Putting it all back together
 

I’ve finally (after an expensive battle with the magneto) got the case open and am looking at what I need to replace before I start putting it all back together again.

My reason for opening it is that the bike had just half a litre of oil in it when I got it and I had no idea how long it had been ridden like that. So I’ve spent the last year riding it and wondering if every knock and rattle was a sign of impending disaster. I decided the only way to be sure was to open it up over the winter, renew where necessary and put it all back together for some carefree riding next year.

The oil on the inside of the case is rust-coloured and filled with loads of tiny black particles. They are too fine to feel with my fingers but I can see them. Most of the ‘rust’ seems to be coming from the main bearing which I guess is shot. I’m thinking about replacing all the bearings anyway just to be sure.

Attachment 20482

I also have some doubts about the crankshaft. There is some blueing around the pin joining the crank halves so I’m guessing there has been overheating at some time. There is no noticeable up and down play in the rod, but sideways it moves up to 1.4mm (the manual says 0,8mm should be the max).

Attachment 20483

- Given these signs should I get it rebuilt with a new big end bearing, rod and pin?
- Kedo seems to be a good, but pricey, choice but I’ve been quoted a much better figure for a Mitaka set. Does anyone have any views, good or bad, on this brand?

Thanks as always for the help.

the blueing at the crank is normal, my guess is they use in the factory some kind of induction heating when pressing together the crank. a true burned big end would feel very sloppy...
if the side to side clearance is ok and you dont feel pure up and down play, you are fine.
wash the bearing with some paraifn to eliminate the oil so you get a true feeling for the play

Given the visually rusty main bearing, I would personally replace ALL bearings (and seals) without hesitation, including the big end - it may be "ok" but taking it apart - again - when you could have done it all in one go and be DONE is not worth the stress of wondering imho.

Do it once, right. :thumbup1:

C4 bearings
 

Hi there,

if I remember correctly some of the bearings are C4 bearings, and on my journey around the world I replaced all bearings at 100.000km and at 200.000km with genuine Yamaha bearings. Pls make sure if you dont use genuine bearings that you use the right ones.

crankshaft. I would give the crankshaft to a workshop that is specialised in overhauling them, a long time ago Kedo offered this service but I dont know if they still do it.

all the best.

mika :scooter:

Agreed, it takes expertise to do the crank. I've done lots, and seen what can go wrong even when you need what you're doing and have all the right tools, like a 10 or 20 ton press and an alignment setup. It needs to be RIGHT.
Replacement bearings SKF or FAG are excellent quality bearings, take yours into a local supplier and have them pick out the right replacements. Don't buy weird brands and don't try to pick them yourself, every detail stamped on the bearing matters. Guys that know what they're doing can match you you up easily.

Side ways movement on a crank is totally normal. As is the blueing. It's from the process where the rod is pressed on.

I'm assuming you have a detailed workshop manual for the bike. They often give the specifications for how much movement is acceptable. When sideways movement is too great, the rod will float and create up and down movement (Rod-Knock). So 'usually', if there is no rod-knock, the sideways movement is acceptable. But measure it all the same.

If there is no up and down movement in the Connecting rod then I would use it. But measure the small end internal first.

Rusted bearings need inspecting. It could just be surface rust from sitting dry. Sometimes it will wipe off with paraffin or brake cleaner. But If the bearing balls are not clean and shiny underneath then replace them. And be prepared for a big bill. They're often odd sized and not available as pattern parts. Sneaky buggers.

Main bearings will generally last the life of a life if they're kept lubricated and not contaminated.

Before you re-assemble this motor make sure the inside of the cases are IMMACULATELY clean, all oil passages are cleaned out with compressed air and mating surfaces are dressed.

You don't mention the condition of the barrel liner, piston and top end etc.

These are the first things to suffer when you have too little oil in a motor.

Thank you for all the advice. As always I’m blown away by how the people on this forum are so willing to share their experience and knowledge.

The main bearings on my 3TB have identical markings – Koyo 6307 SH – which I have read stands for special heat and means the bearing will last ten times longer. The right hand one is listed on MSP for 83 euros. I did a quick internet search and found a C3 Koyo 6307 (which I’ve read will do the job just as well) for under 14 euros. The SKF C3 6307 was under 12 euros. Am I missing something?

I'm no bearing engineer. But bearings can differ massively in quality and application.

