Author Topic: GS500 Classic Trials Project  (Read 12462 times)

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Offline Paul K

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GS500 Classic Trials Project
« on: February 26, 2017, 01:53:17 pm »
Well, I've managed to create some room in the garage since the arrival of a new bigger shed so work on the project can continue  :) .  The GS500 engine just about fits in the GS250 frame.  The GS450 swinging arm fits the frame a treat (same swinging arm bearings and same width at the pivot tube).





Next task is to fit the DR650 front forks with their new machined steering stem, install and align the front and rear wheels, then check the sprocket alignment to ensure the engine is sitting correctly.  If it's not, then it's out with the grinder and the welder again.

Watch this space for news on progress, though, don't hold your breath, this is a long term project and has to be fitted in with everything else I'm doing.

Offline Jason Potts

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Re: GS500 Classic Trials Project
« Reply #1 on: February 27, 2017, 06:39:48 pm »
That looks superb Paul. That really is snug. Did you have to make all new mounts or did some lign up to get you started?

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #2 on: February 28, 2017, 10:09:40 am »
I had to fabricate all new mounts.  The GS250 engine is a bulky unit and the engine is not far off the same external dimensions as the GS500 engine, but they're not exactly the same.

The engine is tight; to adjust the valve clearances involves removing two mounting bolts and tilting the engine forward to allow the cylinder head cover to be removed.  As the valves are checked every 6,000 miles (I think), it won't happen too frequently for a trials bike.  Say once every 5 or 6 years?






Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #3 on: March 16, 2017, 02:51:02 pm »
So hereís the next stage in the project. New steering head bearings and the yokes installed with the new steering stem, new swinging arm bearings and the wheels temporarily in position. Ignore the rope round the steering head; that's just to stop the forks fully extending while on the trolley. The sharp-eyed will notice the top nuts are missing because you can see the tops of the fork springs.




The forks were stripped and the spacer above each spring removed for research purposes. The forks have as standard about 250 mm (10 in.) of travel, which is far too long for me (short legs) and would give too much ground clearance.  I reckon I need about 175 mm (7 in.) of travel so that involves a shorter spacer above the springs and a new tubular spacer below the spring in the damper tube (a bit difficult to see this spring in the image). Effectively, this should reduce the travel and lower the forks. The final dimensions of these four spacers (two for each leg) will be worked out when the bike is fully weighted with engine, etc. The fork length at rest will also be influenced by what length rear shocks are available in order to maintain the required rake.


Currently, the approximate dimensions are working out at wheelbase 1,400 mm (55 in.), rake 27 degrees, ground clearance 230 mm (9 in.). Chain clearance and sprocket clearance are tight, but acceptable.




What I would like is some advice on the suspension travel other members are using on any big twin, e.g. Cheney Triumphs.

Offline Jason Potts

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Re: GS500 Classic Trials Project
« Reply #4 on: March 17, 2017, 07:41:12 pm »
That's looking very tidy Paul. Does the standard tank fit or are you fitting something else?

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #5 on: March 17, 2017, 08:40:28 pm »
Well, not quite sure at the moment. I bought a GS250 tank, thinking it would fit the frame. However, the tank is from a GS250T (cruiser-style with a pear-drop shape  tank) whereas the frame is a GS250X (road bike style with a coffin-shape tank, I think that's the description). The two tanks are not interchangeable  :( .

So the option is to get busy with the hammer on the tear-drop tank I have to make it fit, or try and buy a coffin-shape tank and hope it doesn't foul the engine. But and a big but, I haven't seen a coffin-shape tank anywhere  :( . And I have been looking, for example, I had to buy the GS450 swinging arm from a Dutch website.

I could have an alloy tank made up, but I'm trying to keep within a reasonable budget  :-[ .


Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #6 on: April 22, 2017, 08:37:18 am »
Work on the project progresses again now that the Lands End trial is over  :) ; I had to devote some time to prepping the XR400 for the trial.

