SJ410 -1985 'Cabrio', engine rebuild

[binge]

Got back in my garage this evening with a clear head.
Cranked the heating up, stuck the kettle on, and had a good look at this engine.
Whipped all 4 pistons out. The rings and bores all look okay. Bores are a little shiney / polished for my liking, so thinking of new rings and a hone.

Shells are defo shot, can see the wear in them.
The crank, has some very light marks on it, but nothing too nasty. Can only feel a few of them if you really dig your finger nail into the marks.
I measured each journal on the crank with a vernier, vertically, and horizontally. And there was about 0.2mm difference in it. Is there a tolerance to go by with these engines?

I then wire wheeled the engine and head, and decided to go all classic-Mini on it, and give the engine a paint.



RS125 engine in the background, one of my other projects which has been pushed aside thanks to this SJ...





And ring gap, which is .013"





Ben

[donkeychomp]

Nice work. Love the colour of that engine...can you tell me what paint you used? Looks like the same stuff on my bikes brake discs.

[binge]

Its just gold hamerite mate. Smooth finish.

[donkeychomp]

Looks amazing...hope this engine works!

[Ladaman]

0.2mm out of round on a crank journal is massive!

I'm sure Darrell or someone will be along with the actual tolerance soon, but i'd have thought it should be around 1/10 of that figure.

[ScottieJ]

Nice work. It's not finished yet but you can find all the clearances in this thread.

http://forum.suzukiclubuk.co.uk/vi ... =13&t=3537

[Ladaman]

That table shows bearing clearances. Roundness of the crank will need to be a much smaller value than the clearance to work correctly.

[binge]

Posted quite late last night, 0 was on the wrong side of the .

.02mm




Ben

[Ladaman]

Well that's a lot more like where it should be.

I've had a look in the manual now, and this is what it says.

Crank.JPG (46.28 KiB) Viewed 5803 times

You're still double the tolerance, but that could just be measurement error, as we are talking very small amounts here.
If as you say the marks are very slight, I'd think the crank will be OK and just new shells needed.

[gp7186]

You may bring this 0.02mm down if you measure with a micrometer as most vernier calipers have a tolerance of either 0.05mm or 0.02mm whereas most micrometers have a tolerance of 0.01mm