Changing a driving shaft joint

I just saw an ad about a 1983 Seca900 for sale at a very good price, main reason being the driving shaft joint has to be replaced.

How big of a job is it? What could be the cost of the parts I'd need? Would it require special tools of skills?

Don't know a lot about the bike except mileage is average (63 000 km), one tire and brakes are one year old (I'm sure brake lines are original) and float seats and needles are new on all four carbs (so the seller says). Bile is all black.

It looks like a decent bike.

 

it's liver is sick, watch that cholesterol

 

It 's amazing what difference one letter could make ! Too late to edit, I guess.

 

I just looked at a swigarm( drve shaft) from an xs 750.
It looks like the "U" joint would hammer off and new one would hammer on.
Remove wheel , remove , swing arm taker the driveshaft off the hub , pull out the drive shaft , hammer off the u joint, clean it up grease and hammer on the new u joint to the shaft.
Looks like it could be done in a day,
I remember years ago changing a cv joint in a mazda car, the joint hammered off and on like that, from the cv shaft.
I am just assuming that the seca is very similar to the xs 750.
Alan

 

Four cap screws hold the u joint / driveshaft connecting to a drive flange of the engine, under the rubber boot at the front of the drive shaft , good chance to change that boot if it is cracking

 

ONe problem could be removing the swing arm iiself, sometimes they a re a bit stubborn on some models.

 

the worst part is getting those 4 bolts out, their real tight. the swingarm needs some love too, it hasn't been greased in 30 years, so a little effort is worth it

 

While it is helpful to remove the swing arm, it's not absolutely necessary.

1 remove the wheel.
2 remove the final drive from the swing arm

3 pull the driveshaft

4 peel back the u-joint boot

5 with the aid of a pipe wrench, remove the 4 bolts holding the u-joint to the output shaft.

6 noting where the match mark is, remove the u-joint.

7 install the replacement u-joint, reversing the order of the steps, and using medium strength thread lock on the bolts.

 

Should a damaged u-joint on a 63 000 kms bike worry me about the condition of the rest of the bike? I mean, is it automatically a sign that the bike has suffered repeated beatings?

 

Interesting procedure, thanks. I suppose that if there isn't any free play in the swing arm, there is no reason to remove it.

 

Not at all. The U- joint is usually good for around 50,000 miles, but it also has 30 year old grease in it, so that could be the cause for failure ( mine was on its way out at 20,000 miles) Even so a thorough inspection is always warranted.

 

Oh, I'd still remove it to clean and repack the bearings, but it isn't necessarily something that would have to be done right away.

 

Thanks k-moe for your super fast answers. I hope i'll have more infos about the bike this evening.

 

Daft question deleted - misread.

 

Inquiring minds want to know

 

Good to know. Is it possibleto do a good inspection of the u-joint just by sliding the rubber boot and rolling the wheel back and forth?

 

Doing that will show you if a u-joint had already failed, but it won't tell you if it's getting close to failing or not. Once a u-joint begins to show signs of failure you'll notice it more when riding as the binding is slight, but it throws off the rotational balance of the assembly. Once a bearing has failed there will be a pronounced clunk; prior to that there ay be an increase in vibration, but that typicaly starts shortly before bearing failure. The best inspection method is removal and manupilating the joint by hand to feel for smoothness of travel.

 

All right I understand the diffrence, thanks for the info.

 

I wondered if the joint was greaseable, but then realised that I'd mis-read the 'greasing of the swingarm' and conflated it. Been a long time since much larger car uni joints were greasable, let alone bike ones.

 

Yep. Totally sealed at the factory bearings. They can be taken apart and new bearings put in, but that requires a fixture, and some skill. Chacal has been doing that for a few years and offers rebuilt u-joints. I have had some success with using a needle injector to flush and grease them, but it's not nearly as good as having a proper rebuildable u-joint.

 

So here is an update. I've talked on the phone with the seller for at least 30 minutes. The bike has another big issue besides the damaged u-joint: 2nd gear often slips out, to the point that the seller uses to skip the 2nd gear and goes from 1st to 3rd gear. I think the fix requires to split the cases, right? I'd say it makes me a lot more enthusiastic.

Other than that, rear shocks are shot. The only good news is that the u-joint is almost ready to be changed: rear wheel , swingarm and driveshaft are already off the bike at the moment.

 

Yep, there's a small shop in the UK (Luton, Reco-Prop), I'd send one to for rebuild, when necessary. When I lived there, they did all my car and bike shafts and can do just about anything that's thrown at them, for reasonable prices, too.

 

Yep, there's a small shop in the UK (Luton, Reco-Prop), I'd send one to for rebuild, when necessary. When I lived there, they did all my car and bike shafts and can do just about anything that's thrown at them, for reasonable prices, too.

 

Sounds like you have more leverage for making a 'good' price a GREAT price!
That will lessen the blow when SWMBO finds out about the extra bike in the garage . . .

 

On the 1100's you can turn the bike upside down with a fair amount of prep work & pull the oil pan and side covers. The transmission shaft can be removed and gears changed for the second gear repair or replacement. I am not completely sure if the 900 engine can come apart the same way or not. If you have to split the case it would be a good time to replace all the wearable items in there anyway.

 

Yep, hogfiddles told me the same story in a private message, sometimes it is posible to fix the 2nd gear without splitting the cases.

 

"sometimes" like on the third tuesday of a month with a R in it ?

 

Well, it makes eight days a year, gives me plenty of time

 

I should clarify that the guy who flipped his over to do to the 2nd gear fix did that on an 1100. Maybe the others were, too, I don't know. May only be an 1100 thing than can be done that way....

Thinking about it-- the guy that i know that flipped his 1100 over to do it is listmember 'BluesBass'. The rest I can't remember.....check with him-- he may know more for the 650/750/900 possibility.

 

I tried to start a conversation with him but it says his inbox is full, so I hope he'll see this and do some maintenance !

 

I very much doubt that it can be done on the 650/750/900. There is very little access ot the gears withoug splitting the cases. I'm fairly certain tthat it would have to be done with the gears and shafts in place.

 

I don't see the 2nd fix as a priority, since I already have a parts bike (the Yellow Seca) with a good engine and transmission...well, so said the seller one year ago...

CHances are I will swap the wheels with new tires, the brakes, the battery, the carbs (known to work properly according to the seller) , the fuel tank and the aesthetic parts from the one I would buy (the Black one) to the Yellow one.