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5hp 2 stroke yamaha self accelerating !!

T

trent stratton

New member
in neutral...small turn on the handle causes full acceleration...in gear...idles ok but as soon as handle turned it loses power almost to stalling...motor is haunted!! any ideas? 1989 model
 
Hey there

With the cowling off, can you see what is happening with the throttle linkage at the carburettor? There may be something weird going on there. The stalling as you take off is usually a too lean condition where you are getting more air than fuel. This could be a clogged carburettor or a vacuum leak. The two symptoms together are a bit weird though! Here's a vid on carb cleaning: https://youtu.be/ye_Ui9D8dBE To check for a vacuum leak you spray something like an unlit gas torch around the intake manifold of the engine and listen for a change in idle RPM as the gas gets sucked in through the leak.

Let me know how you get on,
Stuart
 
Thanks Stuart...cleaned as per instructions. prior to cleaning choke was fully closed to start and if adjusted engine died almost right away. after cleaning choke was adjustable for a short period ...seconds...then back to the same conditions prior to cleaning...!I cant keep it running long enough to try the vacuum leak test. if it was bad fuel it would just not run at all, right?...linkage etc all good and was working before this problem. Any further suggestions would be appreciated
 
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