Changing out different sized front sprockets on 250r atc

[sunnyday]

The only person who can honestly answer that question is you. With a GPS, 11 tooth and 14 tooth sprockets and a run using both. Anything else would be a well informed guess..

There was a gearing calculator on the internet but it seems to have been removed.

Okay...I thought someone kinda had a good estimate of how many mph is lost off top end speed , per tooth that is deducted from front sprocket.

Ive read that 1 tooth changed on front sprocket is equivalent to 3 teeth changed on rear sprocket.

[briano]

While being repaired are you going to put rocks in your other bikes?

[sunnyday]

While being repaired are you going to put rocks in your other bikes?

Nope, im gonna take em out now . The damn things get in the way of the piston and cylinder.

[Mr. Clean]

Here ya go. Keep in mind this calculator does NOT take into account any "real" world factors (friction, drag etc....) Also looks like you need a Tach for RPM's.

http://www.ljsoftware.com/DS/GearSpeedCalculator.html

[sunnyday]

Here ya go. Keep in mind this calculator does NOT take into account any "real" world factors (friction, drag etc....) Also looks like you need a Tach for RPM's.

http://www.ljsoftware.com/DS/GearSpeedCalculator.html

apppreciate it...

and you helped out, without adding anymore sarcastic troll remarks.

:}

now thats the kinda help/advice people are probably looking for on this forum.

[sunnyday]

While being repaired are you going to put rocks in your other bikes?

Looks like we have another troll/baiter !

I guess all these posters dont abide by the forum rules ?

good to know.

[4x4van]

Just to add something here;

Stock gearing on a 85-86 250R is 13/39, so 1 tooth front is equivelant to 3 teeth rear at that initial starting setup. But since you started with a 14 on the front (I am going to assume that the rear is still 39?), then one tooth up front is no longer equal to 3 in the rear, it's equal to 2.78.

Personally, I would never go lower than 12 on the front of a 250R, as it is so small that a number of problems will occur. The chain will dig into the plastic chain guides too much, wearing them out and wearing the chain out. It creates such a tight radius turn at the front sprocket that chain wear will be accelerated from that as well. And finally, it allows a larger gap between the chain and the stock casesaver under the countersprocket cover. That gap could easily allow the chain to double up and crack the engine cases if it becomes loose, breaks, or even if it is just slightly out of adjustment.

The reality is that the top speed is irrelevant unless you are going to ride it at top speed. It will go as slow as you want it to go. Want to go slower? Downshift. The stock gearing on a 250R is great all-around gearing, even for slow woods riding. I have to agree that running 25" tires and 11/39 gearing on a 250R is ludicrous. So is the type of riding you want the bike for. At low speeds, it will run hot because of lack of airflow through the radiator. Sure, you have every right, but those of us who want to see these bikes (particularly 250Rs) well maintained and not abused are shuddering at the thought of intentionally turning a thoroughbred racehorse into a plow horse. And when we hear of rocks for silencer packing? Wow, not much more to say. That's not "thinking outside the box", that's simply not thinking, period.

[RIDE-RED 250r]

I have to add that when you go to larger rear tires it will gear it back up counter-acting to a degree your gearing down by going with a smaller drive sprocket.

Don't go any smaller that 12 teeth on the drive and stick with 20" tires.

And pay attention to the advice you are given, particularly about prolonged low speed riding on the R. The old R's don't have those nifty little electric fans that will kick on when she starts to get hot like the newer quads do. They rely solely on free air flow through the radiators to stay cool. So, hot summer day+prolonged low speed riding=undue wear and tear and possible failure of the topend.

This 2-stroke is a high performance, race intended machine. Not a YT125 that can putt around all day in 1st gear without issue. Using it the way you say you want to will be problematic, I guarantee it.

[swampthang]

sunnyday you seem like a very stubborn person. You ask for advice but seem to already have you mind made up and will not except others advice. Most of these guys on here have been riding or racing trikes sense day 1 and have TONS of useful knowledge. If you have to down gear you R that much to ride in the woods with 21" tires there must be something wrong with your bike. A good running stock R will have gobs of power in 1st,2nd,and 3rd for woods riding. Have you ever seen footage of the old blackwater 100 race on youtube? Those guys rode 250r's threw some of the nastiest terrain imaginable and I guarantee they didnt have crazy low gears or monster tires to do it. Whats wrong with your Big Red? Maybe you can find the info you need on here to fix it back up. Honestly if your having trouble riding your R in the woods the Big Red might be a better machine for you. But thats just my opinion take it or leave it, but I know others onthe board feel the same as i do.

