A forum for owners of Yamaha TTR250 trail and enduro bikes!

I'm a RAID owner with a standard rear shock unit that looked as though it had never been touched.  Given that my bike is a 1994 model, time for a strip down, clean and oil change etc.  I acquired an old standard rear enduro shock unit from ebay and decided to strip both units down simultaneously, so that any differences could be checked - although most seem to have been catalogued already.  The end goal was so refurbish the shock, plus swapping over the superior remote reservoir from the enduro model, which features adjustable compression damping.  This is not a step by step repair guide, since such a document already exists on this forum, courtesy of Brian and Steve.

So, to list the obvious differences. 

Raid model has a shorter spring in black as opposed to yellow.  I am yet to try and test the spring rates, but may find time to do this... using some dubious method.

Raid model has a slightly shorter shock cylinder, which I can only assume means this model has slightly less travel available.  The reduced overall shock length appears to be compensated for by a slightly longer mounting assembly at the bottom end.

Raid model has a different type of bushing at the upper mount, which appears to offer superior longevity - mine is perfectly in tact and functioning, the enduro is falling to bits.

Enduro model features a different oil hose linking to the remote reservoir, with banjo at one end only and straight screw in fitting with o ring on the other.  Raid has banjo both ends.

Raid model has a steel mount at the lower end, enduro is aluminium.

Remote reservoir is a completely different capacity, the enduro model being larger bore and featuring a rubber diaphragm and compression adjustment knob.  The raid model features a piston with an oring, in place of the diaphragm, and has no adjustability other than choice of ultimate gas pressure extending beyond 130 psi minimum.  The raid model is mounted on the bike with the gas side of the assembly facing the sky, enduro is the reverse.

Internally, I couldn't find any real differences, but didn't bother to take apart the shim stack assembly pf the enduro shim by shim, as others have already catalogued this information pretty well.

In terms of the work itself, I had a read of the step by step methodology document prepared by Steve and Brian, which has been on this forum for years.  There are a few things I did differently to make the job easier, such as taking off the oil hoses completely and draining some oil, before attempting to compress the remote end cap to get the hidden circlip off.  This enabled me to the job with just finger pressure on the raid, but the enduro still needed a gentle squeeze with a G-clamp.

I also took the whole shock assembly off the bike from the battery side, just so you can be sure it is possible.  Had to undo the entire exhaust however, so would probably go from the other side next time.

These are the parts laid out before cleaning.  I used gunk for most of it, as petrol smells inside part of my house... causes the lady to explode.

This is the reassembled piston with Sachs branded new seal head, new end cap and adding a bump stop.  This is a slightly deeper piston type than stock, so I hope it doesn't limit the travel of my shock.  The usual All Balls seal from the TTR shop was out of stock at the time I looked, which is why I sourced this.  Sachs is more expensive, but the new cap is a useful inclusion, as I find the originals tend to crumble a bit as you lever them off.

I have fitted everything back together and filled with Rock oil SVI 7.5, quite a thick oil as I believe I want more general stiffness....  but have come across a slight snag. 

The drilling and tapping of the remote reservoir cap to take a schrader valve, using a 7.3mm drill and 8 x 0.75 tap didn't work too well.  The threads bind increasingly as I tried to screw the valve into my newly tapped hole.  The reason for this would appear to be that the schrader valve thread is not actually quite that size of tap, but is just slightly off.  Schrader valve dims are apparently 7.747 x 32 TPI.  This requires a very special tap size 8v1-32, which only appears to be available to order from china.  This put a stop to the whole repair.  I tried two different brands of schrader valve from old inner tubes, but none would go all the way through my tapped hole.  I am going to have to counterbore half of the hole out at 9mm, then force the new valve all the way in with plenty of locktite to lubricate and seal the dodgy threads.  In truth the threads are extremely close, things should work out fine in the end. Steve and Brian did not appear to have this problem, which is odd / lucky.

I will follow up with some "strength" tests on the two springs and perhaps some notes on setting of the sag, if anything worth sharing is found.  The preload adjustment was at maximum when I took the unit off the bike, having never been adjusted by me to date...so we will see.  I weigh around 93Kg (pre christmas that is).

If anyone needs any further info to assist their own works, just let me know.  I have found this maintenance work to be straightforward so far, however I should point out that the shocks can simply be sent off in the UK for around £120 I think.  I don't know whether this price includes fitting a new seal head, but it seems good value for the time it will save you.  Personally I like to take things to bits myself, to get a better insight into the way they function...

9 December 2019 - post continued....

To continue where I left off, the dodgy threaded reservoir cap has been counterbored around 12mm, following which the valve squeezed through no problem, sealed with high strength loctite.  As an aside, I already owned a special schrader valve with BSP thread on the other side (suggested as a solution by one member)... however the version I own is a tapered thread type, which as far as a I know, should really be matched with a similarly tapered and threaded hole to achieve a gas tight seal - impossible to create (?) in the home workshop.  I therefore opted to make the standard schrader valve work, as this solution seemed neater to me, and less uncertain.

 At this point I noticed another major difference between the original Raid shock and the enduro....there is no bleed valve on the Raid shock!  This was making it quite difficult to get the air out, so I decided to quickly pull things apart again and swap over the shock cylinders .....

The downside of the approach was the need to deal with the commonly faulty upper shock bearing on the enduro unit (which is a different rubberised type on the raid, that never seems to degrade).  So to remove the bearing, just one circlip was removed from one side and the bearing, which was then "tapped" out with a lump hammer.  I found no need to drill a hole into the shock body down one edge of the circlip to remove it, as per some instructions i found on this forum....a sharp screwdriver worked for me.

I now have the option of a slightly "bodged" but practical cost saving polybush, using the kit supplied in the TTR shop.  I'm not too keen on this method, since the intended "pivot" design at the end of the shock will be compromised, by becoming more of a fixed "moment" type connection.  Original yamaha parts are also available, at around twice the price of course.

I also have to consider powder coating the yellow spring (thanks for the pics Brian and Steve), since I now require the longer length Enduro spring version, having changed to the slightly longer shock body.   I need to use the bike soon, therefore timescales might affect the work i do at this point...

Somebody asked whether the Raid or the enduro shock is better.  The short answer is that the enduro version seems to be better, but only very slightly - the design is nearly identical.  There is compression adjustability on the enduro shock and there seems to be a slightly greater amount of shock travel, plus a bleed valve to help with maintenance. 

Both shocks were in fairly sound condition at the start, with no leaks being apparent.  The old oil that was removed from the raid was thinner than water and dark black, which means it probably wasn't functioning very well for damping purposes.

I am hoping to do some special spring "strength" tests shortly, comparing the black Raid spring with the slightly longer yellow enduro spring.  I'll let you know what happens....