Gearing help needed fast!!

[lammer205]

Hi all,

Just went to fit my new lth clutch ok, went on my engine spec printout and dyno printout from dealer who built it spec sheet states gearing 46/19 ok, cracked casings open and take out rear sprocket very cleary on it is the number 47 front sprocket is 18, now it,s sunday i cannot get the dealer who built it to question him on this fook up, and also do not want to send my clutch back to Austria , i'm on the west coast of Ireland with time running out for the rally next week the chances of me getting time midweek to sort this are slim so can someone please give me advise on what i can do or am i fooked, gearing not a strong point ,, thanx Lammer205.

[Monty]

have a look on this
http://avantone.wordpress.com/ he has a gearbox visuliser.
Basically you tell it what gearbox you have front and rear sprocket and wheel size and it gives you info based on your max revs that you are likely to get. Forget what you thought you had its a 46 x 18 and your option is now a 47 x 18 or stay as it is. I just had a look on a standard 150 italian box and the difference between a 46 and a 47 is about 2 mph you will need an 82 link chain but with your existing setup it shows a stretched 81 or an 82 with a chain tensioner.

[lammer205]

Thanx Monty for that info, just some more detail the engine is a Ts1 ported with a franspeed road pipe , in the shed i also have a 16 and a 17 front sprocket on other casings, i have an 82 chain on the scooter and an 80 chain also the scoot also has a broady chain spreader, what would the preference be here? as far as i know the gear box is an A/F close ratio box i would just like to get the new clutch in and get the gearing close to where i was prior to splitting the cases, can i use the of what i have to get me up and going again thanx, Lammer205. As i've already said gearing to me is like jetting= black magic!!

[joespeed]

assuming your on gp box this will be ok unless you need to pull 120mph on a down hill section of motorway,it will help with hills ,two up and luggage chances are you will be pootling about doing 55mph.lol

[lammer205]

Hi,

if i go with a 46/18 set up on a 82 chain would this be ok for my motor and will the MRB spreader take up the slack on the chain? Thanx .
Joespeed mostly motorway work on this scoot

[Monty]

Your original post said you have the dyno print out for your original set up. The gearbox spread sheet has boxes to add the max revs that most can only guess at.
Using the only AF gearbox shown and your original set up 18 x 47 you would pull 74 mph at 7638 rpm (your dyno sheet will show if you can achieve this or not
Your 18 x 46 new clutch will pull 76 mph at 7678 rpm so you should gain 2mph.
To me its a small change and not going to make a big difference as long as you could reach the power band on your pipe on your original set you should be OK
You will go faster without a slipping clutch so that has to be better.
The 82 link chain should fit without a problem. I presume your tensioner pulled down to loose the slack on the original set up.
Fit it

[lammer205]

Hi Monty and again thanx, on my engine i have an mrb chain guide top and also lower chain guides so not a tensioner but could these be adjusted to take up any slack on the chain or will it need a chain tensioner to pull the chain down, thanx again fella, Lammer205.

[Monty]

OK if it was a 82 link on the 47 crown it will be slacker than it was. so you may need a pull down adjuster.if its too slack.
Its not ideal but a 19 front will match your chain to the 46 but your final ratio will change to 4.84 it was 5.22 on your original set up so may be a step to far.
The 18 x46 gives 5.11 and is not far away from your starting point hence saying go for it if you can get round the chain. I would not go for a stretched chain as they are buggered before you start.
The black art is maths but your riding style and pipe has the biggest factor at the end of the day. If you are riding balls out and like to keep in your pipe power band you may find the 19 a step to far. if you have low down grunt and dont like it reving its nuts off it could work. My guess is that as you have dynoed it its the former.

[lammer205]

Hi Monty, the chain needs a pull down tensioner so i'll be getting one of those as it will be the easiest option at the minute , as for riding style this scoot suits motorways and fast a roads so as you said i,ll not be far of the original gearing and that will do me for now, cheers again and thanx Lammer205.