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I have just tried to solve the problem of a poor running Derbi senda 125. we took the carb apart checked the jet it wasnt blocked cleaned the plug and took the air filter off. it runs on full choke but will not run without it. Anyone know what else I should check
Your carb should have another jet. What you cleaned was the main jet in the center of the carb. There should be another jet called a pilot jet. Often it has a metal plug covering it up so the setting can not be changed at that point. Instead, they want you to change the setting with the pilot air screw. In each case, if you remove the screw, count the number of turns for removal and put the screw back the same number of turns.
The pilot jet controls the idle. It picks up gas from the float bowl then the gas gets metered by the jet and the air screw then passes through a circuit (drilled passageway), in the carb casing and comes out in the center of the carb close to the needle jet. You will need to get the jet and circuit cleaned.
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Blocked fuel injector in the carb, usually gunk in bottom of tank gets pulled through into carb so idle jet is ok but when you give it the beans the main injector is blocked and the idle jet isn\'t enough to produce increased power demand, ends up just sucking in air only.
Hi there, The true top speed of the Derbi Senda DRD 125 R/SM is actually supposed to be 77mph, having the same bike but the SM model I can say confidently it doesn't go that fast unless it is my weight!
If the lad you have bought it off put in a 115mm jet into the carb this could be a reason why you are lacking speed People believe by upjetting their carb it makes the bike go faster but this isn't always true, you usually upjet to cater for other modifications such as big bore kit, sports exhaust or performance air filter. Personally I would change the jet back to what it should be and try from there, unless you wanted to spend countless hours fiddling with the air/fuel mixture trying to gain the right amount of air for the size of jet
check for spark at the plug. no spark? check for wet electrical connectors. yes spark? drain float bowl of gas. water may have entered during cleaning process. Shoot carburator cleaner into carb inlet and try to start engine.
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