Sq4 MkI - engine blow up and rebuild

[Gui.dorey]

As the riding season draws to an end, I mustered the courage to pull the the Sq4 out of the darkest corner of the garage and start disassembling the engine.

I got the head and barrel off, disassembled the primary and timing side, and soon shall be pulling the bottom end off the frame.

Here are the first pictures of the damage. Actually I consider myself lucky as the cases survived with minor damage. Con rod and piston on Nr 3 are gone of-course. The liners in Nr 3 and 4 were heavily damaged, nr 4 piston had bits broken off the skirt, one of the guides for the cam followers had a chunk broken off, the case suffered some damage near the camshaft actually blocking the camshaft rotation, and the big end on nr 3 likely needs a regrind. On the bright side the top end is all right and the push rods are all straight.

[Gui.dorey]

Some more

[Gui.dorey]

Shopping list for now:
1 working pressure relief valve
4 con rods
1 big end shell ( size to be determined)
2 pistons
2 liners
1 guide for the cam followers
1 crank regrind
Assorted gaskets and seals
Lots of patience and work and dirty words

[Paul_Linden]

I offer my condolences for what happened to your engine, and am glad to hear you are going to rebuild it.
Are the current liners on standard bore size? If they are oversize then it might be cheaper to change all four liners to standard and avoid reboring them, although the cost of new pistons will need to be factored in.
The good news is that all the parts you seek are available, either from the club or shops (Morgo, the oil pump people, make and sell cam follower guide blocks). You will need to check the cranks didn’t twist and the coupling gears aren’t cracked (sorry to state the obvious).
Good luck and i look forward to reading about progress.

[simon.holyfield]

Good luck Gui! We are all eager to see it running again.

[allan.walker]

Not wishing to add to your shopping list, but the camshaft lobes look bad. If they are, the cam followers would need to be examined closely.
All of that 'shrapnel' inside would lead me to send the oil pump back to Morgo for checking/testing etc.

I'd be interested to see pictures of the OPRV once you have removed it and also the sump oil filter gauze.

Come rebuild time, I would look at the drain hole in the crankcase, where the oil vented from the OPRV is meant to find its way into the sump. I've commented on my replies to your other thread that I believe that this drain hole is inadequate when using a Morgo oil pump.
Looking at a Mk2 set-up, where the OPRV is attached to the pump and vents into the timing case, the additional size of the drain holes in the Mk2 timing case into the sump is far greater than the size of the drain hole under the end of the front main bearing cap in the Mk1. This suggests to me that Ariel realised that there was a need to improve the speed of drainage into the sump when they redesigned the bottom end.

I'm thinking about whether I can drill out the oil drain hole on my engine to allow greater flow, without having to take the engine apart again....

[Gui.dorey]

Allan,
you can see some pictures of my OPRV in the thread when disaster struck - http://forum.arielownersmcc.com/viewtop ... 8&start=20

[allan.walker]

Thank you Gui.

[Gui.dorey]

Here are some more pictures of the insides. The cases suffered some scrapes and some damage under the bridge, but thankfully no cracks - phew!

The big end on Nr 3 actually seems better than I feared. It will have to be checked of course, but it seem it is not actually scoured. What I thought was heavy scouring looks to be just a thin layer left over from the big end shell.

The cams are also OK. They were just covered with debris. I’ve also included a picture of the sump and filter as requested by Allan Walker. The filter is banged up and debris all over, but otherwise all is fine and can be returned to its original shape.

So now it’s time to brake the piggy bank and start the hunt for parts. I hope the club is well stocked

[daveleek]

Hi Gui , imd are doing a good deal on liners and pistons with what appears to be free Standard delivery to Europe , you might have seen it , but heres the link


https://www.ebay.co.uk/itm/165740429905 ... media=COPY