Motor strip

[tlmark]

Hi, guys so after draining the sump plug during the summer I noticed some swarf on the magnet 
And due to a having a pretty lousy year last year I put her to one side until the winter to do a strip. So the results so far are right piston sloppy fit (she always was a bit smoky on that pot). So barrels are at SRM being rebored +.40 and stove enamelled.
and on looking in the crankcase I think I found the cause of the swarf, worn camshaft. see pic.
 so a couple of questions if I may? The idle gear shaft has some marking on the bearing surface. does that look ok?

Also is this amount of conrod big end play normal?

https://www.youtube.com/watch?v=vwXRxOuhbEM&feature=youtu.be

I had planned on fitting new big end shells on the rebuild but I'd like some advice on if this standard slop.

cheers guys.

[Billybream]

As you have already advised you intend to split the crank cases, the best method is to inspect and accurately measure the journals, there will always be some side ways movement.
While the engine is stripped down you should also check and clean the sludge trap.

[tlmark]

Yeah cheers Billy the sludge trap is something I'm looking forward to 

[Greybeard]

Yeah cheers Billy the sludge trap is something I'm looking forward to 

Side to side movement of the conrods, (without being able to rock them) to me is normal;  visible up/down is not good! 

After stripping the engine doing the sludge trap is not too bad. Plus, if you find and remove loads of muck from there you will positively glow with self rightious pride and you will start to preach from the book of Crud as I do! 

[chaterlea25]

Hi tlmark,

It looks like the "usual" wear cycle that happens to A10 engines

Wear on the timing side bush due to mileage, lack of oil changes, dirt in the lube system and or worn and leaky
oil pump
The lower oil pressure does not open the pressure relief valve that diverts oil to the cam trough
The cam and followers wear and throw shrapnel at the pistons that chews them up and scores  the bores
More metal particles gets into the return oil side which makes crap of the pump and onto the oil tank where it
then feeds back down to the oil pump doing its worst on its way round the system

Time for a full bottom end rebuild

John

[coater87]

 That timing pinion shows some wear, but a quick clean with an external hone and a new fitted bushing should make it perfectly usable.

 The cam is junk, but at least you can still get them.

 Lee

 

[Alex kettle]

I suffered the exact same thing the other year. I too asked for advice on this great forum and got all the help I needed. I stripped and rebuilt the motor with great success and now the engine tone is much crisper than before. It is disheartening when something like this happens but when you’ve finished you will have the biggest smile on your face .

[KiwiGF]

As you have already advised you intend to split the crank cases, the best method is to inspect and accurately measure the journals, there will always be some side ways movement.
While the engine is stripped down you should also check and clean the sludge trap.

I second the measurement of journals, you can also inspect the surfaces for scoring etc at the same time. The slop you can see is not unusual so you may well get away with new shells, but measuring the journals accurately for size and ovality is needed. Accurate use of a micrometer is required. Ovality indicates the wear, journals generally only wear on the top and bottom of the stroke, not sides.

New shells as a fix only works if both old and new shells were both made accurately to standard dimensions. This was a given with OEM shells but I wonder if the aftermarket is good in this respect.

Cams can be re ground or polished to remove small imperfections but it’s probably better to get a new one, I bought a 356 cam from srm for not a small sum, and I was not too impressed as it took ages to arrive, and was made with 020 less than std lift, srm said this was due due a lack of correct blanks at the time and offered to replace it, but the shipping cost and t8me to nz made that impractical.

[tlmark]

I suffered the exact same thing the other year. I too asked for advice on this great forum and got all the help I needed. I stripped and rebuilt the motor with great success and now the engine tone is much crisper than before. It is disheartening when something like this happens but when you’ve finished you will have the biggest smile on your face .

   Hopefully your right, 

I only bought it in 2016 and the more I've ridden it the more I found needs sorting so in a way, I'm glad to do a ground-up rebuild and then know that everything is as best that I can make it.
Just waiting on a crank pinion puller(none of mine fit) before I can spit the cases.

[Topdad]

hi , when I was doing mine I phoned SRM to order a puller and was to to carfully use a large flat screwdriver ,they always do. It worked very easily,cheers Bob

[RichardL]

At the risk of exposing a long string of my embarrassing kludged tools, here is what I did with a puller that cost about $5:

 https://www.a7a10.net/forum/index.php?topic=8738.msg62472#msg62472

Sadly, "Ol' Cheap-Ass" (the puller, not me) has gone to tool heaven.

Richard L.

[KiwiGF]

I’m an even cheaper (ass) I made this one up, not the box has most of all the rest of the tools made up for various jobs 

[RichardL]

Looks like some good ones. Not saying it's a must, but if you want to share them for eternity (that could be expecting a lot from Erling  ) you could describe them here: https://www.a7a10.net/forum/index.php?topic=368.msg18578#msg18578

Richard L.

[tlmark]

all good ideas but I had already ordered this one from fleabay.

and it works brilliantly

here's the link if anyone fancies one.

https://www.ebay.co.uk/itm/Bsa-twins-A7-10-crank-pinion-puller/263428014723?hash=item3d55888283:g:T1cAAOSw0exaAC-T

[tlmark]

The cases are now split    not what I was expecting, primary main shrapnel...

And the big ends are going to need to replaced too as I could rock the conrods.

this is gonna get expensive