Changing Fork Seals on a Honda Bros

I have a customer with a 89 400 Bros. It is is desperate need of some new fork seals. I have recently acquired some new tools for this job. This includes a depth syringe so the fork oil can be sucked out of the stanchion until it sits at an exact height. I did not end up using this I just poured in a desired quantity. I also bought a slide hammer to know down 41mm fork seals without causing any damage.

 Firstly I strapped down the rear end of the bike to raise the front wheel off of the bench.

 Pinch bolts need to be loosened before the axle can be un done.

Caliper must be removed to get the wheel out. Then the fork brace and mudguard.

I always loosen the top clamp and then loosed the fork caps, keeping the lower stanchion tight so the fork doesn't just twist. Take care not to hit the tank like I did.

The dust seal can be pried off with a chisel of wide flat head screw driver.

This will uncover a corroded C clip that slot into the fork slider. This is fairly easy to pry out using a small ended driver.

To separate the slider and stanchion the allen bolt in the bottom of the fork needs to be removed. This will be held in with loctite and so the slider should be mounted in a vice and then when an appropriate socket it fitted into the bolt it should be hit with a hammer to break the loctite's bond.

This should undo fairly easily. Then it is just a case of sliding the slider off of the stanchion, this will take a few attempts it takes a bit of force so dont be scared to really pull it off. Probably worth noting that once the allen bolt is removed fork oil should start leaking everywhere. So pop a bucket on the floor.

With the fork cap off also the internals can be removed. It is good practice to have a manual handy and to be mythodical. Its is easy to fit things the wrong way round.

 Old and new seals.

 The upper most section of the stanchion has high levels of pitting, I use some plastic sheet to protect the ID of the seal from damage.

I also make sure all of the seal are wet with fresh fork oil before assembly.

This slide hammer houses the oil seal nicely, it also pushes the new dust seal into place.

 I apply loctite the the allen bolt on assembly, the internals are just a simple clean and re-fit procedure nothing was changed this time.

I annealed the washer to soften the copper and allow it to seal once again. This involves heating it up until you see a change in colour and letting it cool slowly. The forks were filled with fresh oil and re-fitted to the bike, the owner has notice a subtle but very pleasing improvement of the bikes ride and handling.

New Bikes mean New Problems

I have recently purchased a Honda Bros 650 1993 which is a later model bike with three spoke wheels and a PGM ignition. Its is exactly the same model as the other bros which I have blogged about before. The main difference is this bike is all mine which means I get full say in what modifications happen. The bike runs and rides ok the rear brake feels powerless however it has just had new pads so I will give it some time to bed in. Also the rear shock feels like it has a low spring rate the damping is adequate.
In order for me to ride the bike legally I have fitted two restrictor washers to the bike, they slip into the intake rubbers. I haven't found much difference in the performance except at full throttle.
To try and overcome the loss in power I have fitted two pod K&N filters, the bike revs up and down fine which would suggest the mixture was running rich as standard.
When a bike is running lean the main characteristic is the revs not dropping or dropping slowly once the throttle has been shut. The revs should drop almost immediately, the inertia of the engine prevents it happening instantly. Fitting pod filters means the bike will pull in more air per stroke so it tends to make your mixtures weak which is easily fixable with a bit of carb adjustment. Since my bike ran fine with pods it suggests the bike must of been a bit rich in the first place.
The characteristics of running rich are alot less noticable, it will show up as high hydrocarbons in an emissions analyzer. It also will give high fuel consumption, a build up of black soot around the exhaust and a black debris build up on the plugs. Its does normally give slightly more power and make the engine run cooler both of which are desirable.

 So I have just taxed, insured and MOT'd the bike. On my way home from the MOT station I noticed steam following me around. I decided to take it easy the rest of the journey by keeping the bike in the highest gear possible and keeping the revs below 3000rpm. This was to try and prevent the bike overheating I just needed to limp home and make an assessment as to where this steam (coolant) has come from.

Alot of dirty coolant showered the bike. I started by looking at the thermostat, I notice a build up of white debris on the underside. This is a good indicator of a slow coolant leak.

 It seems pretty conclusive that the thermostat is at fault. It has three pipes, a breather and a pressure relief cap. Anyone of these could be at fault.

 There is only one stud of bolt that mounts the thermostat to the frame, a good tip would be to remove all of the clamps bfore removing the mounting screw.

Problem found, the housing has two lugs on one side. One of mine has snapped off, it appears to have worn off I dont knwo how this could have happened but I have a spare thermostat and pipes so all is not lost.

