peterb

Hi MJB, The 2 ex pipe's are completely different, the JTX will not fit on the PRO. Bye, PeterB.

Hi David, That's a good response. My Alpina based Sherpa must be from that 78 era as the triple clamps were the wider Pursang type with heavier wheels. Had a massive Amal MkII concentric too, too big. I reckon Gordon should hang out for a Sherpa, these were made for trials. If you were keen on the Alpina, and wanted to change the internal gears, you would need the complete set of gears and the final drive gear, one tooth different to the Sherpa. Also, the gearbox casting needs machining away to clear the larger diameter trial gears. Bye, PeterB.

Hi gasgas, When I fit up the crankshaft in the cases, I always install the main bearings first as they are an interference fit into the cases and the LHS bearing has an oil drain hole that must line up with the crankcase bearing housing drain hole. I prefer to put the bearings into the freezer for an hour and use a heat gun on the housing to fit up the bearings. The crankshaft fit into the bearing ID is not as tight as the bearing OD into the housing, the crank can then be gently tapped with a nylon hammer to centralise in the crankcase by eyesight. I haven't noticed any centralisation problem with this method. There should be no play (endfloat) in the crankshaft and it is normal for the crank to line up centrally. Are you sure the LHS bearing drain hole is aligned? Bye, PeterB.

Hi ax, I don't know what S.O.L. means. There may be a chance of locating hydraulic seals that are similar or the same as the Telesco damper units from a hydraulic seal outlet, they would have to be for sliding stem as distinct from a rotating shaft. I haven't heard of any seals being available for these shocks. Bye, PeterB.

Hi zulu, that's fine, The P/N's are 5160.074 for a std piston kit, over sizes are +0.25mm and +0.50mm. I just measured the bore - luckily it is in good condition, it is 78.25mm diameter, the piston crown has a marking of 0.25 so I imagine then that the piston is a first oversize, of 0.25mm and the std bore would therefore be 78.00mm. Bye, PeterB.

Hi Gordon, I used an Alpina motor as a basis for making a 352cc Sherpa (it was a 350 model that had a 64mm stroke), not so straight forward. The gear ratios are different to the Sherpa plus the overall ratio is higher meaning that you need both a very small front gearbox sprocket and a very large r'wheel sprocket to get the gearing low enough for a trial bike. The wheels are heavier than the Sherpa, the front is 1kg heavier but has a brake good enough to do nose wheelies - doesn't look right on an old bike somehow. Not sure what size carb is on the 250 but a 26 or 27mm choke size would be right for a trial motor. The Alpina forks have wider yoke centres with the bar clamps set further forward - a good thing I reckon. I guess that if you can experiment with the overall gearing (sprocket sizes) then it is worth a go. Bye, PeterB.

Hi Jaan, You had another posting somewhere about fatbar clamps, now I know what you mean! I thought you were referring to the original Montesa (Akront) fat bars and not the more recent fatbars fitted to most trials bikes. I have a set of Akront bars you can have, maybe not that straight but quite a long way away! There were some after market clamps available to fit the 7/8 inch diameter bars available at the time, I have some for my 348. Without looking at the top triple clamp from the 348, I would imagine that a set of Hebo fat bar clamps and bars would fit, just need to drill out and tap an extra M8 thread to fit the wider spread of the Hebo clamps. The Mont triple clamp is flat, just need to have a look tomorrow to check for sufficient room and strength. Bye, PeterB.

Hi zulu, I have a parts manual in the workshop which may have this info, failing that, I have a 348 motor in bits that I can measure up but will be later in the week. Bye, PeterB.

Hi Jaan, If you want to save the chrome, I recommend heating the kickstart up prior to bending, with boiling water from a kettle, it's better than cold bending. Bye, PeterB.

