Lotus Elan and Lotus Elan Plus 2 Forums

nebogipfel wrote:Hello Bob, Welcome to the forum and to ownership of one of the best cars in the world.

FYI Miles Wilkins is in your neck of the woods..... http://fibreglassservices.com/index.html He wrote the book on the Lotus twincam (literally )

There are some clever chaps on this forum but FWIW my approach would be to go back to basics and check things in a methodical fashion. I always start with sparks and then go on to fuel.

iancockshull wrote:Bob

Have you got the original airbox with the engine breather connected to the airbox backplate, near No. 4 carb? (assuming Weber or Del Orto). The black soot on No4 plug might be coming from oil mist being burnt in the rear cylinder.

Best regards
Ian

bobm3142 wrote: The plugs are clearly all new with a gap of 0.070". It's definately electronic ignition so a large gap is OK.

hatman wrote:

bobm3142 wrote: The plugs are clearly all new with a gap of 0.070". It's definately electronic ignition so a large gap is OK.

Really? That wide? (My own, admittedly limited, understanding is that after-fitment of electronic ignition enables an increase in plug gap of the order of 5 thou, not 50 thou. Even modern engines designed with in-built electronic systems only run gaps around the 40 thou mark from my experience.)

bobm3142 wrote:

UAB807F wrote:

bobm3142 wrote:
sounds like a problem i had with my sprint,which also had aldon's module fitted.check,with a very good timing light,one that can measure advance in degrees,that it advances correctly.aldon set initial timing at 10 degrees ,not 12 as stated in manual.the advance is mechanical and cannot be altered,it should be 14 degrees(max) at 2,500 revs,this is why you need a good quality timing light.all details as said previousl are in the manual. my dizzy,after strip down,had only one return spring...sent it back to aldon who repaired it and it made a hell of difference....good luck.

I don't know much about Weber carbs but I'll locate the accelerator pump to see if I can clean the jet(s) without altering the other settings. I know that they do work (to some extent at least) since: a) the acceloration is good at high revs and, b) I use a couple of pumps prior to a cold engine start (and too many pumps or on a hot engine and it floods all too easily). Thanks for your help. Bob

The pump jets are within the carb body and it is fairly significant dismantling to get to them. From what you say about starting then it sounds like at least some of the 4 are working as when mine have been stuck the car has been very difficult to start.

Roughly what is the rev range that this "feature" happens over ? I recall several road testers commented on a flat spot just after tickover and I wonder if this could be the problem you're experiencing. My first thoughts would be to work through the electrics starting with the ignition timing at tick over and a couple of spots in the rev range (the settings are in the manuals for every 1000rpm). If that looks strange, it might be worth checking distributor advance weight are free to move & not stuck.

If you don't have a manual yet (and you really, really, really do need a proper Lotus one) then I dare say a PM to most forum members would get you the relevant page posted

Brian

Thanks for the reply, Brian. It runs well at any revs including tick-over, but from tickover up to about 2000 rpm it dies if I don't accelerate gently. It might be that the acceleration at higher revs will improve too if I sort this problem (wow! is all I can say to that). I am going to start from the state of the plugs and work my way through the ignition and then ignition timiing. It has electronic ignition so I have yet to work out how the auto advance and retard. works. Modern electronic ignition sorts the whole thing out but mine might still rely on the distributor for the auto advance.

The response has been anazing. Thanks guys I'll let you know how I get on.

Cheers,

Bob

types26/36 wrote:Welcome Bob,
Before getting too involved with tuning and by the way you describe the problem I would first check that the accelerator pumps are working and/or the pump jets are not blocked.

UAB807F wrote:Hi Bob,

If you are checking air flows through the individual chokes, then I use a gunsons carbalancer kit. It's basically a length of tubing with a variable intake at one end and a manometer at the other. It looks and is quite a cheap piece of kit, but I've found it works remarkably well and makes it very easy to set the chokes to the same air flow. It probably takes longer to pull off the air box cover and replace it afterwards than it does to set the chokes up using the kit.

Brian

ps - no affiliation to the seller, but this is the type of thing

http://www.amazon.co.uk/Gunson-G4053-Carbalancer/dp/B002WN0TT0/ref=sr_1_1?ie=UTF8&qid=1321078167&sr=8-1

types26/36 wrote:Welcome Bob,
Before getting too involved with tuning and by the way you describe the problem I would first check that the accelerator pumps are working and/or the pump jets are not blocked.

Spyder fan wrote:Bob,
Something that is often overlooked on the pump jets is the tiny aluminium washers that are used as a seal. Go back to Brians post with the pictures of the carburettor and the location of the pump jets, you can just make out the shiny silver of the washer on the jet in the last picture. Sometimes these washers are missed off completely in a so called rebuild and can also be flattened or damaged by over tightening.

When I still had a twincam with webers in my car I had your problem with no pickup from low rev's and a set of new washers on the pump jets cured it.

See this exploded diagram for details, it's item 49 (washer) and fits to item 57 (pump jet)http://petrolpowered.com/include/pages/tech/spitfire/images/diagrams/dcoe45.png

You can buy them here, http://www.ebay.co.uk/itm/WEBER-DCOE-PUMP-JET-ALLOY-WASHERS-SET-4-NEW-/200647679021possibly the best ?3.60 you will spend in a long time.