Tom_Arundel

Tube in the ear is good fun  

Take air filter off

 Check  WOT achieved and is the same on both throttle bodies with engine OFF. With engine warmed up and running and throttle closed, listen with a length of tube down each trumpet...should sound the same

OR

Make and use a vacuum gauge ( plate with breather hole  and small bore tube + water) at closed throttle with engine running. DO NOT blip thottle or water will go in engine! 

Or

Buy a flow meter/syncrometer (lots available from your local website)

AND

Balance on centre screw, set revs on end screw, set throttle pot...and again....and again....etc.   Best of luck, they are a pain to get (all 3) right but it passes the (a lot of) time!

Note:-  I have seen several Caterham throttle bodies which are not machined or matched as a pair or matched to the head ports. These cannot be properly balanced without a lot of fettling and realignment.

Is it with baffle plate?....If yes I`ll have it

Did you go over a bump going in to the fuel stop? could trip inertia switch

Some inertia switches have the wrong loom plug.....the plug does not lock onto the body and can come loose

Only go out in the dark!

Halfords socket on dash between gauges straight to battery (has fuse in line) I plug charger in here.

I know this may not apply to your LSD but when I built mine with an open Sierra diff. 10 years ago the diff was so noisy that you could hear is a quarter of a mile away across Bruntingthorpe! Needless to say I took it out and back to Caterham who gave me another with no questions asked. Th replacement was almost a noisy as the first, so I decided to change things...First I turned the crown wheel bearings in 3 notches....that`s better....another 3 notches ...much better....changed the oil to Redline heavy...    almost silent...no whine...no clunks...no worries!  Its done 32,000 miles since ....so things can be improved.

I`ve used one in Rugby for the last 7 years.....no fails.....nice guy (biker) I usually give him a hand to do the test.

( I sometimes get a discount for doing it!) but I think any reasonable MOT station will be OK

Why do you desire to change? More performance? More low speed grunt? More `get me there quicker` or just for a change?

There`s a lot that can be done to improve the Sigma for not a lot of cash My current set up is about 12 -15 bhp better than the 150 in low to mid range and gets to about 148 bhp at the top. Torque is 124 lb ft. Performance is much better overall than the 150 and cost about £250 plus a few days work.....well worth it... and it will do 45 mpg!.

I can point you in that direction if you want to get your hands dirty!

Yes wrong springs for road use.

1 1/2`` step/spacer is the lower circlip groove that you need to move to get lower ride height. Circlip is up inside the black sleeve

The lower lock ring (silver anodised) appears to be for the 1.9`` springs  that you need. You can swap them over for the 2.25`` that are currently in use but you will need new top spring retainer or get them turned down to 1.9``(assuming you can get the springs)

Love the word `farkled` takes you all sorts of places!

`Never thought Brexit would be like this!`

photos

I got so fed up with the fiddling that I made this. It extends the top of the pedal, gives a quicker throttle action, avoids the cable bending and fretting and is easy to access.

Don`t forget that there is a pedal UP stop as well as a WOT stop and a choice of pivot positions

Closed throttle must be set on the throttle body stop not with the throttle pedal stop. Cable should be just slack at closed throttle

Just a simple check...take the air filter off and look down the throttle bodies at full throttle. Are all the throttles open the same?

(should be fully open and exactly the same) It needs vacuum gauge/flowmeter to balance them and easymap to set the TPS

The throttle potentiometer (Ford part) is also unreliable 

If you are stuck I (or someone else) could turn (machine) them down for you. Where are you?

Cold Ashby...Green and yellow S3

There should be a centre hole in the end of shaft that should run true if you can get your dial gauge into it. If its an ex Grads car it may have had an impact on the rear wheel at some time and bent the stub axle a bit

On a scale of 1-10,   1 being a slight irritation and 10 being about to crash, how bad is the vibration?

Are you sure that it is at the rear of the car?

Prop shaft runs in a plain bearing sleeve in the rear of the gearbox extension, bearing can wear and can be replaced ( with some difficulty)

Does the gear lever vibrate?

I think you have the decimal point in the wrong place in your readings otherwise they are insignificant

I presume the diff is full of the correct oil

Caterham do a stick on carpet kit that helps if you have bare panels.

I adjusted the crown wheel in 6 notches and use Redline heavy shockproof oil...silence!

Mmm...I can hear every bird that sings as I go by and every other rattle in the car now.

The diff gets very hot, due to its hidden position and reduces the oil viscosity... an air scoop will help but that`s another story.

Some 150 sigmas had a problem with the Ford TPS failing and the two throttle bodies can go out of sync.They are a bit of a pig to set up without the right gear. The lambda sensor is also a bit suspect but that usually gives idle/low speed problems and high fuel consumption but can be checked/eliminated by disconnecting it (under drivers footwell).

Sorry to hear of the recent events in Christchurch...so sad.

Will the car accelerate through the misfire and does the misfire clear at higher rpm / lower gear or is it only at constant speed on level road?

There is an engine vibration period at about those revs which can show up any bad connections. Check ALL engine bay plugs and connections especially earths, including battery.

As Jim said plug gaps should be 0.9mm....standard Ford gap has caused problem?

Is the air filter reasonably clean?

Lots of other possibles including poor fuel quality

How tight is the belt...can you twist it on the tension (other) side?

The throttle pot. setting is incredibly sensitive to position and voltage at closed throttle and does give your symptoms. At a minimum it requires Easymap and a lot of tries to get it right but it can be done and is `sweet` when achieved.

Where are you?