thedktor 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=380102953223S_M I have just bought one of these! But......... After washing my 349 and giving it a good 10 min run up the road, and left overnight, when I took the head off there was still water in the cylinder bolt recesses.... Which means that after 29 years use the (Allen) bolts are rusty, and completely solid. The 7mm Allen key I could feel starting to bend and open up the heads so have paused for now. An engineering friend has suggested grinding down a larger, stronger key to get a better fit for the next attempt. Otherwise I will have to drill off the heads.... Steve Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 13, 2009 Report Share Posted February 13, 2009 Yes that is a good idea your friend suggested. I ground down an 8mm section of hex key to 7mm A/F and turned it with a single hex socket and yes it was tight all right having never been off before. Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 13, 2009 Author Report Share Posted February 13, 2009 Here's an article on Montesa stuff, written by a fella who's had some experience.......... He explains the process required to drill out the nasty 7mm fasteners that have seized the cyl to the engine. Has anyone needed to do this to a 348?? Also, are these 7mm "nuts" or are they "bolts", that secure the cyl to the engine? http://rmmontesa.com/montesa%20articles.htm Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 14, 2009 Report Share Posted February 14, 2009 Here's an article on Montesa stuff, written by a fella who's had some experience.......... He explains the process required to drill out the nasty 7mm fasteners that have seized the cyl to the engine. Has anyone needed to do this to a 348?? Also, are these 7mm "nuts" or are they "bolts", that secure the cyl to the engine? http://rmmontesa.com/montesa%20articles.htm Aha I discovered that yesterday! - very useful. So, my story so far is that the two inlet side "nuts" came off but the exhaust side nuts refused to budge even with a very snug fitting cut-down larger Allen key. So I had to drill 'em (will post more detailed write-up and photos in near future). The nuts are cylindrical, about an inch long, and fit over studs sticking up out of the crank cases. The problem is not so much the thread as the remains of the nuts are still stuck solid in the cylinder! A mixture of dried up muck and corossion has glued them inside the recess. I am hoping to find some thin tube that fits over the nuts to cut them out, like a disk cutter. Maybe this should have been the first course of action before attempting undoing. In fact it is! All in all a right pain! Steve Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 14, 2009 Author Report Share Posted February 14, 2009 Hummm, I guess that I can anticipate the same troubles as others when i's time to remove the cylinder on the 348........ Steve, if the problem is not drilling the stud threads from the nuts, and it's corrosion holding the now-drilled nuts in place, could you just get a pair of needle-nose vise grip pliers in there, grab hold of the nuts and tap / wiggle the nuts up and out? That along with a good soak of penetrating oil......... Not having had the head off the engine, I'm only guessing at what the situation looks like. Quote Link to comment Share on other sites More sharing options...
tony283 Posted February 14, 2009 Report Share Posted February 14, 2009 Ho, ho! .....as I said in an earlier comment Spain's revenge for sinking an Armada. Snap-On make a 1/4 drive 7mm long shank allen which fits perfectly down the barrel holes and because it fits it won't slip out or bend. A long handled socket drive usually gets them free. Oh yes, when rebuilding make absolutely sure there is none of the lower gasket left as the smallest microbe will be enough to cause an airleak and squealing noise. Strange as the top end without a gasket doesn't leak at all. Tony Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 15, 2009 Report Share Posted February 15, 2009 Thanks for the further tips Tony. Spokerider, yes, in theory! However the nuts fit snuggly and needle nose pliers will not get a good purchase. I'm sure the remains of mine will come out once soaked in fluid for a while - I have half-jammed a drift in them from the other side and bashed with a hammer and they will not budge at the moment! A small expanding bolt might be the answer, and bash away merrily at that. Blimey yes, revenge of the Spanish armada indeed Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 15, 2009 Author Report Share Posted February 15, 2009 Right on, thanks. I'll search for a 7mm long hex socket and get the cylinder off for a look at piston, bore, clearances, and small end bearing condition. My bike has an engine sound similar to this; http://www.advrider.com/forums/showthread.php?t=365136 but not as bad, maybe one third to one half as loud as this guys rattle. More thoughts.......it seem that the Amal carbs on vintage bikes are pretty much worn out, even the MK II carbs are suppose to wear out easily.........before sinking any $$ into an old MK II [ on my bike ] how complicated is swapping a Keihin PWK 28 or Mikuni 26mm carb to the 348? Can the OEM manifold / airbox rubbers be used with these carbs or is there some other, different parts required for the swap? Can the same throttle cable be used? [ I just bought and installed a new Domino trials throttle and cable ]. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 16, 2009 Report Share Posted February 16, 2009 A 26mm VM Mikuni will fit directly to the engine side connector, but the Mikuni inlet bell OD is smaller diameter than the AMAL mk2, so you would need to fit a sleeve. I have done a test fitting on my 348 with a 26mm VM, but am persevering with getting it to run right with the AMAL at this stage. Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 16, 2009 Author Report Share Posted February 16, 2009 A 26mm VM Mikuni will fit directly to the engine side connector, but the Mikuni inlet bell OD is smaller diameter than the AMAL mk2, so you would need to fit a sleeve.I have done a test fitting on my 348 with a 26mm VM, but am persevering with getting it to run right with the AMAL at this stage. Good to know, thanks. Making a sleeve to accept the smaller diameter Mikuni carb bell sdhouldn't be too much trouble......... What are you doing to the Amal carb [ MK II ] ? to get it "to run right"? I've ordered a gasket kit for mine as it leaks a little fuel. I'm reluctant to put more $$ into the Amal at this point. The carb on my 348 seems to work just fine, for now, but alas, I hate having stuff on the verge of breakdown or on it's last legs..... I'd just as soon as put a new carb on it and be done with it. Of course, keeping the original for future resotration purposes is a given. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 16, 2009 Report Share Posted February 16, 2009 Good to know, thanks. Making a sleeve to accept the smaller diameter Mikuni carb bell sdhouldn't be too much trouble.........What are you doing to the Amal carb [ MK II ] ? to get it "to run right"? I've ordered a gasket kit for mine as it leaks a little fuel. I'm reluctant to put more $$ into the Amal at this point. The carb on my 348 seems to work just fine, for now, but alas, I hate having stuff on the verge of breakdown or on it's last legs..... I'd just as soon as put a new carb on it and be done with it. Of course, keeping the original for future resotration purposes is a given. With new slide, new needle (U) and new needle jet (107), standard pilot jet and correct float level, it tends to 4 stroke just above where the pilot jet effect is strongest - and runs great everywhere else. I've then raised the slide cutaway in stages as far as I can and the 4 stroking is still there. The next thing I want to try is a 106 needle jet instead of the 107, hoping to get it slightly leaner at that part of the needle. I've also ordered a needle as used in the 238cc Sherpa T with Mk 2 AMAL to experiment with if the 106 needle jet doesn't get me what I want. Yes it costs a small fortune to buy the AMAL parts and economically it would make much more sense to fit a new Mikuni - but I seem to enjoy the challenge. If I wanted things to be easy, I wouldn't ride 35 year old Spanish trials bikes. Quote Link to comment Share on other sites More sharing options...
vintagecota Posted February 16, 2009 Report Share Posted February 16, 2009 The trick to getting the barrel nuts off is to use the long hex socket, tap it into the nut firmly and then give it a good thwack with a hammer right off the bat. Then don't give it enough torque to break the tool or round out the nut. Use penetrating oil beforehand and have a propane torch handy for some soothing warmth. When you retighten the nuts, torque them to spec, give them another thwack with the hammer and retorque. You'd be surprised how much this loosens them. It saves retorquing them after a heat cycle. Where in BC are you? Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 16, 2009 Author Report Share Posted February 16, 2009 The trick to getting the barrel nuts off is to use the long hex socket, tap it into the nut firmly and then give it a good thwack with a hammer right off the bat. Then don't give it enough torque to break the tool or round out the nut. Use penetrating oil beforehand and have a propane torch handy for some soothing warmth. When you retighten the nuts, torque them to spec, give them another thwack with the hammer and retorque. You'd be surprised how much this loosens them. It saves retorquing them after a heat cycle. Where in BC are you? VintageCota, what about using an impact driver.......the kind that you hit with a hammer and it gives a partial revolution to the fastener......after using some penetrating oil [ x a few days ] and tapping the 7mm hex well into the nut recess? I'm in Victoria. Quote Link to comment Share on other sites More sharing options...
thedktor Posted February 17, 2009 Report Share Posted February 17, 2009 The trick to getting the barrel nuts off is to use the long hex socket, tap it into the nut firmly and then give it a good thwack with a hammer right off the bat. Then don't give it enough torque to break the tool or round out the nut. Use penetrating oil beforehand and have a propane torch handy for some soothing warmth. Agreed, but I will say that this did not work with mine as they were too coroded. My bike had been used as a trail bike, in mud, so I would not expect most bikes to be so bad. The point to make is, take the head off, and try and find some means of scraping the muck/rust from around the nut before undoing... Steve Quote Link to comment Share on other sites More sharing options...
spokerider Posted February 18, 2009 Author Report Share Posted February 18, 2009 (edited) I took the cyl head off the engine today. There is some dusty rust / crud in the 7mm cyl nut recesses, so there's penetrating oil soaking things loose right now. The barrel will come off in a few days...... I bought a long 7mm alllen socket that'll work fine for the job once I grind the ball end off of the business end of it. I see that a previous owner has had the engine rebuilt once before, as there is a .025mm oversize piston in place. I can see the cross-hatch pattern in the cyl bore. The cross hatch is more visible on the sides of the bore and less obvious in the fore / aft cyl wall. No scoring or really shiney areas either. No carbon build up, just some thin oliy soot. Top ring looks fine from the inspection so far...... I can't make the piston move fore / aft in the cyl with pressure applied by two fingers on the piston crown, as in piston slap, but I CAN rotate the piston as if trying to spin it in the bore, with the same pressure from two finger tips. This holds true with the piston at all stroke positions that I tried. It moves about 1mm-1.5mm as a guess. Perhaps there's wear on the small end needle bearing? Big end bearing?? Is this movement abnormal? Thanks. Edited February 18, 2009 by Spokerider Quote Link to comment Share on other sites More sharing options...
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