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What's The Correct Belt Tension on an S1?


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6 replies to this topic

#1 gtookey

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Posted 30 July 2008 - 11:45 AM

Hi all, going to tighten up my timing belt on my S1 later today. The workshop manual says it should be adjusted to 95lbs. After reading this from an earlier thread:

It's a brand new belt supplied by SJ; can't recall the belt's manufacturer.

I read from an earlier post last year that referred me to an even earlier post from a chap called Tim Engel/s (I think) that a reading of 55 lbs on a Krikit KR1 gauge is equivalent to the appropriate reading on a Burroughs gauge.

I used my Krikit at 55 lbs on my last Esprit (the one that decided to incinerate itself a couple of months ago - the insurance company are starting to be a pain in the arse about my claim!) and that seemed to be fine; no vibes at all.


Now I'm not sure. The belt is approx a year or so old with about 1200 miles on it, and I'm using the Kritik KR1 to rate the tension.

I would tend to go with the workshop manual but can someone please confirm.

Thanks.

Gavin

Edited by gtookey, 30 July 2008 - 11:47 AM.


#2 ghe67

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Posted 30 July 2008 - 11:54 AM

Hi,
this is an extract from Tim Engel sheet.
He is always right!!

907, with trapezoid belt tooth shape.
Burroughs Gauge BT-33-86A 5-20
Midway between auxiliary and inlet camshaft pulley
Cold engine (ie, before it's been started for the first time that day).
Do NOT attempt to tension a hot engine.
15 - 25 C (59 - 77 F) ambient temperature
At TDC after rotating crankshaft a minimum of one turn clockwise.
Take three readings at 120 crankshaft degrees and average.
Elite Eclat Workshop Manual (1974, re-issued '76 & '79 with Service Bulletins)
Burroughs: 44.91 kg (90 lbs), COLD. 54.43 kg (120 lbs), hot
Krikit KR1: 50 lbs COLD or 60 lbs hot.
Lotus Service Bulletin 1977/1, (15 Jan 77)
Burroughs: 95 105 units, cold. (120 125 units hot).
Krikit KR1: 52 58 lbs COLD, 66 69 lbs hot
Lotus Service Bulletin 1978/19, (24 July 78), and
Esprit S1/S2 Workshop Manual (1978, re-issued 1982).
Burroughs: 90 95 units, cold. (120 125 units hot).
Krikit KR1: 50 52 lbs COLD, 66 69 lbs hot
Esprit S3 / Turbo Esprit Service Notes (1985, re-issued 1986).
Trapezoidal Belt Tooth Prior to 1986 MY
HTD Belt Tooth 1986 Onward
Cantilevered Burroughs Gauge T000G0025J
Burroughs: 90 95 units, cold. (120 125 units hot).
Krikit KR1: 50 52 lbs COLD, 66 69 lbs hot


910 & 912, with HTD belt tooth shape.
Esprit S3 / Turbo Esprit Service Notes (1985, re-issued 1986).
Trapezoidal Belt Tooth Prior to 1986 MY
HTD Belt Tooth 1986 Onward
Cantilevered Burroughs Gauge T000G0025J
Burroughs: 90 95 units, cold. (120 125 units hot).
Krikit KR1: 50 52 lbs COLD, 66 69 lbs hot

Or, the short form

For checking Lotus 9XX Timing Belt Tension:

Lotus specified tension gauges:
Non-cantilevered Burroughs Gauge BT-33-86A 5-20
Lotus Part Number T000T0290A.
Cantilevered Burroughs Gauge
Lotus Part Number T000G0025J.

Burroughs sold the gauge line to SPX Kent-Moore.
US$250 -- Out of series production, special order only.


Aftermarket Belt Tension Gauge
HMC International Division, Inc.
Krikit KR1 Belt Tension Gauge, Model Number 91107).
US $17.00 suggested retail / US $14.00 at NAPA.


Tensioning Procedures
From Lotus Workshop Manuals & Service Notes
1) Midway between auxiliary and inlet camshaft pulley
2) Cold engine, before it's been started for the first time that day.
3) Do NOT attempt to tension a hot engine.
4) 15 - 25 C (59 - 77 F) ambient temperature.
5) Rotate the crankshaft a minimum of one turn clockwise.
5) Crankshaft at TDC.
Take three readings at 120 crankshaft degrees and average (0 , 120 & 240 )


Tension Spec's
From Lotus Workshop Manuals and Service Notes

1974 Burroughs 90 COLD, 120 hot
thru Krikit KR1 50 lbs COLD 60 lbs hot.
1976 Trapezoidal Toothed Belt

1977 Burroughs 95-105 COLD, 120-125 hot.
Krikit KR1 52-58 COLD, 66-69 lbs hot
Trapezoidal Toothed Belt

1978 Burroughs 90-95 COLD, 120-125 hot.
thru Krikit KR1 50-52 COLD, 66-69 lbs hot
1987 Trapezoidal Toothed and HTD Toothed Belts

1988 Burroughs 95 COLD, 125 hot.
thru Krikit KR1 52 COLD, 66-69 lbs hot
HTD Toothed Belts



Hope this help.
Cheers

#3 gtookey

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Posted 30 July 2008 - 02:19 PM

Thanks for the info. But what I don't get is a measurement in lbs is the same no matter what gauge you use. Both the Burroughs and Krikit gauges take a tension reading in lbs. So why would the lbs value be almost 1/2 when using the krikit? surely they should be the same?

Edited by gtookey, 30 July 2008 - 02:23 PM.


#4 JonFairhurst

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Posted 30 July 2008 - 09:49 PM

I would think that the difference could be in the spacing between the "fingers".

Personally, I've always done mine by hand. One one occasion I had set it a bit tight, and I could hear the difference immediately. I figure that it doesn't have to be perfect - just not so loose as to skip a tooth, and not so tight as to damage the belt.

Using a tool is great, but don't trust it 100%. Depending on how you hold it, the level of sticktion and how much belt is between the cam sprockets, the tolerance is probably huge. Make sure it feels right, isn't floppy when running and doesn't make any zipper noises either.
Jon Fairhurst
1986 Lotus Turbo Esprit HCI

#5 lotus4s

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Posted 30 July 2008 - 11:43 PM

The Burroughs measures in UNITS not LBS. They are not the same unit of measure, hence the difference.
1995 S4s
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SOLD

#6 gtookey

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Posted 31 July 2008 - 03:30 AM

my workshop manual says:

'Set tension using Burroughs gauge to 95lbs', not units

Right now my krikit KR1 says the tension is 50lbs and the belt is whipping under load.

Edited by gtookey, 31 July 2008 - 03:30 AM.


#7 gtookey

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Posted 31 July 2008 - 06:03 PM

Gentlemen, I am sorry I did miss read my manual. The reading of 95 is for units and not lbs. I apologize.




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