Upgrades for CRF250

[Farangwithaplan]

11 hours ago, Gnasher328 said:

Hi Again

The original info is on Ride Asia, specifically :-

https://www.rideasia.net/motorcycle-forum/threads/crf-mods-and-improvements.2338/page-3

 

Note the comment by 'TwoWheels' below my post. My comments on the gears said 'as low as 3rd now 5th 6th' that is I can use 5th instead of third. Now no need to change sprockets.

 

You mean the part in the thread that you linked where it states " Another difference between the 2 bikes is 1 Gnashers is a dirk bike and mine a motard. "

 

According to a quick check, the motard and the dirt models have different tuning, different rim radiuses to go with the different environment and that would back up the different tuning. They also most probably have different gear box ratios.

 

I stand by my original points.

 

 

[Farangwithaplan]

43 minutes ago, Farangwithaplan said:

 

 

delete

[AllanB]

1 hour ago, Farangwithaplan said:

As I said, total airflow is not always the most important thing in regard to an airbox. Reread my post. All engine manufacturers balance a fine line between power and legislation for noise and emissions. Why keep the airbox at all if removing air restriction is the only factor? You could just have an open air filter with a shroud over it to protect it from weather?

 

If you don't agree with lighting the mass of moving parts then you are disagreeing with physics - not me. But yes a smaller sprocket will lower change the gearing and is a common option. But power output will not change and you still have the heavier parts to turn to get movement.

 

a 13 tooth front is getting a very tight radius and might be fine for the CRF, but I would go to a larger sprocket at the rear. Chain will last longer and so will the polyurethane chain guide on the from top of the swing arm near the front sprocket. Ratios are easy to work out. What is front and back standard teeth?

I think you should re-read my reply:-

1. I have already screwed up Hondas good work by changing the exhaust characteristics, so whatever I do now is experimental. Plus the legislators have lead Honda away from the ideal power/torque figures, in terms of their noise and immisions specs. If my fiddling alters these slightly I don't care.

 

2. I didn't say lightening parts made no difference, I said it would make little difference to the torque on this bike. Indeed increasing flywheel weight for example, can have a positive effect on torque, so this is no simple equation and IMO, the idea is not economically viable.

 

3. You are correct about increasing the driven sprocket as it reduces component wear, however going 13t is the way to start, for the following reasons. 1. It is cheaper, as it employes the same chain. 2. It is easier, as the rear wheel doesn't have to be removed. 3. It can easily reversed if it doesn't work. 4. When the chain does wear out and the new ratios are proven to work, you can upgrade everything then, which is correct practice.

[thaiguzzi]

4 hours ago, Farangwithaplan said:

 

a 13 tooth front is getting a very tight radius

The first and easiest and most popular mod on a Big Red CRF250L. 1000's of owners worldwide cannot be wrong.

Lowering the gearing by fitting a bigger rear sprkt increases the chances of buying a new longer chain.

 

My ty250 Yamahas run a 10T front sprocket. Stock gearing. On a 520 chain. Most trials bikes run a 9, 10 or 11T front sprocket with 520 chain.

You were saying?

[Farangwithaplan]

1 hour ago, thaiguzzi said:

 

My ty250 Yamahas run a 10T front sprocket. Stock gearing. On a 520 chain. Most trials bikes run a 9, 10 or 11T front sprocket with 520 chain.

You were saying?

I said exactly what I said. Reread it without looking for problems that aren't there. I said the radius is getting tight. Will A tighter radius cause more guide wear? Yes it will. Basic geometry.

 

I have also noted in  two previous posts that a smaller sprocket is a common option and is fine.

 

I don't doubt anything you say. What is your point? Can you actually highlight where I disputed what you say? I'll bet a coke you can't.

 

What is the radius at the front of the swingarm mount on your trials bike? What is the radius on the swing arm mount of the CRF? I'd be willing to put a few beers on it that a 9 tooth sprocket will not fit on a CRF and I have never bothered to look at one.

 

9 tooth sprockets work on trials bikes because, you know, they are designed to. Because trials bikes by their very design have less chain revolutions than most other bikes and are ridden a lot less distances, of course you are going to see a lot less wear. Start comparing apples with apples.

 

 

 

 

 

[Farangwithaplan]

4 hours ago, AllanB said:

I think you should re-read my reply:-

1. I have already screwed up Hondas good work by changing the exhaust characteristics, so whatever I do now is experimental. Plus the legislators have lead Honda away from the ideal power/torque figures, in terms of their noise and immisions specs. If my fiddling alters these slightly I don't care.

 

2. I didn't say lightening parts made no difference, I said it would make little difference to the torque on this bike. Indeed increasing flywheel weight for example, can have a positive effect on torque, so this is no simple equation and IMO, the idea is not economically viable.

 

3. You are correct about increasing the driven sprocket as it reduces component wear, however going 13t is the way to start, for the following reasons. 1. It is cheaper, as it employes the same chain. 2. It is easier, as the rear wheel doesn't have to be removed. 3. It can easily reversed if it doesn't work. 4. When the chain does wear out and the new ratios are proven to work, you can upgrade everything then, which is correct practice.

