spokerider Posted February 11, 2009 Report Share Posted February 11, 2009 I just recently picked up a Montesa Cota 348 and I am in the process of replacing some parts to make the bike tight and functional again. Alas, it show it's age and use, despite being well maintained by it's previous owners. To date, I've bought new brake shoes and installed, replaced the rear wheel bearings and seals, repacked the front wheel bearings [ they were still good ], replaced a badly leaking shifter-shaft seal, changed trans and clutch oils. I also lightly filed the points and reset ignition timing. I discovered that there was a small hole punched in the case from the kick-starter "bump / stop" on the shaft, allowing chain grease and dirt to enter the ignition case. After cleaning the inside of the case, flywheel and stator etc, I patched the hole with JB weld epoxy. Hopefully that'll fix the problem....... Now I'm waiting on a set of new points, once I locate a set to purchase. My local dirt bike dealer still had a few old Montesa parts about from years gone by, so I bought a 78.50mm piston kit, crankshaft seals, swingarm bushings, and a few other parts to re and re. There is a "rattle" in the engine that seems to come from the cyl head, so I'm thinking it's time for the piston kit........ The airbox has a few small cracks in the plastic, 1.5cm long or so. I'll seal them up too. It doesn't appear that too much dirt etc got into the engine and the inside of the airbox was relatively clean. The air filter was the original however, squished almost flat over the years. There's new air filter foam in there now....... The seat has a tear in the vinyl, so I'll recover it, and the fiberglass gas tank has a few chipped edges and a scorch mark where it touches the exhaust system. Iplan on touching up the fiberglass and doing a repaint. The rubber hold down straps are long gone......no kidding eh? lol. Bars are original. The levers are some cheapo plastic version that I'll replace. I just installed a new domino trial throttle and cable [ not oem I know, but try and find oem stuff!!] Have a carb gasket kit on order. I plan on replacing the carb gaskets soon. The exhaust is stock. There is surface rust on it. I'm looking into sanding the rust off then painting the exhaust with high-temp black paint. The shocks have no damping left, and will prolly be replaced. The forks will get new oil and seals. The wheels have been trued / tightened and have new Dunlop rubber. I don't know the condition of the inner workings of the engine and trans, such as con rod bearings, crank bearings etc........... I'm *hoping* that they'll be fine. Not wanting to delve into the inner workings of the engine as I've never split an engine case before. Plus, I'll prolly end up having to make all of the necessary gaskets by hand, as they seem to be very scarce. For those of you with 348 experience, do you have any advice or experience with this bike to pass on? There are no "how to" manuals for it, so I'm learning by the seat of my pants as I go........ Cheers and thanks! Spokerider in BC Canada Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 11, 2009 Report Share Posted February 11, 2009 (edited) If you want to stop the hole getting punched out of the ignition case again, use the RH footpeg to stop your foot when you are kicking. That way the kicker can return forwards out of the way when riding. A less ergonomic approach is to fit the kicker vertical when is the stored position to prevent over-rotation of the shaft when kicking. Tell every one that rides your bike how to kick it. Don't put much air pressure in the forks if they are the type with soft springs and air caps - the seal friction makes the forks sticky. Add spring preload and use heavy fork oil if they are too soft without air pressure, or buy stiffer springs. The gearbox output sprocket is on a taper. When you need to replace it, a 100mm angle grinder can be used with care to remove the old sprocket. Once you get to within 2mm of the shaft with the grinding wheel, the sprocket will come loose. To change the LH crank seal you will need to know this: The primary drive gear on the crankshaft is on a taper. Finger type pullers will not get it off, even with heat. A suitable puller can be made or probably bought from a Montesa parts specialist. If you do a search in these forums you will find photos of one I made at home. There is a Facebook Group dedicated to the Cota 348. The rubber straps are still available but not cheap. The clutch engagement action is interesting. If you use the sort of oil that is normally used in wet clutches, clutch engagement is very sudden and harsh (these bikes were never meant to be ridden on the clutch). You can successfully use very heavy oil in the clutch and primary drive to reduce the effect without causing problems with drag, provided the clutch opens evenly. I use car manual transmission oil quite successfully in mine. No matter what oil you use and even with the fanciest cable and lever, the clutch pull is a fair bit heavier than other trials bikes of the era, and the clutch spring preload is not adjustable. After many years I find I just ride it with the clutch out and control tight turns with the rear brake. If the motor is tuned well it will not stall even at incredibly low RPM. Some people remove the primary drive side flywheel. I don't know why because they accellerate great with it in place anyway. Don't rush to rebore it because of a top end rattle. They do tend to rattle a bit even with everything in perfect nick. Standard thickness for the crankcase centre gaskets and crankshaft seal carriers is 0.5mm. If it still has the MKII AMAL concentric carby, you will find that the needle and needle jet require frequent replacement due to wear. Be careful to get enough torque on the ignition flywheel nut - they are known for the flywheel location key shearing. The handlebar levers need to have high leverage ratio similar to the original AMAL levers, or you will probably have trouble pulling in the clutch. Dont worry about using a Domino twistgrip. Your Domino will be much better than what came on the 348. If you have the original 1" Akront handlebars you are lucky, they are a great shape and very strong. If I think of more I will do another posting Edited February 11, 2009 by feetupfun Quote Link to comment Share on other sites More sharing options...
