Bearing Doctor!!

Discussion in '2-Stroke Engines' started by recon chris, Jan 12, 2012.

  1. recon chris

    recon chris New Member

    Hello everyone.

    I'm starting this thread to once and for all end the needless forum searching for the proper bearing codes that belong to the 66cc GT-5 two stroke engine (and later all the other Chinese engines). This includes ALL bearings inside the engine. I believe there are 6 but if IM wrong please tell me.

    Upper needle bearing
    Lower needle bearing

    Crank shaft bearings x2 matching

    Clutch shaft bearing x2 matching

    What I need is ether
    1) the complete dimension of all bearings (or any bearings you may know of)or

    2) a researchable replacement bearing ID number.

    This is it! No more taking bearings to auto stores trying to match by size. No more buying replacement bearings form the same dealers that sold you the engine with the Chinese bearings in the first place. No more "eyeballing". No more "just making it work with my old bearings" type BS. And no more buying bearings that aren't specified to the job it has to do inside the engine. No more forum searching in 7 different places to try to find all the ID numbers. AND NO MORE NEED TO ASK THE QUESTION "what are the proper replacement bearings for my engine" AND GETTING ONLY 3 UNSATISFACTORY RESPONSES. This is it its all going to be in one place now.

    Now what is going to happen?
    I'm going to use the information you guys provide me to do a host of beneficial things.

    1) I'm going to make a extensive list listing all the bearings that could posibably work for every bearing application in the engine

    2) I'm going to list bearing sets that will be geared to different attributes you may desire. (speed, noise, longevity, price, material,my recommended set up Ext.)

    3) I'm going to list the company that make all the bearings for this engine so you have selection instead of using just SKF

    4) I'm going to list the sights were you can buy these bearings (don't worry I'm not a vender and i will not be pushing any particular sight I'm just trying to make obtain these bearings easier for you.)

    So help me do this guys any bearing specs you may have would be great! Ill find out all the sizes one way or anther but if you know and told me that would be a great help

    Last edited: Jan 12, 2012

  2. motorpsycho

    motorpsycho Active Member

    This is a good idea but you must take a few things into consideration.
    #1. you're new here and sometimes people tend to not take the "newbie" information as being correct.
    #2. you should also consider that it is possible that not all 2 stroke, h.t. bearings are the same. a crank bearing in one engine may not be the same size as the crank bearing in a different engine.
    I may be wrong on that because, in general, "all of these engines are the same" (externally).
    BUT, i would guess that there are a few mfg's that may use different sized bearings.

    The problem with this is determining who mfg'd the engine in question to give the correct info.
    sometimes, people do not know who made their engine, and this is where all of the guessing or trying to match bearings comes into play.

    for example: an engine that is sold by bike berry may not have the same size bearings as an engine sold by boygofast. even tho they look identical on the outside, the bearing sizes may be different because these engines could have been made in different factories by different companies.
    the sellers of ALL 2 stroke h.t. engines are not the manufacturers, and sometimes people just don't know where their engine came from.

    #3. the other thing is that there are a few vendors that claim to replace the original bearings in brand new engines with higher quality ones before they get sold to the public.
    This is just speculation, but, if this is true, this would be another peice to the puzzle, trying to figure out what bearing size so & so puts in their engines. If you are looking for a specific bearing, the best thing to do (in my opinion) is tear your engine apart and measure the bearing in the engine, and then order that same size bearing.
    i think it would be difficult to come up with a list of bearing sizes that would be 100% accurate.
    I do not know one person who would order parts based on a list before they tear their engines apart (engines in general) and measure the bearing in question.

    lets say that you think you have a bad crank bearing and you order the bearing that you think is in your engine based on a list of numbers.
    you get the engine apart, get the new bearing, and then find out that it's wrong. this, in my opinion, is a huge waste of time.
    I'm not saying that what you're doing is wrong, and i think it could possibly work,
    but the trick is to nail down the exact bearing sizes based on the engine mfg's, and when you are looking for parts, to know exactly where your engine came from.
    to me, measuring the bearings that are in your actual engine is the best way to find replacement bearings.

    Just like if you are rebuilding a 350 chevy engine base don the fact that it has a million miles on it and needs a re-build. it's safe to assume that the rod bearings, main bearings and rings are std. but, it is possible that it may need oversized bearings due to previous work, or oversized rings do to a previous overbore to the cylinders.
    Measuring before you buy is the best option in my opinion.

    There are people who buy used h.t. engines, and who knows what the previous owner did to the engine. You know that if there was something in question, the seller would more than likely not tell the buyer.
    so when the buyer has a problem, and he assumes that it's all stock internally, this could be a problem if he tries to order parts from a list.

    again, i'm not saying that your idea will not work, i'm just saying that you need to cover ALL bases, and all engines with verification before you make the list.
    And you should come up with a way for people to determine where thier engine was made. so far, i know of nothing on these engines that can determine where they were originally built (what factory).

    Just my opinion....don't know how good that is.
    Last edited: Jan 12, 2012
  3. recon chris

    recon chris New Member

    A 22 line response….and absolutely no bearing information anywhere.

    Look I’m not asking people if it’s ok or if you think there is a problem with what I’m doing I’m just going to do it. Its information I’m collecting that will finally be consolidated in one place and maybe just maybe, make a few people’s lives easier.

    HOWEVER you did bring up a good point although all Chinese engines look the same on the outside that doesn’t mean that they all run with the same parts on the inside. I would really bet they do but just to make sure when you submit your bearing information to me make sure you tell me what engine you’re talking about like I did (GT-5).
    Last edited: Jan 12, 2012
  4. motorpsycho

    motorpsycho Active Member

    wow, you actually counted how many lines i wrote?
    I'm just saying that what you're doing is going to be difficult, and if you can get the correct info for each and every engine, more power to you.
    I don't have any bearing info to offer because i have never had to tear any of my engines apart.
    if any one of my engines take a dump, i won't re-build, I'll buy a whole new engine.
    a whole new engine would be a quicker fix and they aren't that expensive to replace.
  5. blue 48

    blue 48 Member

    amen psyco, ive seen it many times before. 2 identical comonents same brand 2 different countries of origin. these being air compressors for a couple of trucks ive rebuilt and some things were so different that samples had to be supplied to ensure they were correct. so if it was this hard for precision made units to keep it uniform then what chance do these chinese cheapies have

    ive found that TIMKEN bearings are very good with matching bearings to suit and theyre pretty good quality too

    these engines run em till they blow i reckon then replace em. they are a CHEAP form of transort. they are fun though:)
  6. HeadSmess

    HeadSmess Well-Known Member

    keep the bearings, change the motor! :jester:

    i think the bearings are the best bits in these! **** of a lot more precise than some of the shafts that run in the bearings, ive noticed...

    the bearings only as good as the shaft, and what with the dirty big tool marks in the shafts, i dont think theyve been finish ground to within +- .005mm... not to mention eccentricity...
    Last edited: Jan 19, 2012