d250b Posted January 23, 2015 Author Report Share Posted January 23, 2015 Thankyou all for the replies and suggestions, theres a lot to think about there, just have to make a decision about which path to go down. The blacksmith who did the original welding and who made an excellent job of the Sherpa, is reluctant to go at it again because he's really annoyed about what happened. This makes me lean towards the epoxy/putty idea for simplicity. Ive watched a youtube video for Pschrauber's Knetmetall and it looks pretty good; I can get a small tube for about £11 so its not too pricey either. (is that water/aqua blast finish on your casing? looks very nice) The youtube video is all in German but I take it you just work it a bit in your fingers to warm it up and then apply, no hardener or anything? (The loctite needs a hardener) I also have a broken edge like yours which I was just going to leave but having seen your repair I think I should do it too. I'm not aware of anyone with a milling machine but there are so many garages and motorsport people round here theres bound to be someone that could do it. It is the older more rounded sort of case with the proper drain plug and the filler at the front and there seems to be a few available in the US but I'll leave that as a last resort but I want to keep the bike as genuine as possible. Perhaps the path of least resistance would be to try one of the puttys first before milling or rubbing down, I just hope that putting a rough surface on the edge doesn't require removing so much metal that milling down won't leave me with enough clearance.....to be continued Thanks again for all the replies, much appreciated! D Quote Link to comment Share on other sites More sharing options...
pschrauber Posted January 23, 2015 Report Share Posted January 23, 2015 In own experience, the "putty" works quite well, I have repaired some really wicked places with that stuff. Here a link / picture from another trials forum were a side case of a YZ 175 of the non matching year model was modified to fit to the TY, These modifications were also made with "Knetmetall" http://trialforum.net/index.php/Attachment/18776-IMG-1987k-jpg/ 1 Quote Link to comment Share on other sites More sharing options...
big_e Posted January 26, 2015 Report Share Posted January 26, 2015 I've had exactly the same problem with casings. The old Triumph casings were such good quality aluminium that they welded beautifully with little distortion and cleaned up blemish-free. Bultaco didn't use such a high quality grade, so if they get cracked on rocks there is only one way to fix them and it is NOT by welding. If the dent is not too deep then you can tap it out, but it will be cracked, however shallow the dent is. This crack will be contaminated with oil (the ignition side is not so bad obviously) and in my opinion the best way to clean the crack is to use carb cleaner, unless you can get your hands on some carbon tetrachloride. After getting the shape of the case back to something like, rough up the surface around the damage to give a good key, especially on the inside where you can afford to build up the repair thickness slightly, and then use an epoxy putty like QUICKSTEEL Steel Reinforced Epoxy Putty metal repair. It comes in 2oz tubes and you can get it on eBay for £5.85. When this stuff is dry, you can re-shape it to suit the original case. It is roughly the same as machining aluminium, so even just a file is good enough to get the shape back. Use wet and dry to get a final finish and then paint the case as normal. Polishing is out I'm afraid! I've even rebuilt the Bultaco lettering on the clutch side. The finished article is distortion free, oil tight and petrol proof and will easily cope with engine casing temperatures. I hope this helps, it has certainly worked for me. Regards. 1 Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted January 26, 2015 Report Share Posted January 26, 2015 I have never had any trouble getting Bultaco aluminum alloy welded. Over the years I have had a fork leg welded, several cases, a fin off a head, a fin off a barrel and the last bike I purchased had been pulled apart as the lug that sits behind the countershaft sprocket [rear mounting lug for the ignition side case] had been broken off leaving a hole in the main engine case. I have used a couple of different welders over the years, it pays to do your research when choosing a welder as well. I always make it as easy as possible for the welder by making jigs if necessary and by always dressing the area to be welded, then heating it gently with an oxy torch to burn out any oil etc and then cleaning with wax and grease remover and a stainless steel wire brush. Take your time to find a competent welder. I have previously used a fellow who was making bits and pieces for turbo cars - manifolds, airboxes,etc. Currently using a guy who works in an auto radiator shop repairing radiators, he also does one off fabrications for modified cars, 4wds and bikes. These guys are very skillful and the work I have given them has been a 'piece of cake' compared to what they normally do. By the way welding the lug back on to the engine case was a lot of work for me [shaft in position in case, cases bolted together, plate on the outside to secure the lug in the correct position, prepare the weld etc, a days work for me] the guy took about five minutes to weld it back on and charged me $40. Cheers Greg 3 Quote Link to comment Share on other sites More sharing options...
