Sabb diesel problem

[TonyTitch]

Can anyone with knowledge of Sabb diesel engines tell me how to get the rocker cover off my 8hp Sabb HG.
Thanks all

 

[halcyon]

The dome nut on top in the middle.

It's dead simple, what problem have you with yours?

Brain

 

[bluedragon]

Mine has a ring attached to the bolt. Just put a bar through and turn. It's so obvious, that I wonder if you've some other setup? Can you explain a little more?

 

[TonyTitch]

No dome nut

 

[TonyTitch]

I'll certainly try that. I'd always assumed that the ring was there to take a rope, etc lifting the engine out of the boat. The real problem is poor starting probably due to a lack of compression. When I try to solve this by squirting oil into the cup on top of the rocker cover, it does not drain into the combustion chamber, but just sits there. When I poke a drill bit into the hole in the centre of the cup, it comes up against something metallic about an inch in. I wish to get the rocker cover off to see what's going on inside.

 

[bluedragon]

Right...I can help you here. Firstly the cup itself is for oil lubrication to the valves & rocker arms only. The pipe for oil injection to the cylinder is the centre tube in the cup. This is a copper pipe leading down the push rod tunnel, then turning towards the front of the engine into the inlet port. It might be that this pipe is a) blocked, or b) not bent correctly into the inlet port, or c) you've been putting oil in the cup only. The previous owner of my boat was not convinced that this was working properly and always squirted oil into the starting cigarette / glow plug port. I've re-run the pipe into the inlet port and am testing at present to see how effective this is. Over the last few months of winter I've needed the glow plug and oil injection to start the engine, even though the valves were replaced last year. Mine is a Sabb Type H, which is reputed to be a bit difficult to cold start (warm start is fine). Getting the rocker cover off is easy. Just unscrew the ring. If the cover comes straight off with no resistance, then it's likely that the oil pipe is run straight down the push rod tunnel. If the oil pipe is run correctly, then you'll find that after the cover raises about an inch, you have to juggle it around (tipping it forward) to get the bend of the tube out of the inlet port. Make sure it is correctly bent when you re-assemble. Might as well grease the rocker arms whilst the cover is off as well (nipple on top).

Hope this all makes sense!

 

[TonyTitch]

Thanks a lot. I got the rocker cover off OK by turning the ring, to find that there was no tube to the inlet port, nor can there have been one. There is only one outlet from the cup, the hole in the centre, the base of which is solid, and from that run two small copper pipes, one to each front (the flywheel end) corner, to drip oil on to the ends of the rocker arms. Each contained a sort of wick. All I can think of now is to drill a hole in the rocker cover and fit a piece of copper tube leading to the inlet port. To do that I'd need to know a) Is the inlet port a hole into which the tube has to be fitted?, b) is it easy to locate? and c) what size tube?, d) must it be copper, or would some sort of synthetic material be OK?
Hope you can help
Thanks
TonyT

 

[halcyon]

Must vary with model, mine had four pipes, to either end of each rocker, and the centre one hooking into inlet valve.
Have you tried putting oil into inlet and checking compression and starting? before rebuilding rocker cover.


Brian

 

[TonyTitch]

Thanks. I do much now till Tuesday as the boat's on a mud berth, the tides are at particularly small neaps, and it won't be afloat till then. I'll contact you again if I need to. Thanks for your advice so far.
TonyT

 

[bluedragon]

Obviously different to mine. Oil as a cold start aid was an integral part of this engine, unless with the HG type Sabb felt it wasn't needed? Actually I don't know of a model HG. There were G types (and the early ones did not have an oil pipe to the inlet port), and H types for the single pot engines.

I would try a few squirts from an oil can directly into the pre-combustion chamber through the cigarette holder before considering modifying the rocker cover. It's bit of a nuisance unscrewing this before each cold start, but at least the oil gets straight into the cylinder.

The inlet port is a few cms down the push rod tunnel. I don't know about alternatives to copper though...nylon might be OK??

 

[TonyTitch]

Thanks. The HG model seems to be different from the H by lacking the variable pitch propellor mechanism. That's what it looks like in the manual. The number of mine is HG65 104. I've had a go at undoing the cigarette holder , but it obviously hasn't been unstuck for years, and won't budge. I've got the manuals for both the G and H models, plus the extra explanatory leaflets produced by Mike Challis before he retired. If you need any of that, I might be able to run off a copy.
Regards
TonyT

 

[bluedragon]

Thanks Tony...but I have all the info. Good luck with your mods.