Hi Jaan, You are probably referring to the schrader type air valve fitted to the fork top nuts on the 70's Montesa's. They worked on the Monts but were not really taken up by other trial manufacturers, I think about 12 psi was used to assist the springs, which really sagged without the air assistance. In engineering thoughts, there would be less friction with pure air versus springs, which may bind on the inner fork tubes. Depending upon use, a set of fork springs could last over 20 years or more - hard to put anything definate on springs. Bye, PeterB.

Hi Jaan, Are you talking about the rear silencer (muffler)? You just need to bend out the mounting bracket so the silencer clears the tyre. I don't recall any riders changing silencers on these bikes, they were fine at the time, quite a nice exhaust note. Bye, PeterB.

Hi Jaan, I have a 1979 348 in the workshop, it has the original fatbars that I will replace with a proper set of Renthal's when I get around to it (It's not at the top of my bike rebuild priorities). If you are stuck for a pair of fat clamps then I may have some for you here. Let me know. Bye, PeterB.

Hi Jan/Jon, There is no spare part for just the sealing rubber, but.......a friend of mine managed to make one from an old h'bar grip, cutting the end to suit - it worked. With the spring clip in place, you can tie it quite sturdily with wire or cable ties by tieing the spring tops together and then tieing this around the hose to prevent it from popping out. Bye, PeterB.

Hello bruce from the 'boro, If you have melted 2 fan relays then the problem is with the supply voltage. If an 05 model 125, then I think the system is a Kokusan and you will therefore have a 12V voltage regulator which is probably the problem (for the relay melting). The regulator is encapsulated in a small black housing just under the headstock - check if it has an earth wire very firmly and cleanly connected to a piece of bare frame. If all connected properly, then the regulator is probably faulty and best to fit another to prevent further meltdowns. To electrically check this, use a volt meter set to AC and check the voltage between a still connected yellow wire, probably at the relay connector, and the frame, it should be approx 12v. The relay, is a rectifier module to convert AC to DC voltage to drive the fan motor, this needs DC power. If you find that your clutch action has become harder, then the water in the gearbox will have affected the plates (they swell) - let us know on the forums if this happens. Ta ra, PeterB.

Hi B40RT, It is a bronze bush, it is a bit tricky to get into the motor but it can be done - prise open the motor housing carefully then separate the 2 halves, usually no lube is required because of the bronze bush. If it is making a noise then I reckon the shaft surface has deteriorated and lubing is a short term answer. I agree with Jan, WD-40 is not such a good lubricating oil and it does tend to dry things up eventually. Bye, PeterB.

Hi andyc, I wrote that there should be a locking washer between the crank nut and the flywheel, eg: a lock washer under the nut. Only use a lock washer here, not a plain or worn out spring washer - if unable to find such a washer, use a little loctite on the threads after first cleaning the oil off male and female surfaces. Bye, PeterB.

Hi there, I am not aware of any glaring differences between the 02 and later 250 cylinders. I am almost 100% sure that you can use the later style piston in your 02 cylinder without any problems, I don't think that you would find one of the older style pistons with a dykes style ring. From memory, the later model 250 just has transfer port skirt cutaways. I know what you mean by having the intake port cutaway in the back of the piston, it's not for timing of the inlet charge with a reed v/v motor, it may be to assist in scavenging after combustion. I have fitted later non intake skirt cutaway pistons to much older GG motors that previously had such an intake window in the piston, without any loss in performance. Give it a try. Bye, PeterB.

The 300 does tend to need a certain hefty kick to spin it over. I've noticed problems with difficult hot starting with these bikes fitted with Ducati ign, fixed this by adjusting the ign pick up sensor to have an air gap (between it and the flywheel) of around 8 thou or less, usually set to anywhere over 30 thou. Other problems as Jon mentioned with the DellOrto float height's coming out from the factory (Italy) set up lean. Bye, PeterB.

Hi jsp, 500 ml is fine, any extra may exit out the breather pipe, not that it causes a problem though. A straight mineral 10 weight works well, I wouldn't use the 10/40 mineral, tends to cause the clutch plates to drag. Bye, PeterB.

