Upper Conrad Bearings

PerryP180

New Member
Jun 24, 2011
79
1
0
Atlanta, GA
I have a Grubee 66 cc motor bought new June 2011 that I ran for 1600 miles before it died. Starting at around 1200 miles it began to make a rattling noise that gradually got worse. This was present at idle or running and it was not piston slap. When it died it sounded like something gave way. I can manually turn the motor over and it just sounds strange while not cranking. I've read countless posts and determined that bearing failure is common and that the upper conrad bearing is a likely culprit. The work I've done on these motors has been minor(replace magneto, clutch pads, clutch plate adjustment, clutch pin and bearing lubrication) but I want to try and replace these bearings. I got the bearings recommended in a post so I'm ready. The only problem is that I don't know where the "upper conrad" bearings are or if that is what they are really called. Can you give me an idea where to look and any other bearings I might see in case those need replacing? Thanks.
 

inked1974

Member
Apr 11, 2011
278
0
16
46
Palo, Iowa
The upper rod bearing is the one that holds the piston. If you remove the 4 head bolts, remove the head and cylinder. What you will have left is the piston floating on the rod. The bearing in question is between the piston and the top of the rod. There is a clip on both sides of the piston retaining the wrist pin. After removing the "G" clip you can slide the pin out and replace the bearing. Of course there are many things to consider when reassembling the motor. Gaskets,rings etc... But that's just my 2 cents. I'm a 2 stroke novice. If you need a quality bearing alternative let me know. I have found a stihl chainsaw bearing that seems to work awsome and is heavy. Hope I helped a small bit
 

PerryP180

New Member
Jun 24, 2011
79
1
0
Atlanta, GA
I appreciate the info. I'm a novice here also but I love tinkering. From your description I thing I can handle it. One thing I'm totally in the dark about is do I need to replace the rings during this procedure. Are the rings normally replaced anytime the cylinder is opened like this even if they are not damaged? Here is a copy/paste of the post where I sourced the bearing. Thanks for your help.


Yep Aleman hit the nail on the head here I do believe, sounds like the wrist pin bearing/upper bearing.

Don't run that engine anymore until you replace it because if it fails you will be rebuilding the entire top of that engine at the very least.

Here is a link to motion industries were you can at a very small price get a replacement bearing that is much higher quality than the ones that come in the engine and the ones most MB site sell as replacements because they are just the same stock soft weak bearings that may hold up a long time or may not.

here is the link:

Motion Industries - Product Search --

if it doesn't show the bearing info. just type KBK 10X14X13 in the (SEARCH BOX) and the choose (Manufacturer Part Number) in the next box and then leave the last one at (All Manufacturers) and just move over and click the GO button, you will now see the bearing details but NO Price will be listed you will need to either call or just go to a local Motion Industries and they will order the bearing for you, I ordered 6 of them back in june of this year and they were $3.69 each, there is a K 10X14X13 also but the KBK is the best of the two, get one of these in that engine and you wouldn't have to worry about that issue any more, and while you're at it you may as well pick up a couple of higher quality crank seals for when you need them for only $2.74

Seal # and description is...

SKF Sealing Solutions
17X29X5 HMS5 RG GREY NITRILE SEAL
17x29x5 RG Oil Seal - Metric SKF# 563933

Item No. 02508698

the picture that is shown of the seal on the motion industries site is the wrong picture so dont be concerned about that, but the seal is the correct seal.

Again.........!!!! DON"T.........!!! run that engine with that rattle in the top...... just go to one of the local vendors on the forum like Thatsdax.com and order a new (correct) either 6mm or 8mm stud size jug to case gasket if you dont have the tools to make your own and order the bearing from M. Industries and you can have that thing going again in no time.
 

inked1974

Member
Apr 11, 2011
278
0
16
46
Palo, Iowa
All of the info you pasted is "spot on". If it was my motor, I would take the top apart and inspect it very well. Rings and even a jug and piston are very cheap to replace if needed. I am sure that just replacing a bad bearing and putting it back together would "work" but if you are in the thick of the mess, you may as well replace what you can for the sake of longevity. Open it up and throw some pictures when you are into the motor. Pictures may help in the advice process