Hard start/rough idle until warmed up

[drolds72]

I have a 2003 T50TLRB, that takes between 3 and 7 key bumps to start, and idles kind of rough for about 3 or 4 minutes until it comes up to temp. I have replaced the plugs, and removed and cleaned the carbs, as well as syncing them. I tested the primestart plungers and they extended after they got hot. Engine runs perfect after warmed up. Seems like engine is not getting enriched when cold, but I am not sure why. I paid extra attention to the ports in that area of the carb. I did not replace anything in the carbs-are there any o-rings prone to leaking if not changed? Is it possible that the plungers are not retracted when cold? Factory manual has a length spec for hot but not cold.... Should I be looking at anything electrical related to the cold start mapping? Any advice appreciated at this point. thanks.

 

[robert graham]

Re: Hard start/rough idle until warmed up

Does your starting procedure include pumping the primer bulb until hard and keeping the neutral throttle control in the fully closed(down) position? Have you checked your fuel pump and spark plug condition for rich mixture/fuel wet plugs? Good Luck!

 

[drolds72]

Re: Hard start/rough idle until warmed up

Yes- I can pump ball 4 or 5 times till firm. Fuel pump is actually brand new (I broke a nipple off of it removing a hose), and I do not advance the throttle at all until it runs on its own. All 4 plugs are dry and light brown.

 

[robert graham]

Re: Hard start/rough idle until warmed up

I believe there is a diaphragm in the prime start system that calls for service or replacement every few years. My Yamaha is a 1999 and I've never checked mine since it starts and runs good, so far. Maybe check that diaphragm and passages to be sure prime start is enrichening your mixture properly and sufficiently. Sounds like the prime start system could be your problem, hopefully one of the prime start guru's on here can offer a bit more help on operation of this system. Good Luck!

 

[drolds72]

Re: Hard start/rough idle until warmed up

I had the chance to compare the primestart plunger to a known good when when they were both cold, and they were the exact same length. So this eliminates the chance of it sticking in the warmed up position and staying there. It will fire, but not want to stay running until the 3rd or 4th keybump. Then it will run rough for 3-4 minutes until warm. Then it runs perfectly all the way thru WOT. Boat's fuel side, from pickup to connector was all replaced last year as well.
Could I be overlooking something, or am I looking for a problem that does not exist? Have a friend with the same engine, and his fires up first time everytime, and runs good from the getgo...