• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

Are my bevel gears toast?

Shrek

Tuned and Synch'ed
Joined
Sep 16, 2015
Messages
96
Location
Australia
IMG 2137 IMG 2132 Hi All
On my last ride i noticed a high frequency driveline vibration through the pegs at around 4400 revs,all gears.
I pulled the swingarm to check the Uni,s and carrier bearing.
The carrier bearing seemed fine but the Uni,s fell out of the bearing.
Both bearing journals were 0.2(8 thow) undersize.
A quick glance at the bevel gears showed no signs of doom.

Stuck it back together and bingo(so i thought) the vibration dissapeared at 4400 revs but reappeared at 2400 revs,all gears?Head scratching.

Pulled the bevel box off again,washed the gears and found this.
Pitting around the top edge of the crown teeth and bottom concave side of the pinion teeth.

All bearings seem fine.No perceptable movement in the pinion bearings but a slight rattle when shaken?

These gears and all bearings were replaced 60,000 km,s ago.
Good oil with Moly used.

Do i need new gears already? I think i already know the answer.
Could a slight vibration,looseness off the uni diametre to carrier bearing cause this?
Has anybody else chewed through gears with this amount of k,s.
The first set only lasted 97,000 km.
Is this just been badly set up.

Please advise.
 
That pitting is why I don't recommend using moly. If exposed to moisture and heat it can form acids. No other manufacturer recommends using moly I believe for that reason. Also I have observed pitting on the inner side of the hub bearing surface from acid formation. A good synthetic gear lube is fine for the rear drive without moly. Yes I would recommend replacing the gears even though you could probably get many more miles from this set since it is already apart. Since the vibration is at the same RPM, I don't think it is related to the rear drive. I would check the gearbox input bearing for issues since that rotates at engine RPM. If your input and output gears haven't been replaced with steel cage bearings, this would be a time to do that.
 
Hey Shrek,

I agree with John on replacement. Many years ago I lost my rear drive on a ride 1,000 miles from home. It was a complicated, costly, and time consuming ordeal to get the Eldo back on the road. I was fortunate that it happened close to my Dad's place and I could use his garage and tools (and extend the visit).

Also, I would just like to add, shim the gears properly. If you are not familiar with that process, or don't have the tools, have it done by an experienced Guzzi person. That bit of cash flow will pay nice dividends for many years to come :cool: .

How's the weather down there? We're flooding here in San Jose Ca. The States.

Alex

BTW I strongly discourage showing off doing wheelies on an Eldorado.
 
Did you say the u-joint just fell out of the carrier bearing when you pulled it apart? If so, that's not OK.

The u-joint is supposed to be a press-fit into the inner race of the bearing. This loose condition usually shows up as a vibration felt through the right footpeg at low speeds when the drive shaft is unloaded, like when you're rolling through a small town with almost no throttle or coasting. It's the joint chattering in the loose inner race. You haven't said what model bike we're talking about but I can't think of any Tonti frames that this doesn't apply to. You'll need to replace the carrier bearing and the u-joint. Or, if the joint is still really good Moto International used to have a guy who would turn down the end and sleeve it back to proper diameter at lower cost than a new joint. i did that on my 850T.

I've mentioned this before, but I think it prudent to check the receiver for the bearing with a bore gauge while you've got it apart. I think Guzzi turned out an occasional lemon swingarm. The reciever on my T was .005" under the OD of the bearing in one direction, and .003 under in the other, so it was oval and squashing the bearing, and they ran so hot you couldn't hold a finger on the housing after a highway ride. The bearing gets hot, expands, and lets go of the joint. Then it wears. Took me three replacements to catch on to this. The second to last time, I replaced the joint and used loctite when pressing the joint into bearing. Then I noticed it suddenly was cool after a ride, checked, and it had failed again, melted the nylon seals out of the crosses, and was probably a few miles from blowing up and putting me on the pavement.

II took the arm to a cylinder boring shop and they opened it up to proper fit. No problems since then, after 40K miles.

The proper interference fit for a bearing this size is .0002-.0004, TENTHS of a thousandth. I've had a chance to measure four Tonti swingarms at this point, and all were at least .003 under, even if they were round. I'm suspecting somebody at the factory shifted a decimal point, and nobody noticed. Who knows how long this went on, it was the 70's.
 
