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break in oil and proceedure???

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Hi All...

I have just finished a rebuild on my xr250r... 280 kit with wiseco piston- .002 thou piston to bore clearance - stock original cam.

I am planning on using MOTUL 3000 20w50 for the break in- its a mineral oil- is this suitable?

Also, i am planning on heat cycling the engine a few times (4-5) with moderate riding...

1st cycle, take bike out, no more than half throttle but let the bike rev, not too much load... once hot, let cool

2nd cycle, two thirds throttle, no big hills but let bike rev out- not labour in a tall gear... cool

3rd cycle, a few blips of the throttle and increaseing load on the engine- nothing major though - still no WOT...cool

4th cycle- some blips of WOT and more load on the engine, increasing some taller gear work...cool

Then ride the bike "normally" but not complete flogging the bike- riding to about 75%, but being gentle on it either...

AFTER ONE TANK OF FUEL- drain oil and change oil filter, replace with the same mineral 20w50 oil.

AFTER 4 OR 5 TANKS OF FUEL- change oil and filter and replace with full synthetic.

Anyone got any other ideas? I know some guys advocate loading the motor quite heavily to seat the rings- but I have read conflicting advice... Ie that its more important to heat cycle and let the motor rev out rather than "loading" the engine, as the load creates combustion chamber heat, and has a greater likelyhood of glazing the cylinder...

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Your proposal sounds very close to what I did on my XR Poweroll build.

Sounds good to me but I suggest adding a pre cycle: Use a generic a 10W-30 oil for the pre cycle. Limit the first cycle to less than 1/2 throttle and no high revs, just a warm up, maybe cruise around the block. This allows you to check for oil leaks, adjust the carb, listen to the valves, etc. Drain the oil into a clear container and examine it; you will probably find gasket cement debris and hopefully no big metallics. Then use the HD Dyno oil and finish break in.

My next two cycles were easy trail rides, gradually exploring more throttle and higher revs. Powroll said they get best power output after twenty five hours and I felt the the power output was improving during that time.

The Moto Tune method is fine for the right combination of rings, cylinder, clearances, etc, not uncommon on some industrial engines but I'm hesitant to try it on a garage rebuild. I had a high output marine diesel rebuilt and it was a twenty minute warm up on a dyno and then a full load run to certify power output. The operator chained the motor to the stand to prevent it from flopping around in the dyno cell if it seized.

My oil change interval followed yours, I'm now on Mobile 1 10W-40 oil, nice smooth clutch action.

Edited by chuck4788

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The mototune method descibed is actually very similar to what I am planning... They "market" their break in as "hard" riding but its not- its controlled... Very different to just going out on a track and riding it full blat from day 1...

The only thing I disagree with is they claim no need to heat cycle... I believe heat cycle is good for two reasons- correct me if im wrong...

1) Needed to cool the cylinder as excessive cylinder temps can cause glazing and stop rings from seating- makes the cylinder wall very smooth and glassy...

2) As the forged piston expands and contracts quite drastically on heat up and cool down, it makes sense to create an environment where this hapens in a controlled fashion during the first few runs- may not be 100% nessesary, but seams a common sense precaution...

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Sorry I was confusing that method with the "ride it like stole it" school of breakin. In addition to what you posted the heat cycles are important because new engines have high friction and generate enough local heat to cause damage. The short heat cycles reduce the risk. My example of breakin on a dyno was with OEM kits that included a matched liner, piston, rings, and pin for each cylinder. Also water cooled engines are susceptible to cold seizure when the piston heats up faster than the cylinder.

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