Rear engine output shaft breaks off at nut?

[Cdnlouie]

Has this every happened to anyone before? This one has me a bit perplexed. My 85VR, the output shaft to which the drive axle yoke bolts on to the engine (left side of middle gearbox just behind rubber boot) retaining bolt snapped clean off laying in boot.

 

The only indication I had, that sent me looking was a recent oil leak on the left side. It most likely happened somewhere during my recent 4000km trip, probably on the way back. Can't remember anything taking place except I came back loaded up a bit heavier than going down.

 

Looks like a winter job and might as well pick up the second gear pieces as well although she is not currently due. I wonder if it is any issue driving it for a bit as long as the oil leak does not worsen? I guess I made it for the last 1000 miles since I noticed the leak. At the moment it can't go anywhere but it can work on the output shaft as it is not under torque.

 

Thought I would share that little gem with you all, who knows I could be the first! Lucky me!

 

P.S. I did install the engine about 15,000 miles ago as a replacement and it could have been damaged by someone previously, but it is strange that it would last so long and then break. There was no partial cracks that showed rust, just a clean fresh break.

[Squeeze]

Hi,

 

is this the Nut inside the U-Joint you're talking about ?

 

Besides this, i can't imagine what Part you're describing ??

 

I'm dumb ....

[Marcarl]

My first thought is that when it was lastly installed it was over torqued. Then, over time with heating and cooling, it would snap or break. Torque specks are there for a reason, this being one of them. I can see no other reason for it to break seeing as there is no tension or otherwise any flexing going on.

[muffinman]

Cecil if you are talking about the nut holding the U joint in that broke that is exactly what happened to Dragon riders bike after the first Vogel. I replaced the entire unit with a used one and he has had no problems we did have to remove the oil pan to get all of the broken gear pieces out but Lewis has been riding on the repair for 2 years now.

Start by removing the swing arm and then remove the 3 bolts that hold in the gear housing then loosen the 2 pinch bolts and wiggle the unit out pay close attention to the shims as you will need to reuse them to get proper back lash.

Jeff

[PEIslander]

Another member ( maybe Dragonrider) had this happen a while ago and had a post with pictures of the broken shaft. It was the nut inside the u-joint yoke on the output shaft. I tried to search for the post but it may have disappeared when the site crashed last year. You'll need to replace the output shaft but the good news is you won't have to split the case to do it.

[Cdnlouie]

Hey fellows, thanks for the good input here. You got exactly what I was talking about. I am quite certain this came from the factory and has not been disturbed and it really had me puzzled as to how it could just pop the shaft nut off so easily. It must be a defective shaft situation here that shows up only on a few bikes. This engine was an 84 production model.

 

I am really jazzed :cool10:about the idea of not having to tear down the engine. If I can remove the drive pinion gear output shaft without taking the engine out then I will be exuberant. I think I can even forgive Mama Yamaha for making a few defective output shafts if she did this for me.

 

It has been a while since I took one of these down and I could not remember if the shaft could be removed without transmission dissassembly. I happen to have my old engine with the bad second gear issue, so I have an output shaft ready to go. I will need to get informed about the gear lash setting (I have the factory manual as long as it is clear) and if it changes with a different output shaft.

 

I really appreciate your info on this and if you run across anything else it will be a bonus. Thanks for taking the time to dig up the research.

 

Cecil

[Squidley]

I had a member come over with a "Noise" on his bike. We tracked it down and it turned out to be the same as you. A PIA but unfortunately it does happen

[Cdnlouie]

I feel much better knowing that it does happen. Searching for the explanation of "what did I do to cause this?" is far more unnerving. I had pulled the rear wheel and greased my drive shaft before my summer trip and even wondered what might have contributed to this event. Everything came apart and went back slick so can't be related to that (I.e. no use of hammers).

 

After 25 years you really get to know all about the Venture. Every part has been tested by every possible scenario over a long time and it is amazing that the bike stands up so well.

 

Thanks again for the good comments and any other thoughts for those who may have done this with the engine in the frame, let me know, I like learning from those who have gone before me.

 

Cheers all,

[Cdnlouie]

Okay, it's late winter and time to fix the driven pinion output shaft! (The one that comes out of the engine and bolts on the drive-shaft yoke).

 

I believe that many first generation owners have a problem they may not know about:

 

I believe the problem is a "collapsible collar on the driven pinion output shaft" or "improper factory torquing".

 

Today, when I went to replace my broken shaft with a used one from another engine, I noticed that the drive-shaft yoke was loose. According to the Yamaha manual the nut on the end of the driven pinion shaft (out the back of the engine) is torqued at 29-36 ft lbs and loctite is applied as well (at the factory).

 

Now there is no way that nut is going to move! I also checked the broken shaft and noticed the nut had not backed off (measured threads) either, but was locked in place at the original factory install position.