SKF etc, do make good bearings. They also put their names to cheaply made pattern parts made in sweat shops. A brand does not tell the full story.

It's all about the codes.... Sorry I can't tell you more. Simplybearings website has some info and guides if I remember correctly.


Many people buy genuine for this very reason. To remove the confusion. But with a little more research you should be able to save at least 50% on OEM prices.

However, if they're special cut bearings (Honda are a bugger for this) then you will have no choice but OEM.

Ted makes good points, especially "it's all about the codes" - and that's why I said take the originals to a bearing supplier to make sure you have the right ones.

Substituting an SH for a non-SH would make me nervous. They specified an expensive special bearing for a reason. You can be sure they tested with a cheaper standard type bearing first, and subbed it for a much more expensive one because they had issues.

If in doubt buy OEM.

Beware of fakes too they are out there nowadays :

Anti-counterfeiting

Counterfeit SKF bearings seized in West Yorkshire raid

The C4 and C3 designation is the bearing tolerance for internal sizes . A c4 bearing is actually a little looser than a C3 , Yamaha used it possibly due to the heat expansion of the parts . As the motor heats up things expand and the bearing should get tighter , maybe too tight so they went with a looser bearing . This has been discussed here before and many have used the more common C3 without troubles.



.

I've researched everything I could find on here about bearings and learned a lot about C3 and C4, but I'm still not clear on which one, if either, is the equivalent of an SH.

This would be a good left side bearing , https://bpracingatv.com/product/rapt...crank-bearing/

still looking for the right .


.

Well I finally got enough money together to do the rebuild properly and am now waiting for a delivery of bearings, gaskets, oil seals and other bits from Kedo along with a con rod kit from ProX. I hope I've got all the bases covered but have got two questions I hope someone can help with.

- My manual says I should replace the oil strainer that sits inside the crankcase (part no. 5Y1W13430000) but the MSP site says this part is no longer available and all my internet searches come up with it being obsolete. Is it ok to just put the old one back as it is or can it be opened and cleaned without totally destroying it?

- Can anyone recommend a good crankcase sealant for putting the two halves back together? The dealership here in Portugal looked mystified when I asked for the Yamaha bond No. 1215 that is recommended in the manual.

Thanks as always for the help.

i'm pretty sold on loctite 518 for crankcases closing

it's anaerobic, so will harden only when the two halves are pressed, will never gum up into balls that can fall off, neat...

a bit pricey though

to clean external surplus use nitrocelulose thinner

For the instant gasket use Three bond 1215. I just went through the same process looking for yamma bond . Needed a finger full for the pv cover on my 300, ended up with a 250ml tube cos thats the smallest one they do. I think it just ovef ten quid from Demon Tweeks.

If you pay for the postage I'll send you the 95% unused tube I've got here. Guaranteed it will be set solid by the time i need another finger full of it.

I use Dow Corning products. I'm a little bias because I'm a BMW tech and it's what we use on BMW engines. But it really is great stuff. BMW use it instead of gaskets on their new bikes. And I've NEVER EVER seen it fail.

07580397777 BMW Sealing Compound Dow Corning - 35ML - 2WheelPros


However, from BMW it's very expensive. £40 a tube etc.

However, there is no reason not to use their standard RTV sealant.

https://www.antala.uk/dow-corning-70...ngine-gaskets/


Last note. Anything with a "Yamaha" brand on it is basically just something else re-branded but 4x the price !!

So don't be thinking you to spend big bucks on big brands.

More than often, you can buy any generic high temperature RTV sealant.

https://www.ebay.co.uk/itm/Simply-Hi...wUKxYk3OP#rwid


However, for the main engine cases, it's always nice to have that piece of mind to have a good brand sealant. Because if your build has gone right, those cases won't be coming apart again for a long time ! IF EVER !

Thanks for the advice and the generous offer of free sealant from Timus. I've found some 518 in the local auto shop so will go with that. Just waiting for my rebuilt crankshaft to be finished so I can start on the very scary job of getting all those bits back into the crankcase in the right order.

Putting it all back together
 

Long time i looked for the meaning of 'HS' on Koyo bearings, now found this site below:
http://www.koyo.com.br/upload/koyo/c...20Bearings.pdf
So it may be a good idea to use the correct spec bearing.

