Burt Munro's Scout

**wbks** · 27th February 2009, 16:52

I was wondering today, how something that began life not being able to reach open road speed could clock 200mph without a different engine? What performance mods do you vintage guys do to extract a lot more power from your engines?

**skidMark** · 27th February 2009, 17:04

Originally Posted by wbks

I was wondering today, how something that began life not being able to reach open road speed could clock 200mph without a different engine? What performance mods do you vintage guys do to extract a lot more power from your engines?

Something in the water in invercargill....

Spelt Burt btw...

**wbks** · 27th February 2009, 17:07

Originally Posted by skidMark

Something in the water in invercargill....

Spelt Burt btw...

Meh, can't change the title now... Re-casted internals with different materials for lighter weight?

**tri boy** · 27th February 2009, 17:16

Its all about fuel n head work.
Get it in (at high volume), squeeze it to within a nano of explosion, and get it out quick.
Everyone likes good head work.

**wbks** · 27th February 2009, 17:28

So re-casted alloy high comp pistons, re-made barrels and such? Sounds like fun stuff to me...

**JMemonic** · 27th February 2009, 17:32

As I understand things it was a different engine that Burt hand built from ground up as he rebuilt the original scout each time he killed it, I guess some of the casings remained unchanged but we know he converted it to OHV built new barrels and piston, the crank and rods were hand built.

By an reckoning what he archived was brilliant and the result of years of persistent trial and error. Now days you just buy a chip.

**Brian d marge** · 27th February 2009, 17:35

Originally Posted by tri boy

Its all about fuel n head work.
Get it in (at high volume), squeeze it to within a nano of explosion, and get it out quick.
Everyone likes good head work.

and Valve curtain area .. good combustion shape , delays detonation get as much of the boom boom juice through as you can per second ...( 60mm inlets now ..... )

We have done a lot of work with Enfields , they are topping out at 41. 42 bhp without major engine work , using evil juu juu juice ...

Mine is in the region of 32 bhp , and gobs of torque .... I got that with , high comp , and good squish ..its the limit for me ....

Stephen

**wbks** · 27th February 2009, 17:40

Does that cruse at 100 easily enough?

**pete376403** · 27th February 2009, 18:23

it went from a single cam side valve to a quad cam pushrod overhead valve for a start. Capacity increase from around 600cc to around 900cc
Munro made virtually everything in the engine apart from (IIRC) the crankcases, carb and magneto, and even these would have been heavily modified. There were many many years of trial and error, and much hard work. Imagine *filing* a con rod from a solid piece of truck axle. These days we have no concept of the time and effort that Munro took to make a piece that may have lasted all of five minutes before a blowup.
"Offerings to the gods of Speed" indeed

Tim Hannas book, "One Good Run" explains it better

**wbks** · 27th February 2009, 18:50

I'm reading Tim Hannas book on John Britten at the moment, pretty good. I'll get One good run when I'm done. And filing a conrod out of a truck axle... Dedication

**GaZBur** · 27th February 2009, 19:46

Makes you wonder if he had given up on the Indian and moved onto something more modern (1970's) what final speeds he could of managed instead of continuing to push on with a 47 year old bike.
I was at a 2 day meeting in Ingll in the mid-late 70's and Burt turned up, but sadly his bike wouldn't start. He was looking quite old and sick then as I remember. One of the guys there from Dunedin, Errol Healey said he had raced against Burt many times. He would take off on the bunch at the start but eventually the rest would pass him with his bike blown up, apparently he had had time to roll and light a smoke by the time the rest caught up.(might be stretching it a bit but that was the story I was told). Sounds like he entered a lot more races than he finished but won most he did finish in. He also competed on other bikes as I have seen some pics at eh bike club of him competing in Dunedin.
Wonder what he would make of the Burt Munroe weekends.

**Paul in NZ** · 27th February 2009, 20:54

He did try a few other engines... Most were not as 'forgiving'....

One question you need to ask - when does an 'indian' stop being and indian? How could anyone get get 214mph out of a pre unit T110 and give birth to the Bonneville...??

Answer - both men were fecking mad as meat axes and it has been my great privilage in life to meet them both....

**PeteJ** · 28th February 2009, 09:25

If you want some initial clues, get hold of a copy of the Phil Irving classic text Tuning for Speed. It was first published in 1948 ie in era. I believe - from a conversation I had with Burt in the early 70s - that he used a lot of the Irving findings and reasoning.

BTW, my Enfield 350 Bullet was built for classic racing in the early 80s, using a lot of ideas from Tuning for Speed, and was clocked at a sprint at over 100mph.

It presently shows mid 30 rwhp on the dyno (in its early days, was late 20s rwhp), largely as a result of having had the head on a flow bench and gas flowing it using newer ideas than Irving's.

It still has the standard bore and stroke (70x90), because the NZ classic rules require retention of original bore and stroke. This does limit it.

Cheers

Pete