engine rebuild

[Stevepshipley]

Hi chaps, need some help please.
couple of years ago i bought a spare engine (spanish S3 200) to strip and re-build mainly so i could learn. When i rebuilt it with new crank and electronic ignition etc the crank web was catching on the oil seal retaining plate. I changed the plate and still had the same problem. I did a bit of reading and its mentioned in the manual that MB sell shims that fit between the crank and the drive side bearing to solve this problem so i got one and it seemed to do the trick.
Put it all together and it almost immediately starting burning oil. Took it out of the scooter and stripped it again, nothing obviously amiss so just rebuilt it and got exactly the same problem. Threw it to the back of the garage and left it.

Since then i've done a few jobs on my scooters, including re-fitting a crank with new seals etc without problem. Also invested in a leak test kit. Just started looking at the problem engine again and before i stripped it did a leak test and sure enough there's a big leak from the drive side bearing. Stripped it all down and cant see anything wrong. I really dont want to just re-build this and end up with the same problem.
Am i doing the right thing using this shim or could this be the cause of the problem? When i pull the crank through I use the bolt and the front sprocket pillar thing and pull it until it wont go any further. This is ok with the shim, but without it the crank locks solid, If i re-build it and do a leak test will that prove the seal etc is all ok?
I'm getting frustrated because I cant see what I'm doing wrong. I'm reluctant now to go any further until I find out whats causing the seal to fail,
any suggestion gratefully received.
thanks Steve

[MickYork]

A friend was rebuilding an engine and had a similar problem (no shims involved though). We eventually got 3 oil seal retaining plates and measured the thicknesses of them......they varied by nearly 0.5mm. We fitted one of the thinner steel plates and it worked fine.

I've also had issues with the counter sunk heads protruding slightly.....another thing to look out for.

[Warkton Tornado No.1]

You're doing nothing wrong but if I were you, I'd try this:

Remove crank & the drive side oil retaining plate.

Refit crank with no shims & test that it turns (it almost certainly will)

Remove crank & with a better understanding of 'all' that the drive side oil retaining plate does, just try that on the loose crank, well greased/oiled on the sealing lip. The seal spring should face the crank & you need to rotate it as you push the drive side oil retaining plate on. It should grip the journal that it runs on but allow you to turn it easily (if that makes sense) Going through this exercise enables you to appreciate how easy it is to invert the seal lip & understand the forces involved, twisting as much as pushing.

Once you 'get' the feel for what's involved, you can look @ any issue like the drive side oil retaining plate being proud of where it should & if it is, be prepared to linish the face for clearance, rather than use a shim.

I hope this long winded explanation helps.

[Delboyli150]

As Mentioned by WK1 make sure the seal is the right way round a common mistake, also a leak test is a big yes especially as you have one, when I did a leak test that's when I realised I have put the seal the wrong way round, Doh!

[Scooterdude]

As above make sure the oil seal is the right way round i.e. spring facing the crank webb. Also it's vital to turn the crank gently as you draw the crank through the drive side bearing otherwise it's all to easy to pop the spring off the seal and cause the whole thing to jam up, put plenty of grease around the seal and on the crank before you begin.

Another thing to look at is he thickness of the halite washer, some of the ones found in the generic gasket sets are a little on the thick side and don't allow you to tighten the plate home fully, making the crank jam against it.

Replace the slotted head countersunk screws with Allen headed ones, this will allow you to get a bit more purchase when tightening and make them easier to remove.

Don't forget to grease the halite washer!

[dickie]

I had a leak through drive side bearing on a recent build. I could see where it was coming from by using soapy water. It was on the outside face of the oil seal where it seals against the machined face of the casing. I smeared a little threebond 1215 on it and that cured it.

[Raveydavey]

Stating the obvious, If it's burning oil it's not sealing, which is either the seal itself, halite washer, retaining plate or the bearing is not fully seated. The latter would also cause the plate to sit higher which in turn would make the crank bind.

Personal experience on that one

[Stevepshipley]

You're doing nothing wrong but if I were you, I'd try this:

Remove crank & the drive side oil retaining plate.

Refit crank with no shims & test that it turns (it almost certainly will)

Remove crank & with a better understanding of 'all' that the drive side oil retaining plate does, just try that on the loose crank, well greased/oiled on the sealing lip. The seal spring should face the crank & you need to rotate it as you push the drive side oil retaining plate on. It should grip the journal that it runs on but allow you to turn it easily (if that makes sense) Going through this exercise enables you to appreciate how easy it is to invert the seal lip & understand the forces involved, twisting as much as pushing.

