Advice prior to firing up after top end rebuild?

knightscape

knightscape

Member
So after I nuked my cylinder/piston/rings last weekend, I found parts to rebuild it with for enough less than a replacement motor to make it worthwhile to me to just rebuild. BGF shipped me the stuff so fast I hadn't even gotten the motor off the bike when the new stuff arrived, so props to them for that, really wasn't expecting to be trying this out again so fast. Last night I replaced the cylinder, piston, rings, headgasket, lower fiber gasket, exhaust gasket, carb, fuel filter and ground out the extra metal constricting the exhaust manifold.

Given that this is a brand new cyl/piston, any sage advice for me before I fire it up for the first time? Is there any consensus on oil mix, from searching, seems like people say 16 or 20:1 for the first couple gallons, no WOT, vary the throttle and not running or idling for too long while breaking in. Am I understanding that right? Run for a few minutes and then torque the bolts down again? I don't think I've ever broken in a new 2 stroke myself before. Most of my equipment is oooooooold.
 
You seem to have all the points covered well.

Except... short 2 or 3 second long bursts of WOT helps break in the rings for a tighter seal against the cylinder wall. This does NOT mean ride fast, just quick full throttle bursts while keeping the RPMs reasonably fast. Don't hit redline or anything. Space them a few minutes apart, and keep the first few rides about 10 minutes long.
 
16:1 or even 20:1 is a bit too much oil. I think you'll find that the general consensus here is to go no more than 24:1 and many will suggest 32:1.
16:1 will not protect your new parts but it will foul your spark plug and possibly the exhaust system cause poor performance and lack of power.

Break in procedurees are a matter of opinion. You'll get lots of opinions on the proper way to do it. I'm in the bunch that says, "ride it hard and put it away wet" in other words I don't baby a new engine. I typically ride a new engine just like I do one of my older ones. I don't abuse them, but I don't treat them like fine China either.

The analogy I like is to compare a bike engine with a new chainsaw. How many professional loggers/tree trimmers do you see running their new saws like some of the suggestions we see here for breaking in? Not many me thinks.

Tom
 
IT'S YOUR BIKE, RIDE IT YOUR WAY. I'm ALSO in the bunch that says ride her hard and put'er away wet.
Hey Tom, sounds like ya got a little country in ya. I Heard that old saying growing up near a horse ranch that our friends owned.EVER saddled up?
fatdaddy.
 
Run 32:1 and ride it normally. Don't scream it's guts out for at least the first tank of fuel.
 
2door said:
Break in procedurees are a matter of opinion. You'll get lots of opinions on the proper way to do it. I'm in the bunch that says, "ride it hard and put it away wet" in other words I don't baby a new engine. I typically ride a new engine just like I do one of my older ones. I don't abuse them, but I don't treat them like fine China either.
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Yep, I find if I'm riding it the first few times it has troubles getting a good amount of top speed. Then when I go downhill I go WOT till I feel its unsafe to push harder (usually around 8000 RPM). After a couple runs like this (usually only 2-3 hills) I find its much more willing to go to higher speeds. 38mph on a 44T on a stock motor is impressive IMHO.
 
Fired right up, good times. Looks like I'm back in business with my 49cc. Ran it around a few short rides today letting it cool down in between, tightened everything up again. Then this evening coming back from my folks house after a family dinner, I had my wife give me a head start, she finally caught up with me 6 miles down the road and clocked me at 25mph, and not at WOT so I'm pretty stoked. Then I loaded up in the truck for the rest of the ride home since it was starting to get dark anyway. Now I can start thinking about some upgrades. Happy camper today, thanks for the tips guys.
 
Congratulations but don't rush into adding go-fast parts. You essentially have a new engine, as far as the top end goes so put a couple of hundred miles on it then start looking at performance upgrades. When you start to add stuff, do one thing at a time and don't change several all at once.
Good luck, have fun and ride safe.

