13 Tooth front sprocket

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13 Tooth front sprocket

Post  JimmyO23 on Mon Jan 10, 2011 3:38 am

Has anyone outfitted their pig with a 13 tooth sprocket?? I was wondering if you had to change the rear sprocket. I was told by a KTM owner (I know, what the hell does that s--t head know) that you have to add 5 teeth to the back for everyone lost in the front.

Also let me know what sort of difference it made in your ride.

Thanks
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Calculate what you want to effect beforehand

Post  BuRP on Mon Jan 10, 2011 9:24 am

Some have yes, there's a recent post here somewhere about this.
Nothing wrong with a KTM, but maybe you're referring to the owner? Shocked Could be, dunno the chap Wink
However, for every tooth dropped at the front add 5 at the rear???? That depends, on what gearing you have and on what you actually want to effect - a shorter or longer gearing, more or less speed?

Say you have 14 front & 42 rear >> that makes for a (chain-only!) gearing of 3:1 (42 / 14 = 3).
You want more speed? Then you have to DEcrease that (gearing)number, by either reducing teeth at the rear or increasing them at the front, eg (rear) 14/40=2.86 or (front) 15/42=2.8. Or do both at the same time if you like, but calculate the number first!
Obviously, when you want a lesser (top)speed INcrease that number, and then just lessen teeth at the front or add to the back - or, again, do both.

Calculating the ratio beforehand is best, and this will give you a proper indication of what you will effect.
Say your bike does 150 (Km/hr) with 14/42=3, and you want only 120 as topspeed. Then calculate 150/120=1.25, multiply your current gearing-ratio by this, ie 3*1.25=3.75, then find teeth-combinations which will match this closest - for instance 13 front & 49 back >> 49/13=3.77

Personally I like odd teeth-numbers, front & back, as the chain will not wear the sprockets with the same link-type at the same tooth all the time, and therefore the sprockets (chain too!) will last longer.
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Re: 13 Tooth front sprocket

Post  Mauser on Mon Jan 10, 2011 2:58 pm

I run a 13tooth on the front and love the way she rides, back is 51tooth. great for the back lanes and off-road of course. You won't want to do much more than 55mph to be honest but I like riding less than 20 even down the lanes, more enjoyable to watch the world go by slowly.

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Re: 13 Tooth front sprocket

Post  JimmyO23 on Mon Jan 10, 2011 5:46 pm

BuRP wrote:Some have yes, there's a recent post here somewhere about this.
Nothing wrong with a KTM, but maybe you're referring to the owner? Shocked Could be, dunno the chap Wink
However, for every tooth dropped at the front add 5 at the rear???? That depends, on what gearing you have and on what you actually want to effect - a shorter or longer gearing, more or less speed?

Say you have 14 front & 42 rear >> that makes for a (chain-only!) gearing of 3:1 (42 / 14 = 3).
You want more speed? Then you have to DEcrease that (gearing)number, by either reducing teeth at the rear or increasing them at the front, eg (rear) 14/40=2.86 or (front) 15/42=2.8. Or do both at the same time if you like, but calculate the number first!
Obviously, when you want a lesser (top)speed INcrease that number, and then just lessen teeth at the front or add to the back - or, again, do both.

Calculating the ratio beforehand is best, and this will give you a proper indication of what you will effect.
Say your bike does 150 (Km/hr) with 14/42=3, and you want only 120 as topspeed. Then calculate 150/120=1.25, multiply your current gearing-ratio by this, ie 3*1.25=3.75, then find teeth-combinations which will match this closest - for instance 13 front & 49 back >> 49/13=3.77

Personally I like odd teeth-numbers, front & back, as the chain will not wear the sprockets with the same link-type at the same tooth all the time, and therefore the sprockets (chain too!) will last longer.


Thanks for all the info Burp. No, the "chap" is a good guy, just too pro KTM for my liking. I went riding with him and another KTM owner and after lunch he asked me if I felt out of place because my bike didn't have an oil leak under it like theirs did thats funny
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Re: 13 Tooth front sprocket

Post  JimmyO23 on Mon Jan 10, 2011 5:48 pm

Mauser wrote:I run a 13tooth on the front and love the way she rides, back is 51tooth. great for the back lanes and off-road of course. You won't want to do much more than 55mph to be honest but I like riding less than 20 even down the lanes, more enjoyable to watch the world go by slowly.

