How hot to heat engine

[SS109]

If that bearing wasn't smooth from the get go then something is wrong. There is no situation where any sticking/binding in a crank bearing works out ok. Sorry.

On your bearing installation problems... how long are you heating the cases for and how long are you freezing the bearings and crank for?

 

[Noobi06]

Oh well, I guess i need to buy another. Bearing spins so good now tho with the crank.
When I installed it, I used a torch to heat the cases very hot, then I used cooling spray on the bearings

 

[SS109]

I've done more a few engines and never had one that the standard heat and freeze method didn't work like a charm. Something is causing interference in your cases if that method, regular oven heating and the freezing of the bearing in a standard household freezer, doesn't let the bearing just drop in. Check the case recesses for burrs, gouges, or anything else other than just raw aluminum.

 

[Noobi06]

Is it bad to mix a Koyo Bearing with an SKF bearing on the crank? Can I use koyo on one side and skf on one side?
2. Can you use C3 bearing on one side and c4 on one side?

 

[SS109]

Mixing of brands isn't an issue. However, only use the style of bearing that is called for. If it calls for a C3 then use a C3, not a C4 or any other. GasGas, and every other manufacturer, has a reason for why they spec a certain type of bearing for any given location. Don't mess with that.

 

[Zman]

I am 95% sure the GG 125 bearings cross over to YZ125 and CR125 bearings of similar years. Do some research and you can find good deals for a pair of bearings on Ebay or at industrial supply houses.

 

[swazi_matt]

Mixing of brands isn't an issue. However, only use the style of bearing that is called for. If it calls for a C3 then use a C3, not a C4 or any other. GasGas, and every other manufacturer, has a reason for why they spec a certain type of bearing for any given location. Don't mess with that.

that being said, nobody managed to work out why the 2010's had sealed crank bearings

 

[Noobi06]

Btw, how do I know if the crank needs balancing? I know if you dont do it when it needs to, your engine is going to have a massive fail

 

[SS109]

that being said, nobody managed to work out why the 2010's had sealed crank bearings

LOL, so true!

Btw, how do I know if the crank needs balancing? I know if you dont do it when it needs to, your engine is going to have a massive fail

Most two stroke dirt bike cranks don't need to balanced beyond what the factory did. Most aftermarket rods and pistons are designed to be within the parameters of the stock balance the factory designed in to it. So, not absolutely necessary. However, getting a custom balance when having your crank rebuilt should make the engine run smoother which of course will make all bearings live longer (how much is debatable) and you will get less vibration through the handlebars.

Personally, I wouldn't worry about it. I've had numerous cranks done with aftermarket rods and pistons and never have had one balanced nor have I regretted not doing it. Truing the crank is the critical thing. Maybe one day when I have the extra cash and I'm doing one I'll try it just to see if it's actually worth it (ie; how much of a difference it makes)

 

[Noobi06]

That makes me calmer. Thanks for the answer
Ill be ordering new bearings, hopefully this shitpile will be running within a couple of weeks

 

[Zman]

While it may be challenging at times, you are learning considerable knowledge along the way. I commend you for taking on this project and continuing to work through the challenges. You will be amazed how much of what you are learning will apply to other things you encounter in life.

 

[Noobi06]

I bought 2 brand new Koyo 63/22 c4 crank bearings.
The ones in the case right now are exactly the same but have no play.
The brand new ones have play (I havent even installed them, they are out of the package)
Is that normal? I mean they are brand new but I feel like they have too much play

 

[Zman]

Can you describe where they feel loose?

 

[Noobi06]

Im pulling on the inner race. I can feel it go up and down a little. It feels more than usual though, especially since they are new

 

[Zman]

Just to clarify, are you saying a) the inner race has slop and can move radially toward the outer race or b) the inner race can move axially perpendicular to the outer race?

 

[Noobi06]

Ok, ignore what I said before.
Im actually gonna loose my mind.
Today I installed the bearing. It dropped right in (finally, first time). I had oven at 125C and bearing in freezer for 1.5days.
I was really happy and bearing spun without any noise or any bad stuff. This was when it was still hot because it absorbed the heat from the cases after installing.
After it cooled down, the bearing is now binding up (it gets stuck sometimes). What the fuck is going on, im gonna loose myself.
Is it some dirt that has gotten into the bearing? Or possibly because there is no oil?
Im going to wash it with petrol and oil it and see if that makes a difference

 

[Zman]

Was the engine clean when you assembled it? Are both of the crank cases together or is one side off? Is it possible the crank needs to be realigned?

 

[Noobi06]

Yes, engine cases was completely clean. I wash with petrol serveral times and also dish them like cutlery.
They were binding when cases was apart, meaning no crank. If I were to install the crank, it would spin completely free (had same problem before)
This time I was lucky and it actually stopped after 10 more minutes of waiting. I still dont know why it happens tho, but I was lucky this time.
At the time of writing, engine is almost done. Tomorrow will probably be startup
I have learnt so much at this point. I can assemble an engine with higher quality than a workshop now, in less that 6 hours. I can also replace bearings myself now. For me, the trick was bearings in freezer for 1-2 days and cases in over at 150 celcius for at least 30 minutes.

 

[Zman]

I am glad it is getting easier for you. Good luck tomorrow!