1. I did reread, thanks and I understood what you said but my point still stands. Good luck with improving your power output with the breathing of the airbox. It can be fun modifying things.

 

2. I'm not about to do the math to convince you.

 

3. I agree. If the extra wear is not an issue and the ratio change is not too much for your style of riding, enjoy it. Just curious, how many KM do you have on the chain and sprockets now?

 

 

 

[Kwasaki]

19 hours ago, AllanB said:

You say "Exactly it would be a waste of time two up and luggage on a 250." Don't quite undestand that, I rode VN on a 100cc well used Wave and plenty of guys out there are riding the range on a 125, why is 250cc not enough.

 

My issue is with nothing more than the poor torque band, I am not looking to win the Dakar.

Well in that case just the bike as it is IMHO.

[AllanB]

12 minutes ago, Kwasaki said:

Well in that case just the bike as it is IMHO.

My original gripe was the lousy torque band and that is the only problem I am considering.

 

There is no perfect bike, but I bought a CRF and it looks good, it fits me, with the my cheapo seat mod it is quite comfortable, it fits on my truck and most importantly, it handles crappy roads like a dream and means I don't fall off when I hit a pothole/drain/dog/fallen tree/drunk/another fallen biker.

[canthai55]

Want more torque ? Burn more fuel.

Easiest way - increase displacement or forced induction.

Re-engineer the engine ? How is your knowledge of fluid dynamics ? Have a flow bench to check your results ?

Had my CRF for 2 years. Read all the forums, seen all the dyno charts, read about all the mods. Every case - more HP comes at a higher RPM

Best bang for the buck - swap a CB300 engine.

 

[Kwasaki]

16 hours ago, AllanB said:

My original gripe was the lousy torque band and that is the only problem I am considering.

 

There is no perfect bike, but I bought a CRF and it looks good, it fits me, with the my cheapo seat mod it is quite comfortable, it fits on my truck and most importantly, it handles crappy roads like a dream and means I don't fall off when I hit a pothole/drain/dog/fallen tree/drunk/another fallen biker.

Agree but find my 2017/2018 updated CRF no problem two up.

So we can agree to disagree.

[taninthai]

2 hours ago, Kwasaki said:

Agree but find my 2017/2018 updated CRF no problem two up.

So we can agree to disagree.

The problem I found with these bikes 2 up is 1 you are pushed to far forward squashing your nuts agaisnt the tank and 2 there is not enough foot room constantly find passengers foot in the way.. 

allanb you should try fitting quick action throttle so you are actually getting the throttle wide open rather than maybe riding around on 1/4 or 1/2 throttle.......it still will not give you the power you want and I don’t anything will.......my 600cc track bike lacks grunt coming out of some corners but I don’t want a 1000cc so I just accept it for what it is.

[AllanB]

There are certainly some varied ideas to consider. 

[Kwasaki]

2 hours ago, taninthai said:

The problem I found with these bikes 2 up is 1 you are pushed to far forward squashing your nuts agaisnt the tank and 2 there is not enough foot room constantly find passengers foot in the way.. 

I don't have that problem me and the Mrs ain't that big yet. ????

[taninthai]

18 minutes ago, Kwasaki said:

I don't have that problem me and the Mrs ain't that big yet. ????

 

18 minutes ago, Kwasaki said:

I don't have that problem me and the Mrs ain't that big yet. ????

Hey!....I'm only 59 kg with size 9 feet????????????????

 

[AllanB]

On 10/11/2018 at 8:33 AM, Farangwithaplan said:

I said exactly what I said. Reread it without looking for problems that aren't there. I said the radius is getting tight. Will A tighter radius cause more guide wear? Yes it will. Basic geometry.

 

I have also noted in  two previous posts that a smaller sprocket is a common option and is fine.

 

I don't doubt anything you say. What is your point? Can you actually highlight where I disputed what you say? I'll bet a coke you can't.

 

What is the radius at the front of the swingarm mount on your trials bike? What is the radius on the swing arm mount of the CRF? I'd be willing to put a few beers on it that a 9 tooth sprocket will not fit on a CRF and I have never bothered to look at one.

 

9 tooth sprockets work on trials bikes because, you know, they are designed to. Because trials bikes by their very design have less chain revolutions than most other bikes and are ridden a lot less distances, of course you are going to see a lot less wear. Start comparing apples with apples.

 

 

 

 

 

9 tooth sprockets are necessary on a trials bike to get the very low gearing, the reason they last is that trials bikes don't do that many miles. Simple as that.

 

What I don't understand is the correlation between size 9 feet and not squashing your cobblers on the saddle. Are you sure you are riding the bike correctly?

[Farangwithaplan]

1 hour ago, AllanB said:

9 tooth sprockets are necessary on a trials bike to get the very low gearing, the reason they last is that trials bikes don't do that many miles. Simple as that.

 

What I don't understand is the correlation between size 9 feet and not squashing your cobblers on the saddle. Are you sure you are riding the bike correctly?

