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Throttle Problem

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Ben Kelly10/06/2009 19:07:41
167 forum posts
35 photos
Hi, i have just bought a new carb from Just Engines for my old ASP 75 two stroke engine.
However, when i put the new carb on the engine and link up the throttle arm to the pushrod, the servo really struggles to open and close the carb, and if i tighten the bolt that holds the carb in place it wont move it at all.
i have taken the carb off again and it is not stiff or having problems moving when im using my fingers and i cant work out the problem.
Theres nothing snagging the pushrod and the servo is working fine with a fully charged battery.
Any help to point me in the right direction would be greatly appreciated.
Paul Course10/06/2009 19:20:21
85 forum posts
Hi Ben does the throttle pushrod go through a bulkhead? if so is it fouling on the bulkhead because the carb throttle arm isn't in exactly the same place as the old one. and Perhaps a drop of fuel or engine after run oil on the barrel may help
Regards Paul
Ernie10/06/2009 19:36:46
2530 forum posts
21 photos
Hi Ben. 
Surely, the problem must be the pushrod/servo system. Disconnect the pushrod, and if the carb opens and closes easily, then the connection must be the problem. 
Try replacing the pushrod with a length of cycle brake cable, with a clevis soldered to each end. If you are unsure about soldering, just ask, or use a sullivan snake. If the linkage is long, it will need to be supported at intervals


Ben Kelly10/06/2009 19:53:06
167 forum posts
35 photos
ok thanks for the replies, i will go and have another go at it and will report back when i can. 
Ben Kelly10/06/2009 20:31:41
167 forum posts
35 photos
Ok, current update from my shed.
I have taken off the throttle pushrod and tested the servo, nothing wrong there. Theres nothing catching in between the links and nuthing snagging.
I have put the carb back on again and tightened it in place and the throttle arm is really difficult to move using my hand but easy to move when not tightened in place. 
Whats going on???
Martin Harris10/06/2009 22:04:17
9348 forum posts
252 photos
Logically, something must be distorting when you tighten the pinch bolt but it's difficult to imagine what unless the metal is very poor quality.

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