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Please bear with me as I am learing about the Twin Cam 88. I an earlier post on the touring bike forum a comment was made that 2002 was the best year for the twim cam and the last year of the "good bottom end bearings". Would somebody like to educate this shovelhead/panhead guy?

TIA

Russ In Texas
 

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skyguy59 said:
Please bear with me as I am learing about the Twin Cam 88. I an earlier post on the touring bike forum a comment was made that 2002 was the best year for the twim cam and the last year of the "good bottom end bearings". Would somebody like to educate this shovelhead/panhead guy?

TIA

Russ In Texas

In 2003, HD changed the TC88 left main bearing which had been back-to-back Timken tapered rollers to a straight roller which is identical to the right side pinion roller bearing.

Many people don't think that this is as good as the earlier Timken. Personally, I don't think it makes much difference for a stock or even a 95" bike.

I guess if you were going to build a really big engine, say 103 on up, you might want to have the left crankcase machined to take the earlier Timken. That would apparently give a margin of strength so that failure would be less likely.

To say that the roller bearing used in the 2003 and later TC's is per se bad is not correct. Every Big Twin HD sells has the new roller bearing including the SE 103" bikes. It's just probably not enough for the stroker motors with high compression that many are using. Go figure.

My attitude is that if you're gonig to spend $4,000 bucks for an engine modification, what's another $400 for a left main bearing?
 

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On articles I have read, the concensus is, stock is good for 130tq. I haven't seen any test data but my guess is HD engineering has the parameters. Since SE sells the performance parts and they know that their packages are good for 120tq, I'm guessing they would post a warning if they expected a problem.

I'm sure that the anti-HD members will have comments on that but that's my opinion.
 

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csoday said:
On articles I have read, the concensus is, stock is good for 130tq. I haven't seen any test data but my guess is HD engineering has the parameters. Since SE sells the performance parts and they know that their packages are good for 120tq, I'm guessing they would post a warning if they expected a problem.

I'm sure that the anti-HD members will have comments on that but that's my opinion.

I didn't realize that the roller bearing would take that much torque. I wouldn't doubt it, though.

Those of us who spend time reading about Japanese and Italian motorcycles, will realize that roller bearings are used on practically every non-US bike built. Some of these machines are running in excess of 15,000 rpm at top speed with rated horsepowers of as high as 145 RWHP. They can't be all bad.
 

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newultraclassic said:
I didn't realize that the roller bearing would take that much torque. I wouldn't doubt it, though.

Those of us who spend time reading about Japanese and Italian motorcycles, will realize that roller bearings are used on practically every non-US bike built. Some of these machines are running in excess of 15,000 rpm at top speed with rated horsepowers of as high as 145 RWHP. They can't be all bad.
The stock rollers will not take anywhere near that kind of torque on a regular basis. Much over 110 torque you should do the conversion or get the Compensating Shaft Outer Support System. Every article I have read has stated any motor over 103CI needs to have the temken conversion done. The stock rollers can not take the excessive torque. If you are building a 103 I personally would not split the case open without converting the block back to the much stronger temken bearings. The MOCO made a huge error by going away from the tride and true bearings to the weaker sets. They should revert back immediately.
 

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There's no need for them to swap back. Stock motors won't hit 130tq, What do you propose they engineer for 130-150tq? Then you have to go back to chains instead of belts.
 

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I overheard a tech at the Zippers display in Daytona discussing a new bearing conversion kit they have. Might be worth checking out.
 

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Fatb0y said:
The stock rollers will not take anywhere near that kind of torque on a regular basis. Much over 110 torque you should do the conversion or get the Compensating Shaft Outer Support System. Every article I have read has stated any motor over 103CI needs to have the temken conversion done. The stock rollers can not take the excessive torque. If you are building a 103 I personally would not split the case open without converting the block back to the much stronger temken bearings. The MOCO made a huge error by going away from the tride and true bearings to the weaker sets. They should revert back immediately.
It seems that the problem is not torgue per se but rather axial load. The ones that have been reported on the internet show broken retainers on one side or the other that permit the rollers to escape. Some of this may even be attributable to loose compensation sprockets so the failure mechanism is really not all that clear.

I'm not sure that anyone has done any failure testing on the HD '03-on left roller bearing other than HD and they probably wouldn't release any information. I'm sure most would agree that anything other than actual destructive failure testing with instrumentation would only be a guess in any case. Harley must believe that the rollers are good for their SE 103 incher bikes since those are the bearings that they are using.

Even the pre 2003 TC's with the Timkens are not as strong as my old 1982 Shovelhead. That has a steel web cast in to both the left and the right case as with all of the bikes up to the early 90's in the Evos. That way the bearing races press into steel. After that, they just pressed the Timken races right into the soft aluminum. I personally don't think much of that either.

