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2014 Yamaha 250 stroke suspension compared to 250f

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My son has both the 250 2 stroke and 250f 2014 yamahas. Both suspensions are completely stock. My son just turned 15 and he is 6 ft and 150 pounds. He has liked the suspension on the 2 stroke, but we just bought the 250f and he raves about it. The only thing that I have done differently between the 2 bikes is on the 250f, I removed 25cc of fork oil from each fork and I slid the forks up 10 mm above the top clamp. The 2 stroke we bought new and now has about 55 hours on it. The 250f only has 8 hours on it.

Here's my question, are there any differences in the stock suspension between the 2 bikes. If so, what can I do to make the 2 stroke similar to the 250f.

Thanks,

Scott

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If your son ride's/race's motocross (not trail / off-roading)

 

after 55 hours the YZ250's suspension is most likely due for a refresh, oil and bushings front and back.

 

In theory, at 150lbs the YZ250 should be slightly oversprung (spring rates too stiff) for his body weight,

if he's a faster rider then the heavier spring rates are probably fine.

Edited by mlatour

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Yes, the 2 stoke forks do need servicing and I plan to do it this week. He races the 2 stroke in cross country racing in The south. He is an XC2 rider in our LACC series. He is just starting to race MX which is why I bought the 250f. He is a fast local C rider and wants to make a run at Loretta Lynns this year.

The 2 stroke suspension is very good, but he has been blown away by the 250f. Are there internal differences. It seems that the 250f may have different Springs than the 2,stroke and the shock gas chamber is on the opposite side.

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I looked up some specs,

from what I could find there are contradictory infos on what the actual front spring rate are on the 250F

but one thing is for sure it's a stiffer rate than what is on the YZ250.

 

YZ250 2T

front spring rate : 4.3N/mm (about .44kg/mm)

rear spring rate :  48N/mm  (about 4.9kg/mm)

bike weight : 227 lbs.

 

YZ250F 4T

front spring rate : *at least 4.4N/mm (about 45kg/mm)  *perhaps up to 4.7N/mm according to one source

rear spring rate : 56N/mm    (about 5.7kg/mm)

bike weight : 231lbs.

 

The Yamaha part number for the spring is 1SL-23141-10-00

 

Apart from the spring rates, each model will have it's own specific internal valving specs

to match the bike's weight, linkage leverage ratio, chassis weight distribution etc.

 

The YZ250 suspension has basically pretty been left unchanged since 2005-06,

on the other hand the 250F keeps receiving continuous improvements to it.

Edited by mlatour

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Not to mention the smoker is rolling a 06 frame where the banger has a much better frame. It is likely majority of the better feel is from the chassis and mellower power characteristics.

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Here's what I did and I'll update when weather allows us to race Cross country (16+inches of rain over last 2 weeks).

I changed external fluids and put 300 cc in instead of 330. I also raised the forks to 10 mm above triple clamp.

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The 250f is much stiffer all around

The rear suspenesion also has much stiffer "low speed" on the 250f

The 250f rear shock has a different piston size and shaft size as well.

Sadly they are not really comparable between the two bikes but yes the 250f generally feels better than the 250 stock to stock.

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You can definetly make the smoker more enjoyable to ride both are excellent bikes. What's the biggest complaint your son has about the 250

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I had both bikes, and they are difficult to switch between or compare. Thankfully I was on the 2stroke for years, and then on the four-stroke for a few years. The 2014 yZ250F always has more traction. Its configured to weight the front tire more because the motor is putting out smooth four-stroke power which tends to hook up. The 2stroke is setup to favor traction to the rear wheel, but it has a non-linear motor that kicks hard and breaks loose on acceleration. The 2-stroke is a chassis balance compromise (which works really well in sand and sloppy mud) and the four-stroke is much more balanced from front to back.

I am able to stay centered on the four-stroke and keep the revs and momentum up without using energy. The 2-stroke is constant movement of the hips and head. Lean fwd to weight the front on corner entry, and then shift back with head and hips on the exit of the corner and hang on as the bike rips out of corners. Completely different sensations to ride.

 

My bikes were both stock and I was 155lb vet expert offroad.

I reduced the oil level on the 2-stroke and that was a very nice improvement.

The four-stroke was firm, but I ran it that way anyway. It wasn't as comfortable but it is second-to-none at kamikaze.

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There were ZERO complaints about the 2 stroke. He absolutely loved the bike and he is absolutely flying on it offroad.

We bought the 250f because we decided to race MX also. He was blown away immediately. After reading everyone's input, it's evident the frame and bike layout has as much to do with his comfort as the suspension does.

There are some things that I can do to improve the suspension on the 2 stroke and I'll be working on that. We need to do some more testing. My problem is that a 15 yr old who has only been racing for 4 years does not really know when something isn't working correctly until he rides something that is working right.

I can fix, trouble shoot and tune about everything else on the bike. Suspension is my weakness. I need to learn more. Are there any reads that are thorough on how the Kayaba SSS forks and shock work mechanically.

Thanks again for all the helpm

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