MPG and low fuel light

[larrys]

My Cal takes 3.7-3.8 gallons if I fill it soon after the low fuel light comes on and stays on. Usually at around 140-150 miles. My odometer reset knob broke off in the gauge so there's no option for replacement.
Larry

[n3303j]

You can use your GPS to check both speedometer and odometer.

Assuming nothing is broken the odometer and trip meter are fixed ratios that are counting driveshaft revolutions. Either it is correct or it isn't. It can be adjusted by changing the cable drive worm at the rear of the transmission. Changing drive tire diameters will change odometer readings. Final drive gearing change will also change odometer readings.

Speedometer  (assuming all is mechanically correct and needle shaft is not binding) is an eddy drive that pits the eddy drive applied torque against a hairspring (think old alarm clock). Two type of errors here. If the error is a simple number of miles high or low at any speed the fix is to pull the indicator needle and relocate it by the error. If the error is progressive (like +10% of any reading) then the solution lies in freeing the outward end of the hairspring and re-anchoring it in a way to increase its tension by the equivalent percentage.

......or you could just get an electronic unit and eliminate the whole cable drive and all the related problems.

[philwarner]

You can use your GPS to check both speedometer and odometer.

Assuming nothing is broken the odometer and trip meter are fixed ratios that are counting driveshaft revolutions. Either it is correct or it isn't. It can be adjusted by changing the cable drive worm at the rear of the transmission. Changing drive tire diameters will change odometer readings. Final drive gearing change will also change odometer readings.

Speedometer  (assuming all is mechanically correct and needle shaft is not binding) is an eddy drive that pits the eddy drive applied torque against a hairspring (think old alarm clock). Two type of errors here. If the error is a simple number of miles high or low at any speed the fix is to pull the indicator needle and relocate it by the error. If the error is progressive (like +10% of any reading) then the solution lies in freeing the outward end of the hairspring and re-anchoring it in a way to increase its tension by the equivalent percentage.

......or you could just get an electronic unit and eliminate the whole cable drive and all the related problems.

My cali's GPS is a vintage tomtom (2008 maybe?) that can't read time from the newer satellite language, so it can't display current time or ETAs, but it can display speed so I'll check to see if it can track mileage.  (I can set the current time manually and it will keep accurate time as long as it does not get a satellite signal which causes it to revert to displaying 12:00 noon continuously)  If it can display accumulated miles that would be easier than counting mile markers on the freeway.  I need to do one or the other to find out if the mileage is off by the same 1.33 as the Speedometer and if so look for a new worm drive that doesn't cost as much as the bike itself.

The tachometer is also suspect.  It seldom gets above 3000 RPM and I think it reads around 2500 at 60 MPH in 5th gear; I need to check that again to be sure.  This bike has been an interesting learning experience and I find myself riding it more often than my 04 Triumph America these warming days.

[n3303j]

Shouldn't be in 5th gear at 60 MPH. Save 5th for the other side of 75. Don't be afraid to spin that engine. Cruise 3,500 to 4,500 RPM and you'll be in the sweet spot.

Phone have a GPS app with a suitable odometer?

[philwarner]

Shouldn't be in 5th gear at 60 MPH. Save 5th for the other side of 75. Don't be afraid to spin that engine. Cruise 3,500 to 4,500 RPM and you'll be in the sweet spot.

Phone have a GPS app with a suitable odometer?

Got it.  I've learned it does not like to pull below 2000, but not being sure of the accuracy I didn't want to over rev it.  I don't cell phone; the wife does, but she doesn't ride with me.  Still looking up old tomtom info to find if it can track accumulated miles but haven't found it yet.  I think it will do miles to destination if you have one entered, but have not yet found an odometer function.

Too bad for the fellow whose reset knob broke off inside;  fortunately mine was just missing and the new one went right on after a little probing around to find the end of the shaft.

[MMRanch]

philwarner

MY Car does better than your bike ? ???     The V-7 gets 50 to 55 , and the V-9 gets close to 60 mpg.   Remember bike are suppose to be Cheep , Fun , Transportation , when they quit being fun and cheep , it time to replace them !   