Tom
 
Oh, for sure not going to be dumping cash on performance parts. I meant upgrades like a tensioner that won't kill me, 2nd brake, cleaner mounting of the engine, and body position stuff. Mostly stuff I can do out of the parts bin. :)
 
Consider for a moment that Stihl makes more than a million chainsaws every year.

Add to those numbers Homelite, Poulan, Husqvarna, etc. and there are a lot of new units sold every year.

No chainsaw maker tells you to run it at half throttle for several tanks of fuel. In fact, a chainsaw runs wide open under load within a minute of leaving the box.

If break-in was required, the cheap Homelite string trimmers would come with that instruction.

A two stroke running pre-mix receives maximum lubrication at full throttle.

Run good oil at 24:1 Use the throttle aggressively in short bursts, below maximum RPM. Avoid long deceleration cycles - pull the clutch in if you are not on the throttle.

.
 
2door said:
Congratulations but don't rush into adding go-fast parts. You essentially have a new engine, as far as the top end goes so put a couple of hundred miles on it then start looking at performance upgrades. When you start to add stuff, do one thing at a time and don't change several all at once.
Good luck, have fun and ride safe.

Tom
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I respect what Tom has to say a lot but if I can when I build something for myself I start with all the hop ups all at once I did it on my first huffy build and except for the exhaust Im going to use on my schwinn Im doing it this time as well.

I do know that that can cause head aches but from years of experience with autos a new motor tends to like having everything all at once not a part here and a part there added.

Last thing Ill say is when it comes to break in for the most part ride it like you are going to ride it unless the only way you know to ride is wot that is never a good idea on something so close to the inside of you legs.
.trk.trk
 
I find myself agreeing with the both of ya TBH - it's good advice to those new to these particular motors to run one in from new stock first w/o adding any hop-up parts, to learn the thing, to get it runnin' well without any added unknowns... they can be hinky lil beasts with some odd behaviors, things most wouldn't expect from a new engine - let alone some of the aftermarket stuff available, of which each has their own quirks too.

Then again if you've gotten used to these things, know the bits yer boltin' on & hackin' at... well then, there's some stuff you know right off the bat that needs be "fixed" and why, it's not even worth the time to bolt it on if yer just gonna take it off again & chuck it lol

It's tricky to figure somthin' you've not experienced before, stack up a few more unknowns on top of that and it'll get weird ;)
 
I don't disagree even a little, Geoff, nevertheless I try to aim a lot of my advice toward the new and inexperienced builder. They're the ones who need it the most. The more advanced will always have his or her own way of doing things and they might run counter to advice that will benefit a new member who has no prior experience with our little Chinese wonders.

The reason I tell a newbie to add one aftermarket, performance item at a time is so they will have a basis for comparison between before and after and learn what works and what doesn't. When something doesn't work right, or as expected, then they will know where to look. Trying to troubleshoot an engine with several add-ons is difficult for him as well as those of us offering help. Just my view and to clarify my earlier post.

Tom
 
2door said:
I don't disagree even a little, Geoff, nevertheless I try to aim a lot of my advice toward the new and inexperienced builder. They're the ones who need it the most. The more advanced will always have his or her own way of doing things and they might run counter to advice that will benefit a new member who has no prior experience with our little Chinese wonders.

The reason I tell a newbie to add one aftermarket, performance item at a time is so they will have a basis for comparison between before and after and learn what works and what doesn't. When something doesn't work right, or as expected, then they will know where to look. Trying to troubleshoot an engine with several add-ons is difficult for him as well as those of us offering help. Just my view and to clarify my earlier post.

Tom
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Excellent explainationTom and you are spot on in my opinion and I would say probably 99% of the rest of us who have experience with the HT enginess, the suggestions should be just as you described for the noobs, it will likely save them some grief until they have a better understanding of the engine and first thing as far as performance options go should be that they learn to tune the carb which is one of the first mods that needs to be done in my opinion.

Map
 
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