Custom Made Sprockets... gearing issue

[louisb]

Hi KB'ers

I've had my bike for about a month and have done lots of things to it, change oil and filter, new tyres (changed by myself, 4 hours later!!) adjust, lubricate etc...

The other day I found myself having to go on the hwy back into town... at 100 km/h.

The bike was in top gear and doing 100 km/h at 8600 rpm! which to me is crazy, feels like you really need another gear.

I've been trying to get a smaller rear sprocket but the smallest one is only 3 teeth smaller, I need to go from a 54 tooth rear to a 42. After exhaustive research I've come to the conclusion that i need to get one custom made by someone.

Does anyone know of such a place? any ideas what to do next?

I'd really like to go on a long ride somewhere but sitting at 8500rpm..

[Waylander]

Thought most 250s weren't suposed to be able to do 100km/h?

[Motu]

Try doing a google search,there is a good sprocket crowd in the US,I got a gearbox sprocket for my TLR sent out because those here said it doesn't exist.Then I got a blank for the rear (any bike shop will get one in if you give them tooth no and chain size) and had an engineering shop drill centre hole and stud pattern.

[Rainbow Wizard]

I've been trying to get a smaller rear sprocket but the smallest one is only 3 teeth smaller, I need to go from a 54 tooth rear to a 42. After exhaustive research I've come to the conclusion that i need to get one custom made by someone.

Do the ratio sums first as to what you can change your front sprocket to. But a rear 54 to 42 seems excessive to me, that's over 28% difference!!!! I fail to comprehend how a manufacturer could setup that far out from ideal.

Le Voxan standard rear is 40 but Lindsay ran a 45 to get more acceleration on the track. That's only 12.5% difference and it was any amount. Mind you, it redlines at 9200.

I'm sure you could modify a sprocket to fit way cheaper than buying a new one, even if it meant machining the centre out and grafting in a different one.

[louisb]

Thanks Motu,

I've tried to buy a 42 tooth blank but the guy at sawyers said that they don't make 428 chain blanks, which the spada has. He could very well be mistaken.

Also tried looking for a new front/rear set but the spada has an unusual front spline compared to all other vt250's. plus the cost of a new set and chain!

I might ask some more shops in wellington if they can get 428 blanks.

[louisb]

RW,

you could be right, i've done the calculations and worked out that i'd be getting 100km/h at 6500rpm. which should be fine on a flat road. and if i need more power for a hill i can change down.

I'd still like to try a 42 - 44 tooth rear.

[Motu]

The old theory was 6 on the rear equals one on the front,but that changes with primary ratios.So going down to a 50 or 48 would be my choice,the little motor won't pull a much taller ratio,but depends on how and where you use it.Crap about the sprocket - go to an engineering supply shop then,lots of machinery uses chains....that's where we used to buy bike chains years ago before Oring chains came out.

[v.ros`]

Thought most 250s weren't suposed to be able to do 100km/h?


GRRRRRRRRRRR

Ive done close to 140 km on my gz250. worse was, i was racing with a dude in a Jeep cherokee at night on a 50 km zone and even worse and stoopid was i only had a protective jacket and a helmet on.

Thinking bout it now... i was being stoopid

[flyin]

250's go plenty faster than 100kms (not on the road of course...)
my ZZR250 sits on around 8500-9 on th motorway (100-110) and thats just below the 'Z zone' sp plenty of pull from there even 2up.
ive riden my ZZr to Aucks and back sweet as, no issues holding it at around >13000rpm most th way..... should be fine on a 250

you will loose acceleration putting a smaller sproket on the back and theres hardly heaps in a honda 250!! its a bit light to feel safe with a much higher top speed too (should do 180 already?!?)

[Eddieb]

How often do you ride on the motorway vrs street riding. Going that far down in ratios could make it struggle and be fairly unmanageble in low gears around town, especially with Wellingtons hills.
It would certainly make the low end accleration a lot slower and you may find you have to drag the clutch a lot or cane it on starts to get moving.

My gsxr 250 used to pull similiar revs at that speed, maybe even a bit more because I geared it the other way.

[louisb]

hmmm, maybe i'm just not use to the high revs.

I mostly ride around town and on back roads, mainly because it seems to be revving like a bastard at/or above 90/100km/h.

I read a review of the spada.
http://www.users.totalise.co.uk/~spada/Review/review.htm
Page 4, the guy says "...it can only make you wonder about the longterm prospects of engine wear"

I'm not really interested in top speed, only a smoother cruising speed. At sustained 8500rpm my feet are starting to buzz from the vibration.

Maybe something's wrong with the engine??

Does anybody else have a spada and take it on long trips? or any other 250 vtwin for that matter?

[Jonty]

I cruise around town on my ZXR 250 and frequently hit 19,000 - 8,000 is nearly idling for a 250 inline 4 :whistle: Maybe you should get better ear plugs and give it death!

[flyin]

[QUOTE=louisb]
I mostly ride around town and on back roads, mainly because it seems to be revving like a bastard at/or above 90/100km/h.



I'm not really interested in top speed, only a smoother cruising speed. At sustained 8500rpm my feet are starting to buzz from the vibration.

[QUOTE]

the ZZR doesnt feel too smooth at 90-100 either......... i was criusing at 140 cos it feels better on the bike officer........... :whistle: