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  #1  
Old 02-24-2004, 10:53 PM
gregez's Avatar
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Default Best way to break in new top end?

Just did a new top end, piston/ring/bore on old 87 cr125. No manual. Shop manual says refer to manual for break in info. What's the right way for this thing?
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Old 02-25-2004, 02:27 AM
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Default Re: Best way to break in new top end?

This is a very controversial topic! I have had experience in both methods. The ones Iam talking about are; hard,high rev break in AND easy run-in. I have had to perform 3 top end replacements on my 125. I will just briefly outline what happened as I have gotto go.

1. First time I replaced top end I warmed up bike thoroughly then let it cool properly. Then proceeded to ride it easy for 1 1/2 hours. It lasted about 8 months(piston).

2. Second time I took it home and warmed it up. Let it cool then took it out and rode it hard. After 7 minutes it just lost compression and died on me. Took it back to house and pulled head off. immediately saw score marks on bore. Then proceeded to remove cylinder. Ring had melted to piston on one section. The ports had been damaged really bad. Bore needed re-coating as well as the top end kit.

3. After the bore being recoated and top end replaced I warmed it up and then shut it off to cool completely. I rode it in easy for 1 and a half hours. Haven't had a problem since, still ripping!

This is just my opinion. Other may have had different results and findings.

NOTE: This is for 2-stroke. 4-stroke may vary.

I would reccomend going easy for at least one hour!

Oh, BTW use a 32:1 ratio while running it in! Good luck!
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Old 02-25-2004, 03:38 AM
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Default Re: Best way to break in new top end?

i`m for the go easy routine...as it allows time for the rings to properly seat...just don`t let it sit too long after starting it up as there is more than the usual heat being transfered out of the new rings-like get some air flowing...remember,things can get hot quicker than usual untill the rings seat properly...anyways,that`s my opinion...and it also sounds like aussie`s #1 and #3 were much better results than #2...his advice seems very good to me
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Old 02-25-2004, 03:41 AM
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Default Re: Best way to break in new top end?

Thanx Paul!
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Old 02-25-2004, 04:24 AM
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Default Re: Best way to break in new top end?

Whenever I have had 125's. I have run them at 28:1, 250's 32:1. The more oil the better for the life of the motor. Bike are always jetted perfectly to run those ratios. I can't believe how many people run their bikes at 40:1 and 50:1.
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Old 02-25-2004, 05:06 AM
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Default Re: Best way to break in new top end?

I used to run mine at 40:1......But I know feel safer at 32:1. I would rather spend more money on oil than replacing the engine internals while you could be riding instead of waiting for parts to come in. Any way, do you lose any response or power from running bike richer with oil??
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Old 02-25-2004, 08:19 PM
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Default Re: Best way to break in new top end?

Thanks for all your replys. I am running it easy as recommended! My shop manual say to run the oil mixture at 20:1!? Whats that all about?
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Old 02-26-2004, 04:24 PM
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Default Re: Best way to break in new top end?

Quote:
Originally posted by gregez
Thanks for all your replys. I am running it easy as recommended! My shop manual say to run the oil mixture at 20:1!? Whats that all about?
Careful with the 20:1. I was following the book (Clymer manual) which says 20:1. Kept fouling plugs. Got the OEM book and it says 32:1. I think that was the problem. 20:1 is awful rich.
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Old 02-26-2004, 05:39 PM
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Default Re: Best way to break in new top end?

Thanks! No wonder I have oil splattering out between pipe and silencer. 32:1 now.
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Old 02-26-2004, 05:42 PM
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Default Re: Best way to break in new top end?

that is probably the most common rate
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