Poor Fuel Economy, Even After New Emulsion Tubes

[Naur]

I have just bent the clip slightly, and now the fuel levels reach something like 7,4-7,6 or close to that. So I'll start it up, set the idle, and mess a little with the airmix screw. 


I changed the float valves in connection with the rebuild earlier in the spring, yes. 

I'll post back when I have done the above. 

Thanks for your replies! 

Christ this work is hot in the sun, 28 degrees in Copenhagen.. Guess the test trip will be going to a beach

[Naur]

Okay, 

So now it is better, it pulls harder and feels better. 

However, I still feel hesitation when I give 50% throttle and above that. 

When I bought the carb rebuild kit in the spring, I could only get one where the main jet is a #142.5 and as far as I can see in Haynes, it needs to be a 140 for my model ('91 3VD). 

So I think I will swap for a 140 and see what happens.

[Victor]

Where do you guys buy the factory pro kit from? Directly from factory pro? I think that the shipping cost is ridiculously high (48 dollar)... 

[bjorge]

Where do you guys buy the factory pro kit from? Directly from factory pro? I think that the shipping cost is ridiculously high (48 dollar)... 

 

I only get $14 shipping fee added in their webstore - also for Scandinavia. How did you get $48 ?

[Victor]

 

I only get $14 shipping fee added in their webstore - also for Scandinavia. How did you get $48 ?

$14 = Domestic USA $48 International shipping. ?? $14 thats just for USA right?

[bjorge]

$14 = Domestic USA $48 International shipping. ?? $14 thats just for USA right?

I'm sorry, you're right. F%$#@&% 48 dollars! Must be said, though, that you'll never need another set..... I bought 2 sets 50000kms ago and the first set still show no sign of wear.

[Victor]

Thats probably true Björge! When the winter comes and i put away the bike i think its time for a kit and new seals from litetek. 

[Phracker]

I have a 92 3VD as well. Are you running stock pipes? I have #142.5 mains installed and have no issues on the top end, but do run an aftermarket pipe.

 

You could reuse your old #140's after a quick cleaning. It's really just the needle and emulsion tubes that wear out.

 

Top end issues = Main jet

Midrange          = Needle clip position

Low end           = Float height

 

Factory pro is expensive, but I don't regret spending the cash on it. Getting 48mpg-52mpg pending on the day and how I ride.

[TDMberlin]

Hello All,

 

I have a new to me 3VD and it was in need of some care.


So Far:

Valve Clearances set

Oil, Oil Filter, Air Filter and Water replaced

New Discs and R1 Calipers



Carbs Stripped and Ultra sound cleaned

New Factory Pro Emulsion Tubes and needles (3 clip)

137.5 Main

Stock Pilot jet

2 Turns on the mixture screw

Fuel Level/Float as prescribed by FP

New Choke plungers, one was missing a tip.

Carbs Balanced

Electric fuel Pump



GPR Exhaust



When i turn on the ignition i hear the Fuel Pump clicking till the float bowls are full, then it stops.

Throttle response is good throughout the rev range.

The bike starts Perfectly with choke and it can be pushed in fully imediately.

If the outside temperature is over 5 deg it will start without choke and idle. Choke cable has plenty of slack.



Fuel Economy is terrlble.



16 Litres for 200km which is 30mpg. This is mixed riding at least half around town.



I like the bike but the fuel economy is worse than my Fireblade when on Track!!!



Any ideas of what is making it so thirsty?



Thanks for any help

 

Chris

[Snowbird]

Is the leccy fuel pump over pressuring? You say it's clicking so must have been changed as 3VD should have a vacuum pump as standard so depends on which leccy pump has been used.

[bjorge]

Is the leccy fuel pump over pressuring? You say it's clicking so must have been changed as 3VD should have a vacuum pump as standard so depends on which leccy pump has been used.

I tried an electrical fuel pump on my original 3VD carbs and never made it run prperly. Gave up on them and got myself a pair of Mk2a carbs - sorted!

[fixitsan]

If the outside temperature is over 5 deg it will start without choke and idle. Choke cable has plenty of slack.

 

 

I would take that as a sign of running pretty rich, or 'KTM rich'

[dapleb]

Yup sounds rich if no choke required. Whenever the FP needles are fitted there seem to be issues with mk1. Have you got OEM needles in good condition ewe can try wid FP toobs?

This post was last modified: 30-04-2025, 07:59 PM by dapleb.

[TDMberlin]

Thanks for all the responses.



I ditched the Vacum operated fuel pump as it wasn't original and the PO said it was from a Go-Kart. On the Highway at .... 80-100mph the bike would porpoise, slow then accellerate as the float bowl emptied and filled. Basically the pump couldn't deliver enough fuel. I got the pump from AMAZON, advertised as for a R6 and 535 Vriago. 2-4PSI pump and as soon as the flat bowl is full it will turn off.



The Bike rides great and after faffing with the jetting (different mains and the needle clip position) it rides nicely. 



That it requires little or no choke to start it is probably the issue but i did replace the Choke plungers, perhaps where they seat is past its best???



Apart from the TPS, how are the 4TX carbs different?

 

Thanks Again



Chris

[bjorge]

You also need an air filter box. Can't remember if it's possible to modify the 3VD one, but I remember resorting to buy a 4tx one.

[MickC]

Mk2a carbs need a MK2a airbox...Look on EBay or somewhere for a pic of the airbox end of the carbs MK2a has something like a 10mm ring around the carb houseing about four carb jets, they will not fit into a 3vd or MK2 airbox.Mk2 carbs from memory will fit a 3vd airbox.

Bjorge was talking MK2a the term 4TX is a bit vague.

 

Mk2a carbs (with diaphram pump) on my 3VD gives more poke than MK2 carbs which in turn gives more poke than 3VD carbs.

This post was last modified: 07-05-2025, 12:48 PM by MickC.

[bjorge]

What doesn't an old man forget in just 4 years....😂

[TDMberlin]

Have found a set of what i believe to be MK2a Carbs, on their way to me for 50 Euro. Airbox next, ill do some Yamaha parts number comparing to see what go where.



As a side note, the Original "nappie" style exhaust had a slight flat spot in the rev range at 3.5K rpm. Just enough to make anything loose to buzz. With the single GPR Exhaust - which cut a TON of weight together with the center stand delete - the buzz has moved up to 4.5K rpm. Would love to be able to tune this out, literally or figuratively. Or both.



Side note two, while i have your attention anyway. Fork Brace? Transformed my old V50 Monza into a lovely bike to ride. Does the TDM benefit from one? Just not feeling the love from the front end when going a little quicker.

[bjorge]

To enhance the forks you need a pair of RaceTech gold valves (been there, done that) or perhaps the cheaper yss ones (no experience). It profoundly transforms the feel.

Just be prepared for an urge to sort the rear shock as the contrast front/rear will be striking...

[curlylegend]

I agree, Race Tech Gold Valves will transform your forks. So much so that I eventually splashed out on a YSS rear shock....