'My manual says i should replace the oil strainer...' it is possible to open the strainer, carefully, and clean the mesh. Be aware that the strainer fails to protect your engine and oil pump from transmission debris, particularly from 5th gear. Bond some magnets to the strainer trap these in future.

Best,
p

Haha yeah I've spent some time puzzling over that too until I decided to turn the bearing around and read it as SH - or Special Heat as Koyo describe it. (They also claim ten times the life span over other 6307s) Apparently they only make them for Yamaha so I've put my trust in Kedo and fitted the FAG ones they supply for main bearings. I'm not planning on any extreme riding so figure I'm unlikely to need something with ten times the lifespan of a FAG bearing. Which is my cue to go find a piece of wood to touch.

Thanks for the tip about using magnets to back up the oil strainer - I'll open it tomorrow (carefully) and clean. Is there anywhere in particular the magnets should be fitted for maximum effect?

Putting it all back together
 

Here is where you will find some stuff on magnets. I found good ones in old hard drives, cut and filed them, bonded in place with JB weld or high temp silicon.
There is quite a bit on the forum on 5 gear and oil pumps if you look.

http://www.horizonsunlimited.com/hub...solution-80123

I use neodymium bolt on magnets and either use a screw or bolt already inside or drill & tap a hole to mount them https://www.mcmaster.com/#magnets/=1bcwsgb (open the "magnets" icon to get to the screw-on option, this site cuts out the full link)

I usually have one somewhere on the clutch cover down as far as possible , someplace that I can clean it if I have the cover off , plus a magnetic drain plug . It's nice to have them where the oil is splashing near the screen.



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Quick panic here. I've got the crankcase in the oven and the bearings in the freezer ready for the re-install but I've just realised I don't know which way round the oil seal on the balancing shaft goes. Is it metal side in with the U-shaped side facing out?

Just saw this , open side faces bearing .

Thanks jjrider. I had it with the metal side facing inwards as I read somewhere that the markings on oil seals (which are on the U-shaped side on this one) should always face outwards. Fortunately the oven wasn't hot enough so I was saved from making a big mistake.

This seal puzzles me though. If it stops oil from being thrown up the breather pipe how does it release any excess air pressure in the case? There doesn't seem to be any way for the air to escape.

I believe it sucks through the shaft from the clutch side and the seal is so the breather isn't sucking through the bearing itself and just venting from right there . It's been a while since I studied the oiling and venting so it's not fresh but there is a reason for doing it this way . It is an odd setup since the balance shaft has 2 holes usually used for oiling , but they may just be intake holes instead to vent the inner case as well. The E-start motor has another small vent tube right next to that bigger one but doesn't have the one up in the valve cover so they must have thought it could be better.



.

Well the crankcase went together beautifully with a nice even bead of 518 all the way round so I'm guessing it has sealed ok. I've wrapped that bit up in an old sheet while I get on with cleaning up the top end.

I thought I'd come me up with a brilliant idea when I decided to fix scotchbrite kitchen scourers to my Dremel to get the carbon off the valve side of the head. It was working great with wd40 until I figured I'd better check the net to see if this was a good idea or not. All the advice seems to be it is a very bad idea - clogging up oil ways with abrasive aluminium oxide particles and potential damaging the surface of the mating faces. That'll teach me.

It won't be the end of the world , if you stayed down in the chamber area and with the valves installed not much harm done , I take unitized wheels on my small polishing sanders and various scotchbright belts on my Dynafile to polish most of my chambers to a nice shine plus the exhaust ports . It's the mating surfaces that need to be kept away from .

A good and thorough cleaning will remove the grit and debris .



.

That's reassuring. Thanks jjrider. In my ignorance I had already used the scotchbrite to clean half the mating surface on the top face of the cylinder head but it doesn't seem to be damaged. I'll use some 518 with the gasket just to be sure.

I'm stuck on one more thing though - turns out that the Kedo 'full gasket set' doesn't include the gasket that sits between the oil pump and crankcase. The other mating surfaces of the oil pump have no gasket so I'm wondering if I can get away with leaving this gasket off? I know short cuts are generally a bad idea but it'll take another five days to order one in and I'm getting impatient. The sun is shining outside.

Putting it all back together
 

May i betray my complete admiration for Yamaha engineering:thumbup1: but I have not found a reason for this gasket and have not had any issues by leaving it out.
p

Thanks petej. That's great news. I hope I'm not pushing my luck here but can I ask your opinion on reusing the piston pin circlips? I've just bent one of the new ones while trying to fit it and am tempted to put the old ones back in.