Hi Woody, When I arrived in NZ in 1978 (as a very young lad of course) I rode a KT250 for a year belonging to Brian Barnesly (A Brummie - got 2nd best newcommer in the SSDT just behind Mart Lampkin) who worked for one of the Kawasaki shops here. Unfortunately, Brian was killed in an accident in the US and is no longer around to ask, but........he did fit the same motocross cover as per the red KT photo, I wrote about it in T&MX News back then. He did say that it was from a motocross bike but was not model specific. Don't know how to find out either, only that it would have been from a current year bike, 1978. Bye, PeterB.

Hi Jaan, Not 100% sure what you mean here, but I think you are referring to the High Tension (HT) cable that attaches to the spark plug. If this is too short, then you can easily use another piece of copper HT lead and attach it with a tight fitting sleeve, usually a piece of an old plastic breather pipe will do, make off the ends flush and the spark will jump across easily - you can always cut off the head from a long self tapping screw and sharpen the other end on a grinder then insert this into either end of the HT leads to make a physical join - not that it is so necessary. The old Motoplats were a good coil, I haven't found a good replacement mainly as I have a spare Motoplat just in case! I guess you could try an old Japanese 6V HT coil from an early bike. I have experimented with fitting up a Kokusan 2 map digital ign system to my 352 Bultaco, not quite finished - need more time and less work. But this is a bit extreme I guess, I just had a spare system in the garage (flywheel/stator and coil). Bye, PeterB.

Hi George, You can remove the sleeves from the ends of the 02 crank, and use the later sealed bearings if you wish. Bye, PeterB.

Hi fastandyc, You'll need another new woodruff key. The crank nut must have a lock washer between it and the flywheel otherwise the engine vibes will shake the nut loose. The key is only there to locate the flywheel in the correct position and the locking action is fully dependant on the connection between the two (almost) matching tapers. The nut must be tight. If you haven't made up a strong flywheel holding tool (a steel flat bar with two accurately placed spigots that locate in the flywheel holes) then you can use a ring spanner on the nut, holding it into the flywheel with the left hand while at the same time holding your hand around the flywheel then belt the spanner with a heavy leather faced hammer - this was standard practice with the old Villiers motors - they even supplied a "Hammer tight Spanner". I still use this method. Can be frowned upon by purists who advise that the crankshaft can twist, maybe so but in over 30 years this has never happened. Bye, PeterB.

Hi joe, Ask someone from the Eboracum club in York, used to be Colin Cass years back but don't know if he is still going. There was a good quarry to ride in just north of York, used in the Colonial trial but you'd need to ask about that. A bit farther north there was a few properties around Rosedale Abbey. Bye, PeterB.

Hi davey, I used to be in the Guisborough MCC also, a few years back. The rattle you describe is the piston that has either worn, or has deformed which can happen when the motor is drowned and the sudden cooling thermal shock deforms the piston. Usually a new piston kit fixed the problem. New rings never fix this problem for long. Hi Tombo, it is very, very, very unusual for a new GG to have any piston slap after a month from new, the piston bore clearence is extremely tight which is why it is best to run these motors in gently over the first 8 hours of use. Is your bike a std 08 or a Raga 300? Reason I ask is that the Keihin set up on the Ragas are not, in my opinion perfectly set up from new and they tend to run lean from 1/4 throttle onwards which produces the pinging noise when under load as you snap the power on, are you sure it is piston slap that you have and not the sound of a lean carb? The Keihin main supplied is 122, best to run with a 125 and try a slightly richer needle type GJH, in lieu of the JJH. If it is a DellOrto carb, it can be quite normal for these carbs to come out from the DellOrto factory with the float height incorrectly set lower than spec - I have seen many, they tend to run lean because of this. Make sure the float arms look parallel with the carb body/bowl mating surface when the carb is upside down. (There is a measurement of 18.5mm but looking parrallel is fine). The jets are otherwise fine on this carb. Bye, PeterB.