1984 ATC250r break in

[30rack]

both of our 1984 ATC250r's have received complete overhauls from bottom to top. In the past I have blown two top ends and would rather not have to deal with that again, it is a little expensive.

I have the Honda shop manual and I remember seeing something in there about 50 hours, 100 hours, and 150 hours until one can beat it without mercy. That doesnt seem right. Through the forum search I have seen everything from 'ride it like you dont care from hour 1' to 'be nice for a few hours' but so far nothing that seems legitimate.

So, those of you who have spent more time in the shop manuals than I have, please shed some light so I dont ruin two more top ends and have to start over. If possible, cite your sources? One machine has been bored 6 times and the other 7, so another rebuild will involve an entirely new cylinder if we destroy it.

the set ups-

machine 1:

maxxi case and crank bearings, wiseco piston, K&N air filter, some sort of badass expansion chamber, DG muffler, bored 6 times out. It has wasted a chevy 350 powered sand rail (I was thirteen years old!)

machine 2:

boss case and crank bearings, wiseco piston, bored 7 times out.

[tapage]

we got a rhino, after 20 hours its good to ride full throtle... and oil change every 80-100 hours, id recommend every 20-40 hours tho... thats what i would do with a new break in...

[JasonB]

I dont know, I have been through one 250 cylinder and two big bore 300 jugs. I usually do the normal heat cycles, and then after those run the bike like I plan to from there out.

[HondaRidr]

I rebuilt my 83 over a year ago and it still has great compression and it has been run hard. I did 4 or 5 heat cycles before riding it. Then I started out only giving up to 1/4 throttle then gradually worked up till I was giving full throttle by the end of the first tank. I let it cool often and varied the rpms the whole time during the first tank too. After that I ran it like normal.

[RIDE-RED 250r]

Well, Wiseco's recommended service life on their pistons is just 40 hours if I remember correctly. Basically, 3 heat cycles which is start it up and bring it up to operating temp with no load. Meaning do like you would do to get it warmed up before riding. Once up to temp, shut it down and let it cool completely.

After 3 heat cycles, now ride it, varying the throttle, rolling into the throttle up to 1/4 throttle. Do this for about 10 or 15 minutes. Shut it down and let it cool completely. This is a good time to check for leaks and any other issues.

Once cooled completely, fire it up and do the same. Only now roll into the throttle up to 1/2 throttle. Again, do this for about 10 or 15 minutes then shut it down and let it cool.

Once cool repeat this procedure rolling it up to 3/4 throttle. By this time you will have probably burned about 1/2 tank of fuel or so.

At this point after the previous run cycle you can pretty much ride it as you normally would. Just avoid prolonged steady RPM's and keep varying the throttle till you get about 1 full tank of fuel run through it.

After that, done.

Yeah, on a wing-dinger, 150 engine hours is a looong time to be the point it's considered broke in! You would likely be due for a fresh top end long before hitting that 150 engine hour mark..

[30rack]

Well, Wiseco's recommended service life on their pistons is just 40 hours if I remember correctly. Basically, 3 heat cycles which is start it up and bring it up to operating temp with no load. Meaning do like you would do to get it warmed up before riding. Once up to temp, shut it down and let it cool completely.

After 3 heat cycles, now ride it, varying the throttle, rolling into the throttle up to 1/4 throttle. Do this for about 10 or 15 minutes. Shut it down and let it cool completely. This is a good time to check for leaks and any other issues.

Once cooled completely, fire it up and do the same. Only now roll into the throttle up to 1/2 throttle. Again, do this for about 10 or 15 minutes then shut it down and let it cool.

Once cool repeat this procedure rolling it up to 3/4 throttle. By this time you will have probably burned about 1/2 tank of fuel or so.

At this point after the previous run cycle you can pretty much ride it as you normally would. Just avoid prolonged steady RPM's and keep varying the throttle till you get about 1 full tank of fuel run through it.

After that, done.

Yeah, on a wing-dinger, 150 engine hours is a looong time to be the point it's considered broke in! You would likely be due for a fresh top end long before hitting that 150 engine hour mark..

Maybe I saw that in the Clymer manual, I know it was somewhere- I remember telling my dad seconds after reading it.

And if I am to understand this right, after 40 hours I need a new piston AND rings or just new rings? 40 hours seems like some pretty terrible longevity..

At what point during this heat cycle thing do I start riding? I guess both have been ran still up to full operating temperature three or four times easy, and this did expose a leaky head gasket (it required a heli-coil at the exhaust bolt!). I have taken both around the neighborhood a few times for like 3 or 4 minutes and well away from the powerband.

