Go Back   Horizons Unlimited - The HUBB > Technical, Bike forums > Yamaha Tech
80mpg? 80mpg?
Register FAQ Calendar Today's Posts
Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
Photo by Alessio Corradini, on the Salar de Uyuni, Bolivia, of two locals

I haven't been everywhere...
but it's on my list!


Photo by Alessio Corradini,
on the Salar de Uyuni, Bolivia,
of two locals



Like Tree5Likes

Reply
Page 1 of 2 1 2
 
LinkBack Thread Tools Display Modes
  #1  
Old 25 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Sep 2006
Location: Edinburgh
Posts: 106
80mpg?
I was browsing my copy of the Adventure Motorbiking Handbook when I read a bit that suggested that twin carb machines could achieve huge MGP figures by keeping the throttle just below the point where the second carb cuts in. Has anyone here done this, and if so at what revs and will this apply to my 3AJ too?
Reply With Quote
  #2  
Old 25 Jan 2007
Registered Users
HUBB regular
  
Join Date: Dec 2006
Location: Finland
Posts: 29
Mpg
"keeping the throttle just below the point where the second carb cuts in"?
:confused1: Must be a rare make. Anybody seen recently bikes working in that manner? Cars use two-stage carbs but I have not seen any bike (yet)?
Reply With Quote
  #3  
Old 25 Jan 2007
Robbert's Avatar
Contributing Member
Veteran HUBBer
  
Join Date: Sep 2001
Location: Gent, Belgium
Posts: 523
Xt 600
I believe the XT600 does. No experience myself though.
Reply With Quote
  #4  
Old 25 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Jan 2001
Location: Stockholm
Posts: 651
Huh?
Methinks Patrick has never taken a good look at his XT600?
The XT/TT/Tenere 600 and 660 have the YDIS system. Yamaha dual intake system. Means, there's two carbs, each feeding one of the inlet ports. The slide on the first is operated by the cable, the second one by vacuum. Although, at about 1/3 turn of the throttle the valve downstream of the second slide is opened, creating an air flow, vacuum and causing the second carb to kick in.
There's no definite engine speed at which the second carb kicks in. You'll have to remove the tank to see when the throttle starts opening the valve in the second carb.
You'll be easier on the gas as:
- second carb is for the higher speed / power regions. Low speed makes for low consumption
- second carb is set richer than the first, lowering consumption

Auke
__________________
Auke
http://aukemarieke.blogspot.com
Reply With Quote
  #5  
Old 25 Jan 2007
Registered Users
HUBB regular
  
Join Date: Dec 2006
Location: Finland
Posts: 29
Yamaha
Sorry guys, I have an Africa Twin. Actually I started with a Yamaha LT2 back in -73 (100cc two-stroke). Amazing that I have not heard of the Dual Carburettor-system on the XT600. That´s the dark side of living in the countryside.
Yamaha has always been known for very interesting technical solutions.

Once more sorry, I believe you now.

PF
Reply With Quote
  #6  
Old 25 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Feb 2006
Posts: 1,598
Quote:
Originally Posted by patrick56
Sorry guys, I have an Africa Twin. Actually I started with a Yamaha LT2 back in -73 (100cc two-stroke). Amazing that I have not heard of the Dual Carburettor-system on the XT600. That´s the dark side of living in the countryside.
Yamaha has always been known for very interesting technical solutions.

Once more sorry, I believe you now.

PF
Similar system was fitted to some uk fords using the webber carb ( Cortina for one ). There isn't much new, things go in cycles. Another way to get 80mpg is buy a new enfield, or double that and buy a diesel bike
see here http://www.dieselbike.net/commercialproduction.htm
Reply With Quote
  #7  
Old 26 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Jan 2001
Location: Stockholm
Posts: 651
No worries
Patrick. I just sometimes get fed up by unfounded opinions that provide the risk of confusing everybody.

