peterb

The pick up coil measures 182 ohms across the terminals, anywhere around 200 ohms indicates the pick up coil is fine. The high tension (HT) coil shows open circuit between the HT lead and the ground lug (on my meter at least) and between the HT lead and the low tension connector (LT lead). Between the LT connector and the ground lug shows less than 0.5 ohms. We have only ever used Windows XP with the Ossa software, it was developed by Kokusan using XP early on. Are you using a separate 12v battery source to power the wiring loom while trying the software? Would be very unusual for the HT coil to fail. Bye, Peter B.

Cooled off a bit this morning in Auckland as we head off for a practice, probably only 18C and definately have to wear sunglasses. Adele gave a brilliant concert last night with a crowd of around 45,000, no I didn't go, she got a Maori group up performing a haka, would be on the net somewhere. Bye, Peter B.

What a great post, thanks old john for sharing your brilliant workshop tools. Was wondering what you welded on the barrel face, crankcase LHS, is it a repair or did you aletr the mounting for a different cylinder? Bye, Peter B.

Hi ricarver, I haven't read all the posts here so am not sure what your original problem is, but seems to be that you can't start your bike. While these bikes have been difficult at times to fire up, there is no major history of complete failure to start. Was the bike running when you bought it? Problems have arisen with the ECU pins and socket connector suffering from corrosion, particularly in wetter climates (UK) Don't scrape the corrosion off with a screwdriver, best to use a contact cleaner such as Wurth type OL, it works well. We have had an odd problem with a break in one of the wires in the harness that resulted in intermittent starting/running. Very hard to find. Are you able to borrow someones ECU to try out in your bike? The air intake sensor is a type of thermistor, located in the LHS of the inlet hose, needs to be cleaned carefully with a tissue. Noticed the fault code showed the TPS voltage too low, as suggested before, set this to 0.6v with the throttle left closed, then key in "Set to ECU" Clear the historical fault codes and see what comes up again. Check the ign pick up coil at the top right of the flywheel, with an ohm meter, anywhere around 200 ohms is ok, make sure there is an air gap between this and the flywheel, approx 10 thou is ok. The software allows you to perform a few tests, remove the plug (heat range 4 works the best) put it in the cap and ground it to see, and hear the spark when you perform the spark test function, you can hear the click as the spark happens, the test provides 10 seconds of spark more or less. You can test the fuel pump also. Are the 2 earth (ground) wires connected to the silencer/head bolt? All clean. Hope this helps, Peter B.

Hi jsp, The noise occurs on some of the gearboxes when the teflon lined bush wears through the teflon, that supports the kickstart gear stub shaft. The drive in 2nd gear is at the far end of the primary shaft, farthest away from the badly supported stub shaft. The wear allows the secondary shaft to have excess movement at this end, particularly when in 2nd gear as this has the greatest effect on the deflection of the secondary shaft. This creates the whining type sound, particularly when in 2nd gear, it is not the second gear set of pinions wearing. I have fixed these using an undersize ID Delrin bush which needs reaming to fit the stub shaft. Typically the hardened stub shaft wears too. You can access the kickstart stub shaft without having to press off the primary shaft end gear, just remove the secondary shaft circlips and slide out the shaft, then undo the circlip on the stub shaft and wrangle out from behind the clutch basket. You can get the Delrin lined bushes in the UK, I think the std teflon ones are type DU and the Delrin are type DX. Would much prefer to use needle rollers but not enough material there to fit one. ATF at 400ml is fine on these bikes. Bye, Peter B.

Been a few years since I rebuilt a GG water pump, I got it wrong. Checked an old pump I rebuilt as a spare and it is the same as per the photo, the seal is a double lipped seal to prevent leakage from either side. The bare steel casing faces the gearbox oil. The photo is correct. Bye, Peter B.

The photo shows the seal in the wrong way around. The pressurised area is in the impellor side, approx 1Bar, a sprung oil seal always has the spring facing toward the pressure area. Just like crankcase seals. Sorry to disagree with some of you guys, but biff is correct. Bye, Peter B.

Si, habla catalán. Bye, Peter B.