Once you 'get' the feel for what's involved, you can look @ any issue like the drive side oil retaining plate being proud of where it should & if it is, be prepared to linish the face for clearance, rather than use a shim.

I hope this long winded explanation helps.

Thanks WT and everyone else,,
I've done what you suggested putting the crank in on its own without retaining plate etc and it turns ok. Practiced putting the plate and seal on the crank by hand. Before I go any further I'm getting 0.5 mm taken off the face of the plate. I'm already using high tensile Allen key screws. When I get the plate back I'm going to try it without the shim.

[Knowledge]

I would try to source a different thickness of Hallite washer rather than machining the retaining plate. The alternative is the new casa retaining plate that uses an O ring instead of a hallite washer.

[dickie]

I would try to source a different thickness of Hallite washer rather than machining the retaining plate. The alternative is the new casa retaining plate that uses an O ring instead of a hallite washer.

Agree. I've had halite seals so thick that the crank wouldn't turn and too thin to seal. From memory mb ones did the trick for me.

[Stevepshipley]

Thanks chaps,
I haven't sent the plate off yet but been checking more stuff......
I think the bearing is seated correctly but,,,,,,
When I put just the retaining plate on without any seal or halite washer and pull the crank through full without the shim it locks solid against the plate. Plate is 5mm thick and the shim is 0.9mm.
Does that tell me that the bearing isn't fully seated? I'm reluctant to try driving it in further.
Cheers steve

[Adam_Winstone]

Or that your screws may be bottoming out, rather than pulling the plate fully home.

Your bearing may not be fully home but watch out for 'that extra knock' that punches the drive side bearing out the other side of the casing!!!

[holty]

i was talking to martin at chiselspeed a few weeks ago about fitting my drive side bearing, he said no need to drift the bearing home, just get the case warm enough and it will drop in, i tried it on my rotax conversion and sure enough no hammering needed, i did use a blowtorch for a good 5 mins heating inside and out to make sure it was all heated up enough, i was worried about knocking out of the other side of the casing and ive done a lot of work to the casing and could afford to damage it, im sure most people know to heat it up, but maybe didnt realise if its hot enough the bearing will just drop in without any kind of hammering.

[Adam_Winstone]

^... in the same way that a mag side bearing drops OUT if you warm the mag sufficiently. I do mine on a camping stove with a sheet of steel on the top, then sit my mag on this. Eventually you hear 'DONK' as the bearing falls down and lands on the plate

Adam

[Stevepshipley]

Going to try and find a thinner plate,
Tried heat before I bash it but the bearing acts as a heat sink and gets hotter than the casing.

[Warkton Tornado No.1]

By all means use heat, but as it is a deep groove ball bearing, it can handle forces in an axial direction as well as radially. Therefore, you can ‘wind’ them out (or in) using something like M16 threaded bar with large, thick washers that fit just the inner (probably about Ø30 mm) in conjunction with some kind of plate/bars bridging the magneto housing gasket face. Obviously a nut is used @ each end to do the pulling. Installation of a new bearing is the same method but the plate/bars are then bridging the chain-case cover gasket face.

I always use this method & forget the last time that I had to resort to heat, though I pop new bearings in the freezer prior to installation to make life easier.

I hope my explanation is clear & helps

[Stevepshipley]

Firstly, thanks for all your help/input and suggestions chaps....

Feeling a bit more optimistic now. I bought a new retaining plate from MB and its about 0.7mm thinner that the aftermarket steel plate I bought to replace the original aluminium one. (wish I'd kept the old one now, but there you go)
Anyway managed to fit the crank with new seal and halite gasket without it locking against the end plate. all's looking good there now. I've fitted the top end and done a leak test and no leaks showing at all. I just need now to finish the timing etc. and drop it in a scooter to try it out - fingers crossed.

My theory for what its worth is that the shim I was using between the crank and the bearing meant that the oil seal wasn't fitting properly on the crank..... or I could have just knackered the seal when I was pulling it through.

Anyway - onwards and upwards cheers Steve

[Fast n Furious]

I've never needed to use any such spacers but surely the spacer in question should go behind the bearing not between the bearing and the crank?

[Stevepshipley]

I've never needed to use any such spacers but surely the spacer in question should go behind the bearing not between the bearing and the crank?

Well that's why MB sell them??? Their slimmer plate is an alternative (more expensive) cheers