What carb settings, 950 LM1?

Technical Big Block Tonti and Loop Frame models
1

I know that the question I am going to ask cannot be accurately answered (except by running the bike and sorting it out myself) but I would still like to ask for general guidance. Bike is a Le Mans 1, so big valve head but with 950 barrels on and a C:R of 9.1:1 instead of 10.25:1, and a Lanfranconi exhaust. I have some second hand carbs to fit, but settings on them are different to standard LM1 settings.Idle jet LM1 std =60, on my carbs =70Main jet LM1 std =135, on my carbs = 140Needle, LM1 std =K5, on my carbs = K18Needle jet = 265, on mine same.Slide, LM1 std =60/1, on my carbs = 60/3Choke, LM1 std = 70, on my carbs same. Obviously I can (and might) fit what I have and see what happens, but based on the fact that the only difference on the engine from standard LM1 is a lower compression ratio, and larger capacity, I am tempted to take the settings back to standard and go from there. I understand that a lower C:R calls for a larger main jet, typically, but I know a lot of LM1/2 do run 950 conversions, presumably as mine at a lower compression ratio than standard LM1, and wondered if any of you know how your carbs are set up, and what the settings are. My other enquiry is does the LM1 run generally rich when on standard settings on a standard 850 engine? Also the settings in my second hand carbs does not seem to match any standard settings that I have found. So anybody with pearls of wisdom, I would be glad to hear from you before I possibly lay out some more cash.




ReggieV2013-01-21 18:44:26

2

I guess a starting point could be the carb specs from a LM1000.
Idle jet 57. Main jet 145. Needle K19. Needle jet 268. Slide 60/5. Choke 60.

3

There is come "carby " settings in the Aigor site bud

http://www.mypage.tsn.cc/rdd/TT/guzzibear2013-01-22 11:03:36

4

Don’t remember any great jet changes for 950 conversion. As you I think go back to standard sizes, then go by spark plug colour. If looking too light main jet may need to up one step, as a guess. HTH

5

My other enquiry is does the LM1 run generally rich when on standard settings on a standard 850 engine?

Don’t think so. Pumping the throttle in inappropriate situations doesn’t help of course as it just throws great gobs of petrol in which will make it seem rich.
Mike H2013-01-22 13:51:38

6

get your float hight right and go from standard

7

Oh yeah floats! Just remembered something, 950 Spada etc. has a size larger main jet than T3 etc., so yes a step up on the main seems reasonable.

8

Thanks for the replies. I favour going back to standard, but it’s going to cost me another £130+ in parts! On another site I found this;Lots of LM Is with 36s came with the wrong slide BTW. Mine did. I
forgetwhich is correct 60/1 or 60/3. If you have 36 Dellortos make sure you
have thecorrect slide. Mine activated the accelerator pump right off idle
and alwayswanted to fall on it’s face accelerating from a stop until I found
the problemand got the correct slides Does anybody have anyknowledge of the above because ironically the Steine Dinse site identifies 60/3 as replacement slides for the LM1, whereas the parts book states 60/1, the S.D. site suggesting the correct slides might be 60/3? On the 60/1 the pump control cam starts at 10mm and finishes at 20mm.On the 60/3 the pump control cam starts at 2mm and finishes at 30mm. I am wondering if the 60/3 would be better as it has a more gradual ramp, but conversely starts 8mm earlier at 2mm. Is the 60/1 “too much too soon?” I will find out when I get it started up which will be in the next three or four weeks as it is nearly complete.Thanks again for your help.
ReggieV2013-01-22 21:31:17

9

Here’s the standard replacement slide on gutsibits: http://www.gutsibits.co.uk/prod_img/lrg/IMG_2080.jpg Pump profile facing front, looks like a ‘1’ to me (10 & 20 mm). From here: http://www.gutsibits.co.uk/pr/TheShop/index.php?f=e&Shnew=1&Model=7&ModelName=Le+Mans+1%2C+Le+Mans+2%2C+Le+Mans+3%2C+Le+Mans+1000%2C+1000S&Cat=FUA&CatName=Fuel+and+Carburettors&Sort=PriceDesc This might also help - or just confuse things more http://www.dellorto.co.uk/images/parts/Pumpramp.pdf From memory (which is unreliable) can’t remember mine having a long ramp like a ‘3’. Pretty sure more like a ‘1’ (short ramp, delayed) Don’t forget you can still control how much is squirted in usng the pump diaphram travel control setscrew. HTH

10

See also DellOrto UK site PHF spares page: http://www.dellorto.co.uk/merchandise/products.asp?CategoryID=2&PartsectionID=21

11

Thanks for that info Mike.