[jpw59165]

When you install a higher compression piston and CAM does the timing have to be adjusted any different? I am changing from the 249cc/9.5:1 to a 263cc/10.5:1 piston and installing a stage II HotCAM. I am taking to the Yamaha dealer to have the work done, they should know what to do right? I am providing the top end gasket kit, and am also getting a valve adjustment done at the same time. I assume there will be a break in period involved as well?

 

[YamahaBlue250]

Just the valve timing I think since the duration will be different. Don't want your piston and valves to meet on the first start up.

 

[atv4life95]

Timing should be the same.. From what I know, the HotCam recommends a different amount of tappet play.
Yes there will be a break in period. But honestly when you break in an engine you don't have to be that easy on it, and you don't have to be that extreme in the break in period time. In the manual, Yamaha recommends 20 hours of riding no more than 3/4 throttle. But honestly, after like the first 3 tank fulls of gas you go through, you can start riding it like you normally would at full throttle, and it's not going to hurt it..

 

[jpw59165]

So, after my post on jetting, what would be a good base tune on the carb after install? I am currently 137.5 main, 27 pilot, screw 2 turns from bottom, needle clipped 3rd from top. Should I go with 140 main, 27 pilot, screw 2.5 turns from bottom and needle clipped 2nd from the top?

Last, is this something I can probably do myself? I am pretty mechanically inclined, and can read instructions well. I have standard tools, are any special tools needed?

 

[YamahaBlue250]

You could probably do it yourself. The installs seem pretty straight forward. Not sure about tools though.

 

[atv4life95]

After a bigger piston and a cam install? knowing your elevation, I would probably go with the same jetting I have. 140 is going to be way to little for a bigger cam and a bigger piston. And the 27.5 Pilot at 2 turns out is too little also. At 4,500 feet, a 150 main and 35 pilot at 2.5 turns out sounds pretty good...

As for doing it yourself? I would have someone install the cam for you. This is due to all the little pieces and things in the head of the motor that can become very confusing if you don't have clear step by step instructions on how to disassemble/reassemble (cam gear markings, timing, compression release valve, etc.)

 

[atv4life95]

The piston you could most likely install yourself. They are pretty straight forward when installing. If you have ever replaced the top end in a 2 stroke before, you should be fine.

 

[jpw59165]

Thanks, I have adjusted valves and replaced the CAMS in a 16 valve DOHC motor before. That was in a 2001 Ford ZX2 w/ZETEC engine, but haven't ever fooled with this type of engine.

 

[atv4life95]

Thanks, I have adjusted valves and replaced the CAMS in a 16 valve DOHC motor before. That was in a 2001 Ford ZX2 w/ZETEC engine, but haven't ever fooled with this type of engine.

Disregard what I previously said then. You should do just fine at replacing the cam.

So you're in the Air Force huh? I couldn't help but notice the Holloman AFB location under your name.. I'm thinking about going into the Air Force after high school

 

[jpw59165]

Cool, it's an OK gig, just depends on what you want out of it.

 

[atv4life95]

What's your job in the AF? I think I wan't to go in as an aircraft mechanic

 

[jpw59165]

I am an AGE mechanic, I do not work on aircraft, I work on all the stuff that is used by the aircraft.

 

[atv4life95]

oh wow, that sounds like a great job! so do you work on the weapons and the computer systems of the aircrafts?
How long have you been serving, do you enjoy it?

sorry for all the questions, i've been wanting to talk to someone currently serving in the air force, or a recruiter about jobs/possibilities and stuff. You happen to be the first person I can talk to haha..

 

[jpw59165]

I work on the generators, compressors, air start carts, heaters, air conditioners, weapons lift trucks, light carts etc. We also work on all of the adjustable maintenance platforms, tow bars, wheel dollys, engine cowling trailers, run blast fences etc. We are trained on electrics, hydraulics, pneumatics, heating, air conditioning, ventilation, generation, 2 and 4 stroke diesel and gasoline engines, turbine engines, and basic mechanics. I have been in for 13.5 years. I have been to stationed at Okinawa, deployed to Afghanistan, served a remote in Korea, went TDY to Vegas. I have lived in Louisiana, North Dakota, and now New Mexico. I have traveled through places like Seattle, Baltimore, Atlanta, San Francisco. I have seen places like Germany and England. I went through training in Texas, South Dakota and Utah. I really loved it when I was a young single Airman, and I still enjoyed it as a married NCO, but now that I am approaching Senior NCO and have two kids I don't like it as much and am just looking forward to retirement in 6.5 years. I have really learned alot, and have accomplished some things. I have been given opportunities that I would not have in the civilian world. I was never into school, and didn't think about college, but I have managed to acquire 94 credits being in the USAF. You meet alot of people, some good some bad. I am definitely doing 20, I don't regret it, and would do it again knowing what I know now.

 

[atv4life95]

Wow, That sounds incredible! I would love to have a job like that and be trained to work on those different pieces of machinery. I am definitely joining the AF now.
Thank You for answering my questions and thank you for your service :clap:

 

[jpw59165]

No prob, my AFSC is 2A6X2 (Aerospace Ground Equipment) if you want to do what I do. If you want to be an aircraft mechanic, pick something that is used by the AF at alot of bases. If you are a B-52 crew-chief you will be limited to 2 bases, Minot ND and BoSsier City LA. Cargo planes line C-5. C-17, C-130, KC-135 and KC-10s are all over the place. F-15 aircraft are at alot of places too. That's what is good about AGE, we can go anywhere.