What happened to my 250R???

[Blown 331]

Well, it blew up again and I'm not sure what happened this time. Here is what I had. A used 85/86 bottom end, rod seemed good, 1.25 mm over Wiseco and fresh bore. I had ran 3 tanks of gas through it, gentle break in.
My mods are ESR ATC-5 pipe, .010 thick head gasket, 36mm PJ flat slide- 175 main, no air box lid, UNI filter, and RAD valve. I was running 110 octane leaded gas and 32 to 1 Honda synthetic premix. It was running a little rich. I was running at close to 3/4 throttle for about 3 minutes when I heard some noise. I pulled it apart and there was melted metal laying on top of the piston but the piston is intact. I have no idea where this metal came from. The rod is tight but is discolored, when I rotate the motor over it does bind in spots. It kinda looks like the opening on the lower end of the rod is bigger than is should be?? Any ideas what happended? I'm getting a little frusterated since I only had 3 tanks of gas on this motor. The old motor still had the stock piston, it shattered and split the bottom cases out. I guess I'm going to fix it but I do not want to go through this again. I also thought about buying a used big bore complete engine but then you really don't know what you are getting. Looking for suggestions on what to do. I would like more power but I would like to keep it under $1000 if possible.

[Blown 331]

Another

[Blown 331]

Here is the rod, does the opening on the bottom look odd to anyone else? Did I melt the rod? I dont see where else the melted metal could have came from and what would cause that?

[Iliketogofast]

Maybe you should check your carb and jetting and such, you might have leaned out.

[Iliketogofast]

Might just be me being stupid, but that's the only thing I can think of because it happened to me. Radiatior working?

[wilkin250r]

It's almost impossible to melt your rod. The piston is aluminum, which melts around 1200 degrees Farenheight. Your rod is steel, which melts at around 2500 degrees. It's almost impossible to melt your rod without melting your piston, first.

Now, if you have bad bearings or lack of lubrication, friction can cause local hotspots, but it's very difficult to get those spots hot enough to start melting. Parts that are moving are usually subject to stress, and you often end up with structural failure LONG before you begin to actually melt the metel, because the metal will soften and fail way before it reaches an actual liquid state.

With that being said, I have no idea what your failure is, I've never seen a failure of that type, so I can't even begin to help you. However, I will tell you that if you see discoloration and feel binding in the lower end, it sounds like time for a lower-end rebuild, and possibly replace the crank. This may very well eat your entire $1000 just to get running again, without any actual increase in speed or performance.

[Blown 331]

Well this sucks. Can anyone recomend someone to rebuild my lower end? I have 2 of them that need rebuilt. I called the Honda dealer where I purchased a new 2003 400EX and a new 2004 450R and they said they don't work on 250R's because they are too old. WTF? Nice customer service there.
Or where can I buy a new crank shaft? I think I'm just going to say the hell with my $1000 budget and go with a fully ported ESR 310 top end and a 38mm air stryker.
That melted aluminum still scares me, is it possible to melt metal out of your lower cases?

[wilkin250r]

I have no idea where that melted aluminum could come from. You don't see any evidence of any melting anywhere?

There are many places to buy a new crankshaft or rebuild your engine. Just about any racing shop can rebuild the bottom end for you, but such repairs aren't cheap. They'll usually recommend many parts that need replacing. Side cases are very common. Just because it ran fine for a long time doesn't necessarily mean it's good. If they see wear or stress cracks around the bearings and areas in the cases, they'll recommend new side cases, and those things aren't cheap.

I realize it's difficult to spend $400 in new side cases, without any real improvement in performance. But if you want to increase performance and power, yet still retain reliability, such repairs and replacements are often necessary.

If you're not doing the work yourself, you're probably best off sending your entire motor in to a shop and let them do the whole project. Even though you may be able to get a crankshaft for $40 cheaper someplace else, or save $20 on side cases online, it's best to let your shop do the whole thing and pay those slightly higher prices, because they're more likely to go the extra mile and pay close attention to those little details that are so important. It's worth that extra $60 to avoid bad blood on your motor package.

If you're thinking ESR, then send your entire motor to ESR and let them rebuild the bottom end for you. But I got to warn you, it ain't cheap. A $1000 motor package could end up costing $3500 by the time they replace the crank, one side case, a few gears, and install the whole thing.

[250-R-250]

I personally think you might be better off looking for a new motor, you can get a complete one already with an esr 310 for 1000, I see it all the time

[Blown 331]

Originally posted by 250-R-250
I personally think you might be better off looking for a new motor, you can get a complete one already with an esr 310 for 1000, I see it all the time

I'm thinking you might be right but that's what I did last time and now I have 2 blown up motors. lol. I have seen complete 310 motors go for $1000 already but I can't find a deal like that when I'm looking. If I see that again I will buy it up. I'm sure I can sell all my motor parts for like $400 or maybe more.

[Rich250RRacer]

Looks like the bearing cage in the lower bearing let go. I've had this happen before and I couldn't tell until I took a small pick and spun the bearing around. Portions of the cage broke away and traveled up through the transfers nicking the top of the piston. You have to look closely but you can usually see the needles in the bearing really close together or touching. HotRods kits are good for doing this.

[slick250]

Originally posted by Rich250RRacer
Looks like the bearing cage in the lower bearing let go. I've had this happen before and I couldn't tell until I took a small pick and spun the bearing around. Portions of the cage broke away and traveled up through the tansfers nicking the top of the piston. You have to look closely but you can usually see the needles in the bearing really close together or touching. HotRods kits are good for doing this.

Same thing happened to me earlier this summer. Lower bearing seizure and meltdown. Fragments scored piston up real bad. Changed my 86 crank to an 89 style.

Put a CR500 in there :)

[joedirt]

Buy all the parts OEM Honda are the best. You will need a crank, lower end bearings (2) and seals (2), clutch cover gasket, center case gasket, piston kit and top end gaskets and your all set. take it to a good shop in your area and you'll be set. Isn't Service Honda in your area go to them.

[Blown 331]

Originally posted by DierWolf
Put a CR500 in there :)

My neighhbor actually has a very nice 1987 CR500 for sale, runs great, fresh rebuild, piped and everything. He just bought it for $1300 and will sell it to me for the same price. What do you do about your kick starter hitting the fender? I don't want to have to take the fender off every time I start it.

[wilkin250r]

Don't do the CR500. Everybody always says the same thing, very fast, terrible vibration. The motor will vibrate itself right out of the frame.

I've never known anybody that has done this conversion to be extremely happy with the results, and actually ride their machine on a daily basis.