250R Piston Damage: Pics

[1BFC]

Hey all,

So I had some things I needed to take care of on the new 250R before I did any riding on it and today I started working on getting it all done. This is a re-sleeved stock cylinder (I believe) and I think the size of the piston is 72.25mm as that's what is stamped in the top of the piston. Fuel was mixed at 32:1 on 93 octane for this initial testing.

When I took the bike out for a brief shake down run I noticed that during warm up that the base gasket area was a little damp. I sprayed the area with some starting fluid and the RPM didn't change so I thought it was just "sweating" a little (I just purchased this machine so I don't have any idea of it's history at this point).

I was still concerned about it so I rode it very easy just getting it up to operating temp and stayed in 3rd or lower at about 1/2 throttle max for 1-2 seconds duration. I noticed the engine exhibiting signs of running lean because the RPM would not come down and it would rev up when I came to a stop.

I immediately put it back on the trailer and returned to the garage. The base gasket was now obviously blown out as I could see large portions of it squished out around the base.

Note that the engine was fine when I turned it off and it was at no time being run even remotely hard. Take a look at the pictures I've linked to and let me know what you think of the piston/cylinder damage that's present. I originally only planned to replace the base gasket since it was running just fine when I put it on the trailer. However, after seeing the damage I'm considering replacing the piston, rings, etc, unless you guys think it's not so bad.

I've worked on 2 strokes before but they were always jet ski engines and to be honest I just don't know what is a "bad" piston as I've never seen one with damage on it prior to this.

Anyway, if you have some knowledge to share about this I'd sure appreciate it if you commented on it here.

Thanks!

Pictures: http://picasaweb.google.com/OneBFC/250R
note that you can zoom in pretty far on these for a better look as they are fairly high resolution images.

[Yamahondaman]

Look's like a too close of a bore ... not broken in right.... not enough exhaust for a 295-310 motor ...
what was the compresion,is it a long rod motor,is there a spacer plate,how thick was the head gasket ... was it a stock one ? .. where in Fla. are you ? ..
is there any writings on the Cyl. like Trinity-CT-SNR or TDR,ETC ?

[1BFC]

I didn't do a compression check on it prior to tearing it down unfortunately.

Not sure how to tell if it's a long rod or not but I asked if it was stroked when I purchased it and was told that is was NOT a stroked engine.

No spacer plate I'm certain on that.

No clue on head gasket either because it self destructed on removal.. was very difficult to remove actually. However, I will note that the engine was not pinging or anything when running.

No clue if the gasket was a stock one or not either.

Nothing on the cylinder other than factory honda stuff. I'm 99% sure it's a factory unit that's been re-sleeved as that's what the old owner said it was and it looks just like my old 250R cylinder that was stock.

I'm in the Tampa area in FL.

Thanks for the reply!

[1upfront]

Looks like damage from the exhaust bridge not being relieved after boring.

[Billy Golightly]

I concur with Ronnie... Looks like the bore was a little on the tight side.

[lndy650]

defenitly looks like the exhaust port wasnt chamfered...
i dont think its a tight bore because there are burn marks past the rings which usually occurs from a loose clearance...how does it fit in the cylinder loose or tight?

[1BFC]

Well it was running well (other than it was lean from the gasket leak) when I tore it apart to replace the base gasket so I'm on the fence if I should put it back together with that piston in that condition.

Anyone think the piston needs to be replaced and the cylinder honed or bored one size up?

Or does the cylinder need work period before it goes back together?

Thanks for all the replies from everyone too!

[Twilight]

I would clean up the cylinder and that is a exhaust bridge problem, whoever last did that engine didnt go over the ports, looks like the ring just kept on catching and catching.

Piston is junk IMO, it looks heat warped.

[hoser]

Looks like damage from the exhaust bridge not being relieved after boring.

