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 Posted: 01-09-2017 12:53 am
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
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This is a repeat of the set-up chart I posted on 11-11-16.
Just adding the JHPS Store carb's data as provided by Don Burns on 12-27-16:

.............................. Lotus .......... Lotus .......... Per DonBurns
Engine Model: ........ 2.0 907 ....... 2.2 912LC .... JHPS Store .... Bfitz241's
Dellorto Specs: ...... Spec-5, ....... Spec-9 ......... N/A .............. Unknown
Carb Type .............. DHLA 45E .... DHLA 45E ..... DHLA 45 ....... DHLA 45 (45, or 45E ?)
Choke ................... 36 mm ........ 37 mm ......... 37 mm ......... 36 mm
Main Jet ................ 160 ............. 160 .............. 160 .............. 158
Main Air Corrector .. 230 ............. 230 .............. 230 .............. 230
Main Emulsion Tube, 7772-8 ........ 7772-8 ......... 7772.8 ......... 7772.7
Idle Jet .................. 50 .............. 55 (Esprit) .... 62 ................ 58
................................................. 58 (4-seaters)
Idle Jet Holder ....... 7850-7 ........ 7850-9 ......... 7850.9 .......... 7850.9
Float Weight ........... 10 gr .......... 8.5 gr ........... ______ ......... ______
Float Height ........... 16.5-17mm.. 14.5-15mm .... ______ ......... ______
Float Needle Valve .. 170 ............ 170 ............... ______ ......... ______
Pump Jet ............... 38V 42H ...... 50H .............. ______ .......... ______
Starter Jet ............. 70 ............... 95 ................ ______ ......... 95
Starter Emul Tube .. 7482-1 ........ 7482-3 .......... ______ .......... ______

For both the JHPS Store carbs, and Bfitz241's carbs, are they 45s with no letter suffix, 45Es, or some other suffix LETTER? The model ID should be cast into the top side of one of the barrels, inside the oval. It makes a difference... especially the desirable 'E'.

Just looking at the numbers, I suspect the idle jets are too rich for both the JHPS carbs, and Bfitz241's. The 7850.9 idle air correctors are pretty lean (emissions lean), and it appears that larger idle jets have been plugged in to enrich the mixture. It will do that. But it will also increase the idle circuit's capacity, meaning it will run beyond the 3200 rpm point at which the idle circuit should hand-off to the main circuit. The mains will still kick in on schedule, but if the idle continues beyond 3200, then it's double-fueling the engine. I suspect there will be a temporary rich spot just above 3200 rpm. I recommend reducing the idle jet size to only that required to 'just' feed the engine up to 3200 rpm without a stumble... no more. Then if the mixture is too lean, go to a richer idle air corrector (aka, idle jet holder). I get the best results with the 7850-7.

Idle Air Corrector Sizes (aka, Idle Jet Holder): (Rich/ Lean does NOT correlate to number value)
7850.5 .. LEAN, going down the list gets richer.
7850.10
7850.9 .. Spec 9, Spec 10, JHPS Store & Bfitz241 -- emissions lean
7850.4
7850.1 .. Normal -- Spec 1
7850.3 .. Normal
7850.6 .. 6 & .7 are very similar, almost interchangeable
7850.7 .. Spec 5 -- The 9XX likes 7
7850.2
7850.8 .. Richest

Regards,
Tim Engel

Last edited on 01-09-2017 07:00 pm by Esprit2