pschrauber Posted December 8, 2016 Report Share Posted December 8, 2016 Hi folks, I' am looking for an alternative carb for a Montesa Cota 242, the OEM fitted Amal is good but shows some wear especially the slide and cylinder area of the carb body , surplus the bike came from a high mountain area and I live at 50m above sea level so I have to readjust the carb of bike quite a bit. As the bikes I have in the garage are fitted with Dell'Ortos, I would like to keep the inventory of spare parts jets, needles gaskets and so on low . So do anyone have tried to swap the Amal through a Dell'Orto and can even provide their choice of jetting's needle and slide? would be great and ! Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 8, 2016 Report Share Posted December 8, 2016 Patrik, have you contacted Dellorto themselves, they might have the information on file. http://www.dellorto.co.uk Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted December 9, 2016 Report Share Posted December 9, 2016 i would start with the standard settings we have now as listed on the sherco website for the 07 (?) bikes. From memory a 33 pilot and im not sure on main but 144 rings a bell? Quote Link to comment Share on other sites More sharing options...
pschrauber Posted December 10, 2016 Author Report Share Posted December 10, 2016 @BRT40 so I have to ask DellOrto UK? @NigalDabster will look there too In general found a topic about the carb swap at the old ToDo trials form from 2009 the use of the DellOrto was heavily discussed and many settings where posted as too both possible carbs PHBH and PHBL. Without getting a favorit beside the Italian gas air mixer was in favor towards the Spanish Amal. Their jetting set up was quite wide in the range. To make things worse Todo Trials sells now a "ready to race" Mikuni variant too which makes the decision even more difficult. I personal now thinking about the Mikuni clone form DellOrto with air screw and idle jet nozzle or instead the DellOrto VHST which uses the same specs as the PHBH wich a square slide. But still their might be an owner of an 242 which had already done the carb swap and may be can share about his experiences? Quote Link to comment Share on other sites More sharing options...
pschrauber Posted December 11, 2016 Author Report Share Posted December 11, 2016 Well did some research to the Dell'Orto fitted 307, 309, 310 and 310 Evasion they had: Model: 307 309 310 and 310e carb: PHBH26SD PHBH26ZS PHBH26ZS slide: 45 45 45 needle: X11 X32 X4 position: 2nd 2nd 2nd choke: 60 60 60 idle jet: 60 58 58 main jet: 95 92 92 needle jet: 264 BN 264BN 264BN fuel valve: 200 200 200 Sounds good, still thinkin about the Dell' Orto with nozzel jet is the right way. Quote Link to comment Share on other sites More sharing options...
pschrauber Posted December 11, 2016 Author Report Share Posted December 11, 2016 So did a test run and ... Mmmmh ... yes it's running ... but could run crisper, needs more idle and runs a tad rich in my personal opinion, adjusting the mounted carb did not change much beside idle rev. So I took off the carb and took a deep look inside. Well the carb need's an overhaul, the slide is pretty much worn out, never have seen so much wear ! The jets / all screws where assembled with maximum force, on screw that attaches the flange to the rear manifold towards the airbox was sheared, . I would love to get this carb in decent condition back, what type is it as AMAL has some types of the MKII, is it a 2000, 2600, 2900 or a smoothbore I have no idea? Printed carb- number at the top: 625 720 403 Printed carb- number at the side: L25 27 and below 418 So can someone please get me in the right direction which AMAL type carb I have here? Below some pic's of the mess: Anyway I think I get additional a DellOrto for the bike, the same typo like the TXR have with following set up: carb: PHBH type: CS slide: 45 needle: X4 position: 2nd choke: 60 idle jet: 58 main jet: 92 needle jet: 264BN fuel valve: 200 Quote Link to comment Share on other sites More sharing options...
pschrauber Posted March 12, 2017 Author Report Share Posted March 12, 2017 (edited) Testing days are over now. I had some testing involved and finally got an good result, I checked first in the garage, than as usual decided to go with something different but at the field test out side I had to change again and again until being pleased. Montesa 242 now mounted with a Dell'Orto PHBH CS carb, (Yes with air screw as it's advanced in technology compared to the fuel screw type*). I also exchanged the tiny original exhaust tube at the end for the aluminum WES type which reduces loudness a lot is as heavy or light because twice as big. The result: carb: PHBH type: CS slide: 45 needle: X4 / X44 position: 3nd choke: 60 idle jet: 60 winter, below 10°, (58 summer) main jet: 95 winter, below 10°, (92 summer) needle jet: 266 fuel valve: 200 * There is some rumor that air screw Dell'Orto's are a pain, that's not true, they simply are a bit more difficult to adjust but can provide a better performance.To the air screw, it's just the opposite in adjustment, turning in means richer and turning out leaner. The air effect takes time to affect the carb, for proper adjustment, use a slightly higher idle rpm, then really slowly turn the screw and begin with half a turn out until you reached the point where you have most rpm, then the air screw is adjusted. Anything below 1 turn and above 3 turns means you have to use another idle jet or nozzle. Still a tiny bit too lean ... Edited March 12, 2017 by pschrauber 1 Quote Link to comment Share on other sites More sharing options...
b40rt Posted March 12, 2017 Report Share Posted March 12, 2017 Looking good Patrik. Why do you prefer the air screw Dellorto ? What are the benefits over petrol screw ? Quote Link to comment Share on other sites More sharing options...
pschrauber Posted March 12, 2017 Author Report Share Posted March 12, 2017 The air screw sits at the rear towards the direction of the air filter and regulates how much air will go to the idle nozzle, the result is a qualitative setting,The fuel mixing located towards the intake of the engine regulates the amount of gas leaving the idle nozzle (already premixed with the air) which is a quantitative setting. You have more possibilities when using the air screw but too a bit more harder work to determine what's right Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted March 13, 2017 Report Share Posted March 13, 2017 have you done back to back comparisons with the original amal as my 242 runs sweet as a nut with stock carb? Quote Link to comment Share on other sites More sharing options...
pschrauber Posted March 13, 2017 Author Report Share Posted March 13, 2017 The bike did run fairly good with the Amal carb, but was slow in response, it felt supersmooth but was a bit liveless for my personal taste. As the Amal had worn itself down (both slide and body), one screw was sheared off, the zinc die cast is an issue for itself ... So I looked up the PHBH as it's contemporary. The bike changed it's attitude being now much more lively and revs up quicker, it also have now an ultra low idle. However the engine does hold the revs a bit long after closing the throttle in my opinion. In all it's an advantage for me, if it would be for you can be questionable. Quote Link to comment Share on other sites More sharing options...
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