The footrest assemblies with integral gear lever pivot (left side) and brake pedal pivot (right side) have been welded up and bolted to the frame. The folding footrests I bought from Pride & Clarke online; good quality too. The problem with the footrests is the mounting points either side of the frame are not symmetrical, hence the two bolts on one side are above the pegs whereas the two bolts on the other side are below the pegs. This creates a small area in which to mount the pegs to avoid one peg being higher than the other. That took a lot of time with cardboard templates   :( . I had a local guy weld the footrests onto the mounting brackets; my MIG welder doesn't have the power for thick steel  :( .

The gear lever operates the selector rod remotely through a linkage. The reason is that the GS500 gear selection works backwards due to the standard bike having rear-set footrests. A couple of rose-joints and M6 threaded rod allow the remote gear lever to operate the gears in the normal up/down sequence  8) .

Next task is making a bracket for the DR400 rear master cylinder to attach the rear subframe and sourcing the basis for a brake pedal that sweeps above the foot rest  :-\ .

More pictures when I get a chance.

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #7 on: November 13, 2017, 02:58:41 pm »
The projects been on a slow burn for a while  :( .  I've since made new engine mounts that allow the valve clearances to be adjusted without removing some of the engine bolts.  The gearbox lower mounts were remade and welded in the frame by local friendly welder. I've included spacers so that the engine can be shifted sideways should I have got the chain alignment not quite right  ::) .

On the rear brake; the bracket for the DR400 rear master cylinder is welded onto the frame, a torque anchor is welded onto the swinging arm and I've got a brake pedal (still to be modified).

On the intake side, I've bought a K&N filter (for a GS500) and I will fit two long aluminium tubes between the cards and the filter. The benefit is two-fold in that the filter now sits under the seat and, I'm theorising, the longer intake tract will give more torque at the bottom end, hopefully  :-\ .  Some silicon tube connects the carbs to the aluminium tubes.

A plate for the electronics will be mounted above the battery and in front of the rear mudguard.  It's getting pretty full under the seat by now  :o .

The exhaust is planned to be a modified 2 into 1 GS500 system that I have.  It'll run under the right side of the engine and be protected by the engine skid plate.

Engine bars are planned because the engine is wide and the cases are thin. The only downside is that the bike's getting heavier each time I look at it.  But what the heck, If I can't manage the main trial, there's always class 0  ;D .


Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #8 on: May 11, 2018, 10:23:18 am »
An update on progress to date.  After the Lands End Trial and various other commitments, I found some time to work on the project  :).

The electronics plate is installed under the seat and accommodates the ignition module, rectifier/regulator, starter solenoid and indicator relay.  The prop stand switch and associated relay are ditched.  The GS500 wiring loom has now been modified to suit the new location of the electronics and the shorter run from the headlamp to the electronics plate.  The loom also includes a fused live feed from the solenoid up to the handlebars for a route holder and battery charging. A new starter/battery cable has been a pain; the original cables are too short and measure up at 13 mm2 csa, but that seems to be unavailable in the UK so I've gone for a bit beefier 16 mm2 csa cable.  a bit chunky, but it's very flexible so should go in with no headaches.

The K&N air filter with the long aluminium tubes fits nicely under the seat with a bracket to support the weight and stop the carburettors being pulled off.  All looks very tidy under the seat, though, not enough room to store tools :( .

The rear mudguard brackets are tack welded onto the frame and the seat base is sorted now that the position of the rear mudguard is fixed.

The fuel tank is installed with a few modifications, using a hammer, to clear the cylinder head cover and to allow the forks a larger turn angle.

Header pipes are welded up and installed, running under the right side of the engine.

Brackets are made up for the side panels (to be aluminium sheet) and are to be welded on the frame and fitted with M5 rivet nuts.

