Author Topic: Timing side roller conversion  (Read 1964 times)

Offline shabashow

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Timing side roller conversion
« on: 05.09. 2008 22:49 »
Hi Folks,

Has anyone got any experiences/comments, good or bad regarding the roller conversion and end oil feed for the crankshaft?

I've got a 52 A10 plunger, just rebuilt and went to change the oil after the first couple of hundred miles. I found bits of what I think is the main plain bearing in the sump. Endplay when rebuilt was 0.0017, but feels a bit more now the engine has been partially dismantled. Still need to get it out of the frame to split the cases to verify, but from the shape and size of the bits, it looks like the inner 2-3mm of the bronze has come off in pieces up to 3-4 mm square. The bearing was good quaity supplied by a reputable bike shop specialising in these things and a very good engineering company fitted and reamed the bearing to fit the crank.

The bearing looks like it certainly needs replacement, but am in a quandry whether to replace like with like or take the plunge with my plunger and get the conversion to rollers. I don't want a repetion in another few hundered miles.

cheers,

John
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Online Brian

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Re: Timing side roller conversion
« Reply #1 on: 05.09. 2008 23:58 »
Hi John,

My A's all run the original bush set up  and I have never had a problem but others on the forum have. There is quite a bit of debate as to exactly what material the bush should be made of and some have had problems with excessive wear.

The thing with yours though is regardless of what its made of it shouldnt break up. It may wear quicker than normal but should not disintergrate. I can only think you have been unlucky to get some very faulty material or it was very poorly fitted ie. bashed in with a hammer causing the flange to fracture.

It is normal for the end float to increase slightly after the motor has done a few miles. If you put it together with .0017" that should be fine.

I'm looking forward to what you find when you dismantle it and have a proper look.

Brian.
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Offline terryk

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Re: Timing side roller conversion
« Reply #2 on: 06.09. 2008 14:39 »
Hi John, I am very interested to know, did the fitters line bore the bush in line with the bearing hole on the drive side with engine cases correctly matched and bolted together. Also did they make the bush or just reamed out one they purchased from somewhere?
I have had plunger A10s in the past and pulled the engines apart after years of riding and the timing bushes are still ok. I don't see the need or expense to do the conversion. I agree with my fellow aussie Brian, there must be something wrong with the bush for it to be falling apart or bits coming off it.

I'm concerned about using the bushes they sell these days, wearing out the crank instead of the bush. My mate used to do engine recon years ago and made white metal bushes etc. Only trouble is he is so busy doing other things and very hard to get do anything. I may have a go at it myself with his advise.

The main mistake I'm hearing about the bushes is people just press the bush in and ream it to the crank without it being in line with the bearing hole on the otherside, so it chews the bush out, this could be your problem. I have heard there are also bad quality bushes on the market. Some say SRM in UK make good quality ones but could wear the crank more than the bush. I'm still waiting for more feedback about them.

I'm thinking of making a jig that lines up the bearing hole on the drive side and the timing side hole without the bush in it then press the bush in and bore the bush out with the milling machine. I have some ideas in my head. I have an A10 plunger at the moment with new timing bearing ( bush) in it so I will see how that goes. I didn't build the engine though I purchased this bike with recond engine. I'm not sure if it's a white metal or bronze but I dont want to pull it apart to find out. I have another plunger bike that am buiding the engine for so I want to sort this timing side bearing issue out. I may just machine a bush with softer bronze so it doesn't wear out the crank. Anyway enough said this time let us know how you go.
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1950-53 A10 rigid/plungers, 1958-61 A10 super rockets, 1947-50 A7 longstrokes, 1949 Star twin,
1951-54 A7 plungers, 1940s M21, WDM20s,
1948-50s B33s rigid/plunger/swingarm, 1948-50s b31s rigid/plunger/swingarm

Offline shabashow

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Re: Timing side roller conversion
« Reply #3 on: 06.09. 2008 23:04 »
Thanks for your comments Brian and terryk,

engine now fully dismantled, and I can see the problem. When the barrels were removed, the LH piston did not move on the gudeon pin.
When the crank came out, the bearing surfaces looked fine.
Looking up the con rod, the small end bearing looks like it has failed - that would be the lumps seen in the oil. There was a wee bit of play evident at the small end when I rebuilt the engine, but thought it was small enough to be ok, obviously not.
I have full faith in the engineer who did the bearing - don't know the details, but I think he would have sized the bearing up to match the crank, as he did my regrind. I'm sure he does a 'proper job'.
Will be calling on him Monday morning on the way to work, for his expertise in assessing how a repair can be undertaken. Hopefully it wil be just a replacement of the small end bearing.
Pictures attached to show you what I found in my oil that initially caused my concern, a shot attempting to show the underside of the piston (you can just make out something wrong between the top of the con rod and the piston), as well as the main bearing and crank bearing surface.
I feel much better now.
John 
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Offline shabashow

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Re: Timing side roller conversion
« Reply #4 on: 06.09. 2008 23:09 »
somehow the other photos didn't attach.
I'll try again
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Online Brian

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Re: Timing side roller conversion
« Reply #5 on: 07.09. 2008 00:00 »
Glad it doesnt appear to be too bad. Its unusual for a gudgeon bush to break up. No great drama to repair though so you should be back on the road soon.

Brian.
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Offline shabashow

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Re: Timing side roller conversion
« Reply #6 on: 07.09. 2008 00:24 »
As Dr. Neinstein on the old Gerry Anderson puppet tv series always used to say:

Always expect the unexpected!

On a more serious note - It will be very interesting to get a good look at the remains of the bush once it gets removed to see what underlying fault caused it to fail in that manner. I've never heard of a small end breaking up like that.

John
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Online RichardL

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Re: Timing side roller conversion
« Reply #7 on: 07.09. 2008 03:15 »
John,

Back when I was struggling with rods that were over-honed by my "machinist," G/FDave suggested cleaning up casting marks and other blemishes on my old rods (before said machinist made up for his mistake by providing MAP racing rods). I did do this and, had I kept those rods, they were looking a lot better when I was done than when they came out of the engine. Here is the link to Dave's comment.

http://www.a7a10.net/forum/index.php?topic=473.msg2496#msg2496

Richard
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