Does your bike have more wheelie popping ability then it did before?? I ride alot of desert and my bike climbs hills easily but I want to be able to hop the front tire over dips when I have too.
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Re: 13 Tooth front sprocket

Post  Mauser on Mon Jan 10, 2011 11:14 pm

JimmyO23 wrote:
Mauser wrote:I run a 13tooth on the front and love the way she rides, back is 51tooth. great for the back lanes and off-road of course. You won't want to do much more than 55mph to be honest but I like riding less than 20 even down the lanes, more enjoyable to watch the world go by slowly.

Does your bike have more wheelie popping ability then it did before?? I ride alot of desert and my bike climbs hills easily but I want to be able to hop the front tire over dips when I have too.

Hi it doesn't seem to be over keen on pure power wheelies, I am not really into rev'ing the engine either so not really sure what she would be like @ them. Sorry not much help I do find the back end spins easy off-road so maybe it just spins rather than lift the front ?.

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Re: 13 Tooth front sprocket

Post  BuRP on Tue Jan 11, 2011 9:01 pm

Lifting the front (wheelie) over a dip/obstacle:
- stand up
- lean back & hang off the bars (ie taking weight off the front & putting more on the back)
- momentarily close the throttle (so that the front compresses a bit)
- then open it fully (so that the front extends, therefore reduces the weight on the front if not lifts it) and pull the bars towards you simultaneously.
This works most often, but if not (in too high a gear for instance) then feather the clutch a bit too aid it up. And yes, a shorter gearing will help with all this.

Mind you, a pumper-carb (an aftermarket carb with acceleration-pump - which the std-carb does not have) will quite likely ease matters also, as the engine will respond crisper/quicker due to the simple fact that juice is squeezed-in instead of it having to suck it in (which doesn’t happen that sudden, it takes more time).

If, after some practice, this won’t work for you then buy a 490 2-stoke, keep it always on song, and gear it awfully short.
PS: send us a mail from the hospital will ya?  LOL
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Re: 13 Tooth front sprocket

Post  Mauser on Wed Jan 12, 2011 1:27 pm

BuRP wrote:Lifting the front (wheelie) over a dip/obstacle:
- stand up
- lean back & hang off the bars (ie taking weight off the front & putting more on the back)
- momentarily close the throttle (so that the front compresses a bit)
- then open it fully (so that the front extends, therefore reduces the weight on the front if not lifts it) and pull the bars towards you simultaneously.
This works most often, but if not (in too high a gear for instance) then feather the clutch a bit too aid it up. And yes, a shorter gearing will help with all this.

Mind you, a pumper-carb (an aftermarket carb with acceleration-pump - which the std-carb does not have) will quite likely ease matters also, as the engine will respond crisper/quicker due to the simple fact that juice is squeezed-in instead of it having to suck it in (which doesn’t happen that sudden, it takes more time).

If, after some practice, this won’t work for you then buy a 490 2-stoke, keep it always on song, and gear it awfully short.
PS: send us a mail from the hospital will ya?  LOL
Great advice but most importantly don't let your hand slip of the bars when your pulling backwards lol.

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Re: 13 Tooth front sprocket

Post  Hew on Wed Jan 12, 2011 4:18 pm

I'm running 14-52 for trail riding. 60mph is about the max I want to do on the road with knobblies anyway so this is fine. It will run a lot faster but gets a bit buzzy.
Before the last chain and sprockets I did experiment with 13 - 51 and found this to be great for starting off and steep slippy rocky and mucky slopes but just too low in general for me. I had been running 14-51 prior to this
lowering the gearing also has the advantage of bringing 2 and 3 into play for most steep hills and eliminates the embarrassment of finding neutral when the revs start to drop.
Another big plus is being able to ride trickier tight sections with the clutch out which is far less tiring for the arms and better for the bike.

