trum Posted February 7, 2014 Report Share Posted February 7, 2014 Hi, I'm new to here and was just after some advice really, I have a 1978 bultaco 325 trials bike, I've owned this for years and done trials when I was younger, but then it's just been left in the garage due to needing new piston and rings, I've finally pulled my finger out and decided to do it lol, but only to find out the piston was so oversized that I couldn't go any bigger(can't remember numbers off top of my head) so I've managed to get a standard 325 piston for it but now need a cylinder liner, I've got a chap who will line it for me, just wondered if this was possible and if liners were easy to get hold of?! Many thanks Andy Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted February 7, 2014 Report Share Posted February 7, 2014 bultaco uk dave renham is your man if anyone can Quote Link to comment Share on other sites More sharing options...
gasserguy Posted February 7, 2014 Report Share Posted February 7, 2014 http://www.inmotiontrials.com/product-category/bultaco/ Quote Link to comment Share on other sites More sharing options...
sherpa325 Posted February 7, 2014 Report Share Posted February 7, 2014 Late model 325's can be bored to 340, so there should be several available oversize pistons to use before the liner needs replacing Cheers Greg Quote Link to comment Share on other sites More sharing options...
trum Posted February 7, 2014 Author Report Share Posted February 7, 2014 Ok thanks Greg,where would be the best possible place to get a piston from? I'm not 100% sure because I do not have the old piston with me at the moment but I think it says 0.75 on the top?? Is the 340 bigger than that? Thanks Quote Link to comment Share on other sites More sharing options...
trum Posted February 11, 2014 Author Report Share Posted February 11, 2014 I've found my old piston and it's 84.75mm and I right in thinking I can go to an 85mm piston and that's it now, bike is a 159 bultaco 335, and is an 85mm piston easy to get hold of? Any help would be grateful, thanks Quote Link to comment Share on other sites More sharing options...
woody Posted February 12, 2014 Report Share Posted February 12, 2014 85mm is the standard size for the 340 Sherpa so there are oversizes on top of that which means you have a few more rebores left in your liner yet. Contact Bultaco UK/In Motion for a piston Quote Link to comment Share on other sites More sharing options...
nigel dabster Posted February 12, 2014 Report Share Posted February 12, 2014 In case anyone missed it CONTACT DAVE RENHAM AT IN MOTION/BULTACO UK 2 Quote Link to comment Share on other sites More sharing options...
bondy Posted February 12, 2014 Report Share Posted February 12, 2014 as dasbster says inmotion i bought a 85.50 not to long ago not the original MAHLE but there a good after market piston. £165.00 Quote Link to comment Share on other sites More sharing options...
trum Posted February 12, 2014 Author Report Share Posted February 12, 2014 Ok thanks for your help, that's what I shall do, I have just come across another problem though!!this evening I went to fit a new primary chain tensioner as wheel had broke off the old one, and while I was there I gave the weight on the crank a tug and there seems to be a very slight bit of play in the whole crank shaft along with a slight knock Quote Link to comment Share on other sites More sharing options...
woody Posted February 12, 2014 Report Share Posted February 12, 2014 Make sure it is not just the weight that has worked loose, it's not uncommon. When it does and the engine is running it is a very noticeable rumble at low revs What can happen is that when the weight is fitted, the woodruff key gets pushed upwards at the back slightly which stops the weight from sliding fully home on the shaft. When the engine is run, the key may settle a bit after a while which allows the weight to move further up the shaft, enough that the nut is no longer securing it, so you get a slight rumble due to the weight moving on the shaft. Or, the nut just comes undone meaning the weight is loose. If you think it's not a loose weight, easiest way to check if it's the crank is remove the ignition flywheel and see if there is any movement on that side Quote Link to comment Share on other sites More sharing options...
trum Posted February 12, 2014 Author Report Share Posted February 12, 2014 Yes I see what your saying, I will try and track down a puller and take magneto off, I've got a feeling it will need stripping though because I've got top of engine off ready for piston and rebore on barrel, and when I tugged on the weight earlier I could see the crank moving in the engine itself where the Conrod comes up:( ........ More money Quote Link to comment Share on other sites More sharing options...
pschrauber Posted February 16, 2014 Report Share Posted February 16, 2014 Well ... if the crank is sitting "loose" the bearings needs to be replaced, ... that's a pitty = much work. If you have to open the engine completely check the lower con-rod bearing too, if there is too to much play or the bearings might run "rough". Quote Link to comment Share on other sites More sharing options...
bondy Posted February 17, 2014 Report Share Posted February 17, 2014 just had to strip my 199B same thing had the rebore done new piston thought it was all going to well untill i noticed the main crank bearings was loose. so now i have all the new parts awaiting rebuild. Quote Link to comment Share on other sites More sharing options...
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