If it is the ECU at fault, you can replace it with another ECU with either the earlier or later firmware. The earlier firmware does not support the easy start system, which is no big drama. The later firmware can be "flashed" into your existing ECU or into an earlier firmware ECU by a company in Spain. I have had this done, installing the later firmware on a 2012 ECU but must say that it took about as long as building Hadrians wall. Minimal cost. PM me if you would like more info. Also, not sure if I posted this before, but we did have a problem with an intermittent break in one of the wires going into the ECU, right on the tight angle where the connector clips into place. Bye, Peter B.

Had a recent similar problem with a same year GG. The coils and pick up sensor all checked out ok with a resistance check, checked the earth connections, new HT coil, voltage reg and still a faint spark. Replaced the stator and that fixed the problem. Try swapping out the stator with a friends one to confirm the problem before buying. Bye, Peter B.

I have seen this on most, if not all of my trial motors, from Bultaco days on. I think it is caused by galvanic reaction between two (slightly) dissimialr metals, there is always a minute emf (electro motive force) between two different metals, when connected together, this is how thermocouples work. The crankshaft may possibly have a different mix of alloys compared to the flywheel, though both being basically steel, they are still a mixture of various elements. I usually smear grease there (on the crankshaft!) to prevent this. Bye, Peter B.

Hi Johnny Rotten, I have never ran the motor switching between the two available maps, I have just stuck with the one map that worked best with my motor, which in this case was an experimental 300 cylinder from Ossa, where I used a specific 300 map, which seemed to work well. The standard 2013 trial 280 map had too much advance for this motor, in my opinion. Canada280i, I found the carbon reeds, not the Boysen dual stage ones, did not work well with the Ossa, lost low end power. Best were std Ossa reeds or GG Pro reeds which are the same. Yes, going from 100 to 103% richens the fuel/air mixture over the rev range. Bye, Peter B.

The maps or programmes are basically fuel/air algorithms compared to the engine revs. The + - 5% adjustment shifts the start of the algorithm upscale or downscale, maintaining the curve of that particular programme. From a starting point of 100%, setting to a lower value, say 98%, leans off the mixture, conversely going to 102% makes for a fuel rich mixture. Bye, Peter B.

There isn't a history of the fuel injector failing on the Ossa, but still is probable. We have had 2 cases with Ossa's where the ECU terminals at the connector were oxidised/coated/dirty, cleaning with Wurth contact cleaner type OL fixed the problem. The motor had similar symptoms to what you had mentioned earlier. Don't scrape the ECU pins with a screwdriver, as they are gold plated. Also had a difficult to solve problem with sporadic cutting out, traced to a break in one of the wires going into the ECU connector, not easy to find (I didn't sort this one). As a precaution, we use a dielectric grease on all of the harness connectors. Bye, Peter B.

If you are unable to get these from Birkett's, you can get aftermarket Kevlar based plates from Spain from Xiu Rdi : http://xiurdi.com/ossa-tr280i/ Bye, Peter B.

Hi lotus, I might have a spare here if you get stuck. Can you make some space in your messenger inbox, unable to send you a PM. Bye, Peter B.

Hi baldilocks, The left side does narrow down to approx 1mm dia or less when the oil passage ways reach the bearing plate. The right side is open to the gearbox oil as per GG. Bye, Peter B.

Hi Christian, The older Ossa's have a needle roller bearing on the left side, a special made for Ossa to a close tolerance. Later motors have a conventional ball race, you can retrofit the newer ball race (which has better endfloat control than a needle roller) if you can get hold of the later inner bearing plate. The right side bearing is the same as a GG Pro with the same integral viton seals, except that the outer bearing casing has a radial groove machined in there to locate the bearing position screw. The later crankcases have an extremely tight interference fit for the right side bearing to prevent possible crankshaft endfloat, should the bearing begin to move in the housing under stress (high revs). The crankshaft bearings don't have a history of giving up so quickly. It may well be that the gearbox has taken in water, either externally or from the water pump shaft/seal and if this happens, there is every chance that the water can get into both crankshaft bearings and begin rusting up the bearing surfaces. Also, it is important to change the gearbox oil often on these bikes. Bye, Peter B.

Yes. Providing there were was nothing wrong with the clutch assembly. Bye, Peter B.