[sunnyday]

sunnyday you seem like a very stubborn person. You ask for advice but seem to already have you mind made up and will not except others advice. Most of these guys on here have been riding or racing trikes sense day 1 and have TONS of useful knowledge. If you have to down gear you R that much to ride in the woods with 21" tires there must be something wrong with your bike. A good running stock R will have gobs of power in 1st,2nd,and 3rd for woods riding. Have you ever seen footage of the old blackwater 100 race on youtube? Those guys rode 250r's threw some of the nastiest terrain imaginable and I guarantee they didnt have crazy low gears or monster tires to do it. Whats wrong with your Big Red? Maybe you can find the info you need on here to fix it back up. Honestly if your having trouble riding your R in the woods the Big Red might be a better machine for you. But thats just my opinion take it or leave it, but I know others onthe board feel the same as i do.

Id like to reply to your above post on specific points :

1. " you ask for advice ..but will not accept others advice "

If you go back and read my post that started this thread, you will clearly see , im not asking for advice...im asking for information { there is a difference ] . In other words, I did not ask anyone if I " should " change the front gear size " ...I asked how much mph I can expect to be trimmed off top end speed.

2. " other didnt have crazy low gears or monster tires to do it ...

I wasnt aware that going from a 20 " rear tire..to a 21" rear tire { like I have done } would be considerd going to " MONSTER TIRES" ...nor was I aware that going to a 11 tooth sprocket was going to a " crazy low gearing" ...ecspecially considering that stock front gear is 13 tooth and the fact that I was going smaller with front sprocket but taller with rear wheels , which will also compensate for dropping 2 teeth lower then stock gear .

3. " you sound like a stubborn person..

Well guess what , there are a few people on this forum, that sound like assholes and dickheads to me...but so far I havent insinuated those names towards them , because I thoughT there were specific rules in place, to help keep this forum friendly and running smoothly.


and then there was another person who claimed that going to the 11 tooth gear , would surely rub my chain pad away because of the constant rubbing...well I pre checked that , and it is not true on my atc...because when I sit on the bike, it actually raises the chain slightly above the pad so it isnt rubbing .

Now im sure some of the so called " experts" will find some way to disagree with the above FACTS that I just pointed out...and thats fine...

but I seriously do not understand the need for certain people on here to continually use the name calling, baiting, and verbal slights/ wrong assumptions towards me. Evidently this type of behavior is acceptable on this forum, so I think I may also start using such behavior.

Now, all I need to do is to decide how many rocks to put in my cylinder.

Bhwahahahahaha

[swampthang]

Id like to reply to your above post on specific points :

1. " you ask for advice ..but will not accept others advice "

If you go back and read my post that started this thread, you will clearly see , im not asking for advice...im asking for information { there is a difference ] . In other words, I did not ask anyone if I " should " change the front gear size " ...I asked how much mph I can expect to be trimmed off top end speed.

2. " other didnt have crazy low gears or monster tires to do it ...

I wasnt aware that going from a 20 " rear tire..to a 21" rear tire { like I have done } would be considerd going to " MONSTER TIRES" ...nor was I aware that going to a 11 tooth sprocket was going to a " crazy low gearing" ...ecspecially considering that stock front gear is 13 tooth and the fact that I was going smaller with front sprocket but taller with rear wheels , which will also compensate for dropping 2 teeth lower then stock gear .

3. " you sound like a stubborn person..

Well guess what , there are a few people on this forum, that sound like assholes and dickheads to me...but so far I havent insinuated those names towards them , because I thoughT there were specific rules in place, to help keep this forum friendly and running smoothly.

I'm just going to show you in your own words why I responded.

Does anyone know what is the tallest rear tires currently available that will fit on the rear rims of a stock 1985 honda atc 250r and also on the front rim ?

the 22 " tall tires a bit to low profile for riding in my area { woods , trails, with streams, logs to ride over, etc...}

so can anyone recomeend a 24" or 25" tire that will work on my rear rims...along with telling me what size front sprocket I should switch to, so I dont burn the clutch up

this is for a 85 atc 250r

I have 1 rim that has a slow leak around the outer bead/ outer rim of the wheel....will fix a flat seal it ?

the bike had a top speed of 85 + mph

I think your own quotes speak for them self. I'd stay away from the name calling if I was you thats a sure fire way to get banned

[sunnyday]

I'm just going to show you in your own words why I responded.











I think your own quotes speak for them self. I'd stay away from the name calling if I was you thats a sure fire way to get banned

and guess what , almost all those quotes you reposted , in which you insinuate I am asking for advice , is actually asking for information...

