02 Xr650r rod knock

[trail searcher]

My XR developed a deep knock at under a light load. Seemed more pronounced warm. It was not getting worse but I could not stand the noise

so I have pulled the motor down and found that the small end off the rod

has .003'' clearance between it and the piston pin. There is obvious wear

and the ends look tapered. I purchased this bike new and have a second bike so it's like new other than the rod. I even have the oem chain which I'm

sure could have been replaced. Oil changed everyride. Not a notch or grove

in the clutch basket.I'm puzzled that the rod does not have a bearing or bushing in the small end? Looks like I will be installing a new crank. Has anyone attempted to replace the rod with an aftermarket one with an insert? Looks like all modern four strokes are like this. Maybe I should purchase a RCE jig and see if I can replace this rod as a $500 oem crank is the only one I can find. My concern is that this condition will occur again.Wonder why they dont press the pin into the rod? Any advise or wisdom would be appreciated. Thank You!!

[Beyond The Pale]

I think that only 2 strokes have roller bearings on the rod small end. Every four stroke that I have been into just has a pin that fits close to the hole in the rod. The aftermarket rods are the same.

Take a look at your manual. You may find that .003 is not out of spec. The way I read my XR600 manual it seems like they are saying that .005 of pin to rod clearance is OK. Seems like a lot of slop to me. You might want to look at the big end too. Use some carb cleaner to get the oil out and the try moving the rod feeling for movement. It is a lot easier to feel if the oil isn't in there.

The good news is that you can replace the rod for a lot less than $500. There are several sources. Unless you have the tools to be sure the crank is true, leave to job to a competent shop. It takes a big press to push the big end crank pin. I have no problem doing bearings and other such things, but I will not do the crank as I don't have the proper tools.

Wonder if heat had anything to do with it? What does the bottom of the piston look like?

[Beyond The Pale]

I looked it up. The max pin to rod clearance is .0026. At .003 you are over. Unless the pin is worn, it's time for a new rod.

[martinfan30]

I think that only 2 strokes have roller bearings on the rod small end. Every four stroke that I have been into just has a pin that fits close to the hole in the rod. The aftermarket rods are the same.

Take a look at your manual. You may find that .003 is not out of spec. The way I read my XR600 manual it seems like they are saying that .005 of pin to rod clearance is OK. Seems like a lot of slop to me. You might want to look at the big end too. Use some carb cleaner to get the oil out and the try moving the rod feeling for movement. It is a lot easier to feel if the oil isn't in there.

The good news is that you can replace the rod for a lot less than $500. There are several sources. Unless you have the tools to be sure the crank is true, leave to job to a competent shop. It takes a big press to push the big end crank pin. I have no problem doing bearings and other such things, but I will not do the crank as I don't have the proper tools.

Wonder if heat had anything to do with it? What does the bottom of the piston look like?

I agree about the .005" being sloppy. Almost any of our Yota engines would be pin knocking at any thing over .0015".

[HeadTrauma]

Oil changed everyride.

1.) Has anyone attempted to replace the rod with an aftermarket one with an insert? Looks like all modern four strokes are like this.

2.) Maybe I should purchase a RCE jig and see if I can replace this rod as a $500 oem crank is the only one I can find. My concern is that this condition will occur again.

3.) Wonder why they dont press the pin into the rod? Any advise or wisdom would be appreciated. Thank You!!

Unless you're going 500+ miles "Every ride," changing the oil that often is really excessive. It obviously didn't save your connecting rod.

1.) Yeah, lots of people get only the rod replaced, although I don't know of any that have a bronze bushing in the small end. For the average rider and engine it's unnecessary anyway. Under normal conditions the rod small end should not wallow out....not before the engine needs a thorough rebuild, anyway. Sometimes sustained high rpm operation will cause it, however. Then again, sometimes lugging can hammer the rod and crank. If you're the paranoid type, Carrillo has a very nice conrod with bearings at both ends. Most others just have a copper coated upper half.

2.) Like I said, this condition is not that common under normal circumstances. Just have a reputable shop replace the rod. It will be cheaper and easier, especially if you don't have a hydraulic press.

3.) If the pin was pressed into the rod(like many car engines have), there would be no practical way to replace the piston without pulling the engine, pressing the pin out, and having to heat the rod to expand it in order to install the cold wrist pin. In the process, you risk cooking the big end bearing and yourself while trying to muscle around a 60+lb engine bottom end in the vicinity of a heat source. That, and floating pins are lower friction.

[trail searcher]

Thank you for all of your input. I own 2 presses and have been an auto

tech for 30 years. I can afford a new crank. I just have a desire to fix this right the first time as I have a premonition that this is going to occur again.

Installing a new crank is no big deal. I bought this bike so I didnt have to as

after 10 hours a day in a shop the last thing I need is to go home and start

over. This bikes plated and even with 15/47 it vibrates at above 60mph

through the chassis.engine vibration. Just my opinion I think several higher

speed runs may have caused this as the rpm's were held steady.

Thanks again for your interest.

[paul246]

Just curious, but would it be possible to enlarge the con rod's upper end hole and then press in a bronze bushing, then bore that bushing to fit the wrist pin, and finally drill an oil hole through that bushing?

Or would there be another way to achieve the same result?

[trail searcher]

I spoke to a machinist that does my shop work and he suggested we try

this with a HD insert which can be reamed to spec. I think I woud be reluctant to try this as how much material is safe to mill out. My friends

650 rod went through the cases. Cost him more than the bike was worth.

If the falcon or carrillo rod could be serviced in the bike my decision would be over.I worked at a Honda auto dealer as a tech for over 10 years and cant

beleave that they would not have a serviceable rod . Their cars last a long time.

[HeadTrauma]

I was telling someone in another thread that most single and even many twin cylinder bike engines have press-together cranks with one-piece rods. None of those can be replaced without splitting the cases.

I would be reluctant to modify the worn out stock rod also. Saving $200 in the short term won't pay for something like this:

https://www.thumpertalk.com/forum/showthread.php?t=547194&highlight=made+in+japan

[XR250rdr]

Carillo makes a rod for the 650R

[doublediesel]

Same thing happened to me... Bronze flakes in the oil from the small rod end wearing. After pricing it all, I put in a OEM crank with rod and the chain. Why not? It's done with....

[resurrection]

Boy I'm suprised to hear a noise like you discribe from the top of a con rod

I'm thinking you make be hearing more of a octain knock

the specs you speek of are very small .0004 out ?

lets be real you cant even measure that amount in two differant rooms.

Thermal expansion will for sure take up that amount .

And one more thing concerns me engine knocks show there face more when cold.

Pre ignition shows its face after a hot spot maybe carbon build up when hot.

Good luck but I think you may have jumped the gun on a rebuild.

[martinfan30]

I was thinking carbon knock.

[xrfred]

if you have the engine apart already I would definately replace the stock rod with an aftermarket one it is the the weakest link in a fairly reliable motor for its fairly high state of tune. I have been rockin my oo since 03 riding every other day to work off roading and three seasons of racing supermoto. If i was you and wanted to keep the bike for the long term I would think about looking into the larger cam chain and sprockets that is in the hrc kit. that and the rod and you may have a permenant motor.