 The pipes were blocked solid with dry coolant.

 The missing lug.

The replacement thermostat was in one of the boxes of spares we have collected over time. It had new looking pipes so I decided to fit these also.

The plug that sits below the thermostat is often neglected as it is a pain to remove. On the other bros three of the four plugs were new and this one looked like it has been pulled out of an ocean. On this bike it appeared to be much the same story. Coolant had leaked into the plug hole and corroded everything. I fitted new plugs with a smear of copper grease on the threads.

The plug cap fell off which is never good. There is just enough length on the HT lead to snip off the end section and screw into some fresh lead to gain some purchase. I used liberal amounts of wurth contact cleaner on both the lead and the screw within the cap to try and eat away at the blue corrosion that is common on electrical connections.

 I purchased some fresh ionised water to fill up the coolant system, I already have anti freeze knocking around so I poured it in roughly 50/50. Too much coolant and the bike will over heat, too much water and it could freeze and crack your casings!

With the system filled I always lean the bike either side to try and get the last few bubbles out. I topped up the coolant tank and ran the bike up.
I changed the oil also its common practice with any new bike I buy. Just so I know the condition of it.

Bros tanks rub against their seats, its just the way it is. I cleaned the rust away to reveal the bare metal I treated the metal with Kurust this reacts with the steel and prevents any further rust from occurring. I covered this with some black acrylic paint just to cover it up a little.

All covered up.

After a polish the bike looked alright. I have since taken it for a spin and the coolant system is now water tight and working as it should. The bike sounds really smooth although you do get a bit more induction noise due to the pod filters. The bike handles really well and pulls like a train.

Here are my Broses. I am immensely proud of these two bikes however the horizon is full of new ideas and potential for both of these bikes,

Fabricating a Subframe for the New Seat Unit

A huge milestone in the EXUP build was receiving the seat unit from Ragged Edge Racing (website below) the service was second to none and I could not recommend them more. My seat unit arrived with a small dent in it. After sending images to ragged edge I was given an immediate refund in full for substandard work. The dent is repairable with a bit of rubbing down and filler so it was a win win for me.

raggededgeracing.com

I need to fabricate a subframe to mount this seat unit, for the lines of the bike to flow into the seat unit I needed the top of the seat unit to run inline with the top of the tank. I also need to ensure the seat unit is far back enough so I fit on the bike im on the healthy side of 6"2.

 I used an existing subframe as a base. I set about chopping the lower braces off and swapping them over so the left is now on the right and vice versa. This has narrowed the underside of the frame whilst still allowing just enough room to fit in the battery box. The packaging under this seat unit will be very tight but will dramatically improve the looks of the bike.

These braces were roughly marked out and cut off, I used a grinding wheel to cut the edges into a semi circle so they sit flush with the bar they will eventually be welded to.

 I managed to rest the subframe in place, thankfully it seemed to fit well so I decided to go ahead with tacking it up before welding it completely.

 I am using a gas-less MIG welder which is only good for tacking if in honest, my TIG welder is out of action so I had to complete the job by constantly cleaning off the slag and re tacking until there was effectively a seam of weld.

I know nothing to be proud of but it will suffice for the application.

 I regularly offered up the seat unit to ensure the subframe gave me the desired angle, not too much but just enough to fit with the existing lines of the bike.

I really want the top of the seat unit and the top of the tank to flow smoothly, the overall look for this bike is effectively a retro track day/cafe racer which is a bit strange but I think it will make a refreshing change from the streetfighter treatment these bikes are far too often victim to.

A small amount of frame had to be ground off to make clearance for the lower subframe struts.

 These lugs were initailly used as a seat support for the standard plastic seat unit, I decided to drill and tap them through so I could mount a bar across the bike to eventually mount the seat unit off. I decided to drill straight down this turned out to be a terrible idea, I should have kept all of the hole perpendicular to the surface.

And this is why. I offered up a piece of box section however the bolt head and mounting surface were at an angle and soI had to fabricate an angle in the box section to take up this mis alignment of the mounting surfaces.

I was pretty happy with this bar, I am yet to find a safe and robust way of mounting the seat unit, I know I will have to measure it up and drill the seat unit first. However I need a little more time to find a solution. Time is ticking as I will be back at university within a week.

Here are some images to give an overview of the desired look of the seat unit.

 much cleaner lines compared to the standard seat unit which always made the bike look saggy and slow. This new clearance between the tyre and the seat really gives the bike a purposeful and aggressive stance.