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drill marks on crank counterweights #781547 08/15/19 3:36 pm
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tommy Offline OP
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I purchased a 1968 t120 and in the process of rebuilding the engine ive come across many issues. To my finding the bike was upgraded to 750cc and the timing side bearing was destroyed. I decided to bring her back to 650cc, but i have some concerns. The crank seems to have been balanced to some unknown factor. The counter weights have drill markings, 4 on the sludge trap side and 2 on the opposite (not including the factory drill mark opposite of the sludge trap). Ive been told that it should be ok to run as long as the balance factor is within reason. I just dont understand the drill marks on the counterweights. Do they effect balance across the plane of the crank? If one counterbalance it slightly lighter then the other, would it cause issues with the bearings? Any input and explanation would be awesome.

I have one more question regarding the drive side bearing race. I heated the case and the race kinda just fell in without much force. Im concerned that when the engine runs and gets hot, the race may want to spin. It it normal for the race to just fall into the journal with out much force? Could i use loctite 640 as a precaution?

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Re: drill marks on crank counterweights [Re: tommy] #781554 08/15/19 4:24 pm
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Balancing is as much, if not more, about side-to-side balancing as it is up/down. I've had a bike that would "walk" as it was so out of balance side-to-side. Some times, the holes can't be placed on the flywheel to remove enough metal (I think the factory limits holes to 3/16" depth) so drilling the weights takes care of this. I doubt this would be the cause of failure on your timing-side bearing.

Regarding the race in the case, heating is the best way to remove it from the case and I've usually had it fall right out as well. There isn't very much radial force against the race during normal operation that should be of concern (unless the race is loose without applying heat.

Re: drill marks on crank counterweights [Re: tommy] #781555 08/15/19 4:43 pm
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It will move a bit when it’s hot and that won’t matter.

Loctite won’t stop that happening.


Amateur Loctite enthusiast.
Re: drill marks on crank counterweights [Re: tommy] #782087 08/21/19 12:41 am
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thanks for the replys. I also have a question regarding the crankshaft and crank cases. When the crankshaft is installed and the two case halves installed and snuggly tightened down, the crank will bind and takes a bit of effort to get rotating. I noticed when the case halves are loosened the binding goes away. idk what it could be. Any ideas? Also i used a bit of bearing reatiner on the timing side crank shaft and bearing inner race. Maybe that was a mistake?

Re: drill marks on crank counterweights [Re: tommy] #782108 08/21/19 6:01 am
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Did the bearing inners seat hard against the crankshaft cheeks?
Have you tried whacking the sides of the crankcases after assembly, with a mallet?

Did you interfere with the camshaft bushes?


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Re: drill marks on crank counterweights [Re: triton thrasher] #782144 08/21/19 3:24 pm
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The cam bushings were not interfered and the cams are installed. They move quite nicely with no binding. The cases seemed to fit nicely to one another.
I havnt tried whacking the cases yet. Ill give a whack and see it anything changes.

I should mention that it seems the crank is very tight in the case. There isnt any measurable crank float

Re: drill marks on crank counterweights [Re: tommy] #782150 08/21/19 4:11 pm
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have you had the crank checked to see if it hasn't been belted on the end - thus taking the crank out of true.


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Re: drill marks on crank counterweights [Re: Allan Gill] #782152 08/21/19 4:36 pm
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i had the crank ground down, polished checked and trued. Machinist told me everything looks ok.
so i just wacked the timing side case and crank end. The crank seems to rotate will less resistance but it doesnt spin like what i would assume a crank would spin on bearings. to me it seems like it needs a too much effort it get it spinning.

update:
so i heating up the bearings a bit and noticed that the crank will spin smoothly when warm. When it cools becomes difficult to spin. No really binding just heavy to spin. I did use some Lucas assembly lube and this stuff if heavy and sticky. Got me thinking it could be the lube causing the issue.

Last edited by tommy; 08/21/19 5:45 pm.
Re: drill marks on crank counterweights [Re: tommy] #782157 08/21/19 6:15 pm
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My next suggestion was going to be to warm it.

I think it will work as it is, if it spins freely when warm.

Last edited by triton thrasher; 08/21/19 6:16 pm.

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Re: drill marks on crank counterweights [Re: triton thrasher] #782160 08/21/19 7:12 pm
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to me it seems fine now, but its hard for me to make a judgement on how much force it should take to rotate the crank shaft since in dont have a comparison. If i attach the nut on the timing side and rotate with a 1/2 inch racthet it feels smooth but some resistance. Does that sound about right or is the crank suppose to spin like a wheel?

Re: drill marks on crank counterweights [Re: tommy] #782162 08/21/19 8:13 pm
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What ever you do, don’t ever whack the end of the crank, it’s a sure fire way to buggering them up.

Is it possible that the bearing wasn’t pushed on far enough? It often helps to assemble (unless you have a sleeve piece) all the items on the crank and then tighten the nut up to torque to push the bearing all the way home.

I wouldn’t use assembly lube on the roller bearings, there’s a chance that it can cause them to skate thus damaging the bearing. Keep that for things like big end shells, and cam journals. Lubricate anything else with the engine oil that you intend to use.


beerchug
Re: drill marks on crank counterweights [Re: tommy] #782163 08/21/19 8:18 pm
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The crank should turn freely under its own weight, so it’s either too tight on the shins or the gloopy oil is restricting this.


beerchug
Re: drill marks on crank counterweights [Re: Allan Gill] #782167 08/21/19 8:49 pm
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Originally Posted by Allan Gill
What ever you do, don’t ever whack the end of the crank, it’s a sure fire way to buggering them up.


