thedktor Posted February 20, 2009 Report Share Posted February 20, 2009 I'm sure I read a thread where someone was playing with jets to get a Montesa running smoothly but I can't find it! Was I imagining it, was it another bike altogether, anyone help as I'm very interested... Thanks! Steve Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 20, 2009 Report Share Posted February 20, 2009 Maybe it was this one about Cota 348 jetting http://www.trialscentral.com/forums/index....c=23543&hl= Quote Link to comment Share on other sites More sharing options...
tayld Posted February 21, 2009 Report Share Posted February 21, 2009 We have a 1982 Montesa Honda MH349 and this runs cleanly throughout the rev range. The carb is the standard Amal 2627 with jets as follows:- Main jet 145. Needle jet 107. 2B1 needle with circlip in second groove from top. No.4 slide. 20 pilot jet. These are the factory settings for this model. In getting the bike to run as smoothly as it does we have had to change the cranskhaft oil seals, if they are hard or worn the engine will draw air past the seals upsetting the carburetion. Before adjusting the carburettor it pays to make sure the ignition is correctly set, the air cleaner element is in good order and clean (old elements can crumble into bits) and the rubber connector between the carb and engine is flexible and free of cracks. The throttle slide can wear faster than the carburettor body, a worn slide lets more air past at low revs than it should. New slides (and other parts) are readily available from Amal via their website. In setting the pilot air screw make sure the engine is truly warm. Stop the engine. Start by adjusting the throttle stop screw by backing off the screw until the slide reaches the bottom of its travel. Then lift the slide by 1.1/2 to 2 turns of the throttle stop screw. Now gently screw the pilot screw in till it stops then wind it back out 1.1/2 turns to begin with. Restart the engine. We finally set the pilot air screw by listening to the engine revs, turn the pilot air screw slowly in both directions until maximum revs are attained. Turning the screw out weakens the mixture and inwards richens the mixture. Too weak or too rich a mixture will cause the revs to drop or the engine to stop. When the point of maximum revs has been found the throttle stop screw will probably need adjusting to your preferred tickover speed. Once set a half turn of the pilot air screw in either direction should cause the revs to fall. We have set two 349's to both run smoothly but the pilot air screw is a different number of turns out on each bike so an exact setting for the screw cannot be quoted. Hope this helps. Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 21, 2009 Author Report Share Posted February 21, 2009 Goddam it yes it was here, on a thread I Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 21, 2009 Report Share Posted February 21, 2009 We have a 1982 Montesa Honda MH349 and this runs cleanly throughout the rev range.The carb is the standard Amal 2627 with jets as follows:- Main jet 145. Needle jet 107. 2B1 needle with circlip in second groove from top. No.4 slide. 20 pilot jet. These are the factory settings for this model. In getting the bike to run as smoothly as it does we have had to change the cranskhaft oil seals, if they are hard or worn the engine will draw air past the seals upsetting the carburetion. Before adjusting the carburettor it pays to make sure the ignition is correctly set, the air cleaner element is in good order and clean (old elements can crumble into bits) and the rubber connector between the carb and engine is flexible and free of cracks. The throttle slide can wear faster than the carburettor body, a worn slide lets more air past at low revs than it should. New slides (and other parts) are readily available from Amal via their website. In setting the pilot air screw make sure the engine is truly warm. Stop the engine. Start by adjusting the throttle stop screw by backing off the screw until the slide reaches the bottom of its travel. Then lift the slide by 1.1/2 to 2 turns of the throttle stop screw. Now gently screw the pilot screw in till it stops then wind it back out 1.1/2 turns to begin with. Restart the engine. We finally set the pilot air screw by listening to the engine revs, turn the pilot air screw slowly in both directions until maximum revs are attained. Turning the screw out weakens the mixture and inwards richens the mixture. Too weak or too rich a mixture will cause the revs to drop or the engine to stop. When the point of maximum revs has been found the throttle stop screw will probably need adjusting to your preferred tickover speed. Once set a half turn of the pilot air screw in either direction should cause the revs to fall. We have set two 349's to both run smoothly but the pilot air screw is a different number of turns out on each bike so an exact setting for the screw cannot be quoted. Hope this helps. Great post Tayld, Thanks for sharing your Amal 26 / 27 tuning technique. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 22, 2009 Report Share Posted February 22, 2009 Goddam it yes it was here, on a thread I Quote Link to comment Share on other sites More sharing options...
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