2 Stroke oil change

[IM22SNIPER]

Just bought a 00 yz125 for my son for racing. Cranks cold on first kick. Runs beautiful. The guy I bought it from hardly rode it and ran 40:1 Yamalube 2-R semi synthetic. I would like to run Bel-Ray H1R full synthetic at 40:1. I know I should run 32:1 from all I have read but it runs so nice now and cant change the jetting if needed before a Harescramble race this weekend.

1.Can I change to the full synthetic without problems if I drain the tank now?
2. You think I can run 32:1 Synthetic without changing the jetting and not fouling?
3. Should I just stick with the Yamalube?

If someone asked me this question I would say change the top end, switch to synthetic and jet to run 32:1 BUT that is not practical right now. I will do that in the near future.

[monkeyonahill]

Just stick with the 40:1, i run my '01 CR 125 on 44:1 and it does great. Just stick with 40:1, it's rich enough for you, you aren't goin to damage anything by running it. I dont THINK it's goin to hurt switching to fully synthetic. but im not postitive. I've heard if you try to run non-synthetic premix and a cyntehtic premix at the same time (basically u have nonsynthetic in the tank, and u pour synthetic premix in) it will create a black gunk over time and can clog ur jets. I'm not sure if Semi-Synthetic would effect everything. Just run what he was running, if it seems like it's performing great then stick with it! Maybe someone more knowledgable will step in here.
-Andrew

[FallingOsh]

Why would you change the top end? Just to start from scratch?

[Jacquesyz250]

I agree with monkeyonahill here, rather stick with the oil that the previous owner ran the bike on, it will ofcourse only be to your gain! Changing now might work but rather do it in the long run, and at a time that you don't have a race the weekend!

[Dirtbikindad393]

I am a little late on this one but just for future knowledge its is ok to switch to full sythetic without jetting or changing the top end. Drain the tank and carb completely empty fill with the new mix and away you go. Do not mix conventional and sythetic mix oils if you don't have to.