That may be why nobody suggested whacking the end of the crankshaft.


Amateur Loctite enthusiast.
Re: drill marks on crank counterweights [Re: triton thrasher] #782171 08/21/19 9:33 pm
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Originally Posted by triton thrasher
Originally Posted by Allan Gill
What ever you do, don’t ever whack the end of the crank, it’s a sure fire way to buggering them up.


That may be why nobody suggested whacking the end of the crankshaft.

Quote
so i just wacked the timing side case and crank end

I think Alan was suggesting that once was one times too many

Re: drill marks on crank counterweights [Re: tommy] #782175 08/21/19 10:12 pm
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By the time you've got a thou or two of sealant on the case halves it'll be ok.

Re: drill marks on crank counterweights [Re: tommy] #782186 08/22/19 12:02 am
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*** sorry, just noticed this is a T120... this might not apply at all eek ***

Is this a roller or ball bearing motor? Is the crank original to this set of cases?

What shims are you using on the crank, against the drive side bearing?

Are you testing with everything mounted on the drive side (spacer, sprocket, rotor, nut)?



Re: drill marks on crank counterweights [Re: MarcB] #782217 08/22/19 12:05 pm
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Originally Posted by quinten
Originally Posted by triton thrasher
Originally Posted by Allan Gill
What ever you do, don’t ever whack the end of the crank, it’s a sure fire way to buggering them up.


That may be why nobody suggested whacking the end of the crankshaft.

Quote
so i just wacked the timing side case and crank end

I think Allan was suggesting that once was one times too many



Thankyou, and correct.

Originally Posted by MarcB
*** sorry, just noticed this is a T120... this might not apply at all eek ***

Is this a roller or ball bearing motor? Is the crank original to this set of cases?

What shims are you using on the crank, against the drive side bearing?

Are you testing with everything mounted on the drive side (spacer, sprocket, rotor, nut)?





Im far from a triumph expert, but I was assume (dangerous i know) that it will be ball bearing on the timing side and roller on the the drive side, looking at the scematic on Draganfly the drive side bearing is either roller or ball, both are listed.

Either way correct shimming is required.


beerchug
Re: drill marks on crank counterweights [Re: tommy] #782219 08/22/19 12:48 pm
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Triumph does not use shims on crankshaft.

Re: drill marks on crank counterweights [Re: tommy] #782236 08/22/19 3:44 pm
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Is the roller ball bearing held into place on both sides the outer cage then?

Last edited by Allan Gill; 08/23/19 6:35 am.

beerchug
Re: drill marks on crank counterweights [Re: tommy] #782239 08/22/19 4:26 pm
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Allan, I do not understand your question. A 68 T120 has a roller bearing on drive side and ball on timing side. The timing side locates the crankshaft in the cases. I have a primary drive sprocket nut from a pre unit Triumph, the early type that has the Cush drive on the end of crankshaft, it screws on the timing side of the crank and covers the snout that feeds the crank oil. I screw a nut on the end of the drive side of the crank. I then whack both sides the crank with an educated hammer. This seats the crank in place and almost always frees up a crank with new bearings that is tight.
I also always take a old cam and drive the cam bushes fully home before putting cams into cases. Even if you did not change cam bushes you should always seat them home. If the cams were not removed I whack both of them with a dead blow hammer to make sure they are fully seated before assembling. Heating cases to change bearings can make the cam bushes move.

Last edited by RPM; 08/22/19 9:33 pm. Reason: Spelling
Re: drill marks on crank counterweights [Re: quinten] #782272 08/22/19 10:40 pm
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Quote
so i just wacked the timing side case and crank end


I missed that he’d said that.

What’s this nonsense about shimming the crankshaft?


Amateur Loctite enthusiast.
Re: drill marks on crank counterweights [Re: RPM] #782283 08/23/19 12:33 am
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Originally Posted by RPM

I also always take a old cam and drive the cam bushes fully home before putting cams into cases. Even if you did not change cam bushes you should always seat them home. If the cams were not removed I whack both of them with a dead blow hammer to make sure they are fully seated before assembling. Heating cases to change bearings can make the cam bushes move.


i did not know this. i am puzzling over a motor right now that locks up the cams when the pinions are tightened fully, and was presumably a runner. . . the timing side was warmed up to change both gearbox mainshaft and crankcase main bearing race.

i wonder.


every day you do not take a chance is a day of your life that you will never get back.
Re: drill marks on crank counterweights [Re: triton thrasher] #782303 08/23/19 5:25 am
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Originally Posted by triton thrasher

Quote
so i just wacked the timing side case and crank end


I missed that he’d said that.

What’s this nonsense about shimming the crankshaft?


Plenty of blokes who raced them fitted 2 roller bearings, you then had to shim them.
I still think it's not a bad idea as you can centre the crank and stop the tendency for the timing side bearing to move as much.
Just my 2c. Just nonsense i suppose.

Re: drill marks on crank counterweights [Re: tommy] #783021 08/29/19 10:15 pm
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Id like to thank you all who responded to my question.
I ended up getting the crank to spin freely. The timing side bearing wasn't seated all the way through.
The crank now spins like it should, very smooth!
I know wacking the end of the crank isn't a good idea. sometimes out of desperation we (or just myself)) do stupid things. No damage, so i got away with one lol.

I dont want to start another thread but i have a question regarding the fork seal holders. Are the flat washer that sits on top of the bushing near the oring necessary? the top fork tube bushing butts up against the shoulder of the holder. Just curious?

Last edited by tommy; 08/30/19 1:25 am.

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