Crank / clutch bearings

weefek

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Ok I may be beating a dead horse with this one. But I've seen a lot of conflicting information.

Grubee GT5B eng.

Rebuilding a new motor as a spare. Both crank and clutch bearings on the magneto side of the engine case are gritty as hell straight from the factory. I found quite a bit of metal shavings in the engine so far so not really surprised.

I'm looking at SKF 6202 2Z bearings. 35mmx15mmx11mm, Right size for both.

I've heard reports of people buying 4 sealed bearings and just removing the inner seal (or both?) from the bearings to use as crank bearings.

Is this normal? Or should I try and source (2) 6202 with double seals and (2) with no seals?

EDIT: Anyone have a good source for crank seals?
 

DieselTech

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Ok I may be beating a dead horse with this one. But I've seen a lot of conflicting information.

Grubee GT5B eng.

Rebuilding a new motor as a spare. Both crank and clutch bearings on the magneto side of the engine case are gritty as hell straight from the factory. I found quite a bit of metal shavings in the engine so far so not really surprised.

I'm looking at SKF 6202 2Z bearings. 35mmx15mmx11mm, Right size for both.

I've heard reports of people buying 4 sealed bearings and just removing the inner seal (or both?) from the bearings to use as crank bearings.

Is this normal? Or should I try and source (2) 6202 with double seals and (2) with no seals?

EDIT: Anyone have a good source for crank seals?
Just pop the inside seal out of bearing on the crankshaft.
 

ImpulseRocket89

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Rebuilding a new motor as a spare. Both crank and clutch bearings on the magneto side of the engine case are gritty as hell straight from the factory. I found quite a bit of metal shavings in the engine so far so not really surprised.

I'm looking at SKF 6202 2Z bearings. 35mmx15mmx11mm, Right size for both.

I've heard reports of people buying 4 sealed bearings and just removing the inner seal (or both?) from the bearings to use as crank bearings.

Is this normal? Or should I try and source (2) 6202 with double seals and (2) with no seals?

EDIT: Anyone have a good source for crank seals?
Don't buy the ZZ bearings (double metal shield) Buy the 6202-2RS (2 Rubber Seal) bearings. They do a much better job of sealing off the bearing from particles than metal shield bearings.

As far as the rubber seals. Yes, you can quite easily take a small screwdriver or the top of a knife and just pry the seals off.

Also, make sure to buy C3 tolerance bearings "6202-2rs C3" at least for the crank bearings. In simple terms, these bearings are designed with a very slightly loose tolerance when cold so that they are the right tolerance at a designated temperature, usually around 250 degrees Fahrenheit. They are designed to run in a hot environment... like an engine. I run C3 spec bearings for all 4 and have never had an issue, mostly because the clutch shaft bearings are still connected to the motor and still get decently hot.

As far as what bearings to use. These are my personal choice as they have a high dynamic load rating and a higher speed rating. There are cheaper options out there, but FAG is a great brand and these bearings are made in Korea, which is a good thing in terms of quality. I used these in my Phantom build.

Other good brands include Timken, SKF, Nachi-Quest, and NSK. Most of the good quality bearings are going to run about 10 bucks a piece. Worth it IMHO.
 

weefek

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Don't buy the ZZ bearings (double metal shield) Buy the 6202-2RS (2 Rubber Seal) bearings. They do a much better job of sealing off the bearing from particles than metal shield bearings.

As far as the rubber seals. Yes, you can quite easily take a small screwdriver or the top of a knife and just pry the seals off.

Also, make sure to buy C3 tolerance bearings "6202-2rs C3" at least for the crank bearings. In simple terms, these bearings are designed with a very slightly loose tolerance when cold so that they are the right tolerance at a designated temperature, usually around 250 degrees Fahrenheit. They are designed to run in a hot environment... like an engine. I run C3 spec bearings for all 4 and have never had an issue, mostly because the clutch shaft bearings are still connected to the motor and still get decently hot.

As far as what bearings to use. These are my personal choice as they have a high dynamic load rating and a higher speed rating. There are cheaper options out there, but FAG is a great brand and these bearings are made in Korea, which is a good thing in terms of quality. I used these in my Phantom build.

Other good brands include Timken, SKF, Nachi-Quest, and NSK. Most of the good quality bearings are going to run about 10 bucks a piece. Worth it IMHO.

Thank you thank you this is basically exactly the information I was looking for. I've used SKF bearings hundreds of times for projects (I work in industrial automation) and have had really good luck with them so that's naturally what I revert to.

