Smooth bonnie

Triton Thrasher · Oct 12, 2024

Onder said:
If T140's did not get balanced then it is seriously disturbing that Royal Enfield Inters were dynamically balanced. If they figured it out what on earth happened to Triumph?
My '73 Bonnie could remove your tooth fillings. By 71 BSA removed anything bolted on to it.

Enfield were making tiny numbers of Series 2 Interceptors, compared with Meriden’s output.

baz · Oct 12, 2024

I had an oif t120v that vibrated incredible badly but it was bored to +60 without any rebalancing so that may have played a part
I had a tiger tr7 that was ok ish
My t140e was pretty good even after I changed the 7.8 -1 pistons for some t140v 8.5 -1 type
Worst vibrating bike I ever owned was a 750 commando motor fitted in a wide line
Closely followed by a plunger A10 and a BSA B44 that some idiot thought he could change his own big end bearing and re align the crank himself with a big lead hammer ,tyre levers,and a pair of steel wedges!!!

Triton Thrasher · Oct 12, 2024

I arbitrarily raised the balance factor on my current pre-unit 650 Triton by taking off the crankcase filter and cover and enlarging a hole in the flywheel with a hand-held drill.

baz · Oct 12, 2024

Triton Thrasher said:
I arbitrarily raised the balance factor on my current pre-unit 650 Triton by taking off the crankcase filter and cover and enlarging a hole in the flywheel with a hand-held drill.

What difference did it make?

Triton Thrasher · Oct 12, 2024

baz said:
What difference did it make?

I think it helped a bit.

Onder · Oct 13, 2024

Helped a bit?.... well he did say he used a drill....

Onder · Oct 13, 2024

Triton Thrasher said:
Enfield were making tiny numbers of Series 2 Interceptors, compared with Meriden’s output.

Yes but then the workforce was tiny too. Triumph had the people, brains and money to get or make a balance machine. Odd that Hele did not go there. One of the most noticeable things about later brit bikes was bad vibration. Trident was one answer, Isolastic suspension another so clear that the problem was well known and worth addressing.

Triton Thrasher · Oct 13, 2024

Onder said:
Helped a bit?.... well he did say he used a drill....

There’s a new twist!

Onder · Oct 13, 2024

yeah it was SUMP thin else...

cliffa · Oct 15, 2024

As mentioned earlier, some pics or the AV or “Enforcer” frame as Triumph called it. Apparently only 50 bikes were made utilizing it, which is a shame.

Bottom engine mounts..

Rear engine mount and pivot.

It would be pretty simple for a welder / fabricator to replicate.

baz · Oct 15, 2024

cliffa said:
As mentioned earlier, some pics or the AV or “Enforcer” frame as Triumph called it. Apparently only 50 bikes were made utilizing it, which is a shame.

View attachment 116722

Bottom engine mounts..

View attachment 116721

Rear engine mount and pivot.

View attachment 116720
It would be pretty simple for a welder / fabricator to replicate.

How did they mount the silencers?
The main reason I moved away from triumph twins was the vibration ,that and the clutch
This setup may have kept me with them for longer

robs ss · Oct 15, 2024

That is an ENORMOUSLY wide engine for a twin - wider than a honda 4 maybe?

If you hate a big twin's vibes that much - just buy an e-bike

baz · Oct 15, 2024

robs ss said:
That is an ENORMOUSLY wide engine for a twin - wider than a honda 4 maybe?

If you hate a big twin's vibes that much - just buy an e-bike

Or buy a commando as many did I guess

cliffa · Oct 15, 2024

baz said:
How did they mount the silencers?
The main reason I moved away from triumph twins was the vibration ,that and the clutch
This setup may have kept me with them for longer

I’m not sure about the exhaust mounting TBH, but I know the strengthened the front downpipes brackets. ( I always thought they looked tinny anyway (and crap)). But I guess they used bobbin mounts like the Commando?

baz · Oct 15, 2024

cliffa said:
I’m not sure about the exhaust mounting TBH, but I know the strengthened the front downpipes brackets. ( I always thought they looked tinny anyway (and crap)). But I guess they used bobbin mounts like the Commando?

I was thinking there'd be a lot more movement at the exhaust mount with the motor moving in an arc
But I guess if it's only moving a fraction at the front of the motor it'd be fine

Matchless · Oct 16, 2024

baz said:
I seem to remember an article in MCN back when I used buy it that said something like "the Muppets at meriden are finally balancing the cranks"
And I took that as to mean dynamically balanced
As obviously even triumph would have always statically balanced their cranks?

Not sure I'd believe anything printed in MCN, or as we used to call it, Motorbikeysnooze, the worlds best selling anesthetic.
A mate of mine has a 1987 Harris Bonneville with the TSS type crank, all be it with reduced big end diameters, & it feels quite different to my 1977 TR7v, & is really quite smooth.

marshg246 · Oct 16, 2024

I seem to remember someone making 180-degree cranks for 650s and part of the reason being to reduce vibration. That seems simpler than added counter-balance hardware and seems like it would make the static balancing done by the factory easier/quicker.

Fast Eddie · Oct 16, 2024

Matchless said:
Not sure I'd believe anything printed in MCN, or as we used to call it, Motorbikeysnooze, the worlds best selling anesthetic.
A mate of mine has a 1987 Harris Bonneville with the TSS type crank, all be it with reduced big end diameters, & it feels quite different to my 1977 TR7v, & is really quite smooth.

I had a Harris Bonnie in ‘86 ish. I was only a yoof and absolutely caned that bike keeping up with my Jap mounted mates.

It was much smoother than other Triumphs I’d ridden, although time makes direct comparisons unreliable, I do believe my current dynamically balanced T140 is smoother.

Here it is outside its birthplace. Note bottle of oil stuffed into grab rail to keep it topped up !

Matchless · Oct 17, 2024

Fast Eddie said:
I had a Harris Bonnie in ‘86 ish. I was only a yoof and absolutely caned that bike keeping up with my Jap mounted mates.

It was much smoother than other Triumphs I’d ridden, although time makes direct comparisons unreliable, I do believe my current dynamically balanced T140 is smoother.

Here it is outside its birthplace. Note bottle of oil stuffed into grab rail to keep it topped up !

View attachment 116740

I would love to buy one of those to try, but they seem to have been under developed & have too many problems built in. Also, if I blew the engine up finding spares might prove somewhat problematic. Still wish I'd bought a kit from Dave Nourish for my TR7. I did contact his successor about a kit of parts, but luckily started to hear the horror stories before parting with any cash.

Fast Eddie · Oct 17, 2024

Matchless said:
I would love to buy one of those to try, but they seem to have been under developed & have too many problems built in. Also, if I blew the engine up finding spares might prove somewhat problematic. Still wish I'd bought a kit from Dave Nourish for my TR7. I did contact his successor about a kit of parts, but luckily started to hear the horror stories before parting with any cash.

Are you referring to a Harris Bonnie? The vast majority of parts are interchangable / easily replaceable with Meriden stuff.

Regarding Dave Nourish, his son Andy is slowly building up to supply more and more Nourish replacement stuff. He’s just finished some new heads. I don’t think it will be too long before he offers an 8 valve conversion for T140s again.

Smooth bonnie

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