Yamaha 40-HP Two-stroke-power cycle Throttle Linkage

[primaldna8]

[Moderator's Note. This post was made in the INTRODUCTION TO THE FORUM SOFTWARE FORUM. That forum is not a boating forum. Please to not post questions about engine throttle linkage to the INTRODUCTION TO THE FORUM SOFTWARE forum. This post has been moved to REPAIRS and MODIFICATIONS for possible further discussion.]

Q1: what is the proper set up for the throttle linkage cam distance to the roller on a [1991--ALWAYS USE FOUR DIGITS FOR YEARS] Yamaha 40-HP two-stroke-power-cycle engine?

BACKSTORY.

I picked up this engine. The previous owner [and a male relative through his sister or brother or sister-in-law or brother-in-law] "tinkered" with it.

The engine service manual has idle and pickup timing at 7-degrees ATDC. From that I think the roller should be touching and ready to open throttle when moved. The roller seems to me to be out of that position.

Q2: is my thinking about the position of roller correct? To me there seems to be a lot of "slop" there.

Q3: also (from this cdi) are the two lines close together the 7 atdc reference?

PXL_20240604_153924162~4.jpg (63.45 KiB) Viewed 4040 times

Fig. 1. The current cam position in neutral.
[The purpose of the red marks is left to the viewer to intuit.]

[jimh]

Q4: What does "from this cdi" mean?

Q5: what are those crudely drawn red lines pointing to in Figure 1?

Q6: where is the adjustment that changes the position of the throttle linkage between cam and roller? I don't see any adjustment in Figure 1?

My inference is that there is some portion of the roller that may be missing. Often the roller will have a rubber surround that will increase the diameter of the roller. This might also reduced the gap between the throttle cam and the roller that seems to be the focus of your inquiry.

Q7: do you have the OEM service manual for this engine?

If you are now going to "tinker" with the engine, your efforts will be much improved if you have the manufacturer's service manual to guide you.

[jimh]

The previous owner [and a male relative through his sister or brother] "tinkered" with it.

I don't understand the importance of knowing the precise family relationship between the previous owner and the second person who also "tinkered" with the engine will have on your question.

Q8: Is there some element of importance about that relationship that I am missing?

[primaldna8]

Hi jimh. Are u able to delete this whole post? Please do. I'll work on a more detailed one in a better format in the right section

[jimh]

I will move this post to REPAIRS and MODIFICATIONS, and you can append more information there.