That pitting is why I don't recommend using moly. If exposed to moisture and heat it can form acids. No other manufacturer recommends using moly I believe for that reason. Also I have observed pitting on the inner side of the hub bearing surface from acid formation. A good synthetic gear lube is fine for the rear drive without moly. Yes I would recommend replacing the gears even though you could probably get many more miles from this set since it is already apart. Since the vibration is at the same RPM, I don't think it is related to the rear drive. I would check the gearbox input bearing for issues since that rotates at engine RPM. If your input and output gears haven't been replaced with steel cage bearings, this would be a time to do that.
Hi John
Thanks for advice about not using Moly.Guzziology and Guzzi Guru Barry Jones told me to use it.As does the manual.
I guess i cant do much worse by not using it
I have recently rebuilt the gearbox myself after another vibration turned out to be the vanishing plastic cage on the front input bearing.Nearly all bearings and seals replaced and the return spring of course.
Hmmm,i agree it doesnt sound like the rear end.
I also replaced the aging Lemans 1000 engine with a low milage(15,000 miles) 2001 Cali 1100.
The engine hasnt been dismantled apart from recoditioning the heads.It seems good.
The gearbox is rebuilt and shifts beautifully now.

I cant think what else it could be and pray i havnt done something wrong?

Alex,
I have also experienced bevel gear failures on two trips with mates.One made it home with very bad noises,one did not.
I will be replacing.
I do all the work on my bikes myself but chose to get Barry Jones from Italian Motorcycle engineering to rebuild the bevel the last time for that reason.I have no experience with meshing Guzzi bevels so i went to the best person available?
This was after i got another Guzzi mechanic to rebuild it and it failed after one 400km ride.
Too much backlash in the pinion bearings destroyed the gears and he had to reimburse me.

So i think i will do it myself this time.I dont know of anyone around these parts who i can trust.
I have an engineering background and 30 years experience maintaining all types of machinery.Fitter Machinist.
I have a shed full of tools and would rather take the time to get it right myself.

I agree that clutch assisted wheelies are not recommended on shaft drive bikes.

T Bill
I abused my Lemans 1000 in my youth with wheelies and had a catostophic carrier bearing/uni failure which sounded like a grenade and dented the swingarm.
I also discovered that the bearing journal in the swingarm was too tight.
The new C3 bearing upon fitting was grinding with no clearance.
My solution was to grind 0.15(6 thou) from the outside diametre of the bearing which seems to work fine now.
Near indentical tolerance problems to yours but a lazier solution.I always stock a new bearing with smaller O.D.
No more excessive heat from the swingarm and no more failures.
Sounds like a common problem.

Yes my UJ fell out again.It measured 0.2mm under size.As i had already flipped it once,now both ends are undersize.
I refitted it with loctite bearing retaining compound and will monitor.
I can machine it and fit a collar if necessary.

But the main concern i have now is that little niggleing high frequency vibration felt through the pegs at 2400 rpm which i have never felt before.
It feels different to the collapsed bearing cage in the gearbox and the bad UJ/bearing vibration i have experienced several times before.

It is a very fine/low amplitude high frequency vibration felt through the pegs which i know is new and is gonna bite me.

I am hoping new bevels will fix it but doubt they will?
 
Shrek, I've found a machinist marking paint in an aerosol can that works great for visualizing the correct mesh engagement. I'm sure there are similar products in Australia If you can locate an old factory manual for a 750, or 850GT (Ambassador and Eldorado in the US) it gives detailed illustrations on setting up the ring to pinion wit good information on what to move to get proper engagement. The problem with setting up the bevel box (and with new ring and pinion you will have to) is having the correct shims on hand. Also that nut for the pinion is a real bugger!!
 
Shrek, I've found a machinist marking paint in an aerosol can that works great for visualizing the correct mesh engagement. I'm sure there are similar products in Australia If you can locate an old factory manual for a 750, or 850GT (Ambassador and Eldorado in the US) it gives detailed illustrations on setting up the ring to pinion wit good information on what to move to get proper engagement. The problem with setting up the bevel box (and with new ring and pinion you will have to) is having the correct shims on hand. Also that nut for the pinion is a real bugger!!

