When my fuel economy dips under 40mpg riding two up, I start looking for the reason.

Re: diaphragm pinholes, the service manual states nothing about pinholes, but only mentions rips and tears as a reason to do something about.

-Pete, in Tacoma WA USA

'83,88 Venture

[dacheedah]

My comment would be that if it were:

an english made bike they would tell you to take your torch to look at a gas line

 

an american bike would tell you to take use a flashlight

 

 

So the difference between a pin hole vs a rip or tear could be as simple as interpretation. . .

 

just sayin

[Dragonslayer]

My comment would be that if it were:

an english made bike they would tell you to take your torch to look at a gas line

 

an american bike would tell you to take use a flashlight

 

 

So the difference between a pin hole vs a rip or tear could be as simple as interpretation. . .

 

just sayin

I don't believe using a torch to inspect the gas line would be a good idea.

 

At least in the american version of the King's english.

 

Just saying

[KIC]

My comment would be that if it were:

an english made bike they would tell you to take your torch to look at a gas line

 

an american bike would tell you to take use a flashlight

 

 

So the difference between a pin hole vs a rip or tear could be as simple as interpretation. . .

 

just sayin

 

The "torch" sure would be faster.....

[Trader]

The "torch" sure would be faster.....

 

It might not help fix the problem....but it might end it.

[drkvsns]

http://jbmindustries.com/Yamaha650.html

these are the best and cheapest I have found.

 

I'm wondering what effect this condition has on my poor gas mileage problem, and what it means.

 

 

I took the diaphram covers off the carbs.

 

 

All of the diaphrams had 2 to 5 pin holes in them, plus

 

Carb 1 (left front), 2 (Left rear) and 3 (Right front) as your sitting on the bike,

all had a film of dry dirty, greasy coating the inside surface of the covers, and the carb surface behind the diaphrams.

 

The diaphram had a sticky feel to it like wet paint. ( probably partially disengrating rubber coating from previouse pin hole fixes with liquid rubber)

 

 

[ATTACH]71649[/ATTACH]

 

[ATTACH]71650[/ATTACH]

 

[ATTACH]71651[/ATTACH]

 

[ATTACH]71652[/ATTACH]

 

#4 (right rear) was cleaner and wet with gas:confused24:

[hell yea]

so what siez for the 83 venture diafram

[MiCarl]

Not that you shouldn't replace the diaphragms, but when I replaced them on my '89 my mileage dropped. I'm now at the low 30s.

 

My compression is at new spec, valves are in spec, carburetors clean and float levels spot on. Ignitech ignition module too.

 

I was thinking that the needle jets/jet needles are worn and using too much fuel. But a recent mod to the audio system has picked up ignition noise that sounds like 1 cylinder. My current thinking is that I have a bad coil/plug wire/plug cap. A project for this winter........

[greg_in_london]

There's only one sure way to get more miles to the gallon for all of you stateside and that is to switch to proper imperial gallons. You won't get so many in the tank, but they'll take you 10-15% further.

[Venturous Randy]

There's only one sure way to get more miles to the gallon for all of you stateside and that is to switch to proper imperial gallons. You won't get so many in the tank, but they'll take you 10-15% further.

 

 

Yes. and how much is an imperial gallon for you? Right now, a gallon of gas here is about $3 and in some places lower.

RandyA

[frankd]

Carl,

 

Make sure it is ignition noise, not noise from the voltage regulator. On my 89, it took a lot of effort to get the regulator noise to almost dis-appear. In my helmet speakers, I had what sounded just like ignition noise in mine when I bought it. On AM radio, I could hear it, but I could also hear it on FM. FM is almost immune to ignition noise. I also had it on my IPOD input (originally the cassette deck input). Then I noticed when I had the turn signal ON, the noise would go away when the turn signals were lit, and come back when they were off. The brake light also reduced the noise, as did turning on my driving lights. Then I noticed that the noise was missing when the RPMs were low, and there when you revved the motor up.

 

If this is the case with yours also, you probably have the same problem. Originally I upgraded the radio input voltage filter (mounted on the front the the radio compartment), but that didn't help at all. I temporarily hooked up a filtered, 14 volt power supply to the radio, and when I started the bike up, the noise was still there. That said to me that the intercom cables were probably picking up noise because the wires between the voltage regulator and the main fuse run along the same route that the passenger intercom cables take . I disconnected the rear intercom from the radio (unplug the back cable from the radio) and it was gone, which said that it was the intercom cable. I added ground cables that bypassed all of the screws in the brackets that hold the tuner and amplifier brackets, and that helped some. Now my noise would be greatly reduced but if I hit a bump it would come back. I added more ground wires, including one from a bolt under the front of the seat to the radio chassis. I also found that the cable underneath the passenger seat (to the rear audio panel) wasn't plugged in all the way. Then I also noticed that the noise would be affected by what level you had the intercom set for. If I turn the intercom off, the noise gets louder. As I turn it up, it goes lower until it disappears at about 10:00, and then gets louder past that. It kind of nulls out at 10:00, and I only hear it in the helmet speakers, which I use most of the time. BTW, if I turn my speakers on, the noise in the helmet speakers gets louder.

 

If yours has these problems, I'll take pictures on the ground wires I added.

