1985 250R Piston Damage

[Helidaddy]

So I bought this a few years ago and it seemed to run fine. I never REALLY rode it, just about two minutes slowly putting around the parking lot before tearing it apart for various maintenances, and it hasn't been run since. Finally got back to it after a while, took off the exhaust and found a damaged piston.

http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3684.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3684.jpg.html)
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3683.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3683.jpg.html)
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3660.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3660.jpg.html)
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3659.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3659.jpg.html)
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3685.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3685.jpg.html)

When I took the piston out, there were NO pieces of the ring left! So now I'm thinking... do I have to split the case to find missing pieces or do you think they just blew out the exhaust? This may sound dumb, but would it do any harm to rinse out the case with gas or some solvent a few times by turning it upside down to dump it? (Engine is out)

Can anyone tell what may have happened to this one? I mean, I know it got hot but is there any tell tale sings of the cause? I have no way of knowing the premix ratio the guy was running. The reeds don't have the stoppers and I don't know if they're stock or what. The bike is pretty much stock otherwise.

BTW, anybody know what piston this is? Honda? I'm pretty sure it's 0.25 over, due to a marking on the remaining ring that says 25


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[atc300r]

To much oil in the pre-mix. The oil gets between the rings and when it gets hot it expands and blows out the rings. Iv seen this type of stuff with weedwackers and chainsaw a lot . Some people think 20-1 mix is good then 10-1 should be better.Arts pistons are oem Honda.

[RIDE-RED 250r]

Any chance whoever bored the cylinder didn't chamfer the ports and the ring caught a port window?? Or too tight of ring gap on that ring perhaps??

I only ask because rarely do people who don't understand things go with more oil in the premix. Most go with less in an attempt to address what is really a jetting issue and so forth.

But that piston does look to have some hours on it. Hard to say how long it was run like that.

What you say is interesting atc300r, I have not heard of that phenomenon. Although I run 32:1 in my R's and 50:1 in my saws per Husqvarna's recommendation. The richest premix I run is about 24:1 in my 1960 Johnson 18hp outboard.

[Helidaddy]

Interesting you mention the port chamfering. I'll get better pics of them ASAP but whoever did the cylinder did a horrible job IMHO. I think he even forgot one window.

The ring gap is a good point but we'll never know because it doesn't exist anymore, lol. I'm not sure but do the Honda OEM pistons need the gap adjusted like the Wiseco?

And as for the mix I'm thinking I remember what he said when I bought it, me not knowing anything, I thought it was a little too much oil. I want to say he recommended 20:1 but not sure.




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[nd4speed]

Looks like a ring snag and maybe it kept running on one ring?

Bummer....I have had ring gap be ok out the box and other times I had to file them. But , yeah port chamfers are kinda important.

Rings are real hard metal and having them floating around in your crankcase and in your main/crank bearings would probably be not good.

[yaegerb]

IMO you have several things going on there. I agree that one of the rings caught on a un-chamfered window....likely causing it to jostle and crack in several places. I would like to see the piston wash, can you show pics of the crown? To me it looks like too low octane, insufficient cooling, lean jetting or a combination of those. I would also like to see the cylinder. And yes, I would split the cases to find the missing bits.

[oscarmayer]

looks like ya ran lean, got too much water in it or something along those lines.
You were defiantly starting to burn a hole in the top. the bottom charring and discoloration ring outside the black area is evidence of that. I would not be suppressed to find the rod to be damaged. can we see the top of the piston and the dome and plug?

the piston swelled up form over heating due to lack of cooling and/or lean conditions. (lean can be caused by air leak into the area from bad reed cage gasket, bad intake gasket, cracked intake boot, ETC. but it got too much air for sure at some point.

[Helidaddy]

Ok here's the piston crown...
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3686.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3686.jpg.html)

And here's the one pic I have of the jug before cleaning. I was trying to capture the chamfering...

http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/IMG_3687.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/IMG_3687.jpg.html)

I will get better pics of the jug soon. I work all night so it'll be tomorrow.