Thanks John,
I have a can of blue spray on engineering paint which i agree is better than bearing blue grease.
I understand the theory behind setting up bevel gears and confident i could do it.
But shims?
Just spoken with the local Stein Dinse guy who also advised the cost of an assortment of shims would cost more than he would charge me to rebuild it.
So my best option is probably to send it to this guy who i buy parts off and has done many.

Cheers
 
Oh yeah,the weather Alex
Hope your high and dry?
We also had rain last winter(dont get much around here)
My river broke its banks last year,rose 8 Metres and got to within 2 inches of my shed full of bikes.
So i guess i cant complain about all my Guzzi problems too much.
 
After looking closely at these gears,theres evidence that the pinion may be shimmed out too far.
There is wear on the pinions shoulder behind the back of the teeth indicating that the crown wheel has been contacting it.Corresponding wear marks on the top edge of the crown wheel teeth seem to back this up.
This damage is in alignment with the pitting along the bottom edge of the pinion teeth.
Could the particles from this damage cause the pitting along this face?i think probably?
And could the crown be shimmed out too far too cause the tops of the crown teeth to wear the bottoms,only,of the pinion teeth?

I guess this irrelevant to some degree now,but i would appreciate your opinions because i like to have a root cause and understanding to ease my mind.

New gears will be fitted to the std box at some stage and Syn gear oil without Moly from here.

But i hope to up pick up a complete low mileage Cali 8-33 box first.
I wanted to try 8-33 gearing with the 1100 motor anyway so now i have an excuse to do both.
I am taking a punt that it will fit,but with a moderfication to the axle spacer length only,i think it will?
I am hoping to be able to press this steel axle spacer out of the housing,machine it and press it back?

If not,i will atleast have a spare for the Cali if i dont break it in the process?
 
You are correct, only the axle spacer needs to be changed. With that gear ratio, the speedometer may actually give correct readings!!
 
You are correct, only the axle spacer needs to be changed. With that gear ratio, the speedometer may actually give correct readings!!


Hi John
Thanks for the reassurance that the Cali box will fit.Thats helps make a decision.
Ha...are you insinuating that my 950 motor was not good for 230km plus?
Cheers Wayne
 
You'll be able to source most shims from a "bearing/engineering supply shop" but not the large rear drive flange shim.
17355400.jpg
 
T
You'll be able to source most shims from a "bearing/engineering supply shop" but not the large rear drive flange shim.
17355400.jpg
Thanks Amboman,
I am sending the box off today to somebody who has shims and experience to rebuild.
Thankyou everybody for your advice and backup.
Appreciated.
 
Interesting you say you flipped your UJ. Are these bikes UJ's not the same as older Tonti's in that the UJ should only fit in one way?
The outside diameter of my LM2 UJ ends are such that it only fitted in one way. You couldn't tell through sight but a vernier proved the point.
 
This UJ had the same diameter both ends.30mm i believe.
However i believe that both ends were slightly too small as they have both spun in the carrier bearing.
Both ends pressed in too easily for my liking.
I would prefer a tigghter press fit to stop this happening.

However,this is the least of my concerns.
The small outer bearing was a rattleing fit in my bevel housing.
This was probably the cause of premature gear failure due to no accuarate support for the crown gear.
I had to get a new housing to fix this and settled on 8-35 gears to lower revs a little.

After refitting i still had a problem.
When rotating the wheel i could hear a rubber sound like the tyre was touching the swingarm every revolution.
As the tyre wasnt rubbing i removed the wheel to check the cush rubbers.
I spun the wheel on a balancer and noticed the cush drive plate was running out about 1mm.Axially and Radially.
The large diameter plate that holds it all in was buckled and cracked causing the cush drive plate to run out.
This would explain why i snapped a spline off a new drive plate.

While ordering anew plate the guy said this not possible as the cush drive is an accurate fit on the wheel hub(bush)
So i checked the hub and sure enuff it is worn down 0.8mm.
So a new wheel hub was also ordered along with o ring circlip etc

This all explains the vibration i could feel through the driveline.
I will now have all new parts for the rear drive.
A very expensive exercise but i have ridden this bike fast for 24 years and 160,000 km so its not surprising.
 
Back
Top