Auke
__________________
Auke
http://aukemarieke.blogspot.com
Reply With Quote
  #8  
Old 26 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Apr 2005
Location: Oxford UK
Posts: 2,116
I know its not a Yamaha but my 87 XR600 Honda has twin carbs arranged to come in sequentially.
Looking back over my records for the atlantic route (scribbled on a map!) I was getting 95mpg (10.6 litres for 227 miles), 72mpg (9.75L over 155 miles) and 73 mpg over 3 refueling stops.
The first one was so amazing I even took a pic of the pump readout. OK I wasn't trying to break any speed records but cruising between 50 - 60 mph on empty flat roads
Reply With Quote
  #9  
Old 26 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Sep 2006
Location: Edinburgh
Posts: 106
So with BackofBeyond's experience to back up the theory this does seem to be something worth checking out. I'll use Auke's info to see if I can feel the second carb kicking in, I'm riding to Aberdeen tonight so I'll need something to keep me entertained on the motorway!
Reply With Quote
  #10  
Old 26 Jan 2007
Registered Users
New on the HUBB
  
Join Date: Dec 2006
Location: Waiuku New Zealand
Posts: 18
The secondary carb on my XT600E starts to open when the primary slide is only 5mm up in it's travel though this is adjustable. When the slide is at 5mm and the secondary carb butterfly is still closed I would estimate that the speed and revs in top would be down around the "ruin 5th gear" portion of the rev range. I don't think you'd be doing much more than 50-60km in top. Under normal use I get 16 - 17km/l and a range before reserve of 200km at around 100-120km/h.
Just my 0.02c

Andy.
Last edited by YAMXT; 26 Jan 2007 at 20:54.
Reply With Quote
  #11  
Old 28 Jan 2007
Contributing Member
Veteran HUBBer
  
Join Date: Mar 2002
Location: watford england
Posts: 174
Try 70 mpg..
In a 24,000 mile trans americas trip on two TT600RE's ( same carb etc) we averaged 20kpl (57 mpg) but the best was 24kpl. That was fully loaded with ally panniers etc. Cruising at approx 100kph.
Reply With Quote
  #12  
Old 28 Jan 2007
Grant Johnson's Avatar
HU Founder
Veteran HUBBer
  
Join Date: Dec 1997
Location: BC Canada
Posts: 7,304
Imperial - 5 liter approx - gallons or US gallons - 4 liters approx?
__________________
Grant Johnson
Seek, and ye shall find.
------------------------
Inspiring, Informing and Connecting travellers since 1997!
www.HorizonsUnlimited.com
Reply With Quote
  #13  
Old 29 Jan 2007
Contributing Member
Veteran HUBBer
  
Join Date: Jul 2002
Location: Sydney, NSW, Australia
Posts: 1,362
Google -

1 'imperial' gallon = 4.5461 litres

1 'US' gallon = 3.785 litres

Me? 1 gal = 4.5l, I don't track US gallons...
__________________
---
Regards Frank Warner
motorcycles BMW R80 G/S 1981, BMW K11LT 1993, BMW K75 G/S
Reply With Quote
  #14  
Old 29 Jan 2007
Registered Users
Veteran HUBBer
  
Join Date: Feb 2006
Posts: 1,598
If anyone is thinking of modifying their bkes for more Mpg, I can offer this little bit of information.
back in the early sixties I had a speed twin, in standard trim it did 55 to 65 mpg fast touring. The motor was then hotted up After the motor spent some time in a different frame I got the motor back less most of the hot bits. The only thing was it went from 7:1 to 9:1 compression. instead of the twin 1 1/8 fuel injectors it went back together with a single 7/8ths amal carb. and the original cams.
after that it went well, better than a standard speed twin, but the big thing was it returned around 100 mpg. It was fitted with a one tooth bigger gearbox sprocket and avon touring fairing. I 'think' small bore carbs can have a big effect on mpg. The higher compresion ratio being compensated for by starving the engine of fuel/air so the internal pressures were probably the same but using less fuel/air mixture.
Reply With Quote
  #15  
Old 14 Jul 2022
Registered Users
HUBB regular
  
Join Date: Nov 2007
Location: Ireland
Posts: 80
My 1VK has a little white line painted on throttle which will line up with another white line just before second carb operates. Previous owner did quite a lot of touring so presumably did this to get max MPG. Bike sounds different too when that second carb opens up. So the modification is two simple lines of white paint.
Reply With Quote
Reply
Page 1 of 2 1 2

« Previous Thread | Next Thread »

Currently Active Users Viewing This Thread: 1 (0 Registered Users and/or Members and 1 guests)
 

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
 

Announcements

Thinking about traveling? Not sure about the whole thing? Watch the HU Achievable Dream Video Trailers and then get ALL the information you need to get inspired and learn how to travel anywhere in the world!

Have YOU ever wondered who has ridden around the world? We did too - and now here's the list of Circumnavigators!
Check it out now, and add your information if we didn't find you.

Next HU Eventscalendar

ALL Dates subject to change.