For sand riding these are not really what you are after and as BuRp says you are looking for the instant hit of a pumper carb to hoist the front when you hit a dip in a high gear. I've got a mikuni fitted and love the way it leaps forward, even at the point of stalling, when I twist the throttle.
Good luck
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Re: 13 Tooth front sprocket

Post  BuRP on Wed Jan 12, 2011 5:11 pm

Hew,

do us - well, me anyway - a big fav & post a pic of your mounted carb?
Reason being I'd like to see if it is a proper fit, and also how the dual cables will run (won't even consider a single cable only). Somehow I don't like the Edelbrock-carb often mentioned - which I dunno from a bar of soap, however Sunlight I do know.... enter Mikuni. Besides, getting the jets for the latter is much easier for me too.
You bought it as a 'kit' maybe, and what type/size is it? And why did you buy it - std one shot, or you were after that 'hit'?
Lastly, how easy/difficult does it start, and idling-adjustment works how? Reason I ask is I've been considering exactly such carb, but got a 27L tank on it (which kinda 'blocks' the sides).
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Re: 13 Tooth front sprocket

Post  Hew on Wed Jan 12, 2011 6:27 pm

I will take a photo of the mounted carb but it may take a few days if it is not up in a week let me know.

I wanted an edelbrock for the never flooding claim

When it turned up it was a Mikuni I believe they are sold as kits complete with manifold and cables. Genuine mistake by the seller.
Again after some uming and ahing I decided to keep it. Some reading had showed it was a good carb on the XR.

Some more reading gave me the jet info I needed. all the jets were different to what was fitted but readily available.

The supplied double cables were shorter than the originals and would not reach the Renthal dakar high bars I have fitted. The cables just fitted with the original bars but the bike did not feel natural so I had new cables custom made.

First ride put a huge smile on my face. It ripped.
I really don't know about top end performance as its not really where I do my riding but it feels OK
What I love is the instant snap when pulling the throttle at very low or medium revs.

I had largely sorted my issues with the standard carb by the time this one turned up but I would not change back now.
Starting is as good if not better than standard. Sometimes it will keep running on its side other times it will flood if I just look at it.

It fits with the standard tank just needing a slight tilt off vertical otherwise pulling the throttle moves the tank.

I do have a IMS 17 liter tank but have yet to see if this needs modifying. I have again read that some tanks need to be heated up and moulded slightly to give clearance. I found the IMS made the bike feel very top heavy on tight trails so have stuck with the original. There is not as much wilderness in the uK so it is not too difficult to plan a fuel stop every 100KM.
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Re: 13 Tooth front sprocket

Post  JimmyO23 on Fri Jan 14, 2011 10:14 pm

BuRP wrote:Lifting the front (wheelie) over a dip/obstacle:
- stand up
- lean back & hang off the bars (ie taking weight off the front & putting more on the back)
- momentarily close the throttle (so that the front compresses a bit)
- then open it fully (so that the front extends, therefore reduces the weight on the front if not lifts it) and pull the bars towards you simultaneously.
This works most often, but if not (in too high a gear for instance) then feather the clutch a bit too aid it up. And yes, a shorter gearing will help with all this.

Mind you, a pumper-carb (an aftermarket carb with acceleration-pump - which the std-carb does not have) will quite likely ease matters also, as the engine will respond crisper/quicker due to the simple fact that juice is squeezed-in instead of it having to suck it in (which doesn’t happen that sudden, it takes more time).

If, after some practice, this won’t work for you then buy a 490 2-stoke, keep it always on song, and gear it awfully short.
PS: send us a mail from the hospital will ya?  LOL

I will first try playing with the throttle as you suggested. If that doesn't work, I will get on a 500cc 2 stroke.....I see some for sale on craigslist Wink
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Re: 13 Tooth front sprocket

Post  BuRP on Sun Jan 16, 2011 11:06 am

Hew,

appreciate & will be patient.
When you post it though you may want to post a link to where you bought this kit? I just may buy on there too, that's why.