[rocker59]

As an update,  I  got the trip reset knob from MG Cycle and it fit nicely so I can now zero it when I fill up.  I just refilled the tank today after 106 miles and it took 2.6 gallons US for around 41 MPG US.   I also have a tomtom GPS mounted and 80 MPH on the speedometer is 60 MPH on the GPS so the speedometer is reading 1.33 X too high so perhaps the Odometer is reading 1.33 to high also?  That would make the MPG more like 54 MPG.

10% off is normal for a speedo.  Yours is outside that range.  I would look at rear tire size, speedo gear on the transmission, and possibly rear gear ratio.  One, two, or three of those items could be non-stock on a bike nearly 20 years old, causing the speedo error.

Of course, the speedo could be off just because it's broken.

If you have a GPS, you can measure distance against your odometer.  You can also measure distance with the mile markers on I-49.  Take it for another ride and compare what the GPS and the mile markers say vs. the odometer.  If the odometer is off, then you can bet that rear tire size, speedo transmission gear, or rear gearing have been changed at some point.

[philwarner]

10% off is normal for a speedo.  Yours is outside that range.  I would look at rear tire size, speedo gear on the transmission, and possibly rear gear ratio.  One, two, or three of those items could be non-stock on a bike nearly 20 years old, causing the speedo error.

Of course, the speedo could be off just because it's broken.

If you have a GPS, you can measure distance against your odometer.  You can also measure distance with the mile markers on I-49.  Take it for another ride and compare what the GPS and the mile markers say vs. the odometer.  If the odometer is off, then you can bet that rear tire size, speedo transmission gear, or rear gearing have been changed at some point.

(I've edited my text below to correct some backwards thinking at the time)

The fellow who sold me the bike said the final drive gear ratio had been changed by a PO to get better gas mileage, but he had it backwards when he said the speedometer would read low.  He gave me what he said was the original drive gear which has 8 teeth and 10 splines and is scribed with 71E and -0.20 on the end of the gear.  He also said he had the “flange” replaced when he had new tires put on, which I took to mean the driven gear in the rear hub. (no, it is not the driven gear - I assumed wrong) Since stock gearing reportedly was 7/33 (Wrong again, it was 8/33 stock for this bike) and the removed gear has 8 teeth I wonder if this bike was converted to Convert 9/34 gearing.  That would be about 1.25 times higher gearing than stock 7/33 and 60 MPH X 1.25 would be 75 MPH (wrong again, Convert gearing would make the speedo read lower not higher.  Again I was thinking backwards when I wrote this and my bike likely was changed to 7/33 gearing) and if there is a built-in 10% error in a stock speedometer, adding 10% would make it 82 MPH on the speedo which is about what I am seeing.

Anyone know if a Convert speedo drive gear would fit my 96 Cali?  (I've since read that my speedo pinion is probably a 10 tooth and I need an 11 tooth pinion gear if I have 7/33 final gearing)

To MMRanch,  I hope that the low gas mileage I calculated at the last fill up was an error because if my trip odometer is reading too high it would be even worse.

[n3303j]

Do all your corrections to get a correct odometer reading. Go ride some highway mile markers (10 or more consecutive) and calculate the error. Then you have a valid reference point to figure error and gearing changes to correct same.

[rocker59]

The fellow who sold me the bike said the final drive gear ratio had been changed by a PO to get better gas mileage, but he had it backwards when he said the speedometer would read low.  He gave me what he said was the original drive gear which has 8 teeth and 10 splines and is scribed with 71E and -0.20 on the end of the gear.  He also said he had the “flange” replaced when he had new tires put on, which I took to mean the driven gear in the rear hub.  Since stock gearing reportedly was 7/33 and the removed gear has 8 teeth I wonder if this bike was converted to Convert 9/34 gearing.  That would be about 1.25 times higher gearing than stock 7/33 and 60 MPH X 1.25 would be 75 MPH and if there is a built-in 10% error in a stock speedometer, adding 10% would make it 82 MPH on the speedo which is about what I am seeing.

