David, There has to be an orifice (jet) or screw. Are you sure a screw isn't hidden under a plastic cowl?
Get me an exact make and model so I can do some research. Josh On Wed, Jun 10, 2020, 08:08 David Risch via CnC-List <cnc-list@cnc-list.com> wrote: > Josh and Chuck, > > > > Mixture is new with AV gas so no issues there. Only one adjustment screw > on carb. Seems to only affect low throttle. As said all good in neutral > and good up until ¾ throttle in gear. Chuck mentioned if spark plug grey > and chalky, which it is, it is running lean at top end. How does one > adjust top end without adjustment screw. > > > > Thanks in advance. > > > > *David F. Risch* > > *(401) 419-4650* > > > > *From:* CnC-List <cnc-list-boun...@cnc-list.com> *On Behalf Of *Josh > Muckley via CnC-List > *Sent:* Sunday, June 7, 2020 10:17 AM > *To:* C&C List <cnc-list@cnc-list.com> > *Cc:* Josh Muckley <muckl...@gmail.com> > *Subject:* Re: Stus-List Yamaha 4hp 2 cycle > > > > Follow my carb tuning video. Post back with questions. > > > > https://youtu.be/caIdvC8WGDg > > > > Sounds like the idle/throttle screw (T) is keeping the butterfly open too > far with no throttle applied. It just so happens that in gear there is > enough load to slow 'er down. At full throttle is sounds like probably too > much fuel (H). I think that if it was too little it would die. Since both > of these "symptoms could be a result of too much low throttle fuel (L) you > should probably start by dialing it back a bit and see how thing go. By > doing this you will lower the fuel at idle AND lower the fuel a full > throttle. If you're lucky and my diagnosis is correct then you'll kill too > birds with one stone. > > > > My advice is based on having 3 adjustment screws H (high throttle), L (low > throttle), T (min throttle). If you're missing any one of these then it > has a jet which serves in its place. > > > > Josh Muckley > > S/V Sea Hawk > > 1989 C&C 37+ > > Solomons, MD > > > > On Sun, Jun 7, 2020, 09:29 David Risch via CnC-List <cnc-list@cnc-list.com> > wrote: > > So instead of giving it away I rebuilt the carb and half dozen other fixes > this winter. > > Runs and idles great, but at full throttle she bogs down continues to run, > but sounds rougher. When out gear it goes right to full throttle. > > Perhaps overpropped? > > Sent from my Android. Please forgive typos. Thank you. > > > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > > _______________________________________________ > > Thanks everyone for supporting this list with your contributions. Each > and every one is greatly appreciated. If you want to support the list - > use PayPal to send contribution -- https://www.paypal.me/stumurray > >
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