gearing and tachometer on my 96 Cali

[philwarner]

When I bought the 96 the PO had said the speedometer read 15 MPH low because his PO had installed higher gearing to get better gas mileage, but I found the speedo to be wildly optimistic and the tachometer perhaps understating the RPM. I talked with him again today and this time he said his son had used his phone GPS to check the speedo and at an indicated 80 MPH it was actually going 60 MPH which is what I've experienced in the 250 miles I've ridden it so far.

Some previous comments from you guys were:

Most common is 8-33 or 7-33. Likely someone put in a 7-33.  They are a matched set. So if you ONLY got the 8 tooth pinion gear, and did not get the matching 33 tooth ring gear (basically, you need the entire rear drive), you might as well throw the 8 tooth gear away. If someone jammed a 7 tooth pinion into a box set up for an 8-33, it won't last very long, if that can even be done.  Factory is 8-33, many people prefer 7-33.
 
If you are doing (per a GPS or such) 71 MPH at 4000 RPM, in fifth, it is a 7/33. If you are about 80 MPH at 4000 RPM, it is 8/33. The speedo drive gear in the transmission can be changed easily to adjust it. I believe you want a 9 tooth gear. Maybe. They are pricey for what they are.

So I am going an actual 60 MPH at 2500 RPM in 5th gear and I have to assume the PO to the PO had it changed to 7/33 from 8/33 (the old pinion he gave me is an 8 tooth).  The PO also said the shop that put the new tires on also replaced the ring gear which he called the "flange".  He gave me the names of several shops that had worked on it for him so I'll try to verify whether or not the ring gear was renewed with the tire change and whether it matches the apparent 7 tooth pinion.

My two concerns are whether the tachometer is accurate (does 2500 RPM at 60 in 5th sound right?) and what causes the banshee squeal I hear when backing off in gear.  The squeal is pretty loud and I can't tell for sure what part of the bike it is coming from - gear box or final drive.  I have checked all the fluids and they are at the proper levels.

Any suggestions on how to check the tachometer accuracy?  It does not go to zero with the engine off and I think the highest I've wound it so far is 5000 RPM and it sounded pretty wound up then.  I've tried to keep it above an indicated 2000 RPM and going up from 2500 to 4000 in 5th I am sure would add more than another 10 MPH to the road speed.

[Tom H]

2500 RPM should be about 60-65 MPH, I'm thinking a bit closer to 65. 3000 S/B about 70, 3500 S/B about 75 and 4000 S/B about 80.

Not sure how you measured the speed. I have an app on my smart phone that is a GPS speedometer. If you have the phone, grab the app.

Tom

[philwarner]

2500 RPM should be about 60-65 MPH, I'm thinking a bit closer to 65. 3000 S/B about 70, 3500 S/B about 75 and 4000 S/B about 80.  Not sure how you measured the speed. I have an app on my smart phone that is a GPS speedometer. If you have the phone, grab the app.   Tom

Thanks, Tom,

  So 2500 RPM should be 60-65 MPH.  That's about what I think I am seeing.  I don't cell phone and didn't do the GPS check myself - that info was from the PO who said his son used an app on his phone to determine that 80 on the speedo was 60 on the ground.  I have a Magellan GPS on my Triumph America and will probably try switching it to the Guzzi temporarily to check it myself.  One thing is still confusing - if 2500 RPM is 60 Mph in 5th that's 41.7 RPM per 1 MPH and if the ratio remains constant then 4000/41.7 = 96 MPH.  What am I missing here?

  Someone said a 9 tooth speedometer cable gear might be needed?  I looked through the downloaded repair manual and didn't find anything on the speedo cable but I assume it is the vertical cable on the top of the gear case at the back; does the speedo gear just pull up out of the case?  If so I'll check the number of teeth.

[Moparnut72]

You could get a Tinytach to check your tachometer.  They are quite inexpensive.  There are some knockoffs on fleabay for less than $20. They are pretty accurate.  I use one on my race boat.
kk

[Wayne Orwig]

Yes, the speedometer drive gear just pulls up out of the case.
BUT, there MIGHT be a hardened washer on the bottom side. If that drops off into the transmission, it might be a disaster. Be careful.

Stock gearing (8/33) is 80MPH at about 4000 RPM. That is 40MPH at 2000 RPM. Or 50MPH at 2500RPM.

[Tom H]

I stand corrected. Wayne is right. With the tire I have 2500 rpm is 50 mph. 75mph was about 3600rpm.

Tom

[larrys]

Stock gearing (8/33) is 80MPH at about 4000 RPM. That is 40MPH at 2000 RPM. Or 50MPH at 2500RPM.

Yup. That's about what mine does. I don't think that I would want taller gears. I usually don't shift into 5th til 45-50 mph.
Larry

[philwarner]

Yes, the speedometer drive gear just pulls up out of the case.
BUT, there MIGHT be a hardened washer on the bottom side. If that drops off into the transmission, it might be a disaster. Be careful. Stock gearing (8/33) is 80MPH at about 4000 RPM. That is 40MPH at 2000 RPM. Or 50MPH at 2500RPM.

OK, now I am concerned about pulling the speedo gear but I at least know what to look for; too bad I can't turn the bike up-side-down to take it out.

If 2000 RPM equals 40 MPH with 8/33 gearing then I assume if my bike has 7/33 gearing it will be more like 35 MPH at 2000 RPM, but it definitely seemed faster than that so I don't know what the gearing is.  Guess it is time to hook up my Magellan and go for a ride tomorrow if the rain holds off.

[Tom H]

The speedos are notoriously inaccurate.  Use your GPS and get a correct reading.

It might turn out that you can live with it being off a bit. My EV with the tire I have at this point of wear, is about 2 mph off. My Ambo is 5mph off when I'm showing 7pmph, it's really 65.

Tom

[Diploman]

Better yet, fit a GPS speedo which is dead-on accurate and requires no cables, sheaths or drive gears.  Ultra-simple installation, and features a number of other useful functions.  Bezel can be sealed on request.  Speedhut also makes tachos.


https://www.speedhut.com/gauge/GR338-GPS-01/1/GPS-Speedometer-120mph

[philwarner]

Better yet, fit a GPS speedo which is dead-on accurate and requires no cables, sheaths or drive gears.  Ultra-simple installation, and features a number of other useful functions.  Bezel can be sealed on request.  Speedhut also makes tachos.

https://www.speedhut.com/gauge/GR338-GPS-01/1/GPS-Speedometer-120mph

I looked at those on eBay and if they made one that is 4-1/8" in diameter I'd probably go for it, especially since the trip reset knob is missing from mine and I can't reset it at fill ups.  Unfortunately everything I've seen is 85 mm or about 3-3/8".

[philwarner]

I ran across this you tube video and his tachometer does not go to zero either

https://www.youtube.com/watch?v=siIbQXQvnRU

Is that universal or just our particular 96 models?

[Wayne Orwig]

I ran across this you tube video and his tachometer does not go to zero either
https://www.youtube.com/watch?v=siIbQXQvnRU
Is that universal or just ourt particular 96 models?

I believe that is a normal thing for that tach.