 

So, what caused the yoke to loosen and eventually hammer the retaining nut until the shaft breaks?

 

Well, the answer may be that the collapsible collar inside the shaft (over time) collapses (why is that not surprising?) from engine torque, causing play and looseness in the yoke, until one day it just breaks the nut off. This is the equivalent of a steady hammering action due to the looseness of the joint.

 

Now, I don't know if this is limited to early Ventures or it may carry over to the modern day, but one thing is for sure, I would periodically check to see if the yoke is loosening. This is not easy to do because you really need to have the drive axle stationary (there is a tool to hold the drive axle located behind the middle gear cover on the left side of the engine) and then be able to twist the yoke to feel the looseness.

 

While the engine is in the bike, it is also impossible to get a wrench on the nut. You would have to pull the swingarm and the driven pinion section (3 bolts) and re-torque the nut. I am going to do that now, and at the same time replace the collapsible collar with a new one.

 

So what is the explanation for the failure? Well, it is possible that some bikes may have had this nut overtorqued at the factory which may have collapsed the collar too much and then over time, these engines are the ones that loosen up and eventually break off the retaining nut.

 

It may be coincidental, but I have two engines (84 and 85) that both had looseness in the drive yoke so the problem may be there in many first generation bikes, but will only break off in a few that may have high mileage. One engine had low mileage 25,000 and it broke off, another had 65,000 miles and it was loose (so who can really tell)?

 

There has to be an explanation for this phenomenon and so I thought that I would write this up as a plausible theory.

 

 

I would be interested in anyone's comment on this thread,

 

CDNL

[RustyRecycledToy]

Reading this has me wondering if this might be the strange 'noise' I have eminating from my center gear area.

 

I guess I'll be tearing down the VR this afternoon while I'm home. I've gotta know what's going on in there. I can't ride it another season constantly wondering what is wrong.

 

Thanks for the heads up...........I'll post my findings when I get them.

[SilvrT]

Reading this has me wondering if this might be the strange 'noise' I have eminating from my center gear area.

 

I guess I'll be tearing down the VR this afternoon while I'm home. I've gotta know what's going on in there. I can't ride it another season constantly wondering what is wrong.

DITTO what you say... I have a "noise" coming from that area during deceleration.... may well be a similar situation happening here.

[Dano]

Might as well check mine while I have the motor out for the 2nd gear issue! Just something else to do!

 

Dan

[Cdnlouie]

It his been my experience that the loosened output shaft did not produce any noticeable noise. After it broke the retaining nut off, I put about 1000 miles on the bike coming back from a trip, and the only thing I noticed was a bit of leaking oil on the left side (not a lot). The universal yoke was oscillating in the rear seal and causing oil to escape.

 

It may cause a bit of additional vibration, but you probably would not notice it. I noticed a bit more transmission whine but that may have been due to the hot weather and thin oil.

 

If you have the rear driven pinion gear and casing out it's real easy to hold the pinion gear with one hand and twist the yoke with the other to see if it has movement.

 

If you have it off and it moves (any movement at all), you need to retorque it. It would not be a bad idea to cheque the torque period, as it seems the collar is designed to absorb the drivetrain shock and acting like an energy absorption damper as well as keeping the bearings under proper tension.

[Cdnlouie]

I picked up the new parts today in order to put everything back together and I was especially interested in measuring the collapsible collar (width) in the middle of the rear output shaft.

 

It came as no surprise to find that the new collar was 1mm wider than the used collar in my two other engines. The old one was approx. 10.3mm and the new one was 11.3mm wide.

 

The conclusion of the matter is that this is a very sensitive torque procedure (see manual), demanding careful application of torque so as not to crush the collar in the process.

 

Also, over time I am sure that the engine's lash impacts this collar causing it to collapse and become loose, eventually breaking the nut off the output shaft.

 

I would be willing to bet that most first gens. have some looseness in the this nut (over time) and would benefit from a re-torque. Ideally, one would have to replace the collar because there is an extra 1mm of space contributing to excessive pinion gear lash.

 

I might add that this problem may well have some effect on the 2nd gear deterioration as well, since the opposing pinion gear (on the main drive axle shaft) is the one that breaks down in the early 83-85 models. This looseness (causing excessive pinion gear lash) would add additional impacting action upon this washer which is definitely not a good thing.

 

Keeping this rear output shaft properly torqued may well extend the 2nd gear life of these engines (at least the ones that are not updated). I don't know if they have changed anything in later models (86 up), but it would be interesting to hear some feedback on this as some fellows check for looseness.

 

The problem with even checking these, is that you must have the unit out of the engine or you must hold the main drive axle nut (behind the middle gear cover above the shifter) and turn the universal joint to feel movement. Also, in order to torque the shaft nut you must remove the universal joint which pretty much requires access in a vise to push the needle bearings out.