2025 Confirmed Events:

  • Virginia: April 24-27 2025
  • Queensland is back! May 2-4 2025
  • Germany Summer: May 29-June 1 2025
  • CanWest: July 10-13 2025
  • Switzerland: Date TBC
  • Ecuador: Date TBC
  • Romania: Date TBC
  • Austria: Sept. 11-15
  • California: September 18-21
  • France: September 19-21 2025
  • Germany Autumn: Oct 30-Nov 2 2025

Add yourself to the Updates List for each event!

Questions about an event? Ask here

See all event details

 
World's most listened to Adventure Motorbike Show!
Check the RAW segments; Grant, your HU host is on every month!
Episodes below to listen to while you, err, pretend to do something or other...

Adventurous Bikers – We've got all your Hygiene & Protection needs SORTED! Powdered Hair & Body Wash, Moisturising Cream Insect Repellent, and Moisturising Cream Sunscreen SPF50. ESSENTIAL | CONVENIENT | FUNCTIONAL.

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

2020 Edition of Chris Scott's Adventure Motorcycling Handbook.

"Ultimate global guide for red-blooded bikers planning overseas exploration. Covers choice & preparation of best bike, shipping overseas, baggage design, riding techniques, travel health, visas, documentation, safety and useful addresses." Recommended. (Grant)



Ripcord Rescue Travel Insurance.

Ripcord Rescue Travel Insurance™ combines into a single integrated program the best evacuation and rescue with the premier travel insurance coverages designed for adventurers.

Led by special operations veterans, Stanford Medicine affiliated physicians, paramedics and other travel experts, Ripcord is perfect for adventure seekers, climbers, skiers, sports enthusiasts, hunters, international travelers, humanitarian efforts, expeditions and more.

Ripcord travel protection is now available for ALL nationalities, and travel is covered on motorcycles of all sizes!


 

What others say about HU...

"This site is the BIBLE for international bike travelers." Greg, Australia

"Thank you! The web site, The travels, The insight, The inspiration, Everything, just thanks." Colin, UK

"My friend and I are planning a trip from Singapore to England... We found (the HU) site invaluable as an aid to planning and have based a lot of our purchases (bikes, riding gear, etc.) on what we have learned from this site." Phil, Australia

"I for one always had an adventurous spirit, but you and Susan lit the fire for my trip and I'll be forever grateful for what you two do to inspire others to just do it." Brent, USA

"Your website is a mecca of valuable information and the (video) series is informative, entertaining, and inspiring!" Jennifer, Canada

"Your worldwide organisation and events are the Go To places to for all serious touring and aspiring touring bikers." Trevor, South Africa

"This is the answer to all my questions." Haydn, Australia

"Keep going the excellent work you are doing for Horizons Unlimited - I love it!" Thomas, Germany

Lots more comments here!



Five books by Graham Field!

Diaries of a compulsive traveller
by Graham Field
Book, eBook, Audiobook

"A compelling, honest, inspiring and entertaining writing style with a built-in feel-good factor" Get them NOW from the authors' website and Amazon.com, Amazon.ca, Amazon.co.uk.



Back Road Map Books and Backroad GPS Maps for all of Canada - a must have!

Your ad could be here, on EVERY page of the HUBB, or the whole website, or as many as you like!

New to Horizons Unlimited?

New to motorcycle travelling? New to the HU site? Confused? Too many options? It's really very simple - just 4 easy steps!

Horizons Unlimited was founded in 1997 by Grant and Susan Johnson following their journey around the world on a BMW R80G/S.

Susan and Grant Johnson Read more about Grant & Susan's story

Membership - help keep us going!

Horizons Unlimited is not a big multi-national company, just two people who love motorcycle travel and have grown what started as a hobby in 1997 into a full time job (usually 8-10 hours per day and 7 days a week) and a labour of love. To keep it going and a roof over our heads, we run events all over the world with the help of volunteers; we sell inspirational and informative DVDs; we have a few selected advertisers; and we make a small amount from memberships.

You don't have to be a Member to come to an HU meeting, access the website, or ask questions on the HUBB. What you get for your membership contribution is our sincere gratitude, good karma and knowing that you're helping to keep the motorcycle travel dream alive. Contributing Members and Gold Members do get additional features on the HUBB. Here's a list of all the Member benefits on the HUBB.



All times are GMT +1. The time now is 07:58.

Contact Us - Horizons Unlimited Motorcycle Travellers Website - Archive - Privacy Statement - Top