40 replies to this topic

[JA83]

Hi guys!

The ones of you that get 60+ mpg on your bikes...what's your setup?
Like exhaust, airfilter, jetting, float height and so on?
I'm getting like 30 mpg on my bike. Checked brakes for drag, chain slack and so on🙄

[Favs]

Mk1 gurus will be along just now, but I suspect they're gonna say Emulsion Tubes first

[dapleb]

Ewww 30mpg ...emulsion toobs. (☉｡☉)!

Are these UK or Merkin gallons? Either way summat not right.

[JA83]

I think that the UK-version is 35 mpg, it's 0,8 l/10km.
I've does the tubes twice, but might be a production error on the ones I have now.

Edited by JA83, 03 April 2021 - 06:41 pm.

[dapleb]

What toobs did you install? Any improvement straight after new toobs?

I don't think I have got 60+ MPG but definitely never 35mpg either. That's too extreme to be exhaust etc.

[Studley Ramrod]

Exhaust, air filter, jets, etc won't make that much difference really.  Worn toobs, running on one pot (faulty coil or rain getting in can cause this) fuel leak and valve timing out will though.

When you calculate the mpg, are you filling the tank to the brim and then using the trip meter, then re-filling at a certain mileage ?

[fixitsan]

Choke mechanism ?

Just thinking of Boris ....

[Bjørge]

Choke mechanism ?
Just thinking of Boris ....

+1
I never saw this high consumption, but choke plungers saved me quite a bit.

[PICARD]

What about riding style, right hand control and burnouts? 30mpg is seriously high consumption.

[Pedro]

At 30mpg I would include looking for a leak somewhere. It only has to be a few drops ever mile but soon adds up. My '92 still does 50-55 mpg with an arrow can and dynojet.

[JA83]

Well, problem is that I don't really remember when the consumtion went up. After or before the rebuild, had the motor in 200 parts and the whole "bike" of the frame. This was last summer.

New pistion rings and valve steam seals = no oil consumtion though. Also I have a third gear again!

The milage is 130 000 km, 80 000ish miles.

 

I've the FP tubes in it, but they are like 5 years old probably. But they should wear out?

 

Heavy right hand for sure, but I don't get higher mpg even if I drive as a granny.

 

Regarding the choke, it might be the case. I changed the plungers a few years ago. But the mechanism isn't running completely smooth. Also if the timing can cause this that might be the case. The chain is really streched out, I'm almost one tooth off. So the timing might actually cause this?

 

This is my setup now.(Know the starter jet is waaaaay to big, gonna change it back)

The wildcard here is also the fuel height as I had a pain is the a** to get it correct, gave up and ended up riding it instead

Bike is running really well though, just the consumtion that is off. I smell fuel but it doesn't appear on the ground.

 

Supplier Part Size Comments

NRP carbs Pilot jets 42,5 Pilot screw at 2,5 turns

Wemoto Main Jet 142,5  

Wemoto Primary Main Jet(Starter) 142,5  

Factor Pro Emulsion tube PN: CRZ-EMU-100120k  

Factor Pro Needle 1175-90q-70r-45t_ti Third notch

Biltema Exhaust - Without DB killer

Wemoto Air filter - "OEM"

Biltema Fuel pump 120 l/h, 0,3 bar  

Malpassi Fuel regulator 0,1-0,5 bar FPR007, not sure what pressure I'm at -

Fuel height - Not sure, think I was aiming for 8 mm over the line

Edited by JA83, 04 April 2021 - 11:23 am.

[JA83]

And yeah, fill it up to the same level in the tank and use the trip meter.
Last time I check with Maps vs trip meter there was a difference of 4%.

[dapleb]

Wouldn't have thought FPS toobs would wear out in that time but if you did 100,000 miles in that 5years then maybe.

I have done 50,000 miles on FP toobs and no noticeable increase in consumption.

[fixitsan]

 

 The chain is really streched out, I'm almost one tooth off. So the timing might actually cause this?

I don't see that affecting fuel consumption much, because it doesn't affect carburation. The carb creates a 16:1 ratio (thereabouts) no matter how much or how little air flows through it (in a perfect carb), If the cam timing shifted due to a stretched chain, the effect would only be to change the valve's open/close timing windows away from the optimum position they're supposed to be at, and so any change to the timing away from optimum is likely to cause just a reduction in airflow, but no change to the actual mixture ratio created at the carb..

 

 

1 tooth out is going to be causing  enough degrees of late valve timing to make a new chain bring about a noticeable difference, not just for the change in valve timing, but if you have a cam position sensor in the cam cover then that is also generating late signals to challenge the ECU with, due to the late impulse coming from the cams  as they become increasingly retarded as the chain lengthens. So, the best potential performance is never going to be experienced under these conditions. Go with your gut and do the chain anyway !

Edited by fixitsan, 04 April 2021 - 11:06 pm.

[Medmonic]

About excess fuel consumption , i had that in one of my engines and found out that was a late timing in the engine , and i had a lot of pops and bangs in the exhaust and some flame retur in the carbs , in the end i found that engine was  out of timing by one tooth .

the main cause for that was my timing chaine out of specification ....

[fixitsan]

About excess fuel consumption , i had that in one of my engines and found out that was a late timing in the engine , and i had a lot of pops and bangs in the exhaust and some flame retur in the carbs , in the end i found that engine was  out of timing by one tooth .

the main cause for that was my timing chaine out of specification ....

 

Did the engine have fuel injection or did it run on carbs ? How much worse was the fuel consumption, was it down by over 30% ?

[JA83]

Actually, I got the same effects if I lean out the bike. Pops and backfire though the carbs. I might be running it really rich and the moment due to streached chain.

Maybe I'll just have to suck it up and dismantle it again 🙄

[Studley Ramrod]

Are those FP needles the stepped ones ?  If so it might be worth going back to stock needles.  iirc the FP needles are better suited to a modified engine.

[Medmonic]

 

Did the engine have fuel injection or did it run on carbs ? How much worse was the fuel consumption, was it down by over 30% ?

running on carbs and yes down by over 30% 

[fixitsan]

running on carbs and yes down by over 30% 

 

All I can assume about that is that it was running so damn poorly that you had to hold the throttle wide open even to go slowly !

 

I had a chain almost as stretched as that and while there was an improvement in engine smoothness after changing the chain, the fuel consumption did not massively improve afterwards.