New top end - running in

[dcbaaca25]

Hi guys,

Thanks for your help to date great site.

How long do you have to run in a 250cc 2 stroke thats had a new top end (ie piston, rings, rebore etc)?

Thanks :)

[whyzee]

Here ya go. Straight from the 1985 ATC250R's owners manual

http://i183.photobucket.com/albums/x217/kumalogan/photobucket-12304-1364069812744_zps6d8d8d6a.jpg
http://i183.photobucket.com/albums/x217/kumalogan/photobucket-33167-1364069788751_zps5e035edc.jpg

[manbearpig]

i just always mix fat, jet fat, and run at least 2 full tanks through it before i beat on em too hard...

[dcbaaca25]

Thanks and ta for the manual extract!

[barnett468]

Hello dcbaaca25

I would assemble with very light coat of 2 stroke oil, place fan on motor then start, turn idle up slightly to around 1000 and let run by itself for 20 minutes, turn off and let cool for 20 minutes, repeat process one more time, then follow recommended Honda technique which whyzee was kind enough to post.. Although it is designed for motors with full rebuilds ie new crank bearings etc, it is still a safe and sound way to do it after rebuilding too end only also. It may also be good to go up one size on main for now as manbearpig eluded to in his post. For riding portion of break in, install new spark plug rating 8 or 9 [do not use champion there heat ratings are reversed], check plug color after 30minutes, white is bad [lean], light tan is good [just right], dark brown or black is bad[ too rich].

I have a couple questions which answers might help prevent future piston seizure if you don’t mind.

Why did it need a rebore, did the piston seize or just worn etc?

If seized, did it occur while you were riding or did you buy it like this?

What EXACT oil and ratio are you running?

Have you made any performance changes since rebuild ie, new pipe, carb, cylinder porting, compression increase since your rebuild?

What was the previous bore size and what is it now?


The following article was written by my friend Harry Klemm. Builder of many national and series championship bikes including one of mine. Hopefully this helps you.


About Proper Break-In Procedure

We have all met him …. The racer who boldly says “I break em in the same way I race em … just ride em full throttle”. Very sadly, there are a small few sets of circumstances were this bold guy is right.

Short Term Setups for short Term Break-ins - There are a number of engine builders who (for their own reasons) will set up the top end clearances of a high-performance two-stroke (piston & ring end-gap) considerably looser than factory spec. The most common reason for doing this is that the engine is prepared in a way that will cause very rapid wear to the piston and rings. Engines like this, often run very wide exhaust ports with very little radius for the rings. Such an engine would seriously wear the piston and rings before any break-in period could be completed, and so they are clearanced to go into immediate service with no real break-in at all.

In such engines, the loose piston clearances not only accelerate piston collapse and ring wear, but they also induce very heavy wear on the cylinder walls (especially around the exhaust port). While everything about this setup sounds short sighted and perishable (it’s both) there is an abundance of builders setting up engines in this way. At Klemm Vintage, we do not (and will not) build such an engine platform. Our engine sets are built for good long term wear and performance … and as such our setups “do” require break-in….. here is why.

A Bit of History - In the early years of high performance two-strokes, most piston rings were a raw cast iron material that very literally had to “wear-in” to perfectly seal on the new cylinder bore it was fit to. With such rings, it often happened that “full ring sealing” didn’t take place until the ring had been in service for a good number of hours. Getting any racer to run the engine easy for that stretch of time just wasn’t going to happen. To help ease this problem, manufacturers applied a soft Teflon “skin” on the outside of the ring sealing surfaces. This soft Teflon skin “sealed” to the new bore in a much shorter amount of time, making for faster break-in and true “sealed” performance in a shorter amount of time. The down side was that when the Teflon wore completely away, the ring end-gap became excessive for “ideal” performance, and the ring tension against the bore was also not ideal. This was a particular performance problem on high-rpm small-bore racing setups.

Wise engine builders began setting up these top ends with “much closer than spec” piston clearances in an effort to get proper ring-end gaps when the Teflon skin wore completely off the rings…. And it worked great as long as you had an oil with a very high film strength. What didn’t work out great was that the break-in time required for such setups was much longer … and no pro-racer could be trusted to “go easy” on the engine for that long.