Circlips do not deteriorate in use, usually only at the hands of man :smile2:
Using an undamaged pin clip will do no harm.
p

I have to add a caveat to pete j's comment - "usually..."

Personally I ALWAYS replace ALL circlips and seals, and usually bearings. Mostly because you feel like an idiot if a dollar part fails and takes out half the engine with it... or just starts to leak and you have to buy another set of gaskets and do it all again. Cheap insurance, speaking as an ex-mechanic and all around lazy guy.

Yes you can often get away with it if needed; "you pays your money -or not - and takes your chances."

If your old piston gudgeon clip is 100% un-damaged then it's safe to use again.

Every manual will tell you to replace it though.
Because they have to take into account that it was damaged on removal.

To be safe, I would recommend that you replace it.

But you don't have to if you can 100% guarantee that you didn't deform, crack or twist it on its way out.

They're made from spring steel. It's strong and fairly forgiving but once you take it past it's stress point , it's junk.

I always replace them in customers bikes because it's not worth the risk as Grant says. And a customer would expect them to be replaced.

Out of the countless engines I've rebuilt for myself and friends, I have never replaced them and ive had zero failures. But I am very careful when I remove them and use the correct tools. Not twisting them out with screw drivers etc.


Re your gasket question. With modern liquid RTV sealants, it is indeed possible to use them instead of the paper or steel gaskets they come with.
The exception here is multi layer compression gaskets such as your head gasket.

Also, some cases or covers require the genuine gasket as it is part of the tolerance and dimension when the motor was designed. Such as cam cover when the cam carrier is built into the cover.

On engine side covers or faceplates, you're usually okay though. But that does depend on the bike !!

I still prefer to use the physical gaskets. They're just cleaner and easier to use. And if you need to wiggle something you know it's not been wiped off in the process.


Last note.

When building an engine it always pays to take your time and not take shortcuts if you have any doubts. They always bite you in your arse.

I spent twenty years learning that the hardway.

Agree with Ted, I wouldnt worry to much about is.


As for gaskets, the really important one are whre they provide clearence, like Ted mentions about the cam on certain bikes.

Sidecover gaskets can be nescessery aswell, it is on my E-start xt600. Startermotor binds up a bit with no gasket, and on the right side you have the oil return valve which can also act up.

Order the gasket and change circlip, its not like you are doing this same job next week..Its something about that feeling when your done that its all in place and new!

Thanks for all the information. I realised I was letting impatience override common sense so have ordered the circlips so I can do the job properly. The minimum order was five so I've got a few spares in case I bend any more during installation.:smiliex:

Minimum order 5 ?? Huh ?? Never heard of that. Use Fowler's if you're in the UK. All fiches online.

Sent from my Moto G (5) using Tapatalk

Piston circlips are nothing to not put new in , even if they look undamaged from removal and they must come from the piston mfg , not a Yamaha oem if using a Wiseco or JE piston.

I don't remember what the gasket under the oil pump is for on this motor either , if I have one I put it in always , if I don't have one it gets left out . The rest of the motor all gets gaskets .

Honda XR series motors have the valve cover gaskets that must be a certain thickness since they set the clearances for the cam and bearings , at least they have actual bearings on the cam rather than just polished aluminum journals .

.

While you're waiting buy a pair of circlip pliers - makes life SO much easier!

I finally reached the stage of putting the oil back in and was hoping to be out on the road this afternoon. Then I saw the steady trickle of oil escaping through the drive shaft oil seal... It's a brand new seal so all I can think is causing it is I might have pushed it in too far.

Can anyone tell me if this is possible?

When I refitted the cover plate I noticed it wasn't flush with the seal but figured it was just there as a safety precaution. I've double checked with the parts diagram and there don't seem to be any missing bits between the bearing and seal.

Pull it out and install a new one. Apply Oiled cling film over the shaft and slide the new seal on straight.

Thanks ~Ted. Am I right in thinking that I wrap the cling film around the thread to stop it damaging the seal as I slide it on?

Indeed. Lots of oil too. Keeping the seal straight is very important. You need a deep socket or something that will fit over the shaft to drive the new seal in. You can't wiggle them on as that is what damages the seal lips.