Monoshock mod on YBR250/YS250

**modron** · 12-10-2015, 03:59 AM

Hi,

As everybody knows Yamaha YBR250 is a great wee bike for touring in China. Reliability cant be beaten, everything else most likely can

Anyway, I like my bike (though its a bit boring).

Ive been thinking of riding from China to Europe for few years now, but never had time. It looks like finally in 2016 I will get to do it. I have a spectrum of decisions to make and problems to solve starting with what bike to ride. I can ride my old (40000km) YBR250 or buy new Yamaha XTZ125..... I still need to think about it. A HUGE factor in this decision is wether I can or cannot replace YBRs rear suspension. It sucks. Last 14k km trip in China resulted in really bad suspension experience and my friend who rides his YS from China to Africa now, after having his shock replaced somewhere in the STAN countries, said he finally can enjoy riding.

Ive done some research and taobao doesnt really offer anything that fits YBR. On ebay there is custom build suspension but costs RMB 5000. I have to say I was hoping for something cheaper. I found out that YSS makes suspension for YBR but found only one place to buy it and its not adjustable. Im afraid it will be too soft and Ill end up paying for nothing so I dug deeper and it seems like Ninja 250 has a similar shock. Look at this chart

YSS-MOTORCYCLE APPLICATION LIST

BRAND / MAKER

CC

MODEL

YEAR

TYPE

LENGTH

TOP

BOTTOM

STD. SPRING

PISTON SIZE (MM.)

SHAFT SIZE (MM.)

PRELOAD

Yamaha

250

YBR 250 / FAZEN

07-09

MS

280

12x30

F.30x12

46-115-150

30

12

T

Yamaha

250

YBR 250 / FAZEN (HARDER SPRING )

07-09

MS

280-290

12x30

F.30x12

46-135-150

36

16

T

Kawasaki

250

ZX 250 R Ninja L5

08-12

MS

315-325

12x30

F.32x12

46-80-160

36

16

T

This list is from YSS website. Its just an example as there are many shocks for Ninja and the dimensions are the same apart from lenght which varies from 310 to 330.
There is an a much bigger choice for Ninjas. Im not sure if they will fit my YBR and since I dont have any experience changing shocks I was hoping somebody can help me.
To my inexperienced mind (if the bottom 32 can fit) I could compress the shock by 2-3cm to fit YBR which would result in stiffer suspension. Am I right? Im not sure if it can be done.

Here is the pic of original YBR shock

and here the YSS for Ninja Im thinking about.

Of course if there is a different option that you know about feel free to share

**zhu** · 12-10-2015, 04:43 AM

The standard shock certainly lets the bike down.

Seems like you are on the right track if the new shock is a little longer it will just raise the rear of the bike a little which will probably be compressed back down by the time you load up with gear to get to Europe.

Looks like the new shock end fittings can be changed so should be no big problem to fit it .

Having some adjustment for pre load and dampening would be a vast improvement for the Ybr.

**galenernest** · 12-10-2015, 05:24 AM

If the Ninja 250 shock will fit, you might consider using a Ninja 500 shock instead... that was an upgrade folks were doing to their 250's if I remember correctly. I know that the stock Ninja 250 shock was nothing to rave about. You might want to look into it, anyway.

Edit: just realized that you're looking at Ninja 250 aftermarket shocks... so disregard the 500 swap, lol. Good luck! :)

**Zorge** · 12-10-2015, 06:17 AM

My two cents: I think that good solution can be custom made (because those are probably cheaper), adjustable links (no matter are they simple one, with 3 or 5 holes or those with turnbuckles), so called - "dog bones".

Using those, you can adjust seat height and keep standard geometry of the bike regardless of the monoshock length or when the bike is loaded like a mule.

**modron** · 12-10-2015, 07:45 AM

@Zorge
So if I install, for example, these not only will it increase clearance but also stiffen the suspension? (they are quite pricey for 2 pieces of metal)
So the dog bones should be shorter to rise a bike, right?
I will try to find some more info about it.

**Zorge** · 12-10-2015, 08:57 AM

To stiffen suspension - no. That is basically job for the spring preload system (no matter is the one with the 4 or 5 levels or the one with thread).

I mentioned those adjustable length "dog bones" because you are considering purchasing non-stock (longer, stiffer, heavy-duty... you name it) monoshocks. In order to fit longer shocks, and at the same time, to keep the same seat height/bike geometry, you'll need something like those new, different than stocks "dog bones".

Yes, fancy, nicely shaped, powder coated "dog bones" are not cheap, but I already mentioned that. It is not a rocket science to take two strips of hard/thick enough sheet metal and after some measuring, to drill three holes in a row and get something like this:

Or, if difference between each of those three positions are to big, you can make something like this:

Or, something even "more adjustable" - "dog bones" with turnbuckles:

All those things you can be fabricated in every machine shop for peanuts.

**modron** · 12-10-2015, 11:04 AM

By "stiffen" I didnt really mean physically make it stiffer, just the feel as it changes the geometry of the bike a bit. It says that shorter dog bones will make your ride harsher which is caused by different position (angle) of the shock. It works as a lever I think, the shorter the harder is , in this case, to compress the shock.

I wouldnt be concerned about screwing up the geometry of the bike. Its small, slow bike and it doesnt matter as much as on those super bikes. Anyway, that guy, who I mentioned before, replaced his shock and the bike became so tall that he removed his center stand as it couldnt reach the ground hahah He said the bike felt good

I might make some cheap and see how the bike feel, if i like it ill get the real ones

**Zorge** · 12-10-2015, 01:10 PM

It looks that those "Ninja" shocks you mentioned have "Schrader" (or something similar) valve, so I believe that you can do something by changing pressure inside shocks. That is subject that need some clarifications (or simply - practical tips). I know s...about that thing.

Not to mentione that you can probably find some shocks with adjustable compression and extension. You realize that things are not simple as they appear at the first glance.

Another thing, about longer shocks on standard linkage. You must to take in account that too lowered swingarm/raised tail of the bike can cause chain to grind swingarm.

**modron** · 12-10-2015, 02:50 PM

I found some YSS shocks dedicated to YBR for sale, look
http://www.ebay.co.uk/itm/YSS-29-422...8AAOSw~gRVhTYV
unfortunately it doesnt have a nice adjuster like the ninja one below but it has preload adjustment

and here is one for Ninja
http://www.ebay.co.uk/itm/SHOCK-ABSO...4AAOSwEK9T83ep

http://www.ebay.co.uk/itm/YSS-29-423...gAAOSwjVVVhSds

from dimensions mentioned on those sites it seems like the ninja one would fit without mods.

Zorge, good point about the chain!