And the rod... What damage should I look for there?


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[yaegerb]

That crown has close to zero wash which indicates a really lean mixture. The other item I notice is the black spot on the on the underneath side of the piston. IMO, lean jetting and/or insufficient cooling. Better make sure your water pump is also functioning properly. Also I would look into getting that cylinder bored and chamfered correctly.

The rod should have zero up/down play and 1/16th side to side is within tolerance. More than that and get a new rod.

[Helidaddy]

The cylinder is definitely getting bored and chamfered correctly. Now I just have to find a place around Sacramento reputable enough to do it. I'll get pics of the plug tomorrow also, but it seemed black and wet IIRC


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[Helidaddy]

One more thing… I cleaned off the carbon on the crown and you can see dings and dents from the debris hitting the piston. Not too many though, so it looks like it was run like this for a while


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[yaegerb]

One more thing… I cleaned off the carbon on the crown and you can see dings and dents from the debris hitting the piston. Not too many though, so it looks like it was run like this for a while


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What does the dome look like?

[Helidaddy]

Dome looks good but I'll get pics of that too.

Looks like the one thing he got right is the bridge relief. Don't see any damage on the piston from that

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[Helidaddy]

Okay, here's the pics. The plug is a BR8ES
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/DADE7274-A534-4CDF-AF9C-BEF809B064B4.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/DADE7274-A534-4CDF-AF9C-BEF809B064B4.jpg.html)

Cleaned up the piston a little to reveal the dingshttp://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/2E61DE44-1BA4-49C8-A350-8230B16B3E67.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/2E61DE44-1BA4-49C8-A350-8230B16B3E67.jpg.html)

The dome isn't in bad shape. Just a few dings
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/B84F58CC-1E4C-402E-B60E-4B12B0809796.jpg (http://s882.photobucket.com/user/helicopterpilot007/media/1985%20ATC%20250R%20Pics/B84F58CC-1E4C-402E-B60E-4B12B0809796.jpg.html)

And the jug, I'll just put links to the pics; I feel like I'm putting too many pictures in this thread!
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/3924C14F-C9DE-45EF-A78B-8FCA96AB2050.jpg http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/325E151E-50B6-45D6-84F3-2621A659BF8F.jpg http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/2ED94D01-6304-45C5-9F50-3A9A76642FE4.jpg http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/9E728B6A-FE21-419D-8C44-B6CC83738D61.jpg



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[yaegerb]

I am surprised that dome doesn't have more damage...I do see a few nicks in there and that piston is fried. Make sure that when they have your cylinder they also mill the top/bottom of the cylinder and the bottom of the cylinder head. With that much heat I guarantee its warped.

[oscarmayer]

It is fixable. And take your time and do it right. Replace the reeds too.
That plug. Good lord!!! It is nasty!! Like 80 yr old hooker nasty!! Seriously!!


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[poolieZerUK]

I have a Tri z motor bought as a non runner, had the same thing.
Had been freshly bored and virtually no chamfer on the ports, bits piston ring had got into the big end and fecked it showing heat scorching.
Looks to me like whoever had that apart wasn't too competent so it may also have had an air leak as well as all the other suggestions here.
Check the carb boot/manifold condition too.
Good luck with it.

[RIDE-RED 250r]

It doesn't take much run time with bits of compression ring floating around in there to do serious damage.

I would strongly recommend a full tear-down and rebuild. With an entire ring AWOL, it is unlikely that none of it went downstairs. And if some did, some level of damage to the crank bearings or lower rod bearing is likely to have occurred.

Besides, you are going to fix the top-end right, why not do the whole job and be sure you have a good engine top to bottom. You are looking at about $250 for a rebuilt stock stroke crank, $50 for new crank bearings, and $50 for a complete gasket set, ballpark. Just as things like compression rings can do damage to the bottom end if they fail, bottom end failures can do damage to the top end. Little bits blow around like that in a 2-stroke when they let go. I have seen lower rod bearing failures do damage to pistons, domes, and cylinders more than once.

