Tear-down in progress..

I dont see how the chain could be worn out as stated it runs in a oil bath and it is only under strain for a few seconds upon start up.
I come from the world of snowmobiles and they run this chain in the chain case and it is under load constantly when the sled is in motion not only from forward motion but also from braking or slowing the machine down.The chain must transmitt in some cases 180hp to the ground.The only time I see a failure is if the chain was run without oil or if the clutch does not engage untill like 8000rpm and even then the chain will last for a lot of high rpm starts.
So while the chain may get a little stretched, I doubt that I will break under these conditions.I also believe that it is just old age/repeat heat cycles and rubber soakedin oil that causes the chain giude to fail and not the chain it shelf.

 

Dunno about that one.. When I was trying to Locate a Non Yama Source for the DID HyVo chain. I talked with the Canadian DID Distributor at length on this. He claimed he sold literally.. Hundreds ... of DID Hyvo chains every single Snow season. His view was that the average sno machine ate their hyvo's ..at least.. every other season. Dependant on the rider one would suppose.
His problem was with Yamaha forcing Yama Sno machine owners to pay their Usurious pricings. While he was prohibited from selling them his DID chains, despite being the national DID Agent.
It's been a while but... if.... memory serves, the HyVo chain IS the primary drive. Ergo the Name?
It ttransmitts the power, at least on my 2 old engines. There is no gear on the Crank shaft end. The Only other way to transmitt power... besides magic.
That's why it stretches out easily and generally causes enough grief so one dare not ignore it.
It ain't just there for the starter.. or it would only be a teeny chain... like the Cam drive.

 

Yes there can be some faliures but I bet most of those chains sold were either longer or shorter to acommadate gear changes(bigger or smaller sprockets)or alot of guys just like to put a stronger (wider) chain so they can bragg about it to thier buddies.
From what I can see the primary chain in the xj series engines is only for the starter motor.

 

Crank wheel for number 3 cylinder is a gear that drives the clutch and transmission on XJ650/750/900. Check pictures on page two of this thread.
This is another reason I love my bike; No sloppy primary chain drive!
XJ/XS 1100s have a primary chain.

 

Danilo, the HyVo doesn't endure high tension strain except at start-up. It shouldn't ever fail unless neglected, much less stretch. The dynamics to stretch it out just aren't in evidence often nor long enough to warrant concern. That is unless the nitwit runs the starter for minutes at a time. On a well tuned bike, startup is a swift affair and I just don't see where it could lead to a stretched out HyVo. Can you suggest anything else that would be a concern that I might have overlooked? I've only dealt with the HyVo in our XJ's so I don't have loads of experience with them beyond that scope.

Danno, you got that one right. The plastic/rubber/whatever-it-is material used dries out after a few decades and just crumbles. New units are not hard to come by but replacement is usually enough to send the uninitiated scurrying for momma's apron. I was not thrilled at the prospects when I had this issue. The process was actually very easy and I now marvel at the simplicity of the design of our beloved XJ engines.

 

The HyVo chain IS the primary drive on my Fz600 AND Radian engines.
NO if's and or buts.
Darn thing transmitts power from the centre of the Crank (ideal location actually) to an intermediate shaft (which the starter Mech uses only incidentally) with a drive gear on it's end which turns the clutch basket... Period .
The Hyvo primary v commonly wears out... it was a poor choice for an 11,000 rpm motor. Go! yamaha.
Local shops claim these are an Often replaced item as they normally stretch excessively subsequently destroying their guides. Which is a symptom of a knackered primary and THE v last warning before total engine meltdown! No small matter that, as the primary chain is the most expensive replacement excercise in the motor. (labour alone is astounding)

Ummm ...Been wrenching on these Long??
Clearly, someone is lacking even the most Rudimentary understanding of exactly ..what.. drives the transmission and makes the wheels go around

 

"Ummm ...Been wrenching on these Long??
Clearly, someone is lacking even the most Rudimentary understanding of exactly ..what.. drives the transmission and makes the wheels go around"

Yes, it would seem so.

XJ motors are gear primary drive.

FZ600 and Radians are not XJ motors.



As David3Aces has said, if you look closely, and not so closely actually,you will see the gear on the crankshaft just in front of the clutch enclosure. This gear provides the drive to the transmission through the clutch assembly. The Yamaha manual states in the specifications that primary drive is by spur gear, 97/58 ratio.

Many XJ's will run just fine without the starter chain guide in place at all. This chain primarily provides the drive to the alternator, which is why it is so beefy (it is under tension all the while the engine is running). You have to pay for the narrowness of the XJ motor with this bit of added complexity. As most other bikes drove the alternator off the end of the crank, you will not see such an arrangement in many other bikes of the era, if any.

There's nothing wrong with chain primary drive, it was used by Saab on the 900 series to drive the tranny off the front (I believe) of the crankshaft.

