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Bike carbs (2nd attempt!)


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Dear all,

I have an S3 HC Esprit, which on the whole I'm very happy with, but we always want more don't we?!

It runs a bit rough at low revs and after a bit of research (and a visit to a rolling road) I'm advised it needs the carbs refurbished and then properly set up again. However, this will cost upwards of £500 (approx £150 per carb to rebuild and then setting up on a rolling road etc etc).

To me this seems like only a temporary solution as the likelihood is that they'll need doing again soon enough and, in truth, there won't be a massive performance benefit. I don't necessarily want more power (although that's always good of course), but to make the car more driveable/reliable.

It seems to me (after more research) that in order to make the car more driveable there are two paths that one can take:

1/ Upgrade the ignition system (2D mapped ignition via a fabricated crank sensor or full 3D mapped ignition utilising a throttle position sensor as well).

2/ Upgrade the induction system (throttle body fuel injection in conjunction with option 1))

Being only an averagely competent home mechanic I am not confident/competent enough to try fitting either option myself. I have spoken to various companies in regard to supplying and fitting both options and (brace yourself!) option 1 comes in at around £1000+ and option 2 around £2500+!!

After all that my question:

I was wondering if anyone has experience of fitting bike carbs to the Esprit? Good points? Bad points?

I was thinking of (for instance) fitting late Yamaha R1 bike carbs (£150 or so from a well known auction site), which also come with a their own throttle position sensor, which would allow the later upgrading of the ignition system when funds allow. I would, of course, need a custom inlet manifold, which (after yet more research) seem to be available from a company called Bogg Brothers for around £200...

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There's a wealth of experience on here of people making all sorts of mods to their Esprits - several substituting the whole engine and ancilliaries. So I'm sure something like you're suggesting would be possible - if well beyond my experience and skills - though I'd have thought any bike carb set up would be too small to feed a 2.2litre lump.

My real input is to suggest you re-examine your motives. Most of the major mods on here are done by the professional or wannaby engineers who derive pleasure from process as much as the result. Your preamble doesn't really suggest that. You currently own one of the relatively early and lesser powered Esprits (still much loved by most of us!). There's not really all that much difference in market prices of the various models. If you just want something a bit more "driveable" rather than a project, why not swap the car for a Turbo, or even a Stevens SE? It probably wont cost much more than your mod to change and you'll have a lot of fun in something a bit sharper without giving yourself both insurance and resale headaches by going down the custom route. JM2PW - good luck with whatever you decide.

Loving Lionel and Eleanor......missing Charlie and Sonny

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Rebuild the carbs yourself. For the Dellorto carbs a plethora of books exist that will take you step by step on doing it with some simple tools. Kits should be relatively inexpensive and if you can find it, a good quality carb dip to soak the parts. That or invest in an inexpensive ultra sonic cleaning tank. There are lots of tiny passages that need to be cleaned and you will need some compressed air, which if you don't have, a inexpensive small air compressor with blower attachment will do the trick.

Do one at a time and have a large clean table to layout all the parts. If you have patience you will be able to accomplish this task like a pro.

I would say stay away from the conversion unless you have lots of time, money and patience. The Dells, when operating normally, will give you what you are looking for. If you want to get into tuning I suggest the Innovate Technologies Lambda reader. This and a laptop will provide you some great tuning capabilities.



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if you want to see what the pile of bits looks like when you refurb a set of carbs please use this clicky thingy which will give you an idea.

It is NOT difficult, just take it step by step. Lay the parts out neatly in a sequence which aids refitting. Take plenty of reference photos if you feel that will help you with the reassembly. Do not use any abrasives or sharp oblects on any internal part and don't poke anything into the jets... just use aerosol carb cleaner and some sort of air spray to dry things off (we used a small airbrush which was more than up to the job).

So, it's just dismantle, clean everything, substitute the parts/gaskets/seals etc supplied in the refurb kit, reassemble, and refit to car.

Adjustment is a matter of following the instructions in the manual then using a vacuum gauge to set each carb up relative to the others. The penultimate picture in this clicky thing link shows where the guage is connected. The gauges can be picked up at quite reasonable prices on eBay.

Total cost = way below getting someone else to do it for you. Satisfaction = way above.

I would suggest that you get the best out of what you have before you are in a position to judge whether you need any more 'performance' out of the Lotus or whether or not it is actually a different vehicle you need.

There are plenty of people around who have 'improved' things to the point where ok, they go like stink but sound like heaps of sh*t and break down on a regular basis because they have stressed components which are both old and were never really designed to perform in the manner they are being asked to.

Still, at the end of the day it's your money and choice, so good luck with whatever you chose to do.

In theory there is no difference between theory and practice.<br />

<br />

In practice, there is!

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Unless the carbs can be pressurised (and most aren't designed to be), they will be no use on an turbo motor (assuming you are planning to blow through them). Once Dellortos are set up, there is not actually much to go out of tune. If you cant get the carburation correct, you are probably masking a different problem.

Having said that mappable ignition and fuel injection are a major step forward to releasing the true power of a 910 motor.


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