[Helidaddy]

Replace the reeds too

Just curious because I'm new to two strokes… What do you think I need to change the reeds for? Old age? Or possibly leaking? When I bought it, he had a couple of Boyesen stickers on the bike. I should take a picture of the reeds.




That's what started this whole thing… I made a leak down tester after learning about it. I tested the engine and it only lost 3 psi in 12 hours… Started with 7psi, ended with 4 psi. THEN I noticed the piston.

[QUOTE=RIDE-RED 250r;1365342]
I would strongly recommend a full tear-down and rebuild. With an entire ring AWOL, it is unlikely that none of it went downstairs. And if some did, some level of damage to the crank bearings or lower rod bearing is likely to have occurred.

Yeah. I'm doing the rebuild with the feedback you guys have given, which is EXTREMELY appreciated!! As a side note, the rod big end side clearance is .023" and I can't feel ANY radial play in it.


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[oscarmayer]

Since you were running lean some how, there is a possibility the reeds got damaged or were causing the air leak. reeds are cheap. $35 for a nice set of racing CF reeds and cheaper for stock oem replacements. It is a good idea to replace the reeds often. In racing we replace them every 6-8 rides MAX. I know guys that replace them ever 4 rides period. They feel the savings is not worth the end results on a $2500 race motor and I tend to agree. If your going to rebuild it. put a nice set of reeds in the thing and then replace the reeds every so often for insurance. it's like getting a new valve job every so often. It helps it run smooth and purr longer.

[RIDE-RED 250r]

Reed petals need to lay flat on the block to seal properly. When they start to wear and not lay flat on the block, you can experience hard starting, and in extreme cases blowback through the carb. They literally are a 1-way valve. They are supposed to open when there is negative pressure in the crankcase as the piston moves upward to take in the next intake charge, and then close up as the piston moves downward. They move at a very high rate of speed, opening and closing every time the piston moves up and down. I'm sure you can see that damaged/worn reed petals can be troublesome.

Also, reed petals chip and break over time. The reed fragments that break off get pulled into the engine. Sometimes they blow right through and into the exhaust, other times they take the grand tour of the engine and can do some damage. The old steel reed petals were more likely to cause some damage. The carbon fiber reeds are less likely to do any damage, but it has been my experience that they do not last as long before they start to chip on the edges. It is said that reed stops can increase the life of carbon fiber reeds. It makes sense to me.

[*ATC*]

Simular problem this Feb, air box lid left off. you see where I'm going, yes lite sez, but took this long to scrape money up for .25 piston and cr head gasket.
Fired up to night souds great,

[Helidaddy]

Well, I'm glad I took your advice. Even though the case was leak tight, look what I found...
http://i882.photobucket.com/albums/ac29/helicopterpilot007/1985%20ATC%20250R%20Pics/F95662E5-17EA-42EE-B7C9-EFA533FE143A.jpg

So who around here is the best to weld up the case? After searching, I've found a few people happy with BDT. I have some work to do around the sprocket area that needs some material added also, but the case saver bolts up and no cracks there, just some aluminum ground down pretty good from the chain the PO threw.

That being said, What are the opinions on places to get bearings and gaskets. Some people say to get Honda gaskets but can't figure out why they say that. I've heard of an upgrade to the 8 ball bearing from some other bike, I think a CR500, and I'm wondering if it's necessary for a stock motor. Looks like the cost is going to get out-of-hand :( soon for a stock rebuild but love these machines so it's all good.

[yaegerb]

BDT to weld up your cases....bar none...they have an excellent welder named Rob Selvy ;)
Search eBAy for discounts on bearing and seal packages. OEM is piecemeal and expensive but the best way to go in quality...your choice.

[atc300r]

Thats almost identicle to the damage to my 85 250r case, I sent mine to BDT and they did a great job on it.215532 215533

[Helidaddy]

Yep. I saw your thread earlier and I thought that it's weird that you had the exact same damage in the same spot. I'm sending my case to BDT for sure. How long did it take to get it done?

