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Hi everybody, I didn't see a place to introduce myself, so I'll just do it here before I get to my topic. I'm an American, living and working in the highlands of Papua New Guinea. I'm a motorcycle and small engine (and ancient Land Rover) mechanic. I do not actually own a TW200, however, I do work on probably half-a-dozen of them for people in the area where I live, so I see them and work on them fairly often. I've been involved in this sort of work for most of my life, getting my start in the jungles of Peru when I was a kid, (I might want to talk to this guy who calls himself "peruano" sometime!)



Right now I'm "restoring" an older TW200 for a guy here who runs a coffee plantation. It had been sitting out in the weather for some time before it was brought to me and had been somewhat abused before it was parked. I've had to do a bunch of the usual stuff to it, new piston and rings, new valves, new camchain, etc. and have had to replace the seat and all the plastic. In the process of rebuilding the cylinder head, I noticed that a 6005 ball bearing is a perfect fit in the head where the big aluminum "collar" goes. What I want to know is, has anybody tried replacing that "collar" (as Yamaha calls it) with a 6005 bearing before? I'm going to go ahead and do it, I just want to know if anybody else has tried it. I've tried finding info on this on the interweb and that is how I discovered this forum.



Anybody?
 

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Sorry, I can't help you. I've not been into Tdub, yet, but when I do go in I'll be doing some bearings. I was thinking some plain babbitts would be an improvement, but your idea may be better. Let us know how it works out.
 

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Discussion Starter #3
The bearing I used is a sealed 6005 bearing, but I went ahead and removed the seal from the inside of the bearing. I'm reasoning that the oil that drips off of the cam and rockers will flow into the little valley between the valves and will keep the ball bearing well lubricated. I would probably have been fine to remove the seals from both sides of the bearing and then just let the oil from that valley drain straight through the bearing, lubricating as it goes, but I think that by leaving the outer seal in place it will retain more of the oil in the head and cut down on the chances of the engine ever starting with no oil at that bearing.



As an added side benefit, since there is no longer a need for oil to be pumped into the middle of the original collar, the hole in the cam at that point could be plugged and maybe more oil would make it to the cam lobes and rockers, which surely couldn't be a bad thing. I didn't bother to plug the hole on this camshaft, but if I build another one, I might go ahead and do that.



I have a couple of other head here that are scrapped from people running them out of oil, but I am formulating a plan to resurrect them by using the 6005 ball bearing on the big end and then opening up the head a little bit on the other end and possible turning down the end of the cam just a little bit to fit a caged needle bearing in there. I've seen this kind of thing done on small Hondas before, I can't believe nobody's done it on the Yamahas.
 

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I am going to follow this with great interest. The needle roller will be quite a challenge if the needles are to run directly on the camshaft & you have to reduce the camshaft diameter. Got access to a cylindrical grinding machine or toolpost grinder in a lathe?
 

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Discussion Starter #5
I've got access to a milling machine, so I was sort of thinking of just cutting a new hole that way for the cam and needle bearing to live in, but that particular mod won't happen for some time yet--on the engine I'm working on right now I'm just running a 6005 ball bearing on the big side and running the cam directly in the head on the other end. The 6005 bearing mod was sort of a "hey, let's try this!" sort of thing rather than an attempt to address any kind of a real problem. The fact that nobody else seems to have tried it, (or at least it doesn't seem to be a common mod) makes me think that the original set up probably works just fine.



The only ones I have seen melted down were run by people who had leaky, abused machines and who were too cheap to change their oil. I've seen the exact same thing done a depressing number of times on Honda XL/XR100/125/185/200/early XL250 and 350 and early XL/XR500's as well as on the Yamaha TW/XT/TT/AG125/200/225.
 

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Discussion Starter #7
Yeah, this is almost exactly what I did, but I left the outer seal on the bearing and modified the retainer to hold in both the bearing and the seal. I'd take a photo, but I've already assembled the engine and don't want to take it apart again. I've got another head laying around, maybe I'll duplicate what I did on that one and take a photo of that.



Have you put any time on your bearing equipped heads? I can't think of any reason why this wouldn't be a better set-up than what they came with.



I knew there had to be somebody out there who tried this--it looks to me as if Yamaha designed the head to have a bearing there and then decided to use the aluminum collar instead for some reason, probably cost?
 

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Discussion Starter #9
I used a 6005 single groove ball bearing. The one I used was sealed on both sides, but I took the seal out of the inside and left the outer one for reasons stated above.
 

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How's that bearing holding up?
 

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English figure of speech, Christddel. What I meant was "how well is the bearing working so far?"



Thank you for the diagram. Nice to know that it's such a simple installation.
 

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Thank you.
 

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Has anyone ever bored out the rear camshaft journal that is milled into the head and fitted a bearing? My little Honda 125's are notorious for cam journal wear and this is a common repair. I am seeing some scarring and play at both ends of my camshaft.



Looks like there's room for a needle bearing.



 

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The bearings on AAC is of l' old history…

In 1981, the engine of the XT250 Yamaha has 2 bearings on camshaft…

And already with "bearing 6005"...











 

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Cool, thanks.



I wonder if the head is a silmilar cast. I don't want to machine it too thin. I'll talk to my machinist today and see which is wiser, bore the head or turn down the camshaft.
 

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I went and spoke with my machinist (Henry) and he says that he can't get in there to bore it so I'll have to go a few towns over to a larger shop.



Meanwhile, I placed the cam in with the 6005 front bearing and noticed that the cam is turning in the race as well as the outside of the bearing spinning in the head. I wonder if just a bit of high temp loctite on the bearing to head and bearing to cam contacts would stay there and fix this.
 

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The stock aluminum collar shows some wear in this pic.



I found a bearing with a metal seal on both sides and removed one side.



Grainger sells the bearing part #1L012 about $22.00.





Ronnydog
 
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