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Connecting Rod Wear??? And other questions...

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Hey everyone...I'm new to the board and dirt bikes in general.

Have mainly been a road racer until getting into supermoto with a CA street-legal 450X.

I'm in the middle of a top-end rebuild and wanted to get some opinions on some wear marks on the connecting rod.

See the below pic:

dsc00692ry7.jpg

Looks like some of the plating is wearing off on the bottom end of where the pin goes through. Don't know if this will require a new rod or if it is normal.

The inside surface is really nice & smooth, the pin fits well...maybe a little loose but I guess loose engines run good, its just the wearing discoloration that really caught my eye.

Also what do you guys recommend to clean up the head? Or any other servicing to it?

I know to clean off the gasket gunk...just haven't gotten around to it yet.

dsc00695we7.jpg

The cylinder looks really good, still has all the cross-hatch marks and a few light vertical wear marks. Do you usually hone the cylinder regardless of its condition just for good measure?

Thanks in advance.

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I don't like the way it looks, I would like to know how it measures up though. Don't hone the cylinder.

Use a fine scotch bright, with a little gasoline to clean the gasket surface, no razor blades.

Be sure that little oil port (down by the crank pin) is not clogged.

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:lol: ooh that doesnt look too good to me...i havent had to pull one apart YET, but um idk i dont like the looks of it... take it in and get it checked out; or send the pictures to a shop or somthing. and otherwise about the gasket, do what ttr2255 said, its a good method. :applause:

-brian

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I got everything cleaned up and ready to go back together, but I dont know if I should the way the connector is.

The connecting rod is attached to the crank as one piece so I'd have to get a whole crank assembly for around $200 because of that worn area. The thing is its very nice an smooth in there. I have the specs for the inside dimension but no way to accurately measure it.

What to do, hmm...I'm thinking about putting it back together. Run it for awhile, keep an eye on things, order a crank in a few months and go through it again later.

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I'm new to CRF's so i have not suggestions/opinions but do you have an estimation of how much mileage is on your engine?

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I'm new to CRF's so i have not suggestions/opinions but do you have an estimation of how much mileage is on your engine?

I'm the third owner and from what the seller told me its over 3,000 miles.

I've probably put on about 500 miles myself. The engine so far has held up really good and has been taken care of really well. Only one exhaust valve is out of spec by .05mm and I'm changing the top-end because it was burning a bit of oil and I felt like it was a good time to do it. Other than that, the bike runs great!

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ah...the plot thickens.

i was checking eBay and a pic of a new crank and rod shows what looks like the small end dipped in something about the same color as the "discoloration" on my connecting rod. considering the wear on the pin & inside of the rod end is towards the outside edges it leads me to believe the color could be part of the original color left over from NOT being worn! arg...i'll have to consult a mechanic that works with these things to find out for sure and take some measurments.

so has anyone noticed this before on the inside of the rod when doing a top-end before???

thanks for the advise guys i'll let you know how it goes!

41eb_1.JPG

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ah...the plot thickens.

i was checking eBay and a pic of a new crank and rod shows what looks like the small end dipped in something about the same color as the "discoloration" on my connecting rod. considering the wear on the pin & inside of the rod end is towards the outside edges it leads me to believe the color could be part of the original color left over from NOT being worn! arg...i'll have to consult a mechanic that works with these things to find out for sure and take some measurments.

so has anyone noticed this before on the inside of the rod when doing a top-end before???

thanks for the advise guys i'll let you know how it goes!

41eb_1.JPG

yes it is plated with something (looks like coper) , but what ever it is , it is showing were. You should try to barrow the inside micrometer, or a t-gage and outside mic. Measure it, see if it's in spec, and go from there.

It costs nothing to measure it, but if you blow up your engine you will spend 2K to fix it.

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A thought just entered my mind. Becuase it's a moto, and you are not the o owner, it could be worn from riding welies around. The iol pump could have had cavitation from time to time while under a load.

Personaly, I think they should have put a neidle bearing at the wrist pin in this engine.

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A thought just entered my mind. Becuase it's a moto, and you are not the o owner, it could be worn from riding welies around. The iol pump could have had cavitation from time to time while under a load.

Personaly, I think they should have put a neidle bearing at the wrist pin in this engine.

the wheelie thing with the previous owner is likely, but it seems like this one little area is affected...everything else looks great.

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the wheelie thing with the previous owner is likely, but it seems like this one little area is affected...everything else looks great.

Can't say 4 certain, because i have not had the entire lower end apart on this engine, but most all critical friction areas have ball bearings witch would go a lot longer without the use of oil as compared to the wrist pin. That is a very highly stressed point in the engine, and even one time being run low or the pump capitation for a while would cause that scoring.

Your probably now wondering about the piston & cylinder. I would say that to should show some were, but it could have been lubricated by oil splashing up from the crank.

It's hard to say with out a complete inspection of all the critical parts of that engine, and it's even harder to say without having vast forensic experience on this specific engine, what really caused this to accrue.

it's unlikely that it will cause total engine failure (though possible), most likely if it is in spec, and you do run it I think at worst it would size, and than rely on the piston /wrist pin for mobility. I also think that if it is in spec, and you do run it, and you maintain good lubrication, that it will be fine.

Bottom line is that it is showing what appears to be abnormal were, and you need to make the call as how you want to Handel it.

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Thanks alot...you really helped shed some light on this one!

I measured the inside diameter with some dial calipers and it is within spec and seems to not be out of round. I'm going into the dealer tomorrow for a valve shim and I have a print out of the picture to show the mechanics and see what they say.

I'm not cheap and like to do things right...the crank assembly is around $200 and the only thing I'm really worried about is separating the engine halves. I have the manual and it looks pretty straight forward.

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I went to the dealer this morning to pick up a valve shim and spoke to one of the mechanics there. I brought the wrist pin and a print out of the picture. He said everything looked fine as long as it is within spec and is smooth and not galled. Then he showed me a newer connecting rod/crank and it had the same copper coating on it...so if anyone does a top-end on one of these things...its very deceiving but the discoloration is normal and not from wearing through any plating inside! I'm so happy I can put this thing back together and not have to worry about breaking down the whole engine and swapping the crank. :lol:

I'm surprised nobody noticed this before and posted up about it. :applause:

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Good deal, Supermotarded! FWIW, I would not bother shimming the valves. Just replace them and save yourself some trouble.

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Good deal, Supermotarded! FWIW, I would not bother shimming the valves. Just replace them and save yourself some trouble.

thats a little overkill for one exhaust valve that is barely out of spec on the tight-side.

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