What gas mileage do you get ?

[Gearhead]

"I was doing some reading concerning this, as to how Barometric Pressure affects

the flow of the fuel to the Jets. Apparently the Height of the fuel in the Bowl Chamber, changes how much fuel a given Barometric Pressure can force thru the jets.

 

I been looking for more info on this, but as yet have not found a complete explanation of how this works.

From what I have found, this is apparently basic to any Carburator."

 

 

 

George, I believe this is due to hydrostatic pressure. The force that pushes the fuel thru the jets is a combination of atmospheric pressure and hydrostatic pressure. Hydrostatic pressure is simply the weight of the liquid above the measuring point. As divers go deeper they need better diving suits, right? Similarly, as the fuel is deeper there is more weight pushing it thru the jets.

 

Jeremy

[JimRoberts]

My 86 Royale is getting 39-42 mpg on a regular basis since I ride it to work almost daily. As with anything, the more you get in the throttle, the lower the mpg!!!

[JimRoberts]

My 86 Royale is getting 39-42 mpg on a regular basis since I ride it to work almost daily. As with anything, the more you get in the throttle, the lower the mpg!!!

[Mariner Fan]

I like to think and say that I get over 40 mpg. To be truthful, I don't have a clue.

[greg_in_london]

Well - feedback from the trip to Le Mans.

 

The racing (what we saw of it) was good, Team Alf's finished the race, which was good as we sort of supported them (which means we looked at their pit when the pit lane was open on Friday and looked out to see if bike 59 was still going round), the partying was excellent and we met up with a few people from last year. As I had the bagpipes with me, I had a good way of meeting lots of others without the lack of spoken French being too great an issue. The weather was variable - there was some sunshine and while it rained, it didn't stay for so long that you got soaked.

 

But what about fuel consumption ..... well it was a good job that there was more petrol available than other years. After all the work, resetting float heights, fiddling with pilot screws, balancing carbs and blowing out jets, it was using more petrol than when I began. I was getting around about 25-27mpg (UK - 22mpg US ?)), no matter what speed I was travelling at.

That meant that I mostly refilled every 60-80 miles with 11-14 litres or thereabouts.

If I'm now getting the same mpg at 50mph (awful) as at 80mph (tolerable) that suggests that the main jets are fine, but carburation at lower throttle openings is wrong.

 

That's obviously a wind-up for me. I'm not going to have the carbs again for a little while at least, but I do feel that I should be able to make some sort of improvement.

 

I think I would like to look up which pilot air/fuel screw jets are fitted in the different models in the jet block. I couldn't see how to take the jet block out when I was cleaning the carbs - obviously the screws come out, but I didn't want to use too much force to try and lever it out - but from looking at the manual, it appears that this jet may determine the mixture (and it may be thraded and so could be adjustable ???), while the main pilot screw adjusts how much of this mixture is fed in (with the coroallary that there is an airbypass which mixes with it via the cosating enrichment circuit) rather than the mixture itself.

 

Anybody selling any shares in an oil/petrol company ?

[Guest k4sfc@bellsouth.net]

My 2008 RSV has 1,400 miles on it and so far my MPG is 37 to 40. I'm hoping it will improve at least a mile or two as it gets more break in miles. I'm using premium gas and my riding is mostly two-up and combination city/highway riding. Have not had a real trip yet to get a honest on the highway MPG. Maybe the Ethanol combo is affecting the MPG? It's required in Louisville KY due to the EPA.

[greg_in_london]

Okay -so I've been looking at the manual to get my head around the problems, but feel that I'm not 100% sure about how all the fuel circuits relate to each other. The carburettor companies (ie mikuni) give advice on how to ajust their carbs, but concentrate on much simpler models, which obviously is little help to us.

 

One point that I'll come back to later is that there was a small amount of petrol visibly trickling out of the main/needle jet at tickover, even though there was the idle mixture was set well enough that the slides remained closed. I think it was a trick of the light, but it looked as if the needle itself pulsed in/out.