Anyone know if a Convert speedo drive gear would fit my 96 Cali?

To MMRanch,  I hope that the low gas mileage I calculated at the last fill up was an error because if my trip odometer is reading too high it would be even worse.

I think you're onto it, now!

[Tom H]

Ask your wife if she has an old cell phone that she doesn't care about that has GPS. You don't need cell service for the GPS to work.

My EVT, the low fuel comes on anywhere from about 115-130 miles and takes about 3-3.25 US gallons. 70mph is about 3500rpm.

Tom

[philwarner]

Ask your wife if she has an old cell phone that she doesn't care about that has GPS. You don't need cell service for the GPS to work.

My EVT, the low fuel comes on anywhere from about 115-130 miles and takes about 3-3.25 US gallons. 70mph is about 3500rpm.

Tom

I have her old cell phone, a Samsung Galaxy S4, and I can connect it to our home wireless network and use it to make calls on the Magic-Jack we use as a home phone, but I didn't know it could do GPS things without a contract with a phone company, but I downloaded an app called "GPS Speedometer, Odometer" and it seems to work, at least while in range of the wi-fi.  If the rain lets up, I'll check it around the neighborhood.  I think I saw a GPS app for a small fee that is without ads so I might check it out too.  Thanks for the suggestion.

Rain is predicted for the next several days, but after that I'll try this app on the bike and also check the trip Odometer against some mile markers.

[Tom H]

DigiHUD works fairly well for Android and it's free for the basic version.

Tom

[philwarner]

DigiHUD works fairly well for Android and it's free for the basic version.

Tom

Thanks, Tom,

  Got the App and it looks good and no ads.  I can hardly wait for the weather to clear now.

[MMRanch]

philwarner , I didn't know we could change the gear ratio on a Guzzi .  I'd like to have a taller gear on my V-7II , it don't have so much extra power but that stuff of being done with 1st gear in the middle of most intersections seems kinda silly.

A little more relaxed RPM at Super Slab Speed would be good too !   

I did find the speedometer error went away when I went from an 130/80 to a 130/90 rear tire.  Yea its right with the Garmin with-in .5 mph now. 

[rocker59]

philwarner , I didn't know we could change the gear ratio on a Guzzi .  I'd like to have a taller gear on my V-7II , it don't have so much extra power but that stuff of being done with 1st gear in the middle of most intersections seems kinda silly.

A little more relaxed RPM at Super Slab Speed would be good too !   

I did find the speedometer error went away when I went from an 130/80 to a 130/90 rear tire.  Yea its right with the Garmin with-in .5 mph now.

Several ratios came on big blocks.

You're SOL with the small block.

[philwarner]

I think you're onto it, now!

BTW, the rear tire is the stock size 140/80-17 M/C 69V; it is a Continental conti GO!

[philwarner]

Update:

   On the road today the Guzzi's trip Odometer was averaging  1.174 miles higher than my old Galaxy S4 cell phone running DigiHUD speed/mileage app which showed 25.60 miles traveled when the Guzzi trip odo turned over to 30.  So my gearing is 1.172 higher than whatever the odometer gear is designed for and that falls half way between what I'd expect to see if it had 9/34 gearing VS 7/33 (1.248) or 9/34 VS 8/33 (1.092).  Rather confusing if I did the math right.

   The bad news is that it makes the last 41 MPG figure I calculated at fill up even worse if I am not traveling as many miles as I thought between fill-ups.

[Wayne Orwig]

   On the road today the Guzzi's trip Odometer was averaging  1.174 miles higher than my old Galaxy S4 cell phone running DigiHUD speed/mileage app which showed 25.60 miles traveled when the Guzzi trip odo turned over to 30.  So my gearing is 1.172 higher than whatever the odometer gear is designed for and that falls half way between what I'd expect to see if it had 9/34 gearing VS 7/33 (1.248) or 9/34 VS 8/33 (1.092).  Rather confusing if I did the math right.

No such thing as 9/34 as far as I know.

