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SR250 Classic Fork Rebuild/Seal Replacement

August 17, 2017

The left fork on our SR250 Classic test mule had been leaking since we purchased it and it was just getting worse and worse.  It started spewing out fork oil all over the fork brace and even down the leg and onto the brake - making it dangerous.  Even the right leg was leaking a little.  So it was time to replace the seals and fill up with some fresh fork oil as well.  Little did I know, this would be a nightmare to do!  I'll sum up the process below.

 

Leaky forks, easy enough to get off the bike.

 Leaky SR250 Classic fork seals.

 

First step was to remove the forks from the bike obviously!  This means removing the wheel and brake set up.  But here is an important tip before loosening the triple clamp bolts...  At this point, try to loosen the damper rod bolt at the base of the forks.  The tension that the internal springs are putting on the rod should help hold it in place while you loosen it.  If it is too tight, or if you have already removed the springs, the rod will just spin inside the fork and you will not get the bolt out.  As you will see through this process, this was not an option in this case.  So we removed the forks and got stuck into figuring out how to remove that bolt.

 

Attempt to remove damper rod bolt!

 

Trying to remove that bolt with any normal tool didn't work.  So under recommendation, we went out and bought an impact wrench - to try and rattle it out.  That didn't help either.  The damper rod would just spin no mater what.  We needed to hold it in some way.  So it was time to remove the fork cap (removing the cir-clip ring first, then the cap, then the spring, then emptying the oil as well).  Unfortunately, these damper rods (unlike the ones on the SR25o Specials) have nowhere to hold with a tool.  So we improvised and even purchased what we thought was the correct Yamaha tool for the job... wrong.  If you are reading this and have an SR250 Special and want to know how to rebuild the forks on your bike, there is an excellent write up here by David Mucci from Motto Mucci.  Unfortunately, none of that applies to the Classics!

 

Remove SR250 Classic cir-clip and fork cap.

Improvised damper rod holding tools.

 

Absolutely nothing worked.  So I decided to resort to extreme measures.  I figured that there was a very small risk I would effect the forks structural integrity if I drilled a small hole at a strategic location in the base of the fork to be able to lock the bolts head in place while I drilled it out (so it would not spin with the drill bit).  Check out the following pictures, they explain all.

 

Drill here.  On the centreline, just below the axel boss edge.

Drill 2.5mm hole.

Insert nail into hole just drilled into bolt head. 

Holding the screw locked in position.

Actually, use a screw instead - it allows depth adjustment.

 

I then realised it was better to use a wood screw to hold it - then you can adjust how deep into the head it protrudes.  Then you can drill out the head  - being careful to drill deep enough to remove the head, but not too deep so that you mess up the copper washer and its seat.  The perfect drill size is a 9mm bit.  Then you can punch out the bolt and the damper rod. 

 

Bolt head - showing drilled holding hole.

Remaining shaft of bolt - still inside the damper rod.

Hold damping rod and screw out bolt with polygrips.

 

So much Loctite!  Grrrr!

So much that it had crystallised and 'broke' when removing.

Relief to have these bastards out.

 

As you can see, there was a shit load of loctite on these bastard bolts.  Waaaay too much in my opinion.  This is one of the few times I have cursed Yamaha (if it was like this from the factory) for doing something shitty for the mechanics who end up servicing the bikes.  As you can see, there is no way I would have been able to get these bolts out otherwise, with that amount of loctite I had to struggle to wind them out of the damper rods even with the polygrips. 

 

Don't forget the copper sealing washer.

 

With the bolt out, you can inspect the condition of the copper sealing washer as well.  In most cases, you should just replace it with a new one.  But I didn't have any on hand and this one looked ok, so I left it in place and reused it - hoping it would seal.

 

Absolutely nothing on the damper rod for a tool to be able to grip/hold.

So I decided to mask it up and do something about it for next time. 

Cutting in a holding detail.

 

Very carefully I added my own slot, so next time, with the help of a specially made tool, I will be able to hold it in place.

 

SR250 Classic fork rebuild - all the parts.

SR250 Classic fork parts - in exploded order.

 

Once the damper rod was out, all of the individual parts were cleaned internally and externally with a clean rag and brake cleaner.  Then it was down to actually replacing the oil seals!  The whole purpose of the rebuild!  First was to carefully pry out the dust seals without damaging them - because I wanted to reuse these.  Then was to remove the locking ring plus the old oil seals without damaging the aluminium fork lip - using a large flat screw driver and a thin piece of wood as protection/prying shelf.

 

Remove dust seals.

 

Remove locking ring then seal.

 

Once that was done, the seat for the seal was cleaned up a little with fine wet and dry sandpaper - so not to damage the new one on its way in.  I also applied a little fork oil to help this.  It is important when inserting the new seal that you only apply pressure to the strong metal outer ring of the seal - otherwise you damage it.  You can buy special tools for this, but I improvised and found that the an exhaust adaptor fit perfectly.  So with a little tape to soften the edges, I had my perfect (and free) tool.

 

How the seat looks when the seal is removed - nasty. 

Cleaned up a little.

New seals.

Here are the exact specs...

How it all came apart (and goes back together (but with new parts). 

Perfect in diameter for a makeshift insertion tool.

Add tape to soften edges.

Either press or hammer into place.

The result!

 

Now the new seals were in place, the locking rings and dust seals could be added.  Then onto the final step of reassembly, oil addition, spring compression and cap placement. 

 

Straight 20w Fork Oil.

 

This is the stuff I chose - slightly heavier than the manual suggest but I was hoping for a less squishy ride.

Assembly aiding set up.

 

It is very difficult to compress the springs and be able to insert the fork cap and locking ring at the same time.  It would be easy with 4 hands (hint, get a mate!).  But this was 10pm at night and I wanted to ride the next day.  So I rigged up something that worked awesomely.  The pictures tell all.

With the forks fully rebuilt, they were ready for the bike again!

Job done!

 

 

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