fitting bearings

muhuha

Well-Known Member
NEed some advice on fitting new big end bearings. Ive got some polini evolution bearings and on one of the on one side its got a c and two dots. The other bearing also on one side has a c and three dots. Do these mean anything? Also im going to put the bearings on the crank before hand, how far down the crank do they go? Has anyone got a picture?

Thanks
 
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DRXRACING

Well-Known Member
I install the bearings in the cases and then pull the crank into the bearing on the first case , then press the case over the other end of the crank.
 

Ben

Retired
Yeah , this is the best way imo. Instead of putting the bearings on the crankshaft , and then putting the 'shaft in the carters...
 

Ben

Retired
No not really. When I start the first time , the gasoline and 2-stroke oil mixture ( 1:50 ) will grease them automaticly. :)

// edit : Plus , they are pre-oiled when they come out of the packageing.
 

narx

gefufn tjuner
I ment for example do you grease crankshaft and bearing inner ring before you put the bearing on the crankshaft. It will go easier if lubricated but there is probably greater chance that crankshaft will spin inside the bearing, I saw that happen few times.
 

DRXRACING

Well-Known Member
Put the engine cases in the sun and the bearings and crankshaft in the deepfreeze.
The warmer cases will expand a thousanths or so and the bearings will shrink a thousanths or so.
Install 1 bearing at the time, get both cases done.
Let them warm up.
Mean while set up to install the crank into the big case first. After it is installed into the case use 3 bond number 4 sealant on the small case surface and don't forget the dowell pins. Press the little case over the other end of the crank until surface's meet. Have your case screws ready for installation. Put the screws in the case tightly.
Put crank nuts on each end of the crank to protect the threads.
If the crank is stiff to rotate you can center/seat/clearance it by precisely hitting on the end of the crank. I use a brass hammer. This will loosen the crank up within the cases and allow it to spin freely. The nuts protect the threads. You can use silicon lubricant while assembling this if you like. Not grease. Grease is to thick and can take up a thousanths of an inch. Motor oil is 1/2 thousanths.
 

muhuha

Well-Known Member
Whats this 3bond number 4 sealant, i got the std gaskets? Arnt they any good, ive also got locite blue instant gasket. Unsure of grade etc shall look in morning.
 

47lamy

Well-Known Member
The Zip for example dos'nt (I think) have a crankcase gasket available so you have to use a sealant. If you have a gasket then it might be easier to use less mess, there could possibly be a very slight advantage with regards to gas flow when using a instant gasket, as long as you don't over do it with the stuff.
 

50cczip racer

Well-Known Member
use a hot air gun on the crankcases to get them really hot
dont put crank seals in until youve centralised the bearings and crank as drx said when perfect the crank will rotate back and forth like a pendulum you cant see this when seals are installed
 

Ben

Retired
Put the engine cases in the sun and the bearings and crankshaft in the deepfreeze.
The warmer cases will expand a thousanths or so and the bearings will shrink a thousanths or so.
Install 1 bearing at the time, get both cases done.
Let them warm up.
Mean while set up to install the crank into the big case first. After it is installed into the case use 3 bond number 4 sealant on the small case surface and don't forget the dowell pins. Press the little case over the other end of the crank until surface's meet. Have your case screws ready for installation. Put the screws in the case tightly.
Put crank nuts on each end of the crank to protect the threads.
If the crank is stiff to rotate you can center/seat/clearance it by precisely hitting on the end of the crank. I use a brass hammer. This will loosen the crank up within the cases and allow it to spin freely. The nuts protect the threads. You can use silicon lubricant while assembling this if you like. Not grease. Grease is to thick and can take up a thousanths of an inch. Motor oil is 1/2 thousanths.

I woulden't d that if I where you... Deepfreeze is ice , and ic is frozen water.. Water = rust on steel bearings if not done fast enough... Plus , the ice and water could get jammed between the ball of the bearing , and rust the ball AND bearing if still dont fast enonough.

Just keep with the heating the crankcases and leaving the bearings alone. While the crankcase cools down , while the bearing is fitted , it will get jammed between the rounding of the crankcase... No water , no grease , no nothing = no taking risks. :)
 

Ben

Retired
Why would yo even think of making the bearing smaller if you can easly slide the bearings in the holes when heated properly. :?

// edit : Cooling the steel of the bearings extremely isn;t good either. They'll lose strengh and become brittle ( broos , wich is Dutch word for brittle )...
 

Browni

B.A.T tuning
NEed some advice on fitting new big end bearings. Ive got some polini evolution bearings and on one of the on one side its got a c and two dots. The other bearing also on one side has a c and three dots. Do these mean anything? Also im going to put the bearings on the crank before hand, how far down the crank do they go? Has anyone got a picture?

Thanks

You can find the proper way here:

Original user manual:

http://www.rcscooter.net/manuales_taller/yamaha_aerox.pdf


Page 82-83

Use rigid sealant (Loctite)

The manual doesn't talk about the axial play of the bearings after assembly, but it's important. So check it!!

Before you put the oil seals in place check the crankshaft, it's not easy to rotate it, you have to assembly the engine again!
 

butch-182

Killerteam Racing
The way i always do them is by placing the bearings in a airtight bag, and put in freezer for a bit to get them nice and cool, Heat the casings properly with a blow torch and they ususually simply drop in place, if not a slight tap with a rubber mallet and they will go in place. Remeber..NEVER hit the inner race....
 

Ben

Retired
You can find the proper way here:

Original user manual:

http://www.rcscooter.net/manuales_taller/yamaha_aerox.pdf


Page 82-83

Use rigid sealant (Loctite)

The manual doesn't talk about the axial play of the bearings after assembly, but it's important. So check it!!