Yes, Robert, the XJ motor is a wonderfully simple design, but I am constantly amazed how well most all of these old Japanese motors are built, even if they don't have the latest whiz-bang technology. GM bought up a bunch of bikes back in the early 80's to see how they were put together and concluded that the Japanese were basically "building racing engines for the street". Of course, when your product line consists mostly of emissions-choked cast iron pushrod wheezers, your definition of a race engine may be a little broad!

 

XJ550s/FZ600/YX600s also have Primary chains. Sorry.
I forgot the chain set up in the 550. Last time I replaced a set of broken 550 crankcases at our dealership was in 1982.

 

So, been waiting on parts to arrive, so not a lot to do. Also got laid-off, so the bike's been on hold a bit. But no more. Parts are coming in, and I have other stuff to do as well.

Namely, I'd like do some valve grinding. Problem is, I believe AutoZone's valve sprint compressor is a bit too big. And having to guard my finances, purchasing a motorcycle-specific valve compressor is not an option at the moment.

Suggestions? Can I rig something using a C-clamp?

 

Put a block of wood to hold the valve closed & use a clamp with a ring spanner to depress the spring.

 

Sorry for the extended delay. Stuff happened. Back to work.

Got my parts from XJ4ever and some from PartsnMore. All the parts arrived in perfect condition. I did have a couple problems with the orders. I had Len ship the parts to the wrong address (my fault). Luckily, I was able to get them from the address I had them shipped to. Len was more than willing to help in any way he could, for which I am grateful. I also received a wrong part from PartsnMore, part code mixup at their end. They sent out the correct part quickly, at no cost to me, and even let me keep the wrong part they sent (a new starter relay for my model bike). I would recommend both sellers, and plan to buy some piston rings next month from Len.

Wizard, thanks for the advice. I'll try that. Just haven't gotten to the head work yet.

Successfully replaced the primary chain guide, and reinstalled the starter clutch (with renewed pieces). Getting the guide in there without removing the crank was a bit tricky. Honestly, I don't see how you would replace the guide without splitting the case. I suppose it is possible, but splitting really isn't that tough. Just time consuming and organization-intensive. I don't think you need to disassemble the top end to do this (head, block), though removing the engine from the frame would obviously be necessary.

I'll be joining the case halves tomorrow. Any recommendations here? I imagine I need some sort of gasket solution on the mating surfaces, but I wouldn't know which one.

 

Permatex makes a grey Gasket Maker, it's listed on their website and is about $8 where I live. Yamabond in cheap clothing. Get new o-rings for the oil galleries, seals for the shafts and you should be good.

 

So, I used the gray gasket material, and all looks well. New o-rings too. I'm at the valve stem seals now, and a little puzzled. The Haynes manual pretty much skips right over this step, listing only a picture, and a caption telling you to replace them.

I've managed to replace two so far, but I'm mangling them with a set of pliers just to get them out, and pushing them in with my thumb. I haven't damaged anything yet, but with this method, it seems just a matter of time. Is there a prescribed method to removing, and installing, these seals?

 

Went ahead and yanked the remaining six off without drama. Finished working on the head. Once I cut out a spring compressor tool out of some PVC tube, things went rather smoothly.

Installing piston rings now. But I've got a question on the base gasket. I got copper gasket material for the head gasket, read a suggestion for that somewhere. Should I be using this for the base gasket as well? I believe I read somewhere that the base gasket gets no gasket solution, but I just want to confirm. Thanks.

 

My seca 650 ,1982 , had a jamed up shifter,only had first and part of neutral, took out a broken chunk of the rubber starter clutch guide from the shift barrel,now it shifts fine. Can this bbike be run with this broken guide,some call it the primary chain guide, I would imagine parts of the guide are still bolted in place that would still provide some guidance. Am I just wishful thinking?

 

Without part of the guide chain will slap around and remove the rest of the guide and nasty things can happen. It's a major tear down , maybe start looking for donor engine. 750 motor bolts in just jet change or carb swap as well.

 

Ride it until the winter. In the meantime get the Factory service manual and the Haynes and begin reading on the teardown procedure. You can do the job over the winter in about two or three weekends. A used engine might get you by, but the primary chain guide in it is going to be just as old, and therefor just as likely to fail.
Rebuild the starter clutch while you are in there.

 

True, Moe is right old motors have old parts. So for the motor pick up a 750 and do it up as Moe stated then you can have the best of both, new motor and more go-go!
I am looking for donor for my seca .....
Must have more POWER

 

Is there not an oil nozzle that will need to be replaced if the chain rubs it for too long?
I suppose this is dependent on how much of the guide has disintegrated?

 

Yes and Yes. The oil nozzle is quite thick so it will take a while before it gets turned into junk.