peterb

I have a 280 R2, definitely my best bike ever. The motor has a flywheel weight on as standard and a claimed extra 4BHP over the previous standard model. Lovely engine, quicker than the lazy grunt of a 300 but with what feels like similar power/torque. Not like the 250 which, in standard form can provide a jerky low end response in comparison to the 280. The 280 has a very strong, linear power delivery, grips very well, picks up quick and is a buzz to ride.

Hi Lotus, we never liked the original Ossa O rings, they were too large for the groove outside diameters. We have been using GG O rings for many years which provide a good fit, I can give you the P/Ns tomorrow, it's late evening time here. Bye, Peter B.

Hi Lineaway, correct with the crank cases, and to a point with the clutch case for the 2002, this casing did not have any webbing to support the slave piston action and would flex slightly when using the clutch, creating a dragging clutch. The later year casings had an interior web to strengthen the slave piston and prevent casing flex. Hi eddie1, the slave O rings are teflon coated something, which I can't remember and may well be ok for either synthetic or mineral oil, but......you mentioned fitting a 2005 case, this has an O ring plus a cup seal in the slave cylinder, if green then the cup seal is for mineral, if black then this is suited for DOT4. Bye, Peter B.

The flywheel key can shear and allow the flywheel to rotate slightly on the crank shaft, usually because the flywheel nut will not have been tightened up sufficiently. This prevents the motor from running as the ignition timing is now incorrect.. Well worth a look. There is a sensor pick up external to the flywheel. You will need a flywheel puller, a GG Pro puller will work. Bye, Peter B.

As Big D says, quite likely the flywheel key has sheared. Same key as GG and Vertigo. It is tight in there to get the ECU out, but it does wiggle out. The injectors were pretty reliable. I'd check the key first. Bye, Peter B.

If the Evo motor is the same as the Rev 3, then the LHS weight is on a tapered shaft so you will need to fabricate a puller for that, I have the hole centres for the Rev 3 if you'd like this info. Bye, Peter B.

You can replace the 2002 case with the 2005. Pretty sure the master cylinder from the 2002 bike was a standard 9.5mm bore, so a later model mineral oil kit would be all that is needed and as Lineaway says, the clutch hose would need cleaning out. You can't use the original master piston kit as the seals would swell with mineral oil. You should be able to get a metal type cover gasket from BVM if you need one. The only gasket difference between the 2002 and later Pro's was the crankcase gasket, which is specific for the 02 model only. The gearbox casing was "deepened" to allow for more oil in the gearbox and had 1 screw fixing hole set differently. Bye, Peter B.

Hola Gines, yes the crankshaft (cigueñal) from the 2002 motor can be used in the 2003 crankcase when the spacer sleeves have been removed from the shaft, they should not be too tight and you may be able to get a bearing puller behind the sleeve to extract it. Before buying the 2003 crankcases, have a look to see that there is no crack on the bottom gearbox mounting lug. I will send you a message via Trials Central. Bye, Peter B.

Hola Gines, tu inglés, no problema yo entiendo perfecto. I think you can swap over to a newer crankcase but these are very expensive. Why don't you strip down your motor and find out what the problem is, if it is just an oil seal then this is an easy repair. On the 2002 motor, they had a traditional main bearing with separate viton oil seals, from 2004 Gas Gas changed the bearing to a wider design with integral oil seal. If your motor has the original type of bearing, then it is possible the left side crankcase seal has failed allowing crankcase pressure to force gearbox oil out of the breather, or perhaps the crankcase gasket has failed. Note that the 2002 crankcase gasket is specific for this year and any later gaskets will not fit. You should be able to buy the old type oil seal and 2002 crankcase gasket in Spain, if not I have them here in NZ. Also, on the left side of the crank shaft there is a second oil seal to prevent oil entering the magneto housing (el encendido) this should be replaced also. Remember that the oil seals have a lip sealing spring and these must face inwards toward the crankcase. Bye, Peter B.

Simple enough to just use an M20 bolt, with std thread pitch, 2.0mm from memory but check it first. The bolt screws into the anodised sleeve, then allows you to wiggle the sleeve out. Bye, Peter B.