mattylad Posted February 11, 2009 Report Share Posted February 11, 2009 I you need a cheap fix for the rubber straps, bend some coat hanger wire into a flatten loop to hook over the frame and tank. Use an old inner tube and cut a 1" (2cm) going metric inch by inch!!! to make a loop. Feed into wire loops and hew presto. Cheap, chearful and works Quote Link to comment Share on other sites More sharing options...
cotacrazy Posted February 11, 2009 Report Share Posted February 11, 2009 you can download the origional owners manual /parts list from todotrial.com ,or Ive seen them available on ebay uk Quote Link to comment Share on other sites More sharing options...
trialsrfun Posted February 11, 2009 Report Share Posted February 11, 2009 you can download the origional owners manual /parts list from todotrial.com ,or Ive seen them available on ebay uk Do you have a link or a lead to these pages please, I have been on todotrial and was unable to find anything. Thank you TRF Quote Link to comment Share on other sites More sharing options...
edholland Posted February 11, 2009 Report Share Posted February 11, 2009 Go here http://www.todotrial.com/ttclasico/indexttclasico-total.htm and click on interzona 10 on the left (Manuales) on this page you will see all manuals on TodoTrial Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 11, 2009 Author Report Share Posted February 11, 2009 Fellas, great posts! PLease, keep them comng...... Mattylad, I was thinking of doing something like that. I see that the oem straps are available on ebay etc, but not cheap! At this time I'm looking at spending the $$ to get the bike running "better". feetupfun, sounds like you know your Montesa's! Thanks for the great tips. When I was repairing the hole in the case from the kickstarter, I was trying to figure the best way to position the kicker, so as not to re-hole the case. Seems to be a design-fault with that little bump-stop even being able to contact the case...... I'll try orienting it so the foot peg limits the kick stroke, as suggested. Great fork tip. I'll use some heavy oil.......I'm no welter weight lol. It has the air caps on the forks. When I drained the clutch oil from the case, only a small amount of very heavy oil came out, mabye 40-50 cc's.... I replaced it with 200 cc of synthetic Amsol 80w oil. I have yet to test the cluch now. It felt *fine* with that scant amount of heavy oil before. Yep, it has the Amal Mk II carb. I'll try and find the needle and needle jet parts........ Please elaborate on the top end rattle........ is there a way to determine WHEN it's time to do an overbore piston kit job? The compression feels good when kicking the bike over to start it. What shold the compression readings be per kick / max reading after a few kicks? At first, I thought the engine sounded like it had a "chip" to it when running. I asked my local bike dealer what 2-stroke piston slap sounded like and he said a rattle. Well, I guess the chirp sound could be described as a rattle, not severe, but it's noticeable. The engine seems to pull strong. First gear is very low, as you know....... it's sounds like the engine going to grenade when I sharply twist the throtte and accelerate, and I'm still hardly doing 10 mph! When standing to ride, should the bike pull a wheel off the ground when snapping the throtte open? even without pulling up on the bars? Cause it doesn't,......well, maybe an inch or two off the ground in 2nd gear, but no real wheely. Cheers. Quote Link to comment Share on other sites More sharing options...
dave dix Posted February 11, 2009 Report Share Posted February 11, 2009 Sounds more like a new smallend bearing is required rather then a re-bore and if it is piston slap you 'WILL BE' aware of it as it sounds rather nasty on a big 2smoker. I use ATF in my Malcolm Rathmell 348 and ep90 in the box , they are a lot better then just a wheelie machine and my one will pull the wheel by just opening the throttle if required Dave Quote Link to comment Share on other sites More sharing options...
edholland Posted February 11, 2009 Report Share Posted February 11, 2009 (edited) Would like to hear what PeterB has to say about this ! but i woulden,t start it up or ride it anymore. Maybe it's something small like Dave said, cheap to fix now and why take the risk ? Cheers, Ed Edited February 11, 2009 by EdHolland Quote Link to comment Share on other sites More sharing options...
