Get a wiring diagram and begin the process of elimination with a multimeter.
Check the input / output voltage of components leading up to the spark plug I.E. ht lead, coil, rectifier / regulator, cdi, stator. Start from the plug and work your way back.
At some point you may find one of them hasn't got an output voltage despite having an input voltage. If none of them have an input voltage then the problem isn't with the ignition components.
Next try Checking for resistance on regulator / rectifier, pickup coil and stator coils, an open circuit on these is a good indication of a faulty part.
In my experiance stators normalky fail over time with the spark getting weaker and weaker. Unless water has got into the stator windings or some other catostrophic failiure they shouldn't just stop working.
The problem is that no matter how well the rim band is installed at some time it will leak either through corrosion or the rim band rubber breaking down and loosing its sealing capabity.
I recently solved exactly the same problem by putting a blob of heldite ontop of each spoke nut. I don't have a rim band anymore, it's sealed really well.
Assuming all setup correctly (you can adjust the gears a little, there is a video somewhere) id suspect a Worn dog ring or faulty shift fork if it's doing it from 5th to 4th and not 4th to 5th. Possibly wear on the shift drum also.
Not particularly difficult to fix but it's an engine out job, head off etc to give it a thorough inspection.
It wouldn't hurt to remove the stator from the motor completely and brush on a couple of coats of epoxy or winding varnish.
As long as its sealed it will continue to produce current even if its nigh on fully submerged in water - but old coatings crack and peel off so recoating it from time to time is a good idea.
IMO you're better off selling it as a good bike for good money and purchasing a larger capacity good bike for a fair price.
Depending on how much extra power you want it generally goes like this:
More power = more money
More power = less reliability
More power = can often mean less 'useable' power
More power = is it ever enough?!?!?
Then, after you have spent all that time and money investing in more power the bike is still only worth what its market or book value is. People don't generally want to purchase tuned bikes (id prefer to buy a standard bike then one with this that and the other done to it) so you may need to keep the original parts so you can reverse tune it later; what are you going to do with these tuned parts afterwards? You are not going to get another 125, you will probably go bigger cc which is what you perhaps should have done on the first place. Now you're stuck with these parts unless a buyer wants the upgraded parts to come with the bike - you won't get your money back for the cost of tuning it - that I can garuntee!
Just my opinion but it sounds to me like you might naturally be ready for a bigger cc machine. After all the first line in your post says that you've wanted a bigger machine for some time.
To find that out you need to measure the 'squish'. This being the distance between the top of the piston and the inside off the combustion chamber at the perimeter (outside edge of bore).
The norm is to fit the head complete with combustion chamber cap and o rings, screw it down via the cylinder nuts, but not too tight (finger tight is fine). Put a pea sized blob of blue tak or play doh on the edge of the piston and rotate the crank until the piston passes TDC. If it feels really tight your blob of blue tak is too big, don't give yourself a hernia like!
Take the head off again and the blue tak will be squashed.
Use a vernier calliper if you have one to measure it while it's still stuck to the piston (if you lube the combustion chamber earlier it will be) or if you're carefully peel it off and measure it. Record your measurement and repeat a couple of times untill you can repeat the results for accuracy.
With the base gasket fitted the stock setting is a squish of 1.25 - 1.50 mm.
For instance If your blue tak measures 2.15mm then a cylinder base gasket of 0.80mm will put it round about 1.35mm and inside the ball park I.e:
2.15 - 0.80 = 1.35mm
If the blue tak measures 1.85 then a 0.50 mm base gasket will be about right I.e:
Use different clutch steel disks. Thinner ones make it lighter and more progressive, thicker ones make it harder and more like an on off switch (and it's how I like it).
Another way of making your clutch lighter is to take a man up pill and strengthen up your grip, like getting a one of those excersising squeezee contraptions.
1/4" or 3/8th" drive torque wrench with a 'uj' (wobble joint) will tighten it down no problem. You need to remove the coolant hose fitting with (if my memory serves me right a 10mm Allen key) to get access to the cylinder nut.
A spanner is pointless anyway cause you can't torque it correctly.
I'd try and retorque it down first then if leak persists I'd replace the gasket.
Mine had the same problem. All fixed now though. Rewelded the crack up with some 'super steel' filler rods and my trusty oxy/acetylene torch. I had some 3mm 4130 chromoly plate in stock from my car racing days so I reinforced the mount at the same time before re powder coating the frame.
The mount goes from being some 30 odd mm wide to about 10mm due to 'weight reduction holes'. It seems a common failiure on gassers of year 'X'. The combination of constantly knocking the bash guard, stresses from accelerating and bouncing the rear suspension and engine vibration soon fatigues the original chromoly mount which over time is sadly not upto the task.
When you reassemble the complete water pump housing to the clutch case make sure you line up the crosspin to the crankshaft slot before you tighten down the Allen key bolts. It's easy to forget and if you do forget it'll break the water pump shaft and you'll have more metal bits in one of your crank bearings.
Pindie - due to the whining sound in the top gears I take it you are infering that the needle roller bearing had failed causing the 5-6th gear to wobble / jam up on the shifting forks, adjoining gears and selector drum before the selector drum threw its leg out of bed?
The two scenarios in previous posts suggest catastrophic bearing failiure. Lack of maintenance "ahem pindie, shame on you old chap!".
Bobby:
are you able to identify the debris you found as needle rollers? If you're not sure could you post a pic? We should be able to tell you if the bits you found are bearing parts or gear parts - if u still have them that is.
Loosen bleed nipple, fill reservoir and pump the pedal. When all the air is out close the nipple, pull brake in, open nipple, close nipple - do this several times and voila!
Make sure you can blow through the bleed nipple with your mouth before you start. If not then its likely to be full of dirt, get a pokey tool and clear it.
Make sure the reservoir stays full or you will suck air in.
I personally wouldn't beat myself up about it too much it as long as the gearbox changes and engages gear nicely and the kick start operates as it should.
Does yours have magnets on the filling cap and the drain cap (it's a good idea if you havnt)?
The reason I ask is because the oil inside the case has to travel through a small hole (about 3mm diameter) to get from the clutch side (kick start side) to the transmission side.
Allthough not impossible It's unlikely that a shard of 3x1mm would be able to get through this small orifice so you can sort of narrow it down where it has likely to have came from.
If its on the clutch side id say it's likely to be the kick start tooth / gear. Nothing major as this can be changed without splitting the engine apart, so as long as it kick starts ok then this shouldn't be a major head ache to inspect and repair. It may be hard to start as it might not be getting a full kick due to it missing a tooth or two (assuming the two problems are related, or it might just be your technique or even a carb issue etc).
The oil on the clutch side also supplies oil to the crank bearing so any metallic particles here will add premature wear in this area, either by blocking off the tiny oil channel - starving the crank bearing and over heating it or passing through smaller particles that will make the oil gritty and abrasive, again speeding wear up.
If the shards were found on the drain plug (transmisdion side) then it'll come from one of the gears in the transmission. As long as its shifting gear ok both up and down then this shouldn't be much of a problem. I recently overhauled my gear box and found quite significant wear on the 2-5th Pinion gear. Coinidentally The leading edge of all the teeth on the gear had a section of teeth approximately 3x1mm of missing tooth. I did not replace it ias its s a very wide gear (the widest in the tranny if I'm not mistaken) and it was more then meaty enough to handle abuse for a few more years. The cause of this wear was simply that it's probably the most used gear in the tranny, driving second gear; a gear I probably use the most; and fith gear which I probably use just as much as I do ride it on the highway quite a bit.
Anyway hope this helps.
Edit: took me a whole to type this on iPhone so apologies if ive repeated what others have already said - like whipping off the clutch cover to inspect kick start teeth!
Sounds to me like your fan motor is at fault. Try rigging the fan motor up to a 12v dc supply, for instance a car battery and some small jumper leads probing the fan terminals, and make sure it turns on every time. Try several times to see how it acts. Mine had this fault where it would only come on 4 or 5 out of ten attempts and i ended up replacing the motor with a graupner speed 500e motor, £12 from cornwall models.
Worth noting is that you only need to loose a little bit of water from your cooling system and it renders the thermostat useless as a switching device due to the thermostat being so high up in the system.
I know not of the construction of these bikes but if the shaft is worn from the rubber lip of an oil seal you might be able to fit a shaft wear sleave.
These sleeves slide onto the shaft and provide a new sealing surface.
Look up skf wear sleave to get an idea.
These are very handy for a quick repair. Some engines have wear sleaves fitted on shafts as a stock item as it saves having to remove the shafts for repair during the motors serviceable life.
Penrith
in World Championship Chat
Posted
Is / when is this being televised? I always miss the trials on tv... :-/