There is a used trials bike place called North Wales Trials Bikes and parts, run by David Williams, have a look on FB for him, he may well have a few parts for your bike. Tends to deal with the 90's bikes. Bye, Peter B.

Those older GG motors are fine running ATF rated to Dexron III in the gearbox, use 600ml as the fill quantity. The number on the clutch case is the p/n for the clutch case. Check to see that the gearbox oil is not milky looking, indicates water getting into there, usually from a worn water pump shaft/seal. Engine is well put together, reasonably solid, some parts getting hard to find now. Brake pads and linkage bearings are readily available. Bike is considered heavy by modern day standards but these ride well and tend to last ok. Bye, Peter B.

I will have a measure of my steel plates tomorrow and let you know. Arnoux is in Sydney. Bye, Peter B.

There are no workshop manuals around for the GT32, there are parts manuals which would help. Straight forward to work on really, don't break the piston rings they are not easy to find. The GT32 had a silver painted frame, the next year model T32 had a chrome plated frame. Bye, Peter B.

There is a tiny breather hole in the fuel tank cap, is this still clear? Did you have the bike from new and was it ok when new? The brass screw on the throttle body LHS is an air bleed screw, set at the factory anywhere from fully in to 1.5 turns out. Have a look to see how far out the screw is by turning fully clock wise. You can richen up the mixture by turning clockwise. Bye, Peter B.

Is the ignition system a Kokusan or a Ducati? Did you replace the stator with a brand new item? Have you replaced the ECU? If it is a Ducati system, the HT coil has the ECU built in. Then there is another unit, the voltage regulator/fan relay. I once worked on a Kokusan ign system on a 2007 GG where turning the bars would cause the motor to stop. It was a broken connection on one of the pins joining with the ECU, not so easy to find. Bye, Peter B.

Hi Peter, I used to own an air cooled 1989 GG 250 mono, it now belongs to another rider in Te Awamutu. That has the same Motoplat system. I will be catching up with him at this weekends Auckland National event. If you need to know any further info over what was posted above I can try to find out for you. Jim Snell may have a wiring diagram for these on the net, I have a parts list but not much else. Bye, Peter B.

For a 125cc, pilot jet size 50, main jet size 115 For a 250/270cc, pilot jet size 48, main jet size 110 Seems a bit odd though, would have thought the larger motor to have the larger jet sizes. I don't know Beta specific Keihin set ups, but for a 250/300 GG, pilots around 40, main jet around 125-130 needle GJH. The standard JJH needle for GG tends to run lean for me. Bye, Peter B.

Pretty sure the screws tighten up into a steel nut moulded in to the air filter box. Try as lineaway suggests to get at the nut from the other side, break on through to the other side.....couldn't resist. Anyway, if you can't access the nut from the airbox outlet stub the only other way to get the screw out is to carefully cut the head of the screw off with a Dremel type tool then you should be able to access the nut at least to remove the M6 screw. Good luck, Peter B.

I never bother with the sight glass for determining the level. After thoroughly draining, 600mL of ATF rated to Dexron III works well. Bye, Peter B.

Can you send in a photo of the damage. Bye, Peter B.

Dobroe utro, send me a private message with your email and I will send you what I have with Ossa wiring diagrams. There was no specific Explorer wiring diagram, only the trial version. Dosvidania, Peter B.

Yes. You need a new fan. One or more of the windings will have become open circuit thereby rendering that part of the armature useless, flicking the fan blades takes the armature to the next good section.. Bye, Peter B.

There is a bloke in Auckland NZ who has been rebuilding shocks for many years, including trials models. Send me a PM and I will pass on his details. Bye, Peter B.

You can get a water pump repair kit from your local GG dealer or, for more money a complete water pump. Drain the oil as soon as you can, it has mixed with water, the water causes the fibres on the clutch plates to swell creating more problems for you. Perhaps flush out the residual oil with 400ml of ATF rated to Dexron III then dump that and refill again with the same oil and quantity. Other riders use different types of oil but, ATF Dex III has been fine for all my bikes for over 25 years, and it's not expensive! Bye, Peter B.