gregr Posted October 19, 2007 Report Share Posted October 19, 2007 Well after rebuilding my 198 Bultaco engine [all new seals etc] and spending the last week carefully putting it back together and not even rushing the final assy today , the bloody thing still wont run ..... not a back-fire ...nothing ... zipppp ! Plenty of spark , fuel is there and am annoyed / fed-up / going back to 4-stroke & leccy start as soon as I get this bloody lemon going ! If anyone knows the ins/out of a Bultaco engine and can help , even if its "try this carb" I would be so happy to hear from you , am more than happy to bring the bike over to your garage ! Other than that , constructive comments apprecaited ! Going down the pub , Ta Greg Quote Link to comment Share on other sites More sharing options...
rcgods Posted October 19, 2007 Report Share Posted October 19, 2007 Well after rebuilding my 198 Bultaco engine [all new seals etc] and spending the last week carefully putting it back together and not even rushing the final assy today , the bloody thing still wont run ..... not a back-fire ...nothing ... zipppp ! Plenty of spark , fuel is there and am annoyed / fed-up / going back to 4-stroke & leccy start as soon as I get this bloody lemon going ! I rebuilt the engine of my M91 and that would not start for love nor money either. Get down the local motor factors and get Bradex Easy Start, remove the airbox and spray it straight into the carb inlet, kick and it should run, worked for me anyway. Quote Link to comment Share on other sites More sharing options...
gregr Posted October 19, 2007 Author Report Share Posted October 19, 2007 I would love to think that might solve the problem , but its deeper than that maybe the carb is as shagged & cobbleded together as the engine was ...only saving grace was that the previous owner never got it running either which is why its still on its "first" yes first original std size piston ! Am going to try a new trick tommorrw , hold a blow-torch by the carb mouth , if it sucks it in and fires great , if it does'nt n sets fire to the bloody thing , then i'll stand back n warm my hands !!! Cheers Greg Quote Link to comment Share on other sites More sharing options...
john collins Posted October 20, 2007 Report Share Posted October 20, 2007 Gregr Iam going to look at this for you - merely fotr the reason to keep me away from ACU work and maintain my sanity. Step one - Forget blowlamps, aerosols etc to get a Btultaco started - total nonscence. Step two. Please post exactly what you have had done. Or what you have had done . I mean exactly. Step 3 - Tell me what carb you have on it - exact details Step 4 - What ignition - ie - have you changed from standard - the usual mistake made. Step 4 - If standard - tell me how it is wired up ie - what colours you have put where? Just answer these questions first please and we will try and save you some money Quote Link to comment Share on other sites More sharing options...
gregr Posted October 20, 2007 Author Report Share Posted October 20, 2007 GregrIam going to look at this for you - merely fotr the reason to keep me away from ACU work and maintain my sanity. Cheers John , would help my sanity too ! Step one - Forget blowlamps, aerosols etc to get a Btultaco started - total nonscence. Ok , that was pub talk lol Step two. Please post exactly what you have had done. Or what you have had done . I mean exactly. Complete strip-down , all new seals , in the right way [checked with manual & Dave R] , piston is still at original size and so Dave could'nt give me fresh set of rings , so it all went back in but cleaned up nicely yes there is some play but its still got compression! ... no damage to liner etc ...all very carefully put back together ! Step 3 - Tell me what carb you have on it - exact details Now this I suspect is the cullprit .... its a Mikuni VM26 with 208 stamped on the side and heres the big worry the slider has "3" stamped underneath , rest is as follows :- Main Jet #170 Needle # 5D5 ..clip set at 4 from bottom [or second down from top] Pilot Jet #30 rest unsure , float level has been set as best i could to 15mm when fully off , ie: fuel is stopped ! Step 4 - What ignition - ie - have you changed from standard - the usual mistake made. Replaced LT coil , Red to HT coil , Green to ground , Black to cut-off switch , big fat spark & fresh NGK plug .... removed the lighting coil as its not required . New points [set to .015"] condensor and ignigtion carefully set so points start to open at 2.5mm BTDC [set with head off & using dial gauge] Step 4 - If standard - tell me how it is wired up ie - what colours you have put where? Only non-standard thing is removing the lighting coil cos it looked damaged and is'nt going to be used ! Just answer these questions first please and we will try and save you some money Cheers John , I've never know an engine like it , bike is sat in the garden in the sun to get some "heat" into the hole engine , carb off , plug out , at lowest of stroke to open transfere ports and let heat into them as well . Any help , greatfully received , may have jumped the gun but have a new Mikuni VM26-74 [brand new] on its way over from the states , e-bay warning , never go on there after a