[atc300r]

My cases were gone about 3 weeks but I live in NY and had to ship them. If you call them first they will tell you roughly how long it will be. When they got ready to do my cases they called me then when they were done they called me to tell me the price. I have another set Im going to send as soon as I get them ready.

[RubberSalt]

The rings went out a long time ago. You can see the damage UNDER the carbon on the piston. This engine didn't over heat to to bad. Severly over heated pistons will show a 4 or 6 point seisure. This doesn't have any just crown damage. The exhaust side of the piston was NOT prepped for the engine. The 250r should have a 2 holes drilled in the piston for lubrication.

Odds are that incorrect rings were used, to small of a gap. The rings cought a port, snapped off, got stuck under the crank, broke the case, rings went up top and chunked the piston up before leaving the engine. After the hole was formed, it leaned out and got warm.

[86T3]

I've read this thread twice now and can't get over the amount of knowledge you guys have. I look at the picture and think,"Man, that piston I'd dirty" and am happy with my analysis. I guess this is why I have people build my motors. That's it, carry on

[Helidaddy]

So, I have another issue to deal with. When I took the stator cover off, I found the counter balancer bearing holder long bolt had broke off at the threads and was rattling around in there for a while because I could see that the end of the bolt was shiny and smooth. For a while I couldn't figure out what happened because when I looked inside the right-side case where that long bolt goes, you literally can't tell there's a snapped-off bolt in there because it is all smooth like its just a hole that bottoms out without threads. After looking closely I barely made out where the broken part of the bolt is. So how do I get that out? I've snapped my fair share of drill bits while trying to remove broken bolts before and it's something I don't want to ever do again lol. I've searched and read that this is common but nobody logs their adventure of getting it fixed. Does anyone know why this particular bolt snaps off in these engines? All my bearings were in good shape but I'm replacing everything anyway, so I can't figure out why the bolt snapped.

Any help/feedback is appreciated

P.S. YES, I am mechanically inclined

[Red Rider]

I've never heard of that particular bolt being prone to breaking. As with any bolt that has snapped off, I'm sure it was just over-torqued. The only common issue, that I know of, is that the counter-balancer bearing holder ears are prone to cracking off, so you might consider replacing yours with a billet unit. Once your cases are split it should be fairly easy to remove the broken bolt.

[RubberSalt]

Slip a washer over the broken bolt/stud. Weld washer to broken part. Weld a socket or nut to washer.

https://www.youtube.com/watch?v=fs7GTW4ZEDA#t=160

[Helidaddy]

Cases are split already. This bolt is down in the hole where the case dowel is so can't weld to it. I might just have to try my hand at a left-hand drillbit and hope that it unscrews itself and that it isn't corroded into place


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[yaegerb]

Doesn't happen to be the side of the case that needs the repair? If so add that to BDT's list when they weld up your case. Or, figure out the depth of the bolt hole, mark a pilot drill bit with some tape and be sure to drill dead nuts square. Then step up your drill bit size until you can get a bolt extractor in there. Good luck. In my findings there are two kinds of stuck bolts. Those that were over torqued (already mentioned) or those where the steel bolt and aluminum threads have galded together. 9/10 times you are screwed if metals are galded together and it's much easier to drill the whole bolt out and install a time sert or heli-coil.

Here is a set of quality extractors that I use.

https://m.mscdirect.com/mobileweb/product_detail?id=84968866

[Helidaddy]

Unfortunately, the left side is the side of the case with the damage, and the right side is where the threads are broken. Maybe I'll get to it tomorrow after Mother's Day is over with.


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[danbur55]

If you can get hold of a radio antenna that is sectional use that to help keep you straight and start small and step in size removing inner sleeves of antenna pieces as you go up in drill size. Will at least help keep it straight

[Helidaddy]

Ok so I got it out today with a "Grabit" bit from Lowes. Thanks for all the suggestions


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