Lotus Elan

Rough mid-range

PostPost by: Galwaylotus » Tue May 22, 2012 8:40 pm

Ok. Suggestions please. My S3 with Webers starts ok and runs fine at full throttle. During normal part-throttle cruise it starts bucking and missing. I dip the clutch and rev it to clear and usually shift down a gear to get going again. Trying to determine if it's carburetion or ignition. Has anyone experienced this problem before? Thanks in advance once again, folks. :?
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PostPost by: ardee_selby » Tue May 22, 2012 10:44 pm

Before speculating...could you let us know if the "patient" is in the standard S/E state of tune with carbs having the original choke/jet sizes installed? If so, you may be experiencing the S/E flatspot syndrome to some degree apart from anything else.

Cheers - Richard

P.S. Does this thread have any parallels with your prob?

elan-f14/weber-problem-t21985.html
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PostPost by: simonknee » Wed May 23, 2012 3:18 pm

If you determine that it is carbs then join Keith Francks forum on Yahoo, Sidedraft_Central.
Find his tuning white paper and pay particular attention to float level (the manuals and Weber are all wrong, wrong, wrong).
Then set aside a few weeks to read the posts and catch up on what he has discovered/invented.

Please do treat Keith's forum like you are a guest in his house rather than the rowdy pub approach in this one.

Simon
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PostPost by: Galwaylotus » Wed May 23, 2012 5:08 pm

simonknee wrote:If you determine that it is carbs then join Keith Francks forum on Yahoo, Sidedraft_Central.
Find his tuning white paper and pay particular attention to float level (the manuals and Weber are all wrong, wrong, wrong).
Then set aside a few weeks to read the posts and catch up on what he has discovered/invented.

Please do treat Keith's forum like you are a guest in his house rather than the rowdy pub approach in this one.

Simon

Already a member! :D
My main concern is that the engine didn't run like that when I bought it. I haven't disturbed anything on the carbs except the idle speed adjustment; however, I did have the carbs off a couple of years ago to get at the distributor. It ran ok when I got it back together so I assume I had the correct tension on the thackery washers. I might first have a look at the float level if it's determined to be fuel rather than ignition.
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PostPost by: rcraven » Wed May 23, 2012 6:40 pm

If you have a mechanical fuel pump maybe it's faulty and not delivering enough under load at mid revs.
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PostPost by: simonknee » Wed May 23, 2012 8:06 pm

If your already there then you'll already be at 25mm. :D Do recheck your float level. In my experience it can drift unexpectedly (odd but it happened to me) and you can do it my peering down the wells so no need to disassemble.
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PostPost by: twincamman » Wed May 23, 2012 9:03 pm

WELLL FIRST OFF THERE IS NO NEED TO REMOVE A CARB TO REMOVE THE DISTRIBUTOR --- Simply remove the cap --loosen the clamp remove the rotor and withdraw the unit [ with everything at TDC ----get a unyisine and balance the carbs -- if that doesnt cure the flat spot --check your timing is correct with a timing light at idle below 1000 rpm -and treat it to some new plugs -or it could be your condensor on the way out eventually it will quit if it is -ed -------- poor spellers of the world untie
dont close your eyes --you will miss the crash
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PostPost by: bitsobrits » Thu May 24, 2012 2:56 am

Most likely you have a clogged idle jet (which is misnamed as it controls off idle until the main circuit comes in). Remove the idle jets and holders, separate the two, and inspect the orifices with a light. Clean all openings with compressed air or a nylon bristle (no wire, please!). A very small bit I'd crud can make a huge difference.
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PostPost by: Galwaylotus » Thu May 24, 2012 7:42 pm

Thanks for the suggestions, folks. I might get a chance this weekend do dive into it. I'll try the float level and plugged jets first and report back when I have any results.

P.S. I kinow you don't need to remove the carbs to get at the distributor - unless you drop a screw into the block trying to get it back together!!! :oops: Anyway, that was a couple of years ago and it's all good now. :)
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PostPost by: twincamman » Fri May 25, 2012 3:34 am

well theres only one bolt on the clamp ----you must be EXTREMELY talented to have that happen -------I dropped the screw head from a spark plug into the plug hole once .----ed
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PostPost by: ecamiel » Sat May 26, 2012 1:02 am

Most carburation problems are ignition!
Mid range is often max pressure. If you can clear it by running hard try new plugs Bp6ES I believe. If that fixes it, go through the whole ignition system including checking voltage at the coil - another common culprit. It solved it for me after hours wasted on the carbs.

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