 

Right - back to the plot. Below is a picture of the venture carb:

 

http://i252.photobucket.com/albums/hh10/greg_in_london/venture/venturecarb.jpg

 

Air flows in from above through the pilot air jet (2) and travels to where it meets fuel coming through the pilot fuel jet. They bubble together (stop me if I get too technical) and travel together along the long dotted tube over to the other side (it doesn't actually go outside the carb - it's just easier to see this way) where the pilot screw controls how much is let in.

[For those with sharp eyes, there is a dotted air feed in just after the pilot air jet which comes from the coasting enrichment valve. When you are coasting, vacuum rises and this air feed is blocked off, hopefully enriching the mixture - if you didn't spot this, ignore this paragraph, it just complicates matters]

 

Now, rightly or wrongly it seems to me that this pilot fuel jet seems to be determining most of the mixture and that the pilot screw seems to be controlling how much mixture is allowed in, rather than the composition of the mixture itself - a way of making it look as if they're allowing home mechanics to make changes without allowing them to make much difference.

 

Below I've shown the detail of the mixing area itself (sorry if the text is not easy to read):

 

http://i252.photobucket.com/albums/hh10/greg_in_london/venture/pilotjet.jpg

Now when I first saw this pilot fuel jet, I thought it was adjustable, but looking more closely (at the diagram at least - my jet block did not want to come out of the carb and I didn't want to force it) I see that it's just an ordinary screw in jet.

On the other hand, different carbs have different jets and I wonder if this could be a clue as to why some riders report quite respectable fuel economy while others do not - regardless of how the throttle is used.

Here are some examples (thanks to the technical download section of the UK Venture Club http://www.yamahaventureclub.co.uk ):

1983XVZ12TK pilot fuel jet 42.5

1983XVZ12TDK pilot fuel jet 42.5

1984XVZ12LKC2 pilot fuel jet 42.5

1985XVZ12DN pilot fuel jet 37.5

19861987XVZ13DSSCTTC 37.5

1987XVZ13TTC pilot fuel jet 37.5

 

This shows me that there is some variation between years on carb specs, but I wonder if there wasn't more between markets, nor whether the changes were for emissons or to resolve any particular problem.

This next information is from my 83-85 Yamaha service manual

XVZ12TK carb 26H 00 - fuel jet 42.5 main air jet 65

XVZ12TDK carb 26H 00 - fuel jet 42.5 main air jet 65

XVZ12L (XVZ12DL) carb 41 R00 - fuel jet 37.5 main air jet 55

I haven't found any model numbers on the carbs, so presume that the only way to tell is from your bikes serial number (or by dismantling and checking the jet number - but as I said, my jet block didn't want to come out easily, so I didn't force it)

serial numbers were:

XVZ12L 41R-000101

XVZ12DL 41V-000101

XVZ12KC2 47R-000101

XVZ12DKC2 47T-000101

XVZ12TDK 31M-000101

XVZ12TK 26H-000101

 

Obviously I'm wondering if there is a link between which jet people have and what mpg they get tp see if this could be worth experimenting with. If I make changes I may also see about buying new emulsion/mixer tubes at the same time if they're available at reasonable prices.

 

Mine is 41V-000125, by the way.

[Gearhead]

Well Greg, that sucks. I synced my carbs once and had the mileage go down by about 2. Don't understand that. Did you say you checked to make sure your vacuum advance was working? Good spark? Did you check the condition of your coasing enricher diaphragms when you had the carbs apart? Don't know if they'd affect mileage much.

 

 

"Now, rightly or wrongly it seems to me that this pilot fuel jet seems to be determining most of the mixture and that the pilot screw seems to be controlling how much mixture is allowed in, rather than the composition of the mixture itself - a way of making it look as if they're allowing home mechanics to make changes without allowing them to make much difference."

 

I don't agree with your conclusion in the last sentence. The engine at idle is drawing most of its air through the tiny opening of the throttle plate, not through the PAJ's. Those certainly affect it, and give the fuel some emulsification before it enters the carb throat, but that mix then mixes with the air coming past the throttle butterfly. So changing those pilot screws DEFINITELY alters the mixture significantly. I've read that if you need to make GROSS changes to pilot mixture you need to change the pilot jet, and then the pilot screw gives a adjustment within that range. I'm sure the ranges of adjustment from one size pilot jet to another overlap.