 

The good news is that it does not take much time to remove the rear wheel and swingarm and the output shaft so it is very doable. The rear seal, o-ring and collar are all still available from Yamaha.

 

Hope to get it back together soon and check the gear lash.

[dray]

this is a common problem with the 1100 Vstars they break in the same place as your talking about even some of the lill 650s have had the same trouble

[Dano]

So, if I understand correctly, if I hold my middle gear nut on the left side of the case, I should NOT be able to move the u-joint coming out the back. If it does, then replacement of the crush collar is the correct diagnoses? 59k on the mileage. Since I'm fixing 2nd gear anyway, I'm in the area.

 

Thanks,

 

Dan

[Cdnlouie]

That's another interesting piece of info Dray. I'm not surprised because they use the exact same design (I checked the parts catalogue), and call it an "expansion spacer" for the V-Star. This is designed to absorb the shock (maintain tension, etc.) from drive line movement and looks exactly like the Venture design.

 

I was really surprised when I measured the new one and found it to be 1mm wider than the used one.

 

I would love to ask a Yamaha engineer about this one.

 

Thanks for your input,

[DragonRider]

I was lucky that it didnt mess up the gear it engaged with, it didnt have a scratch on it when Muffinman looked at it............but that final drive gear, man was it tore up, looks like a pit bull had been chewing on it for a couple of years, and believe it or not I rode the bike like that for about 4 months till the sound got so loud I couldnt stand it...................I was lucky. If i can find it I will post a pic of it.

 

Thanks to Muffinman and Dokon I didnt have to get rid of it and it still runs great to this day, but I will have to do 2nd gear soon, it still goes in ok, but if I get on it real hard it pops out............and it just started doing that at 80,000 miles.................Great bikes............

Thanks again Muffinman, Dokon, and all the supervisors who helped on that project............

 

Ok I found the pics...............

.

 

 

Cecil if you are talking about the nut holding the U joint in that broke that is exactly what happened to Dragon riders bike after the first Vogel. I replaced the entire unit with a used one and he has had no problems we did have to remove the oil pan to get all of the broken gear pieces out but Lewis has been riding on the repair for 2 years now.

 

Start by removing the swing arm and then remove the 3 bolts that hold in the gear housing then loosen the 2 pinch bolts and wiggle the unit out pay close attention to the shims as you will need to reuse them to get proper back lash.

 

 

Jeff

[Cdnlouie]

Thanks for the great pics dragonrider! My situation did not destroy the pinion gear, but I suppose that would be the advanced case if you keep running the bike with the shaft floating around in it's bearing case. I did not loosen my rear engine pinch bolts as I was concerned about breaking the engine crankcase oil seal (it may or may not).

 

 

Dans says:

 

"So, if I understand correctly, if I hold my middle gear nut on the left side of the case, I should NOT be able to move the u-joint coming out the back. If it does, then replacement of the crush collar is the correct diagnoses? 59k on the mileage. Since I'm fixing 2nd gear anyway, I'm in the area."

 

This is pretty much the correct understanding, but since there is some lash between the pinion gears anyway, it is easier to check the pinion gear after you dissemble the engine by holding the pinion gear (on the output shaft) in your left hand and twisting the universal joint (with your right). Any movement means the nut is loose and it needs to be re-torqued. Ideally, it would be wise to remove the universal joint, remove the nut (clean threads), add lock-tite and re-torque (very carefully, in two stages (check manual) rather than one sweeping motion).

 

Replacing the crush collar would be the best possible idea as well since the original has been crushed with usage. However, I would speculate that a re-torque with the original crush is better than sitting loose. One cannot know for certain how long the crush collar will hold the torque if you don't replace it. It may be metal fatiqued when it reaches it maximum life.

[Cdnlouie]

Okay I have finished my installation (just like it says in the glorious Yamaha manual), but I am not particularly satisfied with the results.

 

Has anyone replaced this crush collar and did a retorque?

 

As I mentioned in my previous post the new collar is 1mm wider than what was in the previous two engines (I am assuming wear - 10.3mm compared to 11.3mm for new collar). Obviously, this is going to give a lot more bearing clearance than what was in originally.

 

After torquing the shaft nut to 65 ft. lbs (nice and slow), there is too much free play in the two tapered bearings (one on each side of the output shaft housing to steady the shaft). I have no measurement from the manual for this (except the procedure) and no way of knowing what is normal or allowable (except a gut feeling this is not right).

 

I have been checking the lash with a micrometer (after installing it) and it is set within specs, albeit it is hard to check the rotational lash with the additionnal slop in the bearings (it was hard to tell about the bearing play until you got it mounted back in the engine).

 

At this point the only thing I can do is remove the collar and shave some of it off to be slightly bigger than the worn ones I took out and then re-torque. I don't want to overtorque as crushing the expansion collar is probably not a good idea.