The solution was to simply let the engine run 60-90 minutes on a stand at a high idle, with a fan or breeze blowing across the fins. This initial run-in wears away the majority of the “skin” off the piston rings. In addition, it gives the cylinder bore and piston-skirts time to “get familiar” with each other in a “low load” atmosphere. This is a procedure that we still use (and strongly recommend) today. It bears noting that after this “static” break-in running, there is still some “loaded” break-in operation needed. However the risk of a piston-scoring event during that break-in ride is greatly reduced.

About Wiseco Piston Break-in - There are an abundance of two stroke enthusiasts that speak with very little enthusiasm about Wiseco pistons. The common response is “you have to give them lots of clearance … otherwise they seize”. We couldn’t disagree more … and here is why.

In the 1970s, we made many attempts to use Wiseco pistons in two-stroke race motors…with very poor results. The truth is that Wiseco (at that time) had numerous materials and design issues that needed resolving. However, Wiseco has done a great job of evolving their materials and designs since the 70’s, and today’s Wiseco Pistons are an excellent choice for most high-performance two-stroke platforms. All that said, Wiseco pistons do have one design issue that they have intentionally have not tried to resolve … longer than average piston-ring break-in times.

The forged material that Wiseco uses for their forged pistons does require “a little” more clearance and a little longer break-in that typical “cast” type pistons … but that is not the unresolved design issue…. It’s the rings. The piston ring material that Wiseco uses is a very tough material that takes much longer than average to “seal” to the bores. While the Wiseco pistons themselves are not a particularly close clearance fit to the bores, the Wiseco rings are. In truth, the Wiseco rings are made brand new with an end-gap that is much too small for full temperature high rpm operation. However if a Wiseco equipped engine gets the slightly longer than average break-in period it deserves, the outer-skin will wear off the rings to result in an ideal “running” end-gap that will give excellent long term wear and service. If however, you try to run Wiseco piston rings prematurely hard, those rings will quickly expand until the ring ends make contact and literally “bite” the full bore diameter in the ring path. Some engine builders incorrectly give Wiseco pistons excessive piston clearance in an effort to resolve this ring end-gap issue.

We respectfully submit that Wiseco pistons can be fit with very close clearances, and offer great service … as long as you let the rings have their break-in time. Our 8500rpm Kawasaki Bighorn road race bikes are equipped with 82mm Wiseco pistons fit at .0035” clearance. These pistons never showed the slightest sign of piston scoring, even after 25+ hours of racing, dyno-passes and high speed testing. You cannot abuse a piston harder than we abused these…. But we did give the rings a long gentle break-in.

About “Dry Top End Assembly” - One step that helps reduce break-in times is to assemble the top end with no oil at all on the piston skirt or cylinder walls. This step has a history worth telling.

In the middle 1960s and early 1970s American muscle-cars were a very popular item on automotive showroom floors. At that time, it was standard procedure for Detroit manufactures to assemble all automotive engines with a generous helping of oil on the cylinder bores and pistons. When these muscle-cars were first fired up, the assembly oil on the bores would burn onto the bores as a glaze that took a very long time for the rings to wear through before sealing.

Unfortunately, this assembly process caused problems for salesmen in the showroom. When prospective buyers took a muscle-car out for a test drive, it was a given that there would be at least one full throttle blast involved. During that full throttle blast, the poorly sealing rings allowed considerable oil to pass, and the brand new muscle-car would leave a big plume of unattractive blue oil smoke that could be seen in the rear view mirror…. Buyers were understandably put off by anything that appeared to be “already burning oil”.

This was a very real problem that Detroit had to address. In time, they learned that if they assembled the top ends dry, with no oil on the bores or pistons, they could avoid this initial burned on cylinder glaze. The result was much shorter ring sealing times (because the rings didn’t have to wear through that glaze), and the absence of blue smoke from those important test drive blasts.

This same rule applies to two-strokes … vintage or not. Some owners shy away from this assembly process because they fear scoring the piston … but it is an unfounded fear. On such assemblies, we do apply assembly oil to all the lower end bearings. In the first moments of initial combustion, that lower end assembly-oil disperses on the bore in even quantities that are easily enough to avert any kind of scoring. In addition, it bears noting that the lubrication needs of an unloaded engine spinning at very low rpm’s are very minimal. We have been assembling high performance two-strokes in this way since the early 1970’s. It works … and it results in greatly reduced ring sealing / break-in times.

Hope this info helps.

