slogger Posted May 15, 2012 Report Share Posted May 15, 2012 I have experienced to the dreaded kickstart stop cam penetrating the outer case of the flywheel area... Stripping the bike down, this looks like the previous owner had it welded up previously but this has bot held up. I have a local welder recommend by the club but was initially hoping that this could be done with the kick start shaft in situe (not the case)...... A was also hoping that the kickstart shaft was easy to remove (not the case)!!! So is their an article or a top line step by step guide to strip this down? I am fairly competent with a set of tools but have never split a crank case on a 2 stroke before.... Quote Link to comment Share on other sites More sharing options...
spawtydawg Posted May 15, 2012 Report Share Posted May 15, 2012 Hi I stripped my cota 349 down a few years ago, although it's not a 348 they would be very similar. It's fairly straight forward, just take loads of pictures with a digital camera and mark items with a blob of paint so you know that it's gone back in the same order/ place/position that you've stripped it down in. Make cardboard templates for the casing and crankcase bolts, again so as you know from whence they came. I suspect the hardest job will be is to remove the primary drive gear, this is on a tapered shaft and can be a real b*stard to get off, you will need a very good quality puller and quite probably some heat. Take your time with it, good luck. 1 Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 16, 2012 Report Share Posted May 16, 2012 Yes removal of the primary gear from its taper is a special challenge, and the sprocket on a 348 is also on a taper and is usually very hard to get off. The cylinder nuts are also an unusual size (7mm internal hex), and usually bound to the studs with corrosion so for your first two-stroke crankcase split, you have got a bike with extra challenges compared with the majority of bikes. I suggest that if you are only splitting the cases to get the case welded where the kickstart makes a hole, then plugging the hole some other way is a practical alternative. The hole in my case was sealed with silicon rubber about 12 years ago and has not been a problem in any way since then. I have another case ready to go that has been welded up to repair the hole, but nothing has gone wrong with the motor in that time so it remains a spare. Quote Link to comment Share on other sites More sharing options...
woody Posted May 16, 2012 Report Share Posted May 16, 2012 The hole in my case was sealed with silicon rubber about 12 years ago and has not been a problem in any way since then. I have another case ready to go that has been welded up to repair the hole, but nothing has gone wrong with the motor in that time so it remains a spare. Yes, that's what I would do to. There is no stress on the casing, doesn't have to keep oil in, so I'd repair it with a piece of alloy cut from a sheet and metal putty or silicon or such like. I've done loads of Ossa ignition cases like that in the past where the chain has broken them in a similar manner to the Cota kickstart. Stripping an engine just to have that case welded really isn't worth the hassle. They can be a real pain to strip, shims in the gearbox and crank, the needle roller arrangement on the gear shafts, the counter weight and cylinder studs as mentioned above. Avoid it until you have a problem which leaves no choioce but to strip it, then get it welded. Until then, just plug it - and position the kickstart so that it doesn't happen again. Quote Link to comment Share on other sites More sharing options...
slogger Posted May 16, 2012 Author Report Share Posted May 16, 2012 All, Many thanks for the advice and encouragement..... the general consensus seems to be "avoid at all costs". Unfortunately 3 DNF's out of the last 6 competitions means that my only real option is to get it welded up. I had originally plated it, with a silicon bead AND metal filled it from the outside but it has now gone from a hole to to total breach (ie the 5mm bead on the outside of the case has given way as way an now the hole is quite substantial. Going onto the UK autumn / winter the comps here tend to get muddy and I really want it as a perm fix. I also have a spare bike I can use for 3 months (albeit a mono.....) but at least I can carry on competing. I would like to get this sorted properly and to be honest I am quite happy to learn about the insides of this bike and do a full strip down So any advice on the order to disassemble would be appreciated (and once again many thanks for the encouragement to leave well alone, sorry I am ignoring them.....) Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 17, 2012 Report Share Posted May 17, 2012 If you do a search on these forums you should find my posting showing the construction of a puller for the primary gear The sprocket is easily removed using a cutting disc in a 100mm angle grinder The cylinder nuts sometimes need to be drilled away to get the cylinder off. Heating/cooling and leaving them to soak for a while with a good nut release liquid may avoid the need to drill the nuts/studs away The subject of working on 348 motors has been covered many times on these forums so you should have plenty of guidance by the time you have read previous correspondence. There is another thing with Montesa motors to remember. The side float for the crankshaft is managed with shims inside the crank seal carriers. A common mistake has people bending their crankshafts due to setting them up with negative float during reassembly. Standard gasket thickness is 0.5mm for seal carriers and gasket between crankcase halves Please keep us up to date with how you go with the motor. Disassembly order: Exhaust off Leave motor in frame Sprocket off Head off Loosening agent on cylinder nuts Oils out of both compartments Kickstart off Magneto cover off Ignition off Carby off Shifter off Primary drive cover off Primary gear nut loosened Clutch off Gear shift mechanism off Primary gear off Loosen crank case screws Undo cylinder nuts Take cylinder off Remove piston Take motor out of frame Separate case halves Remove bearings from near the weld repair Quote Link to comment Share on other sites More sharing options...
slogger Posted May 24, 2012 Author Report Share Posted May 24, 2012 FUF, Many thanks for the dis-assemble order. Most of the clutch side got done tonight. I must say I was a bit nervous using a puller on the clutch basket (the one that has the drive gears which mesh with the primary drive gear on the crank). Especially when it cracked the first time! The small flywheel came of OK but I still have the drive gear attached to the crank to remove. Is this the one which is supposed to be a pig? I assume it is a carefully placed puller and bundles of patient / nerve? Quote Link to comment Share on other sites More sharing options...
feetupfun Posted May 24, 2012 Report Share Posted May 24, 2012 (edited) If you do a search on these forums you should find my posting showing the construction of a puller for the primary gear The important things to note are It is very easy to damage the gear teeth if you use a puller that pulls on the teeth The gear is usually very tightly attached to the taper Edited May 24, 2012 by feetupfun Quote Link to comment Share on other sites More sharing options...
belldane Posted May 25, 2012 Report Share Posted May 25, 2012 That primary drive gear can be a real pig to remove, especially if it has been there for a while. Get yourself the best and biggest puller you can get your hands on. tighten the puller as much as you can and apply plenty of heat to the gear. Oxy I found the only way. Keep on tightenning as you apply more heat but for God's sake keep your head out of the way. It will either pop out gently or come out at a hundred miles an hour. Once that is done you will also have to contend with the sprocket which is also tapered. Plenty of fun times ahead of you I think. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.