d250b Posted January 26, 2015 Author Report Share Posted January 26, 2015 Thank you for the further replies; the welding repairs I had done to the Sherpa, including the clutch case went extremely well and there was no bubbling up from oil in the alloy so for some reason the Sherpa casing hadn't absorbed oil the same way? ( it was almost dry of oil when I took it off but I don't think it's as simple as that:-) ) if I need any repairs of this nature done in the future I will certainly take all of this information on board and hopefully if anyone is searching for this topic in the future it will help them out. After a lot of deliberation I have decided to try to rub down the edge of the casing on sheets of emery cloth on a flat surface ( no luck finding someone who could do milling) and then make my own gasket out of thicker gasket material to compensate for any reduction in clearance. I am going to try a "putty" type repair on a broken flange on the main engine case; on the magneto side underneath the front sprocket and similar to the repair PSchrauber photographed above. Hopefully I can manage as good a repair as he illustrated, it's on a non-critical bit so a good place for a first attempt. I'll post pics of repairs (good or bad) once I get some time to tackle them. Cheers D 3 Quote Link to comment Share on other sites More sharing options...
d250b Posted February 9, 2015 Author Report Share Posted February 9, 2015 (edited) Update on progress in the hope this may be of help to anyone in a similar predicament. I rubbed and rubbed and rubbed the casing down on sheets of emery cloth until I got it flush all round. Pane of glass on the desk, taped down and emery cloth taped to that. I've found a gasket manufacturer who will do bespoke designs and i'm going to get some made in 2mm material; they're only just over £10 but the postage is a tenner too so best to get 3 or 4 to make it worthwhile. Hopefully this will sort everything out and maintain the clearance on the casing with no problems and better than sticking 2 together. Not sure about any rules regarding advertising on the forum but should anybody want the company's information, please fell free to PM me. D Edited February 11, 2015 by d250b 2 Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted February 9, 2015 Report Share Posted February 9, 2015 Sounds like the best solution, are you sure that you will need a thicker gasket. It would be worth trying the std one to see if you have enough clearance. Making your own gaskets is not as hard as you think, gasket paper can be purchased at any good motor accessory shop. You need a 'wad punch' to punch out the holes [can buy cheap ones on ebay] - just remember when punching out the holes to do it on the 'end grain' of a piece of wood, preferably hard wood. Cheers Greg Quote Link to comment Share on other sites More sharing options...
dadof2 Posted February 10, 2015 Report Share Posted February 10, 2015 I find breakfast cereal box cardboard makes pretty good gaskets. 2 Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted February 10, 2015 Report Share Posted February 10, 2015 I find breakfast cereal box cardboard makes pretty good gaskets. Sounds like something the GasGas factory would do, must say I did expect better from you! 1 Quote Link to comment Share on other sites More sharing options...
dadof2 Posted February 10, 2015 Report Share Posted February 10, 2015 #24 I did not want to list where cereal box may not be appropriate but I have used it widely with complete success. I have used it (with a smear or blue Hylomar) for base gaskets, sump pans, differential covers, inlet manifolds, ignition / flywheel cases, primary drive cases, water pumps, thermostat housings, idle speed motor, etc etc In the case of Beta primary drive cases cereal box works better than genuine gaskets which are very narrow and seem to shrink and move in the joint. Rather amusingly I once dismantled a "seized engine" only to find the owner had used Hermetite RTV silicone throughout instead of gaskets. The loss of clearance, in gearbox / mains and increased compression meant the engine could not be rotated. Why do you think cereal box should not be used? 1 Quote Link to comment Share on other sites More sharing options...