 

Some of your data indicates that when the smaller pilot fuel jet is used, the smaller pilot air jet used also. I wonder if those two always go hand-in-hand.

 

If you're compiling data, I have an 87 VR 1300, California model, with stock carburetion. As I said before, it usually gets 38-39 US in normal driving which is about half interstate (80 mph) and half country roads, some signals. My best was about 42 I think riding slowly with small daughter on back.

 

One more idea I just had. How many miles on your bike? One thing that gets worn and doesn't get much attention is the needle jets (emulsion tubes). The needle is constantly working up and down in that brass part and it wears into an oval shape which obviously doesn't meter correctly in conjunction with the needle. I had it happen on my Virago with lots of miles; if I held the tube up to the light I could see the oblong shape of the hole. I had a friend with a Suzuki quad where this condition was very severe. It would load up, foul the plug, etc. I've not had the Venture's carbs apart, but I did replace the slides/diaphragms. When I had them out I shined a light down the bore of the needle jets and they appeared perfectly round, but it's easier to tell if the light source is behind the jet. I could actually measure the oval-ness with a caliper on the Virago.

 

Jeremy

[greg_in_london]

Hi Jeremy,

 

Yes, I checked the vacuum advance the way you suggested - set the tickover to 2000 rpm and then sucked on the vacuum advance and tickover increased noticeably.

 

My Venture has done just over 54,000 miles, so there may well be wear in the emulsion tubes, especially as there seemed to be some fuel escaping when the slides are closed. Last time I asked about prices, they were silly money, but if I can get some at a sensible price I will try them out.

 

I noticed at tickover, though, that the butterflies are completely closed. I can be sure of this because I used a squirty can of carb cleaner, and this actually pooled in the inlet and did not pass the butterfly. I was quite surprised by the effectiveness of the seal, but it does mean that I could be sure that I was only investigating the pilot mix circuit.

 

[i know I also said I saw some petrol escaping from the main/needle jet, but this didn't pool. Maybe it was an optical illusion after all. I can't explain that.]

 

I didn't check the coasting enrichment diaphragms, but it doesn't pop on the over-run and under the circumstances, I don't feel I need to enrich the system any more, so if they're not functioning correctly, I don't think they're critical.

 

Talking to the guy who runs the Venture UK club and website, nobody is getting 37 - 40mpg (US) (45mpg UK) here at those speeds (or even going slower, in fact).

[MikeM8560]

 

Talking to the guy who runs the Venture UK club and website, nobody is getting 37 - 40mpg (US) (45mpg UK) here at those speeds (or even going slower, in fact).

Odd, must be regional? I just toped off the tank today 115 miles and took 2.6 gal (us)

[greg_in_london]

Judging by some of the responses, plenty of US riders get the same (low) figures. I don't think there's a major difference between the petrol in each country (apart maybe from some states using and ethanol additive ??), so there must be a difference in how some bikes are set up.

 

The question is, what is the difference ?

 

It might be because of pride in how our bikes run, because we want to save the Earth's resources, to travel further without looking for petrol or just to save money, but amongst that lot there must surely be enough reasons to find out what makes a difference.

 

If I can get it right, it would certainly be nice to explain to all those new Gold Wing owners why my quarter century old machine is better, faster, cheaper to run and more comfortable.

 

 

 

The odd thing is that posters seem to fall in two camps (for the most part). Some report good mileage and don't believe anyone gets poor mileage for any reason other than an active right wrist. The other camp just say it's a big heavy bike and there's no way that you should expect good mileage and they don't get it. Are there two types of Venture out there ? Can I buy one of the cheap to run bikes ? Failing that I'll keep trying to work out the conversion, but any pointers from someone else who has made the change would be gratefully accepted - except no-one else has admitted to achieving this. I don't understand

[Squeeze]

Greg

 

i just came back from a wonderful Tour with my Max. I've had a complete Spread between 11 l/100 km and 5 L/100km ...