Stock is 8/33. Typically installed is 7/33. A difference of 1.143 (probably your 1.174).
I have put an oddball 8/35 in mine. I did not care for the lower fuel economy of the 7/33. And the 8/33 wasn't real good for towing a trailer like I did.

[philwarner]

No such thing as 9/34 as far as I know.

Stock is 8/33. Typically installed is 7/33. A difference of 1.143 (probably your 1.174).
I have put an oddball 8/35 in mine. I did not care for the lower fuel economy of the 7/33. And the 8/33 wasn't real good for towing a trailer like I did.

I didn't know there was an 8/35.  I got an 8 tooth drive gear with the bike that the PO said was replaced with different gearing by his PO.  He also said the "flange" was replaced when he had new tires put on.  The manuals say the drive and driven gears are always sold in match pairs so I am not sure what mischief may have been done.  I have the names of two local shops the PO said worked on the bike so I need to see if anyone can tell me what gearing is in it.  Being new to Guzzis I don't know if all the whines and noises are normal Guzzi sounds or something to be concerned about.

[Wayne Orwig]

I didn't know there was an 8/35.  I got an 8 tooth drive gear with the bike that the PO said was replaced with different gearing by his PO.  He also said the "flange" was replaced when he had new tires put on.  The manuals say the drive and driven gears are always sold in match pairs so I am not sure what mischief may have been done.  I have the names of two local shops the PO said worked on the bike so I need to see if anyone can tell me what gearing is in it.  Being new to Guzzis I don't know if all the whines and noises are normal Guzzi sounds or something to be concerned about.

Do you mean a large pinion gear, or a tiny speedo gear. I know the tiny speedo drive gear comes in a 9, 10 or 11 tooth.
The ring and pinion are a matched set. Often with a number on it that is matched to the other.
Yes, the gears are normally 8/33, often people install 7/33. There are a few odd ones like the 8/35.

http://www.mgcycle.com/index.php?main_page=advanced_search_result&search_in_descripti on=1&zenid=5031ea1d035f1ea1bd748dddb3e0beca&keyword=8%2F35

I wonder it the flange was the 'cush drive' flange in the rear wheel. Those can wear out.

[philwarner]

No such thing as 9/34 as far as I know.

Stock is 8/33. Typically installed is 7/33. A difference of 1.143 (probably your 1.174).
I have put an oddball 8/35 in mine. I did not care for the lower fuel economy of the 7/33. And the 8/33 wasn't real good for towing a trailer like I did.

Got to go back and recheck, but I wrote down that at 60 mph actual in 5th gear the ENM read 3600 RPM

Then I found this:

https://archive.guzzitech.com/JB-FinalGearSwap.html

for changing 8/33 to 7/33 you need to change the 5/10 speedo gear set out for a 5/11 set (14762510 www.mgcycle.com).  the 5/11 speedo gear set is really much better suited to an 8/37 rear drive. Going from the 8:33 to the 7:33 is a 12.5% change. The speedo gears went from a 5:10 to a 5:11. This is only 9.1% change in speedo cable RPM, thus there will be a about a 3.8% or so error in speedo reading - that is, it will read 60 MPH when you are doing around 57. Not too bad. If one went from an 8:33 to an 8:37; that is only a 10.8% change in gearing, which is closer to the change in the speedo gearing.

33/8 Gearing (Stock)
RPM at 60 mph (want to keep this to a sensible rpm): 3013 (pretty low, even for this low rpm engine)
HP @ 60 mph (Horsepower available in top gear at 60 mph - without a downshift): 32 (not bad)
Top speed: 124,  RPM at top speed 6227  (measure of how ideally the bike is geared for top speed specifically)
RPM at 80 MPH 4018 (ridiculously low for this engine)
Crawl speed (Lowest speed in 1st gear without engine discomfort – let’s you avoid using clutch slipping): 16

33/7 Gearing 
THIS is the best option I think, for someone who rarely goes really fast on the highway.
RPM at 60 mph: 3444 (This is getting towards respectable!)
HP @ 60 mph: 36 (12.5% better than stock, and comparable to other big bore bikes)
Quarter Mile Sec: 12.79 (This is a fabulous 0.42 sec faster than stock. That’s HUGE)
Top speed: 119 (loss of 5 mph)
Avg HP avail 0 – 100 mph: 53
RPM at 80 MPH: 4591 (still ridiculously low for your needs, but acceptable)
Crawl speed: 14 (THIS is GOOD!)
HP available at different speeds in top gear: Now 54 vs 43 hp at 80 mph – 26% better than stock!