[manbearpig]

Barnett...

thank you. very, very much.

we've all been noticing that you take your time to fully answer all these questions that are presented, and that is appreciated. this time you really went the extra mile.

im gonna go back through and read your other posts... i feel like stuffin my noggin with info

[barnett468]

Hello Manbearpig


I hope you never need to utilize this info but in case you do I hope you find it useful.

Thank you for going out of your way to offer the kind words. I have also read yours as I do all others within a “new” topic post and personally think yours are helpful, practical and informative also. I have noticed there are also others here that whether they are extremely knowledgeable or not do the same.

As you will easily see in some of my other posts if you haven’t already it appears to be much easier for a few others to make unjustified, unprovoked comments towards me or simply make posts that have an inherent negative and adversarial tone.

Not sure who you mean by "we".


Thanks again.

[dcbaaca25]

Thank you all for your replies.

Barnett468 - thank you for the article. By way of background I have recently bought the Tri-Z, and the chap I bought it off has done a magnificent job of cleaning her up/restoring her. I am a very happy owner indeed.

To answer your question specifically:

Why did it need a rebore, did the piston seize or just worn etc? It was done as part of the rebuild of the trike (being already in bits), there was nothing wrong with the top end.

If seized, did it occur while you were riding or did you buy it like this? N/A

What EXACT oil and ratio are you running? Oil = Silkolene Comp 2 synthetic premix/ 20:1 ratio

Have you made any performance changes since rebuild ie, new pipe, carb, cylinder porting, compression increase since your rebuild? Non noted; the head was skimmed to get correct original compression

What was the previous bore size and what is it now? 0.25 over standard

Many thanks

[barnett468]

Hello dcbaaca25

Thanks for your positive comment and replies to questions. I'm happy you got a nice Tri Z.

As far as compression goes, I don't know what you mean by "skimmed". If it means removing material, this increases compression which is unnecessary on a stock "unported" cylinder and will increase potential for detonation. The increased bore size increases compression as it is so this along with a machined [cc reduced] head will significantly increase potential for detonation. If you notice "pinging under acceleration just use higher octane gas which you guys have at the pump and we don't, lol. Trying to "jet out" detonation by increasing jet size in an otherwise stock bike is not the proper approach.


Hope this info helps.

[barnett468]

Hello I just realized i pasted the wrong version of my reply from my microsoft word page into post 7. The correct version does not include paragraph 3. Unfortunately I can not find an edit button so I am unable to correct it. Sorry about that.

[RIDE-RED 250r]

You've edited plenty of your posts in the past... What escapes you about post #7??

At the bottom-right of that post you should see an "edit" button right next to "reply"....

Can you not post directly without using MS Word???

[fastatc70]

Hey guys I have found there are a couple of things that you can argue and this is one. Pick and choose what works for you.

Engine building technique and break in procedure are like arguing politics and religion people die for these things everyone is right and they know right.

In my opinion
First go by the Manuel on jetting and break in they built the thing they know best.

New piston, installed by piston manufacturers instructions and spec. Lightly coat with 2-stroke oil non synthetic oil.
Barnett468 good job in explaining dry break in from the 70s.

There is a difference in brake in between 2 stroke and 4 stroke, mostly jetting. 2 stroke run the jets in the carb larger and the needle clip down one. Do not add more oil to your gas it will make it run air fuel lean. On a stock motor it may not fail but if you check the Manuel it usually saids to jet rich.

Heat cycles varying in rpm

Start machine run in neutral 1/4 throttle revving slowly. Keep an eye on engine temp,once hot to the touch. Turn it off and let it cool.
Run three heat cycles.

After 3rd heat cycle and engine is hot ride 1/2 throttle for about an 1/2 hr.

Let cool
Rejet carb back to original jetting.

Now for the first couple of runs just let the motor get hot before running it hard.

The guy that I built engines under was a mechanic for suzuki's road racing program and the lead mechanic for a once large motorcycle shop in the area. Thank you Jeff.

Now there probably different ways to break in a cylinder with different sleeve material but I have found this to best for all.

This info is just my opinion and from my work experience. 2 stroke motors need to be built by experienced builders.

I have had at least 3 250r in the past year come through my garage with signs if seizure due to sharp ports.

I like the do it your self but please do your research and use a good machine shop. A MACHINE SHOP not the guy down the street that builds lawn mowers!!


Thank you for your time and the chance to give " my two cents ". Please be kind this is not ment to offend " just saying that's all"

Fast

[fastatc70]

dcbaaca25

Thank you for the title of running in. Better word choice then break in. Running in sounds so much better. Funny how we call it break in when that's what we are trying to prevent here with this thread.