I suggest you re read this. You possibly have consumed too much of whatever it it is you like to take. Because it seems you have confused my post with others.

 

You unfortunately have lost  credibility and I won't bother with your posts any more.

 

You are the weakest link. Goodbye.

 

[AllanB]

12 hours ago, Farangwithaplan said:

I suggest you re read this. You possibly have consumed too much of whatever it it is you like to take. Because it seems you have confused my post with others.

 

You unfortunately have lost  credibility and I won't bother with your posts any more.

 

You are the weakest link. Goodbye.

 

No, to save time I put points from two posts on my one posting. If you are offended by the insinuations I made about your feet and groonies it was not aimed at you. 

 

You can rest assured there is probably nothing wrong with your riding technique either.

 

Hope you can get over this unintended malignment and move on.

 

[AllanB]

Still in Europe but called my Honda dealer in Khon Kaen about getting a 13t sprocket. He says he has a 13t for a Honda Phantom and says it will fit, is that the case, anyone?

 

If not I can get one in the UK on Ebay. Cheers

[ad61]

Still in Europe but called my Honda dealer in Khon Kaen about getting a 13t sprocket. He says he has a 13t for a Honda Phantom and says it will fit, is that the case, anyone?
 
If not I can get one in the UK on Ebay. Cheers

You can buy a 13 t front sproket for Crf 250 at Bikerzbits.com for 500 Thb.

Sent from my SM-A710F using Thailand Forum - Thaivisa mobile app

[taninthai]

My advice Is to change the rear sprocket first ,but up to you,got this nice shiny gold coloured one ready to go on my spare set of wheels.

[AllanB]

1 hour ago, taninthai said:

My advice Is to change the rear sprocket first ,but up to you,got this nice shiny gold coloured one ready to go on my spare set of wheels.

It is a cheap and easy trial to change the front sprocket and any existing wear will corrupt a 200baht part. When I have proved that it works, then I can consider a rear sprocket change, which, I agree is the best solution.

 

But I can first wait until I have had some mileage out of the existing set up and then change all 3 componants at the same time, which I assume is what you are going to do? Driver, driven and chain.

[thaiguzzi]

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[thaiguzzi]

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[taninthai]

No it’s not what I plan to do,I changed my front sprocket back to 14 after 1 ride on the roadwith 13t,really can’t be arsed to go into detail why I did that or also why I recommend changing rear sprocket first...that’s why I added up to you in my post????????????????????????????????

[AllanB]

16 hours ago, taninthai said:

No it’s not what I plan to do,I changed my front sprocket back to 14 after 1 ride on the roadwith 13t,really can’t be arsed to go into detail why I did that or also why I recommend changing rear sprocket first...that’s why I added up to you in my post????????????????????????????????

That's fine... I do most of my riding two up and want to see what difference it makes.

[Namplik]

On 10/24/2018 at 7:17 PM, AllanB said:

That's fine... I do most of my riding two up and want to see what difference it makes.

I have a LRP myself and I have never considered driving around with a passenger. This is a one mans bike only. Two up + luggage would be extremely cramped driving around with. Not comfortable for the driver at all, why do you need to bring your wife with you all the time? 

[AllanB]

8 hours ago, Namplik said:

I have a LRP myself and I have never considered driving around with a passenger. This is a one mans bike only. Two up + luggage would be extremely cramped driving around with. Not comfortable for the driver at all, why do you need to bring your wife with you all the time? 

Why not, we like each other's company, many people ride with their wives and GFs, it's really nice and we don't find it cramped? For a simple mod of getting a few more torques this is getting awfully complicated.

[papa al]

amen

[properperson]

 

Here's my ten penny worth....

 

If you are happy with the bike 2 up and want some improvements to the performance / pulling power and general enjoyment of the bike....

 

Here's my advice:

 

Fit 13T front sprocket, remove snorkle from air box and remove metal backfire screen from rear of air filter - Then fit (or get professionally fitted) an EJK (Electronic Jet Kit), plus mega bomb down pipe and FMF rear pipe - You will be staggered with the improvements to the pulling power of the bike.....

 

Add sticker kit to improve visual look of the bike...

 

Have the standard seat re-packed with memory foam / then re-covered to improve comfort (standard seat very hard).

 

If you have the "L" model and use the bike mostly on the road - consider getting a set of "M" model wheels, together with Pirelli Angel GT Tyres - It will then go round the back road twisties like a stunt bike.....

.

 

[AllanB]

Back in Thailand now and had a 25km ride out 2 up and back 1 up and surely I have an engine fault? My mate with a CBR250 is back soon and will have a go on his. Rode a new one 6 years ago and recall it was quite smooth, mine ain't, the power band is as I remember, nothing much below 5,000rpm and then a good push. The roughness is really noticeable after riding the Vespa for 6 months.

 

I assume the engine is the same on both bikes, his is an older carby bike and loves it.

 

Trouble is here the dealers here in KK are no help, this void between big and small bikes, anyone know of a decent dealer, I would travel? South of Khon Kaen pref.

 

The bike lay idle for 6 months and started on the button, even the tyres held their pressure.