Jim,

it'll work Bro, same like a 490 2T Cool
Don't forget, when the front's up, to lean forward again eh? That's less weight on the back enabling it to go over whatever you're going over (ditch, stump) easier, and also the landing will be smoother then. Practice makes perfect though - find a smooth road first, then a parking lot with curbs before you tackle fallen trees? Less risk to become a real treehugger this way razz
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Re: 13 Tooth front sprocket

Post  Hew on Wed Jan 19, 2011 1:10 pm

BuRP
I have PM'd the photos to save clogging up the thread about sprockets.
Eddie
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Re: 13 Tooth front sprocket

Post  BuRP on Wed Jan 19, 2011 6:53 pm

Oh, great, thanks Bru!
I'll tell you what: I ordered one already (2 days ago) from XROnly! It was on their list when I ordered a gazillion parts some time ago (which was before I took the carb off, mine's a new one), and I really dunno how I could have missed this item!
So, no link needed, and I appreciate the pics which I'll find as soon as i hit 'send' now..... ;-)
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Re: 13 Tooth front sprocket

Post  bikerman on Fri Jun 22, 2012 2:06 am

burp,
so what carb you have on your piggy now? did you ever change the original one? I was looking into the edelbrook one but want to hear from you guys before I get it. I still have the original tank. no I haven't fix my backfiring yet, been busy sorry guys! eventually I will Embarassed
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Re: 13 Tooth front sprocket

Post  BuRP on Sat Jun 23, 2012 9:15 am

BM,

I go the Mikuni TM40 carb on, and am soooo glad I did!
Hew's pics convinced me to go for it, it is a stupidly simple swap, fits like an identical glove. It comes with a set of cables which are different than the std ones, but I have a fairly high (raised) bar so I got longer cables (ditto clutch & decomp, from the US, forgot where, google for them).
The carb jets easy (XRsOnly carbs come invariably jetted wrong, pls be forewarned) and makes for an immediate 'punch' instead of having to wait a bit, hence lifting the front's a doddle now. Starts first kick, choke's mounted remote (via short cable, it comes like that) hence accessible even with the big tanker on, and this is a mod I can recommend to anyone.

Edelbrock = discontinued!!!!!!! so do NOT buy one, not even second hand, no spares available anymore.
If you want some pics of my carb mail me, you've got the addy.
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Re: 13 Tooth front sprocket

Post  DoctorXRR on Sat Jun 23, 2012 1:41 pm

BuRP wrote:BM,

Edelbrock = discontinued!!!!!!! so do NOT buy one, not even second hand, no spares available anymore.
If you want some pics of my carb mail me, you've got the addy.

What he said on the Edelbrock carb. A buddy of mine runs a shop, customer had an Edelbrock that needed work and no parts available. After messing around with it for a while, they dumped it and put on a Mikuni carb instead. He said even if you find a deal on an Edelbrock online, pass it up.
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Re: 13 Tooth front sprocket

Post  Mauser on Sat Jun 23, 2012 3:26 pm

Hew wrote:BuRP
I have PM'd the photos to save clogging up the thread about sprockets.
Eddie

Poor show and shame on you Hew banana post some pictures on here so we can all see the new carb mad as heck
I could understand Burp not wanting us to see his carb fitted...all that rust and dust would upset us too much BRP smile

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Re: 13 Tooth front sprocket

Post  Chris_w_65 on Fri Jul 08, 2016 8:19 pm

From where can I get the fabled 13T sprocket for my motard?

Regarding TM40, I will be an expert soon and have almost every jet needle and nozzle available - After i get it as damn close as I can get it I will go on the dyno.
First dyno run as a baseline was 49hp on the wheel at 6000ft above sea level - I think we lose 20% power up here.
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Re: 13 Tooth front sprocket

Post  Chris_w_65 on Fri Jul 08, 2016 8:20 pm

Mauser wrote:
Hew wrote:BuRP
I have PM'd the photos to save clogging up the thread about sprockets.
Eddie

Poor show and shame on you Hew  banana post some pictures on here so we can all see the new carb  mad as heck
I could understand Burp not wanting us to see his carb fitted...all that rust and dust would upset us too much  BRP smile

BuRP's bike has not rusted away, I saw it a few weeks back
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Re: 13 Tooth front sprocket

Post  Chris_w_65 on Tue Aug 02, 2016 5:04 am

Talon in the UK claims they make a 13 tooth - Where online in the UK can I buy this unobtanium item? I have someone coming over in a few weeks
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Re: 13 Tooth front sprocket

Post  Hew on Tue Aug 02, 2016 8:32 am

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Re: 13 Tooth front sprocket

Post  Chris_w_65 on Tue Aug 02, 2016 8:49 am

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Re: 13 Tooth front sprocket

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