[TimSr]

Here ya go. Straight from the 1985 ATC250R's owners manual

http://i183.photobucket.com/albums/x217/kumalogan/photobucket-12304-1364069812744_zps6d8d8d6a.jpg
http://i183.photobucket.com/albums/x217/kumalogan/photobucket-33167-1364069788751_zps5e035edc.jpg

That procedure is for a new motor. If you are just breaking in a new bore/ piston and rings, take easy for 20-30 minutes, with all you're normal fuel mix and settings. Its that simple. That's Wiseco's procedure.

[fastatc70]

That procedure is for a new motor. If you are just breaking in a new bore/ piston and rings, take easy for 20-30 minutes, with all you're normal fuel mix and settings. Its that simple. That's Wiseco's procedure.

Hey TimSr
Thank you for posting the factory break in procedure. The increase in jetting is to compensate for a possible cold weather break in, air leak that has not been found or just created, larger piston and or bad jetting starting point. Going rich will help keep a cool combustion chamber, exhaust and give more oil for metal removal from the honeing. Go rich and be on the safe side of caution. Then start to lean out to the proper jet size.

[barnett468]

You've edited plenty of your posts in the past... What escapes you about post #7??

At the bottom-right of that post you should see an "edit" button right next to "reply"....

Can you not post directly without using MS Word???


Hello ride red 250r


I will gladly answer your questions as completely as I can because I think they are fair and reasonable.


“You've edited plenty of your posts in the past... What escapes you about post #7??”

I thought I had edited posts here in the past but I can’t remember right now because since I am also an active member on an automotive site that does have an edit button combined with the fact that I can’t find an edit button on this site I simply thought I was mistaken when I thought this site had one ergo my question as to it’s whereabouts if in fact one did exist.


At the bottom-right of that post you should see an "edit" button right next to "reply"....

Absolutely NO edit button anywhere otherwise I simply would have edit that post instead of creating another to explain it. I would love to prove it to you but I would need to take photo with my phone, send photo to my email, open an acct to photo hosting site, post it there then post the link to it on a post. Seems a little involved and excessive to me.


Below is exactly how it cut's and pastes if you can get them all to highlight at the same time which is hard to do for some reason. I know they are not in order but this is what it did.

Reply Reply With Quote Reply With Quote Blog this Post


Can you not post directly without using MS Word???

I could simply say yes but I will go further for you and tell you why I prefer to use MS so you can see I am trying hard to answer you in detail. I use MS for a couple reasons. 1. I can see more of the text at one time which is just easier for me since the site only has just a small 1 ½” high page. 2. I can paste the post I am responding to on MS and cut/paste/see much better etc. to compose my reply.


If you read my recent posts to Overponder from yesterday you can CLEARLY see that I posted two short replies back to back. If I could edit then I simply would have just edited the first one and added my second reply to the first so as not to have multiple short posts in a row.


RE POST 7 – My MS word double or triple spaces everything. This causes some posts I make which would normally be on one page to actually spread out over two. I think that I might have scrolled to far down and copied more of the text that I wanted to include or didn’t catch it in the second version I had typed,, can’t exactly remember how it occurred. Anyway I already mentioned I did not mean to include it and don’t have the ability to edit it, it is out of my control, my hands are tied.


I know how to use a calculator but I actually know how to do very little on the computer like modify MS spacing, auto caps, font style etc. I can email and type on MS with whatever spacing and features it gives me. Even the head "new projects" engineer who had been an engineer for 30 years did ALL drawings by hand [as I did] without the aid of auto cad back then. It had not been out long and none of us knew how to use it.


These are all the answers I can think of and then some in regards to your questions. have

[barnett468]

Hello again ride red 250r

Another thing you will notice if you look at all my recent posts is that none of them have been edited. I guess you have some way to tell, so this will support the fact that I have no edit button.

[hondawasaki]

Hello again ride red 250r

Another thing you will notice if you look at all my recent posts is that none of them have been edited. I guess you have some way to tell, so this will support the fact that I have no edit button.

I appreciate all of your info, but your formatting is hard to read. Maybe use the quote feature, or some ****'s before the quotes or something. Lol I'm not attacking or disrespecting in anyway, it just makes my brain hurt trying to read some of your posts.

[dcbaaca25]

Brilliant thank you all for your comments. I have more than enough information here. Hopefully others can use it too.