 

I don't think that I can live with the tapered bearing slop (in the output shaft housing) as it gives me the chills thinking what can happen with that.

 

I am wondering if I am missing something here?

[dray]

this is off the 1100 Vstar its the nut that held the ujoint

[Cdnlouie]

Okay, I think that the picture is beginning to come together for me (no thanks to the Yamaha manual).

 

This is my first experience with pinion gears and I was much perplexed by the "standard starting torque" which is stated in the 1st generation manual. I knew it had to be related somehow to the bearing preload, but could not make the technical connection (this is the torque necessary to keep the bearing moving). This is described in no detail in the 1st gen. manual and what is there, is puzzling at best.

 

Apparently, the collapsible collar (expansion collar) works as a spring (it has a rounded centre or half-circle) that bends under tightening until you get your correct bearing preload (more precisely - spinning torque). This does not mean the collar is collapsing, but it is bending which is an important distinction (not described in 1st gen. manual).

 

The new collar is 11.3 mm wide and it does bend down to about 10.3 (which at this point would probably not have its proper bearing preload). The proper procedure requires that you complete this process without overtightening the collar, as it does not spring back or you must replace the collar and try again (a one way process).

 

This whole procedure pretty much demands that you replace the collar when you replace your rear seal, since once you remove the output shaft nut you need to start the bearing preload process all over again or else you cannot be certain you have the correct "spinning torque" (or starting torque) on your output shaft (once you have put the universal yoke back on).

 

The 65 ft-lbs stated in the manual (for the yoke nut) really has no bearing on how tight your yoke nut should be, it just gives you a starting idea of how much effort you need to apply (first time I have ever seen that).

 

After you have tightened the yoke nut (in small stages) you must use the proper torque wrench (this is the key here as it has to be a very delicate instrument) to measure the .4-.5 Nm or .29 -.36 ft-lb of "starting torque". Most likely a beam type torque wrench that will register accurately this small amount of pressure required to keep the bearing (with the torque wrench on the yoke nut) moving (or rotating in the housing). This records the ever so gentle drag on the bearing, and I assume that this drag is measured by gently pushing against the torque wrench with a couple of fingers for about one revolution to see if the torque remainds within these specs throughout the revolution.

 

Additionally, I would think that the bearing should be oiled rather than dry which would probably affect the torque reading.

 

This is all I can figure out about the process, now I will have to give a try.

[Cdnlouie]

An update on this journey of learning:

 

Here is my understanding of how to properly torque the rear output shaft after you replace the seal and inner collapsible collar (and maybe bearings if necessary)

 

When I installed the new collar (on the output shaft between the two tapered bearings) it took up to 85 ft-lbs to get it moving to take up the bearing slack (manual indicates 65 ft.lbs.). This seems to indicate that the new collar has much greater strength than the old one. They may have improved these in later models, or the metal fatiques over time and it looses its "spring tension" capability. It works like an old car "leaf spring" and we have all seen them fatique over time.

 

Here was my installation technique:

 

I did have to bring the torque wrench up to 85 ft-lbs in order to get the collar to begin collapsing, in order to take up the bearing slack. I tightened the nut very incrementally. I started with about a quarter turn (to get it moving) and then reduced it to only about 1-2 degrees each time. Basically just feeling the nut barely move until I had taken up any bearing play (no discernable wiggle in the housing), turning the bearing (several times) and then checking again after about 360 degrees.

 

Once the play was gone, I marked the nut location according to the washer underneath with a marker and then just barely moved the nut in 1mm increments (a clockwise rotation measurement according to the nut and washer marks) for about 9-10 mm (from the zero bearing load position) and bearing load felt sufficient (mechanic's intuition here) at this point. As you can see it did not take very much movement to get up to a reasonable (in my opinion) bearing load. In the ideal world a torque wrench measurement would be perfect (.29 -.35 ft.lbs according to manual).

 

I then installed the universal joints and the shaft back into the engine and set the gear lash to .003 with the original shim so I did not need to change anything and it came back to perfect factory specs (.002-.004). It sure feels good when something goes right.

Now I am replacing my swingarm bearings while I have it apart as they are definitely worn and that will be a nice little winter project brought to completion, just in time for spring.

 

Cheers fellows

 

P.S. I will post a follow-up once the snow clears and it am able to do a road test).

[CrazyHorse]

Any pictures? Since I'm taking the dive into the motor to change to a 2nd Gen tranny with a Vmax rear in a 1st Gen. Im going to be changing this nut out and the seal plus looking into the that oil pressure ring that RandyA had trouble with I also have that loud deceleration whine be looking for broken shafts. Any pictures would be appreciated. Thanks Jim

[Cdnlouie]

Hey, I've got pics, but no way to get them up here! I can email them to you or send them to someone who knows how to post them here.