1987 Yamaha 115 ETLH Carb adjustment

[scott06903]

Hi I am requesting guidance on the initial setting for the Idle adjustment/pilot screw on top of the carbs. I have a manual on order but if I can get a starting point that would be helpful. From the fully seated position how many turns out is the factory setting?

Thanks
Scott

[boscoe99]

5/8ths. Plus or minus 1/4 turn.

[scott06903]

Thanks Boscoe, much appreciated.

[scott06903]

Boscoe, would you be able to tell me the float drop specs? Thanks

[boscoe99]

It is in your service manual. Page 3-16.

12.5 mm. + or - 0.5 mm.

[scott06903]

ok I may have mixed some terms in my inquiry.
When the carb is inverted: from the body edge to the top of the bowl opposite of the pivot point I have ~16mm this is this the height?
When the carb is in the operating orientation and the float drops that measurement (carb body to bottom of float) should be 12.5mm? and this is the drop? I currently have far less.

my manual is still in the mail I appreciate the help.

[boscoe99]

I love Yamaha data.

The SM for your model shows one thing whereas the SM for a later model 115 shows something different. Even though the part numbers for the carburetors are one and the same.

Take your pick.

[99yam40]

maybe the float changed in the later years

[scott06903]

in this case I believe 16mm is the correct spec. The engine ran ok but a little rough when I bought it a week ago. 3 floats were around 16mm one was quite a bit higher when measured as in the pics above. I'll have the manual by Monday.

thanks for the info guys.

[TownsendsFJR1300]

As a general rule, with the carb upside down, get the float even with the carb body, (as shown in picture 2 of Boscoes post)

It shouldn't be hanging down or sitting upward..

[scott06903]

please take a look at the video in the link and let me know what you think. I have an opinion but don't want to bias anyone by pointing out what I think I see/ hear.

https://youtube.com/shorts/HiVmVZL11uA?feature=share

thanks

[99yam40]

sounds like it has a knock

[TownsendsFJR1300]

please take a look at the video in the link and let me know what you think. I have an opinion but don't want to bias anyone by pointing out what I think I see/ hear.

https://youtube.com/shorts/HiVmVZL11uA?feature=share

thanks

Sounds like it has a very solid idle.


As noted above, that knocking sound seems a bit loud for a 2 stroke.

Might try pulling one plug wire at a time and see if the knocks goes away or decreases significantly..

[scott06903]

I did the spark plug disconnect as suggested above, no change. I also removed the gear case and again no change.

This is my Son's engine he only paid $1000 for the boat '84 18' wellcraft cc and trailer. The guy he bought if from said he hit a rock and thought the gear case was damages, that turned out to just be a spun prop. I may just have him run it as is I am not sure it is worth rebuilding. Has anyone done a rebuild on a v4 yamhah 2 stroke that can speak to the difficulty?

[TownsendsFJR1300]

The biggest issue would the age and the many bolts you'll likely find seized/ breaking on you in the disassembly.

I'd probably just pull the reed valve assembly /plate to reach the crank and connecting rod ends.
Then put some pressure / check for any looseness between the rods and crank.