belldane Posted February 12, 2009 Report Share Posted February 12, 2009 G'day mate I have just finished restoring a 348. Split the cases, replaced all bearings, seals. Everything that needed to be replaced was done. Parts are not a problem as most of them are still available. If you need any help email me at belldane@skymesh.com.au. See ya Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 12, 2009 Report Share Posted February 12, 2009 Sounds like yours is a bit low geared. The rear sprocket should be 33 teeth, which is small compared with other twinshocks. When they are running right, a 348 will pull very strongly. Maybe you can gauge the performance if I tell you that on the 348s I have ridden (and there are 5 in our local club, one of which is mine) you can take off in 4th gear sitting down and accellerate to about 60km/h from a start with the front coming up after the first 15 feet, without pulling up on the bars. Standard gearing provides a top speed in 6th of about 120km/h and it gets to that speed very quickly for a 1970s trials bike. Another guide for if your bike needs rings is that I'm 95kg, and find I have to ease it over compression before I kick start the motor. If your "chip" is like a "plink" then it may well need a small end bearing. Piston rattle noise is more of a gentle knock, mainly on overrun. I don't know what pressure it should generate on a compression test. Mine still has the cross-hatching in the bore from new, but has mild piston rattle on overrun from high RPM, and fabulous compression. If you have another 348 nearby, you could compare engine noises. The standard exhaust and air box is very effective at silencing the breathing noises on the 348, so any mechanical noise will seem loud - relatively speaking. Quote Link to comment Share on other sites More sharing options...
helm Posted February 12, 2009 Report Share Posted February 12, 2009 Hi do you have a decompressor fitted? on mine when I brought it and got it running for the first time in at least ten years there was a noise you could describe as a"chirp" this was caused by the decompressor a) the cable binding on release and b)not closing completly whith the cable removed you will need to take it off completly to clean it, with out the decompressor you will find it hard to get over TDC easier to check than splitting the engine cheers helm Quote Link to comment Share on other sites More sharing options...
tony283 Posted February 12, 2009 Report Share Posted February 12, 2009 Ah yes, the Montesa 348 and 349 ! This was Spain's revenge for us sinking their Armada. Certain parts of the machine will test the patience of a Saint ! The original engine sprocket being one of them being on a keyed shaft. This normally has to be removed using a grinder over the key. Strangely the replacement Talon sprocket is just a press fit with no keyway. Also down there the sprocket guard has an interesting and quite worthless bolt that goes all the way through the engine and you will need to remove the clutch cover to get at the other end of it. The airbox as you have already noted was prone to cracking and I've used a podded filter to do away with the entire fitting. They do tend to be plug and condenser critical so keep some spares handy. The engine has its own quirks with NO head or exhaust gaskets, and removing the front pipe is a bit like an Arabic puzzle ring! Spend 20 mins wrestling with it without any result..... walk away and it falls on the floor! If you need to remove the barrel you will need a narrow deep well 7mm allen socket, which of course we all have and while you are sourcing that one might as well get a 4.5mm one as well. Finally the intake rubber boot can often develop hairline cracks so check it and replace. Great bike, have fun. Tony Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 12, 2009 Author Report Share Posted February 12, 2009 Davedix, Hummmm. Perhaps it does need a small end bearing......... The "chirp" noise or "rattle" or "plink" noise is most easily heard at idle, or slighty faster rpm than idle. At higher engine rpm's the noise gets lost [ or diminishes? ] in the louder engine / exhaust noise. When I take the head off and then the cylinger, I'll inspect the small end bearing. Speaking of getting the cylinder [ barrel ] off, the 7mm allen socket, is it an allen key sticking out of a 3/8ths drive socket? Or is it actually a deep socket that accepts a 7mm bolt head? feetup, my bike doesn't pull that hard! Mind you, I haven't tried the 4th gear acceleration from stopped, yet! Thanks for the test-measurement info. It does have a 33 tooth sprocket. beldane, thanks for the kind gesture.......I just may email you with a few questions / advice. helm, the bike doesn't have a decompressor, just two spark plugs. Great thought / advice however, thanks. I would like to put a compressor on it one day. Tony, thanks for sharing your 348 experiences. I haven't had to expand my "french" [ curse ] as of yet while working on this bike, but when a difficult circumstance arrises, it's nice to know I'm not the only one who has struggled with it! Quote Link to comment Share on other sites More sharing options...
348mate Posted February 13, 2009 Report Share Posted February 13, 2009 This is what you want, http://cgi.ebay.com.sg/ws/eBayISAPI.dll?Vi...em=380102953223 S_M 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.