Tri Z Guru's - Carb Questions, Z Tech and Pics

[Rider414]

I just bought a 85 Tri Z 250.

I liked this bike because it was different, kinda odd, and a Yamaha. It is also very complete and stock.

The first major problem I am finding out is that it runs like s&*t. It starts ok. But right off idle it loads up and blubbers (sounds rich) then cleans up ok through the mid-range and then sputters and spats on the top end (sounds rich). Plug looks rich.

Here is where the story starts. The PO said he put a different carb on this trike because the previous one was gunked up. He said he jetted it rich because he wasn't sure if it would be too lean. It didn't make any sense but I bought it anyway. When I first got it, it would barely hit the the pipe so I took went to the needle. It was on the second to leanest spot. I dropped it to the last spot to try it out. It was better. Then I pulled the airbox lid and it got alittle better.

Here is how it is jetted now:

ID Number 38W01
6h3 Needle (top clip position)
490 Main Jet - stock is a 470
Slide 2.0
Cant read the pilot
Spark Plug was wet, black and rich

Question:
1. Could this be a 86 Carb with 85 jetting parts?
2. I saw where someone said the 38W was a 85 and the 86 got the 38W01 carb?
3. My Intake says 38W and the cylinder said 38W01?
4. Is that 490 Main really causing this bike to act rich with a pulled airbox and needle on the leanest position?

I am kind of lost with this one. My only thought is this carb body is a 86 and not a 85.

PICS for Chuckie:
181530
181531
181532

[barnett468]

Put a piece of clear plastic tubing in place of the black one that runs to the cylinder. If that tube gets any gas in it your fuel pump is leaking gas into the engine and needs rebuilding.

[Rider414]

I will certainly try that!

I assume that would/might be causing the excessively rich condition?

[badass350x]

Put a piece of clear plastic tubing in place of the black one that runs to the cylinder. If that tube gets any gas in it your fuel pump is leaking gas into the engine and needs rebuilding.

Yes this is a absolute problem on tri-z's , I myself will always look at this before messing with the carb,,, almost every tri-z I have bought has had this issue as the pumps have never been rebuilt! I have seen guys sell these trikes because they can't figure out what they thought was a jetting issue or carb problem.