Let me try and make it clearer, cause you seem confused :

This question is more of a question seeking factual information : { NOT PERSONAL ADVICE}

" does anyone know the tallest tires that would fit on a 250r "

and then this question is more seeking personal advice ;

" should I put 17 rocks in my cylinder or 32 rocks in my cylinder ' ?

One question is geared more gaining information , and the other question is geared more asking other peoples personal advice.

Now, evidently, as stubborn or looney as I must be { as insinuated by people like yourself} , even I can see the differences between the above points.

Gee, just think, you and others may have learned something from a novice like myself.

As far as the name calling, I agree, its a bad idea to start....and its probably a bad idea to respond to other posters in a way in which you insinuate they are stubborn, or stupid , or liars ,etc.

On this thread, I did not ask anyone " advice" if I should go to a 11 tooth sprocket....I asked how much to speed would be reduced. I have already installed the 11 tooth sprocket and 21 inch rear tires...so there would be no need for me to ask others if I should do it....

furthermore...your claims that " going to MONSTER REAR TIRES" are absurd...going from a 20" rear tire to a 21" rear tire is not a monster tire.

So, we learned there can be a distinct difference between :

asking for factual knowledge

or

asking for personal advice.

[sunnyday]

Id like to add another comment.

There is another thread recently started on this forum, in which somone posts a video of them breaking the law, running from the cops on there atv/atc / riding on the road, etc. It seems that many posters are actually impressed with this thread/ video , as if it were so cool and beneficial to people who ride these vehicles.

IMHO...such actions do not help this hobby , they hurt it immensely...

and yet it seems as though some of the people who are harrasing some of my posts/ questions, are suppporting people breaking the law and running from cops on their atv's..

UNREAL....must be to much fluoride in our drinking water ?

[TimSr]

In response to your original question:
These are rough generalities for most 6 speed sport trike gearboxes

One tooth on the front = 3.5 teeth on the rear
One tooth on the front = 2" of rear tire size (2" in a tire may not actually be 2")
Two teeth on the front = 1 full gear

So if you went from a 14 to an 11, and went from 20" to 21" tires, roughly speaking you'll top out about where you used to top out in 5th gear.

I hate stock 250R gearing for trail riding. Not because there is "not enough power" but because you can't drive slow without clutch feathering. 250R's have lousy clutches that already wear out fast without having to drive while slipping it all the time. Nothing worse than hillclimbing (REAL hillclimbing) while trying to feather a clutch over rough rocks and roots. 11 tooth works fine on a 250R and clears slider - not so good on a TriZ. We have setup TimJr's 250R with 11/42 gearing for 22" tires for the Big Valley harecramble on April 1. I will say 11T fronts wear out a lot faster than 13's, and its better long term to go with a 12T and a 42 rear sprocket if you decide you like the gearing you have now. Personally, I've never found the need to go even 65mph unless you are running 1/4 mile drags.

[sunnyday]

In response to your original question:
These are rough generalities for most 6 speed sport trike gearboxes

One tooth on the front = 3.5 teeth on the rear
One tooth on the front = 2" of rear tire size (2" in a tire may not actually be 2")
Two teeth on the front = 1 full gear

So if you went from a 14 to an 11, and went from 20" to 21" tires, roughly speaking you'll top out about where you used to top out in 5th gear.

I hate stock 250R gearing for trail riding. Not because there is "not enough power" but because you can't drive slow without clutch feathering. 250R's have lousy clutches that already wear out fast without having to drive while slipping it all the time. Nothing worse than hillclimbing (REAL hillclimbing) while trying to feather a clutch over rough rocks and roots. 11 tooth works fine on a 250R and clears slider - not so good on a TriZ. We have setup TimJr's 250R with 11/42 gearing for 22" tires for the Big Valley harecramble on April 1. I will say 11T fronts wear out a lot faster than 13's, and its better long term to go with a 12T and a 42 rear sprocket if you decide you like the gearing you have now. Personally, I've never found the need to go even 65mph unless you are running 1/4 mile drags.

and I agree with your comment about " feathering' when riding in tight woods in 1st gear , with the clutch....so this is something I was trying to improve by going smaller in front sprocket..

I also appreciate your information and ability to deliver it without sarcastic comments.

If I find out that the 11 tooth sprocket doesnt suit my expectations, I can always go up 1 more tooth...no big deal really...

I find it funny that some of these posters act like going from a 13 tooth stock sprocket to a 11 tooth , is gonna blow up the atc....or damage the credibility of 3 wheeler experts around the world.

LOL.