Lotus Elan

Hesitation, back fire, low power - solved

PostPost by: LaikaTheDog » Fri Jun 05, 2020 5:41 pm

I developed a funny squeak, tightening things down, fan belts etc, didn't help.
I also had a problem with power and performance, so I checked timing, coil, leads, fueling...
Just couldn't sort out the power or the squeek !

I then noted to myself how odd it was that when I had bolted up the webers I had not done them up all the same amount.... that made me think that I was suckung air.. this would also explain the backfire, so I sprayed some wd40 on the joint and behold.. the squeak stopped and was replaced by a sucking sound on no.3 inlet ...

Tightening these nuts made no difference so I took off the carbs and found:
20200605_175522_copy_1512x2016.jpg and


Sadly I don't have a spare so I just ordered 4 new ones.
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PostPost by: Bill » Sat Jun 06, 2020 2:22 am

Laika -- Greetings from Lotus Land

Thank you - I just 2 hours ago managed to get home from a drive to town having experienced the same problem! I first thought the squeak / squeal that I had was a slack fan belt - then the strange performance started to occur, and worsened through the drive - cutting our at low speed, backfire ( embarrassing on the main street of our small quiet town). Had to keep the revs above 2000 in stop / go traffic to keep moving. Got home and was muttering to myself about chasing the problem down.

It is obvious to me now and is THE FIRST THING to check.

I "spose that the 57 year old anti vibration carb gaskets could be a good suspect - i haven't done the carbs for 24 years now. Fortunately I have a spare set.

Thanks again for the heads up.

Bill
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PostPost by: awatkins » Sat Jun 06, 2020 6:46 pm

I had the exact same failure on my Europa recently. When I removed the O-ring carrier I could see cracks all around the circumference of the O-ring Unfortunately I don’t know how old they are. I believe the failure incident was triggered by a carb spit-back which is an unfortunate property of the car’s current state of tune.
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PostPost by: Esprit2 » Sun Jun 07, 2020 4:28 pm

Bill wrote:I "spose that the 57 year old anti vibration carb gaskets could be a good suspect - i haven't done the carbs for 24 years now. Fortunately I have a spare set.

Bill,
Rubber does not age well, even just laying about. If you haven't done the carbs for 24 years, but you have a spare set of soft mount O-rings, are they 24 years old? Replacing the O-rings is not the equivalent of bringing the inlet tract up to date, if you use old parts to do it. Up to date means recent work done with new parts.

Just nagging, :wink:
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PostPost by: alan.barker » Mon Jun 08, 2020 5:49 am

If the "O" rings are new old stock they will be the old better rubber mix.
When i assemble i put a little MS4 Silicone grease on the "O" rings.
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PostPost by: 2cams70 » Mon Jun 08, 2020 7:14 am

Good reminder for me to replace the nitrile "O" rings supplied with my new QED spacers with better quality Viton ones.
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