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Author Topic: Camshaft gear  (Read 5500 times)

Montana

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Camshaft gear
« on: March 29, 2009, 06:33:53 AM »
Well I have started to put my 12/1 powerline back together.  While I was cleaning the sharp edges an left ovet metal of the cam gear I found one tooth that must have had some bad casting.  About 1/4 to 1/3 of the tooth is gone from one end of the gear.  I cleaned it up with a dremel tool in hopes that I could get it ti work.  Now Im wandering if that is a good idea to try and save the gear.  I dont know how much of a strain that would put on that tooth.
There is a lot of crap in  this engine that could have been caught if only a little time was spent inspecting the quality.  Im no expert just visual looking could have gone a long way.
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ronmar

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Re: Camshaft gear
« Reply #1 on: March 29, 2009, 07:01:58 AM »
And that is the biggest issue with the Roids.  Just a little cleanliness and attention to detail during assembly could result in a vastly improved final product. 

As for your cam gear, what kind of idler gear are your running, Bronze or iron?  What is your backlash between crank and idler and between idler and cam?  I measure the idler gear backlash by wedging the flywheel in place and use a rod to a dial indicator and wiggle the idler gear.  To measure cam gear backlash, I roll the engine to a point where the cams are not loaded and jam the crank-idler gear by rolling a rag into the gear mesh.  Then I use a longer rod to reach into the cam gear teeth and press against the dial indicator while i rock the cam gear.

Large backlash numbers(greater than .010"-.015") are going to increase the hammering effect felt by the gear teeth.  The cam gear is also under quite a bit of stress as it takes a good bit of torque to roll the cam and IP lobes up under their respective valve and pump loads.  Depending where the partial tooth is in relation to the cam lobe loads, that tooth may not have any real load and may run forever without problems.  But if not, a gear failure could cause other more serious problems, such as gear damage to the crankshaft gear...  My Motto is: When in doubt, change it out.
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oliver90owner

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Re: Camshaft gear
« Reply #2 on: March 29, 2009, 09:43:03 AM »
Go with Ronmar's maxim.  I endorse that fully.

Do the back-lash check now.  An offset idler bolt will be a cheaper option now, than doing it after a failure, if it is required.

Have you done all the other alignment/fit checks?

Regards, RAB

Montana

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Re: Camshaft gear
« Reply #3 on: March 29, 2009, 03:46:24 PM »
All gears are cast no bronze.  Not checked any thing yet.  I bought plasti gauge to check the big end but decided what the heck.  I took std bearings out and put std back in and put the shims that were there before back too (2 under one side 1 under the other). Its stiff but I can turn it by hand.  Im using assymbley lube on all the bearings.  Ill look at the position of the cam tooth.  I guess I should have got a case and all the parts and started from scratch.  I mean it wouldnt have taken expensive equipment (none at all) just a pair of eyballs to have solved 85% of these issues,15% if they would clean them first and use fresh oil.
Oh Crap they are a nuke nation!!!!
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lowspeedlife

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Re: Camshaft gear
« Reply #4 on: March 29, 2009, 03:52:47 PM »
If they build thier nukes as well as the listeroids the Pakastani's have nothing to fear! They most likely will explode on the lanch pads :o

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billswan

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Re: Camshaft gear
« Reply #5 on: March 29, 2009, 07:08:30 PM »
Montana

In your last post you said "Its stiff but I can turn it by hand" that comment concerns me because the way it is worded makes me think you are saying the big end bearing is stiff but you can turn it by hand!!! In my experience a properly clearanced and assembled and lubed with oil big end bearing should never be "stiff".
Please excuse me if you are referring to the whole assembly including piston and rings.
If you are not completely sure that bearing is correct get some help from an experienced mechanic! You may lose a rod and crank if it is wrong.
Question, I am not sure of the side clearance on the rod bearing but it is enough so that if you grab the rod it should move side to side from one shoulder of the crank to the other shoulder with ease. My guess is the clearance is 4 to 6 thousandths of an inch but that is a GUESS!! Please do not confuse the oil clearance with my explanation of side clearance.

Good luck Billswan
16/1 Metro  in the harness choking on WMO ash!!

10/1 OMEGA failed that nasty WMO ash ate it

By the way what is your cylinder index?

Montana

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Re: Camshaft gear
« Reply #6 on: March 30, 2009, 06:38:27 AM »
Ok just checked the location of the bad tooth. 
It appears to start to engage just after the exhaust starts to close on the non loaded side.
There doesnt look like anything is loading up until the tooth clears.   So Im going to leave it in.  I know I should replace it to be on the safe side but Im getting real tired of buying new parts for a new engine.  Its going to work or its going to the junk heap.

Bill the rod moves on the crank (rotation) a little stiff not real loose. I can set it upright on the crank and it will stay put.  If I move it off center a little it will loose its balance but not real fast.  As far as side clearance on the crank it is slim to none.  There is nothing I can do further to the crank if every part is different.  I had the crank polished and new std rod bearings ordered.  Assy the rod with the new bearings and it had a huge gap in the connecting rod shell while the bearings were tight.  If I knew that the bearings were always perfect I would have the rod bored out to get rid of the shims 
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billswan

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Re: Camshaft gear
« Reply #7 on: March 30, 2009, 12:59:02 PM »
Bill the rod moves on the crank (rotation) a little stiff not real loose. I can set it upright on the crank and it will stay put.  If I move it off center a little it will loose its balance but not real fast.  As far as side clearance on the crank it is slim to none.  There is nothing I can do further to the crank if every part is different.  I had the crank polished and new std rod bearings ordered.  Assy the rod with the new bearings and it had a huge gap in the connecting rod shell while the bearings were tight.  If I knew that the bearings were always perfect I would have the rod bored out to get rid of the shims 

Hello montana
If the tooth is where you say it is you will probably be fine.

Now back to the rod, I suppose it could be the assembly lube you talk of, some of that stuff can be pretty thick. I doubt you will need it in a engine of this design. Sounds like you put the rod on the crank out side of the block for testing purposes. If that is what you did and if the parts were clean and oiled with plain 30w engine oil the rod should swing to the bottom once pushed off center if the clearance is not to tight. But with the thick assembly lube ( if it was thick like I am assuming) is in there then that changes things. I am probably alarmed over nothing ::) I wish some of the posters that have a better way with words would chime in!
I have always had a problem putting thoughts on paper. :(
Billswan
16/1 Metro  in the harness choking on WMO ash!!

10/1 OMEGA failed that nasty WMO ash ate it

By the way what is your cylinder index?

oliver90owner

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Re: Camshaft gear
« Reply #8 on: March 30, 2009, 05:50:13 PM »
Simple.  If in doubt plastigauge it.

Lister manual says free to 3 thou.  Sounds like yours might just need an extra 1 thou. shim.  No point in overheating a tight bearing for the cost and time of fitting an extra shim.  How is the bearing nip?

Fitting the bearing: the rod, cap and outside of the bearing surfaces should be scrupulously clean and burr-free; journal and bearing should be lubricated; bearing nip should be checked.  Before plastiguage one would usually remove shims, if bearing were loose (free), until  bearing was tight and then re-insert shim(s) for clearance.  Was simple enough and worked in early part of last century, so should still be a perfectly adequate method now. Bet they don't use plastiguage very much in India.

Regards, RAB