I was wondering about the rubber vs metal seals , I've you've been running them previously with good results I'll take that as a good answer.

Thanks for the info (y)

Now I just have to try and find good replacement crank seals (Haven't looked too hard yet)
 

ImpulseRocket89

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Thank you thank you this is basically exactly the information I was looking for. I've used SKF bearings hundreds of times for projects (I work in industrial automation) and have had really good luck with them so that's naturally what I revert to.

I was wondering about the rubber vs metal seals , I've you've been running them previously with good results I'll take that as a good answer.

Thanks for the info (y)

Now I just have to try and find good replacement crank seals (Haven't looked too hard yet)
The nice thing is, a lot of C3 spec Rubber Seal bearings use a hybrid seal with a metal center to help withstand the higher temps, which is normally what ZZ bearings are better at. The trade off with the ZZ Bearings is that they aren't quite as good at staying sealed against fine contaminants, something the clutch shaft bearings are going to be more exposed to.

If you really wanted to, you could buy 2 ZZ C3 bearings for the crank and 2 2RS bearings for the clutch shaft. I just keep it simple and stick to the bearings I used above in the link. At the end of the day it probably won't make that much of a difference.

As far as the crank seals, you just need to know what sizes you need. Generally there are 2 that are most commonly used on the engines. The YD and LD cases tend to use 2 of the "thicker" seals while the more standard engines use 1 thick 1 thin. I forget the numbers off hand, but they aren't too hard to find.
 

weefek

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The nice thing is, a lot of C3 spec Rubber Seal bearings use a hybrid seal with a metal center to help withstand the higher temps, which is normally what ZZ bearings are better at. The trade off with the ZZ Bearings is that they aren't quite as good at staying sealed against fine contaminants, something the clutch shaft bearings are going to be more exposed to.

If you really wanted to, you could buy 2 ZZ C3 bearings for the crank and 2 2RS bearings for the clutch shaft. I just keep it simple and stick to the bearings I used above in the link. At the end of the day it probably won't make that much of a difference.

As far as the crank seals, you just need to know what sizes you need. Generally there are 2 that are most commonly used on the engines. The YD and LD cases tend to use 2 of the "thicker" seals while the more standard engines use 1 thick 1 thin. I forget the numbers off hand, but they aren't too hard to find.
I prefer to keep common parts as often as possible so I'll be going with the 2RS C3 bearings. Now that you've said that about the Z bearings I can see a small opening in between in the mounting flanges of the seal on the bearings (the chinese ones, anyways) and can actually see the ball bearings through these small openings.

I'm building this engine for reliability. I think I may swap it onto the bike once I'm done with it, and rebuild the one I have on the bike. Or run it until it blows but I'm only at 150~ ish miles so hopefully that won't happen for awhile. I use my bike practically, it's my only way into town at the moment aside from walking or paying for a taxi so reliability is extremely important to me.

I'll look around more for seals after I'm done the pork ribs currently sitting in the smoker outside :ROFLMAO: They're the 3.8 and 7.5 width seals. It's a Grubee GT5B engine which seems to be almost identical to a Zeda 80 minus the ceramic coated sleeve. Maybe it does have a ceramic sleeve I have no idea. Build quality is so-so, not nearly as bad as I've seen with some engines
 

weefek

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Well the only seals I've been able to find so far are the same s****y chinese ones that come with these kits...

EDIT: Yes they are easy to find on ebay / amazon but i have zero doubt these are from the same whatever chinese manufacturer makes the original parts which are garbage. Even the pictures they show look terrible.
 

DieselTech

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Well the only seals I've been able to find so far are the same s****y chinese ones that come with these kits...
You might try googling the seal dimensions & see what comes up. I.D. O.D. & seal thickness. Do you got the seal dimensions?
 

weefek

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I have. Haven't got any good results besides random amazon and ebay posts that sell chinese garbage.

They're the standard for these engines:

(1) 14.8 x 27 x 3.8
(1) 14.8 x 27 x 7.5

The stock seals don't look bad but I know removing them destroys them essentially. I will not re-use seals I've removed.

I found a random post saying Toyo brand seals but haven't been able to find anything

I may need to use some work contacts in order to find some legit seals
 

weefek

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I will email some work contacts tomorrow regarding this. According to everything I've seen on this forum, and others, and google in general, the only real replacements are chinese "OEM" seals. I've found some 15x27x5 and 15x27x7 and 15x27x8 which in theory might work but not entirely sure.
 
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