When I work out how to efficiently load photos, I'll post some. For now, it's back to the garage?  Nah, going for a cup of tea  ;)

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #9 on: May 15, 2018, 06:10:11 pm »
Here are some photos of progress to date.


Fig. 1 K&N air filter (GS500) and inlet tracts with blue silicon hose


Fig. 2 Electronics plate with all the electrical gubbins


Fig. 3 DRZ400 rear brake master cylinder and brake pedal before modification


Online David (tufty) White

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Re: GS500 Classic Trials Project
« Reply #10 on: May 15, 2018, 09:57:57 pm »
I'm enjoying watching the progress. 

Offline Jason Potts

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Re: GS500 Classic Trials Project
« Reply #11 on: May 16, 2018, 07:23:03 pm »
Me too

Can we get a panned out pic with the tank on  :D

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #12 on: May 17, 2018, 07:00:44 am »
The project is at the back of the garage surrounded by the usual junk, but first chance I get, I'll add some photos of the petrol tank.

The seat is underway; the base is cut out of 6 mm plywood and I have the seat foam from a Suzuki DR650 to modify.  I'm still working out the best method of securing the seat to the frame while there is a load of spares and clothes on the bike, during a trial that could get in the way.

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #13 on: May 21, 2018, 06:38:12 am »
The fuel tank and material is not the best shape and type for the intended purpose of the bike, but the mass of tubes that comprise the spine of the frame limit the choice and the budget does not extend to a custom made aluminium tank :( .


Fig. 1 Fuel tank with panel beaten indentations for the fork stanchions  ::)


Fig. 2 Increased steering lock due to the indentations  :)


Fig. 3 Underside of fuel tank

The exposed steel is where the tank has been indented to accommodate the right ignition coil and the right side of the cylinder head cover. The pencil marks on the left side of the tank mark out where the tank is too close to the left side of the cylinder head cover so a bit more denting to happen. The front of the tank may have splayed outwards due to the attentions of the hammer so I may have to attempt to squeeze the two sides together somehow ;) . The fuel tap is going to be relocated to the rear of the tank. Currently, the fuel tap sits above the left spark plug; not a good idea :o !


Fig. 4 Rear mounting, fuel tank

I couldn't locate a new rear rubber mounting for the tank so had to make one up from some rubber sheet and a steel spacer I had knocking about.

Offline Paul K

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Re: GS500 Classic Trials Project
« Reply #14 on: May 23, 2018, 07:02:54 pm »
More photos of progress, particularly a view with the tank on.  Note that the inside of my house looks nothing like as bad as the inside of my garage.


Fig. 1 General view of right side

The tank looks like it's running downhill  :-[, though, I think that's to do with the angle of the frame on the trolley.

The engine bars are now fabricated. They're constructed from GS500 bars, but modified to suit the frame.  Essentially, the only bit that didn't get modified on the right bar was the front bracket. The vertical bars are from the frame's pillion footrest tubes.  Nothing's going to waste  :).  That's not going to be a straight-through exhaust; just working out where the silencer is going to be installed; probably uphill at a 30 degree angle.


 
Fig. 2 Engine bars, right side

The engine bars will, hopefully, save the cases when the bike is dropped  :-[.  The header pipes run real close the front down tube and the engine case. A bash plate will protect the pipes and the sump.  The brake pedal can be glimpsed, currently held on with a pair of mole grips, awaiting modification.


Fig.3  Engine bars, left side

Less mucking about involved with the left engine bar  :); only had to alter the position of the rear bracket and weld a box section to the bottom tube of the frame.  The gear lever is shown without the linkage to the gear shaft; this linkage has still to be fabricated.

Ideally, I'd like to discard the sprocket cover, but it houses the clutch release mechanism.  As it is, I've cut away a lot of the interior webbing to allow the mud and crap to drop through  ;).

Still have some questions on what is the optimum ground clearance and optimum front suspension travel for MCC trials  :-\. Anyone got some opinions?