175 semi close box

Good evening gentlemen,
i have heard through the grapevine of some bod who can convert a 4 speed box into a more usable set of ratios,could be nice for 175 boys.
Mike ,could you let us know whats legal ?
Has anyone run a modified set successfully in the past?
could be the answer to run a 175 right up the front.

Nick

P.S.still waiting for more response on superstock 175 !

Is this bod Frank Perkins?? He used to make /convert the output pair for a 4 speed box 2,3,top were ok but bottom was too low hence what you ended up with was a 3 speed box and a gear to get you off the line? Ask some questions Nick .. are they new bespoke gears or converted road gears??

My view is allow a particular gear mod if it makes prep of a 175 easier, also any 175s on a 4sp(road or roadish) box should free up a 3sp cluster for a 125 runner ....

Opinions gentlemen......

I,ve been working on various ratios already both normal and abnormal ratio,s the Amos 185 already has a close ratio box does anyone now what 1st gear ratio was and did it get off the line okay.
The standard ratio is 2.84:1 I believe 2:1 will be to high and 2.15:1 or 2.3:1 may be a better option ,allot more thought required.
regards Dave

I believe the problem with the 4sp c/r boxes was top gears(output pair) used to break all the time....
Can anyone from the dim and distant past comment on this ... ?

Nick 175s are already competitive and running at the front see 2008 results - most championship wins by a 175 that year...
2nd and 3rd in championship 175's... Just very good seasoned riders.... and before you say it - lap times have not got any quicker...

Mike

distant passed "ok"

but - "dim"! as in low light" or "dim" - as in dim-wit or stupid. ?? ouch!

I agree and some one has already said if it is'nt broken don't try and fix it. ?

"not sure who said this" !

championship positions 2010
125cc = 1st 2nd 3rd 9th
175cc = 4th 5th 6th 7th 8th 10th

Hi Derek
It wase that said if it's not broke don't fix it wen Tim was first stating he's build and to correct you this first four bikes to finish in the 2010 championship are 125cc Michael was on a ex Tom miller sprint engine regards robbie somewhere near a mc donalds

Evening chaps,
sorry Mike fully taken on Board. I should of maybe phrased it something like more capable of outright wins.
we know its all about high & consistant results to net the championship & remember you running the 175 i think a couple of seasons back .

Nick.
P.s Robbie did you do makky ds at Tunbridge Wells

hi Robbie "what all year" !!

I stand corrected then, glad some one pointed that out, hate to get this wrong"

cheers Rob don't forget my primary chains ?.

regds Derek

Yes nick done mc donalds at tunbrige wells have to over 700 stores all over uk even in the
I O M and got to see Manx practice too at southport at mo Derek yes Michael was on a 125 all last year he should go well this with the new frame if we get it done in time

Mike the only problem I have ever encounted with the 4 speed is the drive dogs need to undercut by 3 deg to stop them keep jumping out of first,also the slots in engage point need the same treatment.Still no feedback on the amos cr gearbox 1st gear ratio.
Dave

Okay finally made a decision on my 1st gear issue its going to be a ratio of 2.37:1 . pressed on gear 19 teeth- mating gear 28 teeth.When changing from 1st to 2nd in a 4 speed box this is how my new ratio will hopefully work out

With a crank rpm of 10,000 /primary ratio 2.23=4932.73 rpm at clutch
4932.73 /2.37=2081.32 (new 1st g ratio)
4932.73 x1.83=3808.81 (x 2nd gear ratio)
3808.81 x2.23=8493.66 rpm
At 8493.66rpm this puts me in lower part of my power band happy days.It,s going to take two weeks for a cutter to arrive via ebay,or if anybody can recommend any gear cutting workshops.
cheers Dave

Dave
I believe Trevor has already posted this information some time back, all the gears and ratios previously -

Try looking back at the old posts, Trevor may have missed your request for help on this post, I think he only reads the (interesting) technical posts.

kind regards Derek

Thanks Derek,
I got Trevor,s info forwarded to me ,it,s not applicable because he went the hole hog full close box with multiple sets of gears changed.I did search through all the old posts but nothing new grabbed my attention.Making enquiries tonight about getting the gears wire cut in China ,it would save me a mass of time.
regards Dave

steve wang industries in China - he can help you, We ran a numbner of his companies, manufacturing aftermarket products in the uk,
Directly they will be very cheap, but make sure you supply the metal, you can not rely on metaligy in China "VERY VARIED", I supplied all the metal for mY gears, BS-EN36 to be case hardened 0.040/60" thou depth then ground. except press on gear teeth root issues, especially at at BSA, so depth slightly less, or use en40b and nitride after finishing.

PM Alan on gears.

Derek

Hi everyone,
thought i would dig this up again,i have recently heard some ramblings of a possible new build bike sporting a nice 4 Speed gearbox (is this true Colin).
i am not to sure but i did have a conversation with Rex about this at mallory so perhaps this is something he has developed, would be a nice mod to go with his off the shelf Heads, barrels & and ignitions.
We would almost be at the point of having a 175 race kit available for those who are looking
for a alternative to the BTW barrel.
Cheers Nick