Rotax 350 Engine.

For all that relates to both Armstrong MT 500 and Harley Davidson MT 350
ian
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Rotax 350 Engine.

Post by ian » Mon May 18, 2020 6:37 am

While carring out an oil change I had an opportunity to check out some of the engineering, and materials used in construction. The valve train including roller cam followers and free rotating tappets seem very well designed and built for longevity. Looking up through the bottom of the crankcases reveals robustly forged crank and balance shaft/weight, full skirt piston may not be the fastest mover, but has huge bearing surfaces again for longevity, overall a very well built unit, very robust and long lived, and not limited in materials used by the accountants (unlike todays production) if there is an achilles heel to these engines please shout up as I can't find one. :geek:
0 x
Mt 350 (the Expensive one) :lol:

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lardmarc
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Re: Rotax 350 Engine.

Post by lardmarc » Mon May 18, 2020 7:22 am

Top end is the weakest part of the motor.

Gear box is bomb proof, piston/barrel holds up with regular oil changes.

Only the top ends let go unless you adjust constantly.
1 x
“Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.” (Adams, 2009).

ian
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Re: Rotax 350 Engine.

Post by ian » Mon May 18, 2020 7:40 am

2 thou is tight, so I am assuming the alloy barrel is going to grow a bit with heat :roll: or are there opinions for running with larger clearences🤔 ian.
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Mt 350 (the Expensive one) :lol:

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12royal
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Re: Rotax 350 Engine.

Post by 12royal » Mon May 18, 2020 8:12 am

Valve clearances must be set to manufactures spec no matter how awkward to do.
It doesn’t matter about the barrel expansion with heat because it won’t affect the valve clearances ( unlike pushrods )
Alan
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MT350

nige
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Re: Rotax 350 Engine.

Post by nige » Mon May 18, 2020 8:19 am

The engines across the range, 350- 604 share many of the same part numbers. So, if it’s good for a 604 it’s over engineered for a 350!
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ian
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Re: Rotax 350 Engine.

Post by ian » Mon May 18, 2020 8:43 am

That's reasuring to know, funny thing though, I was engineered to be 6 foot tall but turned out 5 foot 5 inches :( perhaps I will last a long time :lol: still the weakness is definatly the top end though. :roll: ian.
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Mt 350 (the Expensive one) :lol:

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lardmarc
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Re: Rotax 350 Engine.

Post by lardmarc » Mon May 18, 2020 9:10 am

12royal wrote:
Mon May 18, 2020 8:12 am
Valve clearances must be set to manufactures spec no matter how awkward to do.
What he said. You'll get used to how little room there is to do the valves.
ian wrote:
Mon May 18, 2020 7:40 am
Running with larger clearances.
You'll go deaf.
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“Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.” (Adams, 2009).

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Laurence
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Re: Rotax 350 Engine.

Post by Laurence » Mon May 18, 2020 12:21 pm

lardmarc wrote:
Mon May 18, 2020 7:22 am
Top end is the weakest part of the motor.
ian wrote:
Mon May 18, 2020 6:37 am
roller cam followers
Yep, killed that
ian wrote:
Mon May 18, 2020 6:37 am
free rotating tappets
Killed a couple of those as well..
ian wrote:
Mon May 18, 2020 6:37 am
Huge bearing surfaces
And yep destroyed a crank bearing too..


Damn, I’m sounding like Lard :shock: :lol:
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..VFR 400..
..MT 350..
..Enfield Explorer..

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#skippy1970
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Re: Rotax 350 Engine.

Post by #skippy1970 » Mon May 18, 2020 12:47 pm

Laurence wrote:
Mon May 18, 2020 12:21 pm
lardmarc wrote:
Mon May 18, 2020 7:22 am
Top end is the weakest part of the motor.
ian wrote:
Mon May 18, 2020 6:37 am
roller cam followers
Yep, killed that
ian wrote:
Mon May 18, 2020 6:37 am
free rotating tappets
Killed a couple of those as well..
ian wrote:
Mon May 18, 2020 6:37 am
Huge bearing surfaces
And yep destroyed a crank bearing too..


Damn, I’m sounding like Lard :shock: :lol:
You just need to leak a little fluid
And leave a nasty stain everywhere you go :D
3 x
If my brain was to get any smarter it would become self aware and take over my body

MT350 GL36AA

ian
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Location: Market Harborough

Re: Rotax 350 Engine.

Post by ian » Mon May 18, 2020 2:24 pm

Think I need a spare engine as I've done 935 kms on this one, from what I read it could let go at any moment. :o :o :lol:
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Mt 350 (the Expensive one) :lol:

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