 

11 Liter was Flatout on the Autobahn, 5 Liter was riding in Swiss with only one Buddie behind me and going slow due to Speed Limits and heavy Traffic, mixed with City and Interstate.

 

Believe me, may your Bike have a good Setup or bad Circumstances ... mostly it's the twist of the Wrist.

[greg_in_london]

I've had a complete Spread between 11 l/100 km and 5 L/100km ...

 

We don't get that range - we can't get anywhere near 5l/100km (55mpg UK) no matter what we do. As I said above, there are two camps, and those who get good mpg refuse to believe that it's anything other than the right wrist that controls fuel consumption.

 

11 Liter was Flatout on the Autobahn

- that's what I'm getting whatever speed I do at present.

 

From Gearhead:

As I said before, it usually gets 38-39 US in normal driving which is about half interstate (80 mph) and half country roads, some signals

 

Quote from Valhalla on www.yamahaventureclub.co.uk :

Well Greg,i usualy get between 30 -40 to the (UK) gallon on my Venture Royale 1300 , i do get more to the gallon on a long run usualy in the high 30s

Even when solo, cruising at about 50-55mph, I could not beat high 30s to the gallon. If one person gets appreciably better mpg cruising (ie no appreciable acceleration) at 80mph than another who is travelling at 55mph, then saying that it depends on your wrist doesn't really help much. Yes, it may be that my motorcycle is not perfectly tuned, but if that is the case so are a lot of other people's and presumably they would also benefit if we could find what it is that is critical and causes the difference in fuel economy.

[Gearhead]

"Last time I asked about prices, they were silly money, but if I can get some at a sensible price I will try them out."

 

Yeah, they charge crazy prices for carb parts. For the Virago I have two extra sets of carbs that I've picked up along the way. Out of the three total sets, two had noticably worn tubes, one did not.

 

 

"I noticed at tickover, though, that the butterflies are completely closed. I can be sure of this because I used a squirty can of carb cleaner, and this actually pooled in the inlet and did not pass the butterfly. I was quite surprised by the effectiveness of the seal, but it does mean that I could be sure that I was only investigating the pilot mix circuit."

 

That's weird.

 

 

"I didn't check the coasting enrichment diaphragms, but it doesn't pop on the over-run and under the circumstances, I don't feel I need to enrich the system any more, so if they're not functioning correctly, I don't think they're critical."

 

No, but if they're compromised they will cause a vacuum leak which can affect the way the carb meters, although I think it's a very small vacuum leak.

 

 

"Talking to the guy who runs the Venture UK club and website, nobody is getting 37 - 40mpg (US) (45mpg UK) here at those speeds (or even going slower, in fact)."

 

The problem is that you Brits have forgotten how to tell a good fish story! :-)

 

 

"The odd thing is that posters seem to fall in two camps (for the most part). Some report good mileage and don't believe anyone gets poor mileage for any reason other than an active right wrist. The other camp just say it's a big heavy bike and there's no way that you should expect good mileage and they don't get it. Are there two types of Venture out there ? Can I buy one of the cheap to run bikes ? Failing that I'll keep trying to work out the conversion, but any pointers from someone else who has made the change would be gratefully accepted - except no-one else has admitted to achieving this."

 

I did start out around 32 and now get 38-39. (All figures are US, no sidecar or trailer.) I'm trying to remember just what I've done. The thing is, there was no single smoking gun. Looking over my notes from the past two years, here's what I found:

 

- First 4 fillups averaged 32. Did service including oil change, carb sync, connecting crank vent to airbox which had been disconnected. Mileage fell to 31 for the next few tanks :-(

 

- Vacuum advance was not working, fixed it, that was actually good for 4 MPG, getting about 35. You checked this already.

 

- Now it gets a little fuzzy. Some here recommended drilling (4) 1/2" holes in the airbox lid, and I did that. Ran two tanks at 39 and 38 mpg. Then I cleaned up the connections on the TCI and ran Seafoam fuel additive thru about 7 tanks, and mileage settled in at the 36-40 range for some time.