d250b Posted February 10, 2015 Author Report Share Posted February 10, 2015 Thank you! it may, after all come down to a rice crispies packet...i was a bit previous with my last post. Despite having explained clearly over 2 or 3 emails what i needed and also putting a letter in with my original gasket to CLEARLY say that I needed the new ones 2mm thick, I got an acknowledgement email yesterday to say they had received my original and that they would make the new ones out of material 0.8mm thick also although the gasket price was now cheaper at £7.47, the postage had suddenly gone up to £18 from a tenner (apparently the £10 quoted on the website is just for stock material NOT bespoke jobs). I replied explaining that 0.8mm is no use and the reply to that is that they can do 2mm no problem and the price is the same as "material thickness is nominal". No idea what to make of that. Ive also looked at the material they were going to use and it looks like its for high temperature situations and it "generally exhibits good resistance to oil and fuel". Doesn't sound all that great does it? I think it would be easier to just ask for my gasket back and forget it and make my own. Seriously; I'd love to put a transcript of the various emails on here just to show you how difficult it seems to be to specify you need a 2mm thick gasket but Ive rambled on enough. Greg, in all honesty Im not sure that I wouldn't have enough clearance with an ordinary gasket; I just though I was doing the safest thing by recreating the original clearance with a thicker one. Maybe I could stick 2 ordinary ones together with some blue hylomar and that would work? Quote Link to comment Share on other sites More sharing options...
woody Posted February 10, 2015 Report Share Posted February 10, 2015 I'd use Yamabond (or threebond from Rex Caunt) It's designed for jointing metal surfaces with no gasket but I've used it successfully with a gasket as well. It's better than Blue Hylomar and seems to fill imperfections better As for welding, I've had Bultaco and Ossa barrel fins, heads, clutch, crank and timing cases all welded with no problems at all Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted February 11, 2015 Report Share Posted February 11, 2015 Hi, I just looked at your original photo where the size of the gap would appear to be about 1mm. I just checked my M92 by removing the large clutch adjusting 'bung' in the case and the clearance between the clutch posts [the ones that hold the clutch springs in place] and the case is about 2mm. So you may be able to get away with the original gasket, certainly worth checking out before you go to any extra trouble. Also just checked and you can buy gasket paper up to 3mm thick. If you decide to make your own you don't have to follow the internal shape of the original gasket where the mounting holes are, you should be able to make it about 20mm wide [instead of 5mm] and just add some cutouts where required, shifter shaft, chain tensioner?. Cheers Greg PS dadof2 - that was a joke, really hate it when I have to explain my jokes Quote Link to comment Share on other sites More sharing options...
matador107 Posted February 11, 2015 Report Share Posted February 11, 2015 Place your gasket paper(of choice) on a flat surface, apply a smear of yamabond to the edge of your case cover then place it onto the paper.Leave it for a day then run a really sharp razor type knife around the case edge. Once done, use a long drill bit and drill through the various screw holes ,use timber as a base , ream these holes out on the reverse side with an oversize drill bit, by hand. Then use your knife to trim the gasket paper on the inside of case. I've used this method to make crankcase gaskets with manilla office folders, no problems if you use a quality sealant in conjunction. Yes cereal box can be used for base gaskets, I've committed that sin also. 1 Quote Link to comment Share on other sites More sharing options...
d250b Posted February 11, 2015 Author Report Share Posted February 11, 2015 Well I've given up on the bespoke gaskets, going to be too expensive to order a few plus postage and I'm quite sure when they arrived they would be 0.8mm thick! The same company has big sheets of 2mm thick gasket paper on ebay for £16 quid in material suited for oil and ill just order some of that I think. Looked at a cereal packet and not thick enough to give me the 2mm. Yamabond looks interesting Woody ( I wonder; if it's a better gap filler, if it might have worked with the original gasket and saved all this hassle???) and thanks Matador107 for the suggestion of how to cut the gasket, that's pretty clever. Cheers D 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.