Confessions of a 175 race bantam engine - tech info....

I have permission, to publish technical info from 'Jimmys' 175 motor...

Bearing in mind Snowy's new motor is different!! An up-date...

Jimmy's bike was the first 175 to win a Bantam race the Fred Lauchbury Race in 2005!
and in 2008 I attempted to win the championship on it, or parts off it(in 001 chassis) on occasions.

The engine had 4 ports 1 large exhaust 2 narrow transfers and a large inlet port and used a TZ350 piston.
The transfer timmings were of long duration to make up for there narrowness. This was Tom's first 175
motor and he said he should of done a few things differently...

The pipe dimensions are as 175 sprinter info -link from home page.
Carb - Lectron 36mm 5-2 rod 35 powerjet. Ignition timming 1.6mm btdc (PVL)

This is two dyno runs (red & blue) on Jimmys motor done in 2008. First one shows power and the second torque. The third gearings and port timings...

Max Power 22bhp Max Torque 12ftlbs








Please study for information purposes.... We need some faster 175s out there....

ps It says Mick Scutt pipe on 1st dyno sheet it wasn't it was the Andy Bacon -sprinter pipe
Double torque figures and half the rpm printed he didn't reset dyno from previous bike...

Good post Mike,

Will be interesting to see how Andy & James go at pembury ,at mallory James straight lined me on what i am led to believe was
a 2 speed gearbox so i know his speed has increased.Rode teds bike myself so andy will not be disappointed with the motor ,tend to find chassis set up a more personal thing? but he should be competitive.
Like the idea of a fast 175 myself maybe something for the future.
I am suprised that the bigger lads arent all on 175s seems a no brainer to me.

Nick

yes I agree if james has sorted his g/box he should do well, he must be up to something he;s been very quiet.

regds Derek

Mike,

Thanks for that, different approach to my engine but really useful as an insight.

I have a dyno run from my first (2005) "out of the box" Brian White built engine which made similar peak HP (22 I recall ) lower torque (11.5 ish) but didn't have the spread. I will scan and publish all the information next time I get back to Lincoln.

Its true I straight lined Nick with my 2 speed box, but he had slowed down to let me catch up

Unfortunately Derek moving house and work keeping me busy not anything bike related, Al is currently working on the gearbox but as I write I dont have a running motor for Pembrey....sure it will be fine

James

mike so who's currently running this motor

regds Derek

Well knowone??

It no longer exists in that guise... The crankcases, gearbox and other ancillary parts are
in the revamped motor owned by Tom Snow and before you ask? I don't know ! I'm not envolved with it.
I was involved when Jimmy lent me it (006) and I did a lot of things to it i.e. Amal 35 to Lectron 36, Big flywheels
to smaller flywheels(bad move that one) Mick Scutt pipe to Andy Bacon pipe the later being easier to ride but a
little slower ign timming 1mm to 1.6btdc.

I feel there's nothing wrong with bhp or torque figues the problem is they both occur at 9'500rpm, I'm guessing
because transfer duration is to large and transfer area to small?

James be great to see the figures for a multi ported straight from the crate BTW motor....

bettsd wrote:

mike so who's currently running this motor this motor. ?

i think the torque valuse look very low ? but nothing Wrong with the BHP figures.

regds Derek

Derek, (or anyone else for that matter)

Just curious but what sort of Torque figure were you expecting ?

Do you have a target output (bhp and Torque) from your bike in mind that you want to achieve, sensible answers please ?

Had a feeling you did publish something had a look but couldnt find your earlier Dyno posting ?

James

I thought it quite good -- about what Icarus-1 was pulling with 12bhp at 8400rpm at most...

Derek's quoted figure was 240bhp but I think he was Bullshitting???

As promised Dyno trace below from 2005, Brian White Standard build 35mm Carb , 1.5 mm btdc ignition Max power 20.12 bhp max torque 11.5 lbs -ft this was a top gear roll so output in third only, with the bike properly strapped down
[img][/img]

Settings modified later to reduce peak HP and broaden torque to improve lap times and rideability


James

Hi,James,
Great info , could i have your bore dia please and can i assume standard dia crank and rod length values.
I hope i can help with a few observations based on my experience with the 4 speed 186 engine that was
produced by BSA , and , taken over by us from George Todd.

kind regards , Trevor

Hi Trevor,

The build was completed by Brian as per the build a 175 Racer description on the website so 62 bore PE175 Piston, Standard flywheels (two drive sides) Maico 250 125mm Con rod.

If you need anything else, let me know ?

regards

James

Hi James,


What carb settings and pipe were you using for your dyno run if you dont mind me asking.


Regards


Eddie

Ed,

I will see if I can find the data and if I do will post it after the weekend

James

Hi James,


Thanks for that. hope a good weekends racing is ahead, we are gonna try and get to pembrey to spectate on the sunday.



Regards



Eddie

output 240 bhp "Honest"

regds Derek

Derek

Happy Birthday!!! hope you have a great party this weekend!!

Kind Regards Mike

Hi Mike "Many thanks for that"

kind regards Derek

Happy Birthday Derek

welcome to the old farts club

Tony

Hi

Could anyone give me the standard B175 port timings so I can compare with the tuned ones?

Good Evening,

Trevor, did you ever get the information you were after regarding this as i think as you mentioned your observations would be a nice input.



Regards



Eddie

Attn - John Bass

The 2 jagged dyno lines were 2 runs on the 175 with no changes made....

The lines are like they are due to the dyno man not having experience of a
low powered two-stroke with a 3 speed box!!

Talking of 175's of course Team Wildcards Win's (Phil Betty, Miki Sproson) were on an overbored 125 longstroke
(The Famous Josie) 58 x 56 I believe... Phil tell us more??

My impression was that the dyno was too large a capacity where the low end of its measuring/control range was a bit high for a little engine and that the constant -speed control was losing control if you get what I mean -- a dyno operator must know how to control the speed under a given load -- and I don´t think this one did!! -- OR as I said before, it was simply that the stylus was not damped...
No matter -- they were real looking results -- I drew a line through both and used that curve to compare with Peter´s power curve and plotted the energy-stored lines of 4 different (dias & weights) flywheels which did my brain in for a while...
I took the exercise TOOO FAR and TOOO LONG for here and await Peter´s comments `cos I ran into bovver wivv changing Joules & Newtons into HP/ft.lbs of torque but it was good for me -- [(I think???)].

Peter´s gone very quiet -- I hope he is OK. He looked quite thin at Cadwell -- but then didn´t you (Bantam riders) all....!!??

Just bringing this page up to top so 175 interested people can read about Snowy's motor
previous technical life 2002-09