Fresh top end break in technique question

[matt glascock]

Hi friends,

I was wondering how everyone proceeds with breaking in a new motor or top end. I follow Hodaka Dave's directions - namely running at least a full tank of gas through at varying engine speeds short of wide open on standard 32:1 (91 octane non-oxygenated pump gas with Yamalube R2). After that, its off to the races for me. I'm just curious about how others run in a new top end. Details please.

[squid on a 300]

I usually do 4 heat cycles each one a little longer the the previous letting it completely cool down in between. First one about 3-4 minutes. Second about 4-5 third about 5-6. With each one working the throttle a little bit but not going past 1/2. Fourth one an is easy 10-15 minute ride. Once done ride it!

[matt glascock]

Thanks for your reply, Squid. Here's my ignorance shining through. I have heard of the heat cycling technique. What exactly does that accomplish?

[taber hodaka]

Matt see Ed's response to piston wear. parallel to Squids.
Clarence

[taber hodaka]

What does it accomplish? This is not a tech answer but a observed one . On a small bore such as the ace 90 or the ace 100. This break in resulted in a tighter seal and more compression. There were folks that were masters at this and it did make a difference.
Clarence

[matt glascock]

Thank you for your replies. The manuals describe pulling the piston and dressing any shiny (I assume indicating high) sections with ultrafine grit W/D sandpaper. Does anyone perform this maneuver? Thanks again!

[matt glascock]

Also, does anyone run a different gas:oil ratio or use different gear case oil? Do you flush the gear case after a rebuild. Sorry if this is too much stuff to ask.

[hodakamax]

Not too much stuff to ask, all good questions. I usually step it up a main jet or two and just be easy on it. Heating and cooling cycles are good but it's all just common sense. Clearances are close and parts are not totally smooth, just take it easy and don't stress things. You can run more oil in the mixture but a richer mixture carries more oil and keeps things cooler. The smoother the break-in the better it will run down the line. You'll probably be race ready in an hour (or two) with easy does it and gradually picking up the pace.

Flushing the gear case on a totally new engine after a few hours might be in order but probably not necessary on a rebuild.

As for polishing off the high spots on pistons during break-in it could save some time but I personally just drive it at varying speeds for an hour or two. It all does the same thing in my opinion.

Max

PS-- The first minutes are critical in any break-in. Keep the RPMs low and avoid any overheating situations.

[matt glascock]

Great advice, Max. Thank you so much!!