So with a 7/33 gear set, 60 MPH should be 3444 RPM ?  And I was seeing 3600 ?  Got to recheck, but I may have a 7/33 then which would make more sense (ignoring the PO's statement that the gearing had been changed to get better gas mileage).

[philwarner]

Do you mean a large pinion gear, or a tiny speedo gear. I know the tiny speedo drive gear comes in a 9, 10 or 11 tooth.
The ring and pinion are a matched set. Often with a number on it that is matched to the other.
Yes, the gears are normally 8/33, often people install 7/33. There are a few odd ones like the 8/35.

http://www.mgcycle.com/index.php?main_page=advanced_search_result&search_in_descripti on=1&zenid=5031ea1d035f1ea1bd748dddb3e0beca&keyword=8%2F35

I wonder it the flange was the 'cush drive' flange in the rear wheel. Those can wear out.

Pinion gear.  It had  71E and -0.20 scribed on the end of the gear. 

[Wayne Orwig]

So with a 7/33 gear set, 60 MPH should be 3444 RPM ?  And I was seeing 3600 ?  Got to recheck, but I may have a 7/33 then which would make more sense (ignoring the PO's statement that the gearing had been changed to get better gas mileage).

Yes, if the gearing was changed, it is 99% likely to be 7/33 from the stock 8/33. Easy to pull the rear drive pinion and look.
Yes, people oddly claim the 7/33 gears gets better fuel economy. Well, if that were true, just stay in fourth gear, DUH!

The 7/33 does of course give better torque for launching from a stop, and may give a bit better gear ratios in some situations. But I clearly noticed a slight drop in fuel economy. Yes, I emptied out the 4.7 gallon tank in under 100 actual miles once.

[philwarner]

Yes, if the gearing was changed, it is 99% likely to be 7/33 from the stock 8/33. Easy to pull the rear drive pinion and look.
Yes, people oddly claim the 7/33 gears gets better fuel economy. Well, if that were true, just stay in fourth gear, DUH!

The 7/33 does of course give better torque for launching from a stop, and may give a bit better gear ratios in some situations. But I clearly noticed a slight drop in fuel economy. Yes, I emptied out the 4.7 gallon tank in under 100 actual miles once.

Wow! 21 MPG?  That make my calculated 41 sound not quite so bad, but it was probably more like 35 MPG now that I know the odometer is reading 1.172 high.  My Triumph gets 45 to 50 over the same roads that Guzzi traversed.  Good thing I put a new low fuel switch on the Guzzi.

 I see a new 5/11 speedo gear set on eBay for around $40.  I am guessing you can't just swap the speedo pinion without changing the ring gear; is changing the ring gear a big deal?  I did read about having to be careful to not drop the bottom washer on the pinion into the trans.

[Wayne Orwig]

Wow! 21 MPG?  That make my calculated 41 sound not quite so bad, but it was probably more like 35 MPG now that I know the odometer is reading 1.172 high.  My Triumph gets 45 to 50 over the same roads that Guzzi traversed.  Good thing I put a new low fuel switch on the Guzzi.

 I see a new 5/11 speedo gear set on eBay for around $40.  I am guessing you can't just swap the speedo pinion without changing the ring gear; is changing the ring gear a big deal?  I did read about having to be careful to not drop the bottom washer on the pinion into the trans.

The speedo gear is a worm drive, if that matters.

I have changed the output gear as you are doing, and not changed the internal worm gear. I'm not sure they are matched.

[philwarner]

The speedo gear is a worm drive, if that matters.

I have changed the output gear as you are doing, and not changed the internal worm gear. I'm not sure they are matched.

How about it folks?  Can I just change the speedo pinion gear without changing the worm gear?