 

- Did another tuneup, this time valve adjustment, check carb sync (not far off), oil change, and again mileage seemed to suffer. Shortly thereafter I went on a 1200 mile 2-up trip of bad mileage. First 2/3 of trip I averaged 34, riding mostly 2-lane hiways, some Interstate. Overall average speeds weren't too high, no reason to get such poor mileage. Last 1/3 of trip were in extreme heat (100-107 deg F) and riding 80-90 mph to try to get it over with quickly. Averaged 25 mpg!!! After trip mileage was low 30's.

 

- Replaced slides because diaphragms were badly rotted. Bike picked up top-end power, mileage ran around 34-35.

 

- Taped over airbox lid holes for a couple tanks, got 33 & 34, then removed tape.

 

- Mileage slowly "drifted" up to 37-ish over many tanks, don't know why.

 

- I got a speeding ticket. This caused my overall average speeds to come down because I don't want another. Interstate speeds (about half my riding) have dropped from 80-90 down to 70-80. In-town and country road speeds also abated somewhat. Mileage now 38-39 for a few tanks.

 

There's my complete story. Draw whatever conclusions you can find. I'm not sure what to make of it all, honestly, as the results are a little weird in places.

 

I've pretty much conceded that the guys that get in the 40's must be riding slower and easier than me. For sure, high speeds REALLY do hurt the mileage, but your case does seem pretty bad. However, I haven't seen any comparison from another rider with both a hack and a trailer. You mentioned some low-mileage data from before you mounted those things. How reliable is that data? Was it a bunch of tankfuls or just a couple? Did you write it down, or is it based on recollection? My own recollection fails me often. I don't want to insult you, just asking. Is it possible to remove the trailer and hack for, say, 5 tankfuls and get some data?

 

Jeremy

[Squeeze]

Greg,

 

with my List of my latest Experience on my Max, i just wanted to state what Difference is within one Bike and with the same Rider.

 

There are so much minor Parts who influence the overall Consumption. As Jeremy stated, if the Needle Jets are worn, the Mileage goes down. But these Mikuni Carbs with round Sliders, which are used on Ventures and Vmax are not famous for worn Emulsion Tubes. The flat Slide CV-Models, used on several other Yammi Models are famous for this.

 

In your Comparison you forgot to mention the Jet Needles. There are more than 6 000 different Needles available from Mikuni. When Yammi changed the PAJ#1, they easiliy could have changed the Jet Needles to achieve their Goals.

 

The Slide Springs could be worn out and thereby, the Slides open a bit more than they should on each lifting Event. This would cause a rich Condition under every Circumstances.

 

You could have set the Mixture Screws too lean, this would cause Fuel being sucked through the Main System when this should be closed at Idle.

 

Next Thing is, Exhaust. The more free flow the Exhaust System has, the better the Chances are to get a better Consumption. But too much Freeflow will make the Consumption worse.

 

Now, there's much more to check. The Holes in the Cams can be in a 'bad' Position in Reference to the TDC, so there is a negative Difference, even if they are all within the Production Specs. Valve Setting a bit too wide might also be an Option.

 

Tire Pressure, Wheel Bearings, dragging Pads, drag in Tranny, Middle Drive Gear and final Drive ... the List goes on and on.

[greg_in_london]

Hmmmm

The problem is that you Brits have forgotten how to tell a good fish story! :-)

I hope that's not really the case. I'm as sure as I can be about the mpg figures from before I put the sidecar on as I went out of my way to check it. I remember one exception when I went to North Wales on A-roads and might have got about 42mpg, but that was so eceptional I'd doubt that figure's reliability.

When I first bought the bike I took it to a V-max specalist to put it on the rolling road 'just to see'. They said that it was running slightly rich and also that emulsion tubes were a common problem. I was sceptical because I felt that the mileage was so low for such a large bike and I'd never felt the need to replace these parts in twenty years of biking.

Now I'm thinking about changing them, but if it won't make a difference it's a lot of money to throw at the problem. Squeeze seems to say it makes little difference - I just don't know.

 

That's weird.

Tell me about it - so is economy improving when you do nothing. I can't figure out what's making a difference.

 

Squeeze said:

When Yammi changed the PAJ#1, they easiliy could have changed the Jet Needles to achieve their Goals.

