Yamaha air adjustment screw

[123jeffb]

How many turns do I have to back off the adjustment screw from bottom on a 1999 yamaha 155 hp (C115TLRP) with twin barrel carbs? Someone told me 2 1/8 turns, but this seems a lot to me...does anyone know the correct number of turns?

 

[jeffersondodson561]

Re: Yamaha air adjustment screw

You have a 1991 motor BTW I can't find my tune up specs manual but maybe someone here has one, but that does not seem to far out.

 

[123jeffb]

Re: Yamaha air adjustment screw

Yes, It is a 1991, my mistake. I have good compression, timing is good and everything seems ok. I had to clean the carbs...I have a repair manual, but it doesn't say anything about the number of turns on the adjustment screw. It ran great last year, but has been setting up for a few months and the carbs were dirty dirty. After I clean them, it will idle good, but is slow on take off.

 

[123jeffb]

Re: Yamaha air adjustment screw

Yes, It is a 1991, my mistake. I have good compression, timing is good and everything seems ok. I had to clean the carbs...I have a repair manual, but it doesn't say anything about the number of turns on the adjustment screw. It ran great last year, but has been setting up for a few months and the carbs were dirty dirty. After I clean them, it will idle good, but is slow on take off.

 

[99yam40]

Re: Yamaha air adjustment screw

Sounds like you need to clean them a little better and do the link and sync procedure in the manual when you reinstall the carbs.
The manual should have the settings in it,some motors have different settings for different carbs.
What manual do you have? one for a 1999 155 HP like you said you have?

 

[jeffersondodson561]

Re: Yamaha air adjustment screw

If it idles good getting the right mixture is not going to help you, when you open the throttle valves the tranistion/off idle ports take over and then the high speed circuit takes over. How did you measure your floats? And did you use/reuse gaskets? Sierra kits? I have not had good luck with Sierra gaskets.