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VG's grot bikes: CT200 AG & TA02 GYRO


Vintage Grumble

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On 22/02/2022 at 22:46, Vintage Grumble said:

rekt

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OK, so I have a plan to try save the head. Its a bit too rooted to try the method @tortron posted, so I'm going to try machine the rooted bit out on the BIL's mill, and slap a needle roller in there, that has an outer shell (so it doesn't have to run on the alloy) I can't think of a reason this wont work, as long as I can find a suitable bearing, and the cap has enough meat in it, AND I don't fuck up the machining. I think the oil supply to that journal comes through the cam, so I may just have to restrict that a bit or something? Can't really fuck the head anymore, so worth a shot eh. 

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On 17/03/2022 at 19:52, tortron said:

bet you could bang a an125 camshaft in there

SU4_-2090921.png

 

 

mChina OEM Motorcycle Camshaft 125cc Racing An125 Camshaft - China  Motorcycle Camshaft, Camshaft Parts

 

inlet and exhaust may be reversed?

 

8 hours ago, tortron said:

I've found the correct cam and rockers on Ali express, so will probably go Ali on all the big bits, and the small bits I can't find I'll get OEM from webike. I priced all the bits I need from webike, it was around $1150 all up landed. Same list from local Suzuki dealer, $2100. Yikes. Yet to work out the Ali/OEM mix price, but probably closer to $500. Also, no more bikes, one broken one is enough for me (not counting the other two unfinished bike projects). 

So I couldn't find a caged needle roller thin (width ways) enough for the job, but did find a deep groove ball bearing that will work, when doubled up (5mm wide each). The munched end will work out sweet, enough meat in the head to take the bigger OD, I will just have to machine the cam down 1mm at that end. The more I thought about it, I didn't like the idea of bearings at just one end, so I am going to try fit them in the other end too, but I have to take that end of the cam down 5mm, but should be fine. The od will get close to the dowels, but should be ok. Random pics for visualization:

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Hopefully my BIL has a boring bar that will fit inside the center bearing hole. Will start setting it up tomorrow hopefully.

Regards, VG.

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I'm meaning take the 125 cam and pedestal that's already got bearings, and tig it in there. 

 

There was a guy trying to convert to roller bearings on a suzuki savage (which is the same cam in head design) and he couldn't find a needle bearing either. I can't find the thread again, but I don't think he got any further than you have now

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On 20/03/2022 at 08:29, tortron said:

I'm meaning take the 125 cam and pedestal that's already got bearings, and tig it in there. 

 

There was a guy trying to convert to roller bearings on a suzuki savage (which is the same cam in head design) and he couldn't find a needle bearing either. I can't find the thread again, but I don't think he got any further than you have now

Tiginging the pedestal in seems like way more work than what I'm trying? It would probably cause everything to warp too wouldn't it? And that guy with the savage sounds like a little bitch. 

On 20/03/2022 at 11:17, SOHC said:

I had an XL250 motor sport that runs the cam in the head, someone had done a really nice job of making bronze bushes for both ends of the cam

That's not a bad option, but then all the tolerances have to be super spot on. The benefit of bearings is the fit and finish of the machined parts doesn't have to be absolutely perfect.     

11 hours ago, flyingbrick said:

Hi @Vintage Grumble how will you set that up for machining? I just can't work out how you'd get it right. 

Also, how will you retain the bearings at the driven end?

 

 

This is the only thing I have to sort out. There will be a lip on the cam, on the inner side to stop the bearings going inward, but not 100% sure on how to stop them going out. The cam is located with a C clip, so the cam moving is not a problem. Just good old bearing retaining compound may have to do, if I cant think of another plan. Or maybe I can make a little plate that screws onto the head and retains the bearings? 

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Yeh oil feeds into the cam through the center bearing, and then out the side at each end into the bearing. The center of the cam chain end is plugged off, but the other end is open. I will probably plug the open end of the cam and maybe drill a little hole in it, so oil hits the end of the head and goes back through the sides of the bearing. Not 100% sure what to do at the driven end, the oil flying around off the cam/lifters/chain will probably be enough to keep a ball bearing happy.

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The bronze bushes wouldn't be very hard to do, bolt the rocker cover on and bore the bearing tunnels oversize, the bearing at the far end has a stake to stop it turning, and the bearing behind the camchain sprocket had a flange, thing munt of been running like that for 30 odd years.

Honda xr200 2valve engines have a steel bush on the end of the cam

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11 minutes ago, SOHC said:

The bronze bushes wouldn't be very hard to do, bolt the rocker cover on and bore the bearing tunnels oversize, the bearing at the far end has a stake to stop it turning, and the bearing behind the camchain sprocket had a flange, thing munt of been running like that for 30 odd years.

Honda xr200 2valve engines have a steel bush on the end of the cam

How would you set it up though? Only way I can think of is to get a piece of bright bar twice the length of the cam then machine it to fit, clamp it in there with the cover and setup on the bar that protrudes.

Or maybe you could find a few reference surfaces in there and setup to those? Bolt holes and head gasket face? 

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I'm not sure what it's called, but the BILs mill has a drive/chuck sticking out the front of it (horizontally) and he has a doofer that holds boring bars, so I can just bolt the head flat to the bed on the head gasket surface, find the center on the two good bearing surfaces, and then machine away. As long as the boring bar fits through the center bearing surface. If that makes sense?

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