- but I'm not at all sure what you mean. When I checked the carb specs I didn't check if they used the same needles on other carbs. Do different models have different needles - how would we check which spec had best mileage ? I doubt most riders know their carb jet sizes. I wouldn't if I'd not been looking these things up.

 

There are so much minor Parts who influence the overall Consumption.

I have a nagging suspicion that if it were a stack of little things that were making a smal difference each, then with increasing miles I'd expect the consumption to steadily worsen with a wide range of figures reported. I still maintain that figures quoted largely put people into a high or low consumption bracket and that there might be something fairy specific - your 'cam hole' suggestion or something else.

 

That or an awful lot of people enjoy 'fish stories'...

[monwa]

I'm riding an '86 that I owned twenty years ago and sold fifteen years ago to a friend who sold it back to me last September. It's old. When I had it the first time it would always get 45-47mpg. I think it is weak in a cylinder and has 35000 miles now. It is very consistent at 40 mpg. I sure like having it back even though the starter drags, the clutch slips in 4/5th gear at revs, I can't get the head light to work right...let me see,,what else?

 

It doesn't matter. It still rides REALLY nice other wise. Double brown and one the prettiest bikes on the road.

[Red Baron]

I have a 1990 VR that presently has about 84000 miles on it. When out on the Interstate cruising at an indicated 70 -75 mph, I get between 39 -40 mpg. When on secondary roads curising at an indicated 55 - 60 mph, I get between 47 - 48 mpg. I have owned the bike since it had 27000 miles on it and it has always been very consistent with this mileage.

The projected figures from the mag tests back earlier seem to be fairly accurate.

Hope this helps .

Red Baron

[greg_in_london]

Hi RedBaron and Monwa.

 

Your two examples show how confusing this whole deal is. Monwa, even though you've taken a hit on miles per gallon, if you're still getting 40mpg(US) then that's about 45mpg(UK) which is better than any of us are getting over here. It still hasn't done many miles, although of course I don't know what maintenance has been like. RedBaron, if yours is still getting 47-8mpg(US) on back roads, thats about 55mpg(UK), and you've done 84,000 miles without replacing any carburettor parts, then it gives the lie to any suggestion that the carb parts wear quickly and waste fuel.

Have you changed any carb parts, or is that with a worn carburettor ?

[eagleeye]

Hey Monwa,

I've got an 86 like that and always seem to get 38 mpg.

 

Steve

[Gearhead]

"I have a 1990 VR that presently has about 84000 miles on it. When out on the Interstate cruising at an indicated 70 -75 mph, I get between 39 -40 mpg. When on secondary roads curising at an indicated 55 - 60 mph, I get between 47 - 48 mpg. I have owned the bike since it had 27000 miles on it and it has always been very consistent with this mileage.

The projected figures from the mag tests back earlier seem to be fairly accurate.

Hope this helps ."

 

Helps? Not much help for those of us who have done EVERYTHING and can't get close to that! Kinda just makes us want to shoot ourselves in the collective foot!

 

:-)

 

Really, I'm glad you're getting such excellent mileage. Really!

 

Jeremy

[Gearhead]

Oh, Greg, I was going to suggest that you could seek out a set of lightly used carbs from ebay or such.

 

Jeremy

[greg_in_london]

I've been looking every now and then, but they're few and far between over here.

 

I'd still wonder exactly how to set them up to get maximum mpg, though - if I only knew for certain which settings are critical I'd make sure they were right.

 

There's a guy in Germany who's selling carb rebuild kits for old yamahas at quite reasonable prices, but I've seen nothing listed for the Venture (or the XTZ660 either) - just XJ650s and 750s and such like. I did email him but I didn't get an answer - maybe my german was incomprehensible.

 

Anyone got any good sources for buying carb jets etc without paying OEM prices ?

If we found a supplier would other people want a refurb kit ? Doubt it would be that cheap, though.

[Squeeze]

Greg, if i can be helpful, i'd translate

[CrazyHorse]

Hey Monwa,

I've got an 86 like that and always seem to get 38 mpg.

 

Steve

 

 

My 90 gets 38 mpg also.