I don't have a dog in this race since I run stock bikes and just ride them from one place to another. That being the case, I seriously doubt that the roller bearing will cause me any grief. I don't even want a gear drive anymore since I can't be sure that the runout on my crank is less than .003 without looking first so I'm better off not worrying. I'll just change the tensioners now and then and forget about it.

Those of us who like to look at all motorcycles, not just HD's, are well aware that straight roller bearings are widely used in the European and Asian bikes. Some of those are stock bikes that are putting out 180 HP at the crank and close to 145 RWHP at over 14,000 rpm without failures. (Hayabusa for one. )

As long as I can remember, whiich is back to the Knucklehead and Panhead days, people have been hopping up their Harleys though. They do it because they can. :)
 

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wvwayne said:
I heard tell that the 48 Pan Head had weak bearings too,and the 49's were much better...somethings never change.

All of the bikes up to a certain year of Panhead had loose straight rollers packed into a cage. They were nothing to write home about but were ample for the generally low hp output of the bikes in that era.

Sometime in the mid-1950's, HD started using a Timken tapered roller in the left side and that was a good change.
 

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Proper tightening of the comp. assembly is critical for the 2003 and up. From what Ive read, things can get real ugly if it is loose and you dont realize it.
 

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csoday said:
There's no need for them to swap back. Stock motors won't hit 130tq, What do you propose they engineer for 130-150tq? Then you have to go back to chains instead of belts.
I guess racing bikes use chains?? WRONG. They use belts.
 

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newultraclassic said:
It seems that the problem is not torgue per se but rather axial load. The ones that have been reported on the internet show broken retainers on one side or the other that permit the rollers to escape. Some of this may even be attributable to loose compensation sprockets so the failure mechanism is really not all that clear.

I'm not sure that anyone has done any failure testing on the HD '03-on left roller bearing other than HD and they probably wouldn't release any information. I'm sure most would agree that anything other than actual destructive failure testing with instrumentation would only be a guess in any case. Harley must believe that the rollers are good for their SE 103 incher bikes since those are the bearings that they are using.

Even the pre 2003 TC's with the Timkens are not as strong as my old 1982 Shovelhead. That has a steel web cast in to both the left and the right case as with all of the bikes up to the early 90's in the Evos. That way the bearing races press into steel. After that, they just pressed the Timken races right into the soft aluminum. I personally don't think much of that either.

I don't have a dog in this race since I run stock bikes and just ride them from one place to another. That being the case, I seriously doubt that the roller bearing will cause me any grief. I don't even want a gear drive anymore since I can't be sure that the runout on my crank is less than .003 without looking first so I'm better off not worrying. I'll just change the tensioners now and then and forget about it.

Those of us who like to look at all motorcycles, not just HD's, are well aware that straight roller bearings are widely used in the European and Asian bikes. Some of those are stock bikes that are putting out 180 HP at the crank and close to 145 RWHP at over 14,000 rpm without failures. (Hayabusa for one. )

As long as I can remember, whiich is back to the Knucklehead and Panhead days, people have been hopping up their Harleys though. They do it because they can. :)
All that said, I am still glad I did the timken conversion. They should have stuck with it.
 

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Fatb0y said:
I guess racing bikes use chains?? WRONG. They use belts.
Get to point and you need a chain. A chain is stronger then a belt. Somebody else want to eloborate.
 

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The thing I dont get about the left side crank bearing is where is the axial load in this motor?? It seems that there are no axial loads under normal conditions....Can anyone elaborate on why these engines needed double taper bearings in the first place??
 

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S&S did testing on the 03 up bearing and came to the conclusion that they will not warrenty their crankshafts for the 03 up.
Why did HD make this change? Cheaper and faster to assemble.
How do get away with it? The masses that buy them just dont know.
When did the dual Timken bearings first appear? On the first K model of course.
Later appeared on the 1955 panhead.
So, HD returned to the dismal early 50s!
 

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berserker said:
Get to point and you need a chain. A chain is stronger then a belt. Somebody else want to eloborate.
Well, plenty of drag bikes use primary belt drives, but that puppy is at least 3" wide. The final drive is a chain. You can't expect even the 1 1/2" final drive belt to hold up to serious horsepower and a racing environment for long......Bill
 

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Fatb0y said:
I guess racing bikes use chains?? WRONG. They use belts.
I think it depends on which racing bikes you are referring to. Chains are all but universal on GP and SuperBike road racing bikes. I guess some Buells and a few pro-stock bikes might use belts. They wouldn't be my first choice for a racing bike.

The ones on Harleys are good for most ordinary modifications like 95", a cam and some higher compression. Anything more radical than that and you would start shucking belts pretty quick.
 
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