 

Frank

[saddlebum]

There's only one sure way to get more miles to the gallon for all of you stateside and that is to switch to proper imperial gallons. You won't get so many in the tank, but they'll take you 10-15% further.

 

considering that the imperial gallon is about 5 us quarts you can see how this guaranteed to work

[mbrood]

To me, the first action in evaluating poor fuel economy is to pull and inspect the plugs... they will tell you lean or rich and you take action from there.

 

The thinness and compound of the rubber in the diaphragm, in conjunction with the spring are designed for a determined piston response. Heavier rubber (or buildup), residue in the piston sleeve, blocked vacuum paths, little o-ring missing just behind the diaphragm cover will all degrade the design. The piston should have a smooth glide feel as it's inserted, any irregularity needs checked and corrected if possible. Pinholes alter the diaphragm performance but by the increment of the size and numer of the holes.

[GeorgeS]

Any chance the previous owner did some JET, size, modifications on this bike ??

Have you pull the Jets, and inspected the Number on the jets, and compare to the Parts fitch to make sure all 4 carbs have the " Stock Size " jets installed.

 

Note: I believe the front carbs have different size jets, then the rear carbs.

 

-----------------

 

Also, the Needle, on the diaphrams, I'm sure you checked for the Correct number of those little washers being installed on each Main Needle, on the diaphram assembly.

 

------------------

 

Are you absolutley sure all 4 Ignition Coils, are functioning properly ???

 

------------------

 

After a Hard run, Have you pulled all 4 plugs, to determine if " ONE of them " looks any different then the other three ??? IF SO, maby a problem in that particular Carb !

 

---------------

[greg_in_london]

Well it's certainly true that I spend a bit more on a gallon here than you do over there, but you have to pay for quality. We don't get as much gum in our juice as you from what I can tell..

 

We had a thread on this years ago and there didn't seem to be much consistency in mpg figures. Different markets also had different jetting. Nobody seemed able to mention one thing they had changed that had made a big difference, or even made a big difference by lots of tinkering.

[MiCarl]

Carl,

 

Make sure it is ignition noise, not noise from the voltage regulator. On my 89, it took a lot of effort to get the regulator noise to almost dis-appear. In my helmet speakers, I had what sounded just like ignition noise in mine when I bought it. On AM radio, I could hear it, but I could also hear it on FM. FM is almost immune to ignition noise. I also had it on my IPOD input (originally the cassette deck input). Then I noticed when I had the turn signal ON, the noise would go away when the turn signals were lit, and come back when they were off. The brake light also reduced the noise, as did turning on my driving lights. Then I noticed that the noise was missing when the RPMs were low, and there when you revved the motor up.

 

If this is the case with yours also, you probably have the same problem. Originally I upgraded the radio input voltage filter (mounted on the front the the radio compartment), but that didn't help at all. I temporarily hooked up a filtered, 14 volt power supply to the radio, and when I started the bike up, the noise was still there. That said to me that the intercom cables were probably picking up noise because the wires between the voltage regulator and the main fuse run along the same route that the passenger intercom cables take . I disconnected the rear intercom from the radio (unplug the back cable from the radio) and it was gone, which said that it was the intercom cable. I added ground cables that bypassed all of the screws in the brackets that hold the tuner and amplifier brackets, and that helped some. Now my noise would be greatly reduced but if I hit a bump it would come back. I added more ground wires, including one from a bolt under the front of the seat to the radio chassis. I also found that the cable underneath the passenger seat (to the rear audio panel) wasn't plugged in all the way. Then I also noticed that the noise would be affected by what level you had the intercom set for. If I turn the intercom off, the noise gets louder. As I turn it up, it goes lower until it disappears at about 10:00, and then gets louder past that. It kind of nulls out at 10:00, and I only hear it in the helmet speakers, which I use most of the time. BTW, if I turn my speakers on, the noise in the helmet speakers gets louder.

 

If yours has these problems, I'll take pictures on the ground wires I added.

 

Frank

 

Thanks Frank, I'll look into that too.

 

I don't have noise from the radio, CB, or cassette converted to MP3 input. I added a cable to the passenger headset jack to tie in GPS audio. When the GPS isn't connected I pick up the noise. I suspect when I made some mods last winter I lost the ground on the cable shield. When I add a ground with a test lead the noise goes away.

 

I have the noise at all rpm. It's a tick at idle, and becomes a buzz as engine speed increases.

[jasonm.]

Bad mileage has many possibilities. You already identified the holes in the diaphragms. Which limits top speed and efficiency. If Bad mileage w/o holes... Age causes the floats to lose bouyancy...it's the ethanol gas and the water it attracts. Resulting> there is too much gas in the float chambers. This is a crucially important thing. That is why the spec. is in mm and +/- 1mm. Lastly with high mileage bikes, the NEEDLE jet is brass and gets worn out. But changing the jet requires total carb disassembly. A quick solution is the shim the needles down just 1mm. Note: the needle is harder than the jet and do not wear out. I did all listeded above at one time or another. Now I have new needle jets and new floats set to perfection which requires lots of patience. The carb(s) must be perfectly level when this is set. Put in a vise w/wood...and leveled sides. Like I said this is crucial for overall performance. Low speed screws also set using EGA...exhaust gas analyzer. I get 40+mpg below 75mph all the time.