[RIDE-RED 250r]

Well, 40 hours expected life span is a safe number for Wiseco to pick. But it really depends on how hard you run it, what ratio you run your premix, the condition you keep your air filter in and on and on. But if you think about it, 40 engine hours is a pretty fair amount of time for a high performance 2-stroke engine. It's really a different life span based on your specific situation. But I will tell you this, a 2-stroke like is found in a 250r or something is a whole different ball game from what you would find in say a YT125 or something like that. They make alot more power, and the trade-off is more power per cc of displacement=less longevity. That goes for about anything. Same principle applies when you hear of all the 450's that need rebuilding much sooner than their older thumper counterparts. Kinda like comparing power and longevity of a standard 350 smallblock to the smallblock that they run in Winston Cup cars.. Lots more HP in the Cup car engine, but overhauls are much more frequent.

Jet it right, keep your air filter in good working order and run a 32:1 premix with quality oil. Do a compression check periodically. And when you find the compression to be about 10-15% below what it started at after break in, it would be wise to plan on doing the rings and if needed the piston. Only way to know if you need a piston too is to pull the top end and inspect it for cracks, scuffing and general wear. If it looks like it needs replacement, it probably does. If the piston still looks very good to excellent, then a quick deglaze of the cylinder and new rings should do the trick..

Oh, and at this point it sounds like you are ready for the "roll into the throttle to 1/4 throttle" stage of break in... Then take it from there..

[30rack]

Thank you! So far this has been very helpful.

And to make sure I understand this right, I could realistically get the easy break in done in an afternoon and take the trikes out for some good old fashioned showing-up of the quads the next day?

[RIDE-RED 250r]

Yeah, that's about right. After the easy break in is done, I would just be sure to avoid prolonged steady RPM's for that first tankfull of fuel. Vary the throttle.

Glad to help..

[30rack]

OK, and at what point or points during this whole period do I need to worry about carb jetting?

I fear the "machine 1" may have too lean of a jet, but this is speculatory.

[RIDE-RED 250r]

Always jet rich for break in. After break in is complete, then start jetting down one step at a time.

If you fear you already have too lean of jetting, then get it jetted rich now before you run it.

[30rack]

Alrighty, yesterday I finished the last of the heat cycles and I took the trikes drifting through the neighborhood, talk about power!

Anyway, among some things I noticed- once machine 1 is all nice and hot and I am working the throttle, the engine will wind up and then all of a sudden die. it also smokes really bad sometimes from the really high RPM's. I know it is running rich, but it has a stock jet. Does this seem odd to anybody?

[RIDE-RED 250r]

Alrighty, yesterday I finished the last of the heat cycles and I took the trikes drifting through the neighborhood, talk about power!

Anyway, among some things I noticed- once machine 1 is all nice and hot and I am working the throttle, the engine will wind up and then all of a sudden die. it also smokes really bad sometimes from the really high RPM's. I know it is running rich, but it has a stock jet. Does this seem odd to anybody?

Machine #1, that's the one with the K&N filter and DG pipe correct?

When it dies out, is it a blubbering kind of power loss with alot of smoke? Or is it a steady bog? Also, it's important to know exactly what throttle range the bog is occurring at.

Off-idle to about 1/4 throttle is regulated by the pilot jet circuit.

1/4 to 3/4 is running off the main jet circuit, but the slide needle is regulating the fuel.

3/4 to WOT is all main jet.

There is a little overlap of throttle ranges and what fuel circuits are running the show, but that is the basic idea.

SO, what you need to figure out is at what throttle range you are getting the power loss and if it is caused by an overly rich condition (which is OK for break in) or a lean condition.... (Big no-no!) When you figure out what throttle range you are having the problem, do a plug chop to find out if it is too rich or too lean. But, there is a noticeable, audible difference between a rich bogging and a lean bogging.

Yes, running a K&N with an upgraded pipe usually requires a bit of a jetting change. Mainly, a step or 2 richer on the main jet, and possibly raise the slide needle one notch as well.

However, there is no universal, set in stone rule about that. You have to take the jetting where the engine leads you.

There's your homework assignment.

[30rack]

Ok, I went home today to get the trikes fired up and a (now) recurring problem reared its ugly head...

machine 1- the flywheel keeps coming loose. Last time I rode it, everything was going smoothly, killed the engine, and parked it for a week. Today, the flywheel is loose. We did have to "customize" a woodruff key but it fits all nice and tight. There is no way this is normal..

EDIT-ok scratch that. the woodruff key is barely there. Either way, this is the second time this has happened since the rebuild was finished like 5 running hours ago.

[RIDE-RED 250r]

That stinks. Gotta have the right key in there or the flywheel will not seat on the tapered crankshaft properly and loosen up. The flywheel is mainly secured by the tapered shaft fit. The key is really only there for proper flywheel position on the crank for correct ignition timing. The key isn't bearing much of the load of the flywheel.