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Discussion Starter · #101 ·
Yes your right. I’m thinking of upgrading the exhaust cam and have just got a deal on some barrels and high comp pistons. So I’ll go with the upgrade bearing to be safe.
 

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Hi
The Metric bearing was under spec. and could not cope with the torque from the 750cc engine, so instead of fitting a stronger bearing (they eventually did in 1981) Triumph detuned the cams to kill the low end torque and top end power. (Race profile inlet to kill torque and restrictive exhaust to limit power at the higher rpm).
They ended up still having a weak bearing and the same performance as a 650cc, but with power that only started to come in at 5000rpm rather than at 2500rpm on the 650cc. They ended up with the worst of all worlds.
If you are thinking of upping the performance, then good luck on using that weak timing side ball bearing.
regards
peg
PS.
You might find this interesting reading:

Also search for posts by @Truckedup he has a genius for this sort of tuning.
 

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Hi Yazwaz, Certainly nothing wrong with sticking with ball bearing. If… my ball wasn’t such an extreme tight fit on crank I would have used a ball.
I don’t know how factory got the crank into bearing. They have their ways. Roller makes fitting cases onto crank super easy. 2nd reason is I wanted best durability as I put about 5k miles a year on the bike. Still primary reason was the tight fit on crank.

Give some thought to high compression pistons. You must have the octane to support high compression. T140 type motors are prone to pinging & detonation. There are modifications you can do to make high compression work. Hillbilly knows about this. I would recommend getting with him for exact details.
Don
 

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Discussion Starter · #104 ·
Hi
The Metric bearing was under spec. and could not cope with the torque from the 750cc engine, so instead of fitting a stronger bearing (they eventually did in 1981) Triumph detuned the cams to kill the low end torque and top end power. (Race profile inlet to kill torque and restrictive exhaust to limit power at the higher rpm).
They ended up still having a weak bearing and the same performance as a 650cc, but with power that only started to come in at 5000rpm rather than at 2500rpm on the 650cc. They ended up with the worst of all worlds.
If you are thinking of upping the performance, then good luck on using that weak timing side ball bearing.
regards
peg
PS.
You might find this interesting reading:

Also search for posts by @Truckedup he has a genius for this sort of tuning.
No going for the roller bearing. Great article on the cams that will come in handy.
 

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Discussion Starter · #105 ·
Hi Yazwaz, Certainly nothing wrong with sticking with ball bearing. If… my ball wasn’t such an extreme tight fit on crank I would have used a ball.
I don’t know how factory got the crank into bearing. They have their ways. Roller makes fitting cases onto crank super easy. 2nd reason is I wanted best durability as I put about 5k miles a year on the bike. Still primary reason was the tight fit on crank.

Give some thought to high compression pistons. You must have the octane to support high compression. T140 type motors are prone to pinging & detonation. There are modifications you can do to make high compression work. Hillbilly knows about this. I would recommend getting with him for exact details.
Don
When I say H/C cams I mean not the L/C ones so probably standard cams would be a better term. I think they are 8.6:1.
 

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Ball main bearing will probably last 40,000 miles with good oil. I am using ball type on timing side and roller on the primary on my 750 bored 650. 8.6 to 1 will work using superunleaded as long as it is still available in the future. Most people would run these old bikes up to around 80 mph so the bearings would last a very long time. These days they are leisure bikes so too many improvements may be a bridge too far for them
 

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Hi Yazwaz, Hold off on the bearings.
What was clearance on you old drive side bearing? The RHP in your top photo is C2. That may be too tight. One O is C2. Two OO is CN. Also, unmarked is CN, Three OOO is C3. Again no marking in Os or C clearance is CN. So look at both sides of your old bearing. Get the clearance it had in drive side.

My hunch is you'll need CN or drive side.

Timing side you'll need C3. That's clearance you're looking at in bearing listing above.

NUP306ETVPC3 will be a plastic cage

SKF NUP306EM1C3 is brass cage usually made in India, very hard to find in C3.

If you want a steel cage you'll need NSK NUP306EWC3 made in Japan. This is bearing I used. qaulitybearingsonline a UK company. They have USA office, but the bearing was shipped from UK.

URB made in Romania sells brass cage NUP306 C3.

I found many bearing sellers said they had C3 in stock, but in fact they only had CN.

NSK Japan is really good quality, RHP England is good. (member of NSK Group). Other ones I don't know. Made in India, China, Romania I don't know quality. Things change, but at work we found 3rd world made bearings were not as durable. Country of origin mattered, no matter the brand. RHP is boxed in UK. But where is it actually made? I used the RHP CN on my drive side.

Back to clearance for a moment. C2 means less clearance than CN. C3 means more clearance than CN. So the C doesn't just go in order like we'd think. It's C1,C2,CN,C3,C4.
Don
 

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Discussion Starter · #109 ·
Font Material property Handwriting Parallel Document

Automotive tire Purple Violet Automotive wheel system Rim

No markings on drive side bearing so presume that’s a CN. For what it’s worth before removal the bearing had a slight rough feel to it.

thanks for pointing out the plastic cage I can see it now but would have been disappointed when that arrived.I can get most makes no problem here just searching for the best price while maintaining the quality.

Found this supplier in the UK that sells a good selection of classic bike bearings. Looking at the NKE brand that are marked as made in Austria premium brand but haven’t heard of them before. Price wise they are in between budget and top makes with a reasonable saving. Have you ever heard of them.

I’ve attached a letter above that I found on the net you’ve probably seen it before but might be of interest to some. I’m hoping to get some ordered tomorrow.
 

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Hi, I’ve heard of NKE, but no experience with them.
I shop quality (perceived quality??), then price.
Is steel cage better than plastic? I don’t really know. At work we saw plastic cage failures. Brass is best if…. Well made.
Is steel cage NSK Japan more durable than Brass cage URB?? In my perception of quality, it was. I’m I correct?? I don’t know!!

Ons large issue in bearing failure is rust on races during bike storage.
Don
 

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I went for this on the TS...
.
Its not a plastic cage, but a composite cage. It seems to be the way all bearing producers are going for the smaller size bearings.
I am picking up the crank cases this week, so hopefully should soon start reassembly...
 

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Discussion Starter · #112 ·
I went for this on the TS...
.
Its not a plastic cage, but a composite cage. It seems to be the way all bearing producers are going for the smaller size bearings.
I am picking up the crank cases this week, so hopefully should soon start reassembly...
I’ve been looking at the NKE bearings seem well priced without being cheap. Where you happy with the look of them then.
 
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