Here is what he is talking about.
http://12.227.214.171/ExhaustBridgeRelief.htm

[hoser]

The piston is junk, pistons are throw away items, every 30 to 60 hrs (depending on the engine state of tune) you remove them and throw them away buy new.

Can you take more detail pictures of all sides of the cylinder walls, close ups, from the top and the bottom.

What little I can see in the pics the cylinder has damage or wear, you can see the uneven wear pattern on the cylinder wall, most likely its where the aluminum balled up on the piston and reduced the piston to cylinder clearance.

The cylinder needs to be honed with a ridged hone, not a ball flex hone, lightly to see the true condition of the bore, then measured as outlined in the service manual to see if the cylinder is out of round and tapered,

Example of a ridged hone.

http://12.227.214.171/phpBB2/files/dsc03509_261.jpg

Here is a cylinder I used the ridged hone on that was uneven a ball hone will just follow the uneven bore, the tension on the balls will vary as they fall into and come out of the ports, a ridged hone can actually straighten a bore if used correctly.

http://12.227.214.171/phpBB2/files/dsc03528_717.jpg


I cant tell in your pics but if their is any aluminum stuck to the cylinder wall but if their is you can remove it with muriatic acid, the acid will dissolve the aluminum, then you can give the cylinder a lite hone for the new rings to bed into, once the hone is complete you need to measure the cylinder ID, you say the piston says 72.25mm on top most likely the cylinder bore needs to be 72.25mm the only way to really tell is to measure a new 72.25mm piston and see then calculate the piston to cylinder clearance as outlined in the service manual.

Each brand of piston usually has its own required piston to cylinder clearance requirements.

[Billy Golightly]

Damn that cylinder sure has bunch of holes in it, whats it out of?

[hoser]

Damn that cylinder sure has bunch of holes in it, whats it out of?


Not to get too far off topic here, that cylinder is off a 81-84 ATC250R its one of the old Cammex cylinders. Calvin Pollet use to make them http://www.cpindinc.com/

More pics of that cylinder are here.
http://12.227.214.171/trx250r/viewtopic.php?f=6&t=20

[Yamahondaman]

Damn that cylinder sure has bunch of holes in it, whats it out of?

thats what i saw .... looks like a "LUNG" !! WFO !!! :naughty:

[Billy Golightly]

That thing is awesome, thanks for sharin Hoser.

[1BFC]

Well after reading everyones input it appears I should just do a complete top end on this before putting it back together. Additionally some of you mentioned that the exhaust ports looked like they needed to be cleaned up as well.

Unfortunately I'm not sure who or where to go to for this in my area. I don't have the tools/experience to handle it myself either.

Anyone know of a local shop or person that has a good history with this that I could go to? I'm in the Tampa area in Florida and anything within an hour's drive is ok with me.

Thanks again!

[Dirtcrasher]

That hone is saweeeeet!!

[Ryan.]

That hone is saweeeeet!!

looks like you can use it for some horrible torture device too:w00t: :welcome: :crazy: :naughty: :postwhore :beer :TrikesOwn :banned:

[HEAD09]

well were do you live exactly? do you know were rtm's off off florida between bearass and fletcher is?i just got my done for 60.00 in there...... great people drop a me a pm when you get her fix....were do you ridding mostly?

[1BFC]

Update: I've decided to ship everything to rebuild the top end to my old shop in Naples, Cypress Cycle. Terry is a great guy and I trust him to do it right. I'll still be putting everything back together myself but he's going to bore it to 73mm and clean up the ports and make sure everything else is good to go on the cylinder.

I picked up the parts from LA Sleeve so the top end will be brand new after this. I didn't feel any play in the rod so I think the bottom end should be fine.

About the only thing I'm unsure of still is the cylinder head. I think it's a completely stock head and I remember reading somewhere that it's potentially bad to run a stock head on a over sized bore. So, I'm still looking into what to do about that, if anything needs to be done at all.

Anyway, thanks again to everyone that commented and made suggestions!