S1 Engine Compression Check and Workshop Manuals

[GordonMasson]

Hi Folks,

Despite having my S1 engine rebuilt a couple of years back and having only covered a few hundred miles in it sounds really rough.

Can someone confirm the exact way of doing a compression test on the engine.... is it throttle open or closed etc etc.

Also, I am sure there used to be a workshop manual for Full Forum Members on here.... Can never find it though, anyone got a link to it?

Thanks

[andydclements]

Throttle open. In an ideal world, it would be a warm engine so as to get the real-world readings once everything has expanded to normal size, but I doubt many people bother.

Just disconnect the  dissy king lead, remove all plugs and then test each cylinder in turn.

[gvy]

Cilinder compression test

Let the engine warm up , doing a small trip. Let it cool for at least half an hour and do the check.Dont do it when the engine is really hot. 

Unplug the Low tention wires at the HT bobin ( dont let it build up tension inside)

Take all sparkplugs out.

Open the trottle complete and block it . Never measure with closed throttle because readings are worthless.

Start the test: Do the test with a fully loaded strong battery to have correct readings.

Note the following  for each cilinder

• first turn of the engine (how far does the meter jump) All cilinders should jump to about the same value after one turn.
• end reading after a couple of turns = max compression

All readings should be in the same region.

If one cilinder is down it can be:

• cilinder ring
• a valve is not shutting down well

test this by squirting a bit of engine oil in the cilinders and do the test over. If the readings go up significant, the cilinder ring is bad. The oil closes this and compression goes up. If it is a valve the reading will stay low.s or

If two ajacent cilinders are down ( fe cil 2 and 3) , there can be a torn in the cilinderhead between the two cilinders or in the head gasket

 

Cilinder leakdowntest

This test is done with the engine not running and with each cilinder in top dead and the two valves closed. It can also reveal al sorts of engine conditions.

 

Geert

[GordonMasson]

Thanks guys.

The car has been sitting for the best part of a year without running.... stuck piston ring perhaps?

Having said that, Lotus Bits did a full rebuild on the engine about 1000 miles and its always been noisy ... sounded tappity to me but they said although it "sounded horrendous" it was possibly due to one a combination of the carbs needing to be rebuilt and the tubular rather than cast exhaust manifold?? 

Smells a bit humy when running too.... not sure why that would be on a rebuilt engine?

 

[Bibs]

On 07/09/2018 at 12:29, GordonMasson said:

Also, I am sure there used to be a workshop manual for Full Forum Members on here.... Can never find it though, anyone got a link to it?

We offer the parts manuals mate, not the workshop ones sadly. 

 

[GordonMasson]

1 minute ago, Bibs said:

We offer the parts manuals mate, not the workshop ones sadly. 

 

 

Thanks Bibs... that might just be why I cant find it then.... doh!

[gvy]

Gordon, Without actual hearing the engine, I can't have an opinion on what to search for.

I too have a tubular manifold, without the mid muffler and my exhaust note is pretty loud. But that doesn't mean the engine turns lumpy. 

If f.e. the carbs are not syncronised and there is a vacuum leak somewhere, then one cilinder will under perform  and that would be very noticable at idle and result in a lumpy idle.

First you should check the health of your engine : by doing a compression test and may be a compression leakdown test. If all is well after that test, you should concentrate on the carbs. 

• -Are they clean, new gasket set etc.....
• set the fuel level in the barrels
• syncronise the carbs and check if you dont have a vacuumleak somewhere. In the case you do, you wont be able to sync them, so you will know.