Check if the clutch centre bolt has come lose, it is a 7mm allen socket head with a lock washer. If this was loose, the slave piston may foul the top of the socket head and come to a stop, the casing therefore taking any extra pressure. The spring washer below the centre nut does not rest up well against the clutch centre, even when tight, the centre is physically loose on the shaft with visible end float. Prefer to fit a fat flat washer with approx 18mm OD and a bit of loctite on the centre bolt. Bye, Peter B.

The later Ossa's have a very tight interference fit for the RHS bearing to crank case housing. It took me 22 hours to strip out a crank shaft and replace the RHS bearing then re-fit everything, probably the longest time I have ever taken to replace a crank bearing, longer than a Tiger 100 rebuild even. Remember to remove the RHS bearing locating pin (allen head) first. You can make a puller to extract the crankshaft from the casing, quite simply from a flat bar 20mm x 40mm that spans the LHS mag housing using some pieces of hardwood to prevent damage to the housing from the puller. Drill and thread the centre for an extraction bolt. (Hi tensile) I used a hot air gun set to max to heat the RHS bearing housing with a lot of tension on the puller, when the shaft and bearing let go about 1mm with a mighty crack, it is really tight there. Massive heat and tension finally got the crankshaft out. You need a good bearing puller to withdraw the clutch drive gear from the RHS of the crankshaft, it's fine to re-use 2-3 times without losing too much interference. The RHS bearing has an integral VITON seal, same as per GG Pro, except the outer casing of the bearing has a slot milled in to locate the locating screw. Replace the RHS bearing and gear and re-assemble. Have the crankcase baking in the oven at approx 110C for an hour or so, keep the crankshaft in the freezer overnight. Use welding gloves to fit the two together without force. You should use a permanent marker to mark the position of the locating pin in the housing on the inside of the crankcase, and on the bearing, and on the flywheel, so you can use the mark as a guide as you slide the now loose fitting crankshaft into position, make sure you have got the right position by inserting the locating pin, I think I used a torch to see if the hole lined up with the slot. Good luck. Bye, Peter B.

On the motor before the Pro, the factory setting was not a measurement of the squish gap, rather setting the height of the cylinder such that the top was level with the top of the edge of the piston crown at TDC. On the Pro motor, the rule of thumb for the base gasket sizing, to achieve the correct squish setting, was a 0.8mm thick base gasket for the 300, 0.5mm for the 250/280. But, to be pedantic, would require checking the piston height as above rather than rely on the rule of thumb guide. Hope this helps. Bye, Peter B.

Hi Bruce, The first plug that you removed is not the drain plug, it houses the index plunger ball bearing and spring to provide the positive stop when selecting different gears. I think the washer thickness is quite sensetive, as if thinner than standard, then the plug screws in a little further and as the gears are selected, the spring becomes coil bound and does not allow the selector to complete it's movement. As written above by GG249uk, two washers or just one thicker one, would be better than a single thin one. Bye, Peter B.

I had a ride on this bike in Italy in 2013. It is a home built 4T conversion using an SWM 2T motor as a donor. It was really well sorted and looked like it came straight out of a factory. Even made an internal oil pump. Anyway, I'd best let the owner tell you about it all. The motor felt very responsive with good low end urge, more so than a Montesa 4RT for example and was mechanically quiet. I thought it was an excellent piece of engineering, a proper job. Bye, Peter B.

Hi chaser, for the time being, you can knock out the LHS bush and replace it with a new one, it is a shouldered type DU teflon lined bush generally available from good bearing shops, probably only a few pound in the UK. Should never have been supplied in the first instance. If you don't want to head down the milling track, which is the best option as then you can use a decent sized 6004 bearing like what should have been used originally, you can have someone turn up a sleeve to take up the difference between the two new kit bearings, I can't remember the size but they were a smaller OD than a 6004, and the bearing housing, shorten the aluminium bearing separator sleeve (the sleeve in between the left and right bearings) to the appropriate length, then fit everything together packing the new bearings with waterproof grease. I did get a GG year 2000 rear wheel to fit as a spare, but this was a lot of mucking around with spacers, sleeves and getting the longitudinal distance correct for the sprocket and disc. I don't think a Pro wheel would fit, might do, best to try one first, but the Pro axle is a smaller diameter than the Ossa, and the Ossa has a very tight tolerance for the caliper distance away from the swinging arm, different to a GG. Best bet is to get the hub milled out and then it's all done proper like. Bye, Peter B.