Before you put the oil seals in place check the crankshaft, it's not easy to rotate it, you have to assembly the engine again!

Doesn't say what to do with the crankshaft and bearings... Heating , or cooling or anything. :rolleyes: Because there are many ways !
 

Areomyst

Scootin' America!
Here's a bit that I wrote after hearing someone say that heating and cooling the crankcases was "Caveman style". I strongly disagree...

http://www.scooterinvasion.net/forum/viewtopic.php?t=156

So that everyone doesn't have to view the link:

Areomyst on scooterinvasion.net said:
Hello friends,

The subject of crankshaft installation has come up a few times, so I decided to make a quick post about it here. I'd like to encourage everyone to chime in with any added advice or recommendations.

Using physics to your advantage when doing a crank install will make the job much easier. I've made a couple of videos, that many of you have probably seen... they take a few minutes to download, but they do work nonetheless.

http://www.scooterinvasion.net/crankbearings.html

I recently saw the method of using heating and cooling when assembling a lower end referred to as "caveman-style" (or something close to it). Heating the carters and cooling the bearings allows you to very easily drop the bearing into the carter with no force at all. Less stress on the bearings means that they will have longer life and provide better reliability. This is the way that many professionals do their crank installs, and have been doing it this way for years with no troubles.

There's a lot of controversy as to what the best method to heat the carters is. Many people strongly advise against propane, though I personally find it quite suitable and handy, if done correctly. Some alternatives are ovens, heat guns, and 'hot plates'.

The general procedure of installing a crankshaft would be along these lines:

1. Place your crankshaft and bearings in a refrigerator. These parts, when cold, will contract. You can place them in a freezer too, if you want, but I find that freezing them produces much more condensation when you take the bearings/crank out of the cold. Water isn't good on bearings, and the fridge gets them cool enough.

2. Heat one of the the carters with your torch, oven, etc... Usually you should spend about 5 minutes evenly heating the bearing saddle in the carter so that it has a chance to heat and expand throughly.

3. When the bearings are cooled, and the carters are heated, you can remove one of the bearings from the fridge, give it a quick clean up, and ensure that the outer race of the bearing is clean and moisture-free. If the carter is hot enough, you should be able to literally drop the bearing into the carter. It's simple. :)

4. Repeat the previous two steps for the other carter.

5. Now you should have bearings in both carters. If you're using an oven, you can pop the carter halves in the oven to re-heat the carters with the bearings installed. If you're using propane, you need to find a slug to heat, so that you can transfer the heat from the slug to the bearing. NEVER use a propane torch directly on a bearing! It only takes a second to overheat the metal cage in the bearing and render it useless.

6. I usually prefer to install the crankshaft into the right-side carter (the smaller one). Because of it's size, it'll be easier to assemble with the crank in the this half than the larger one. Remove the crankshaft from the fridge, and drop it into the bearing that's in the smaller carter. Let this sit off to the side while you heat the opposite bearing.

7. I prefer to use Permatex Motoseal 1 (Grey) to seal my engine. It's very similar, if not the same formula used in Hondabond and Yamabond. Be sure to spread your sealant on the machined edges of the small carter where the carters join together. Make sure your locater pins or locater dowels, as they're sometimes called, are in place.

8. Once you've heated the bearing in the large half, you should be able to firmly but easily slide the crankshaft through the second bearings, and close the carters together. Install the screws that hold the engine halves together, and you're ready to re-assemble! Don't forget to install new crankshaft seals before you put everything back together.

This is something that can be frustrating the first time around! Take your time, and be thorough and clean about it, and you should be okay. It does take a little bit of practice to get the timing and everything perfect, but it's really not too tough after you get the hang of it.

Just as a little 'backup' to the caveman comment, here's what Eric Gorr says in his book, "Motocross and Offroad Performance Handbook" on page 127.
Eric Gorr said:
Bearing Removal and Installation

The best way to remove or install bearings is to heat the aluminum crankcases with a propane torch, and then use a hydraulic press out gently push them out. Never pound the bearings out with a hammer and punch. The outer race of the bearing is the only part where a press slug should be placed. Large sockets or discs work well as press slugs. Placing the new bearings in the freezer for two hours and heating the cases with the torch will enable you to install the bearings without a press. Fit the bearings into position with as little stress as possible exerted on the crank ends. Some manufactures (Kawasaki) make special tools that wedge in between the flyweights so you can press the crank into place. Other manufacturers use a threaded tool that draws the crank into the bearing.

Eric Gorr said:
Crankshaft Installation

Here is a simple way to install the crank. Place the crank in a freezer for two hours so it contracts in size. Get a cylindrical piece of aluminum with the same diameter as the inner bearing race. Heat and expand the bearing's inner race by heating the aluminum slug with a propane torch for five minutes while it rests on the inner race of the right side main bearing. Drop the cold crank into the hot right main bearing. Repeat the procedure for the left main bearing. Drop the cold crank into the hot right main bearing. Repeat the procedure for the left main bearing and prepare to assemble the cases.

I hope that with this post I've clarified some of the confusion about crankshaft installations. There are some variations that other people take, but in general, the principal remains the same. Using heat to expand and cold to contract the parts so that you can assemble them with no force is the basis behind the whole thing. :)

~Josh

:) Hope that helps!

~Josh
 

adas

Well-Known Member
Aloha, I think everyone can agree on:

1: use a rubber mallet and not a steel one
2: use heat gun and not a blow torch
3: when going into freezer put items into a plastic bag to keep moisture out
4: install seals after you center the crank and it is free turning
5: install bearings into case first
6: then install crank into bearings
7: use sealer sparingly
8: work quickly if you have 1/2 cold and 1/2 hot parts
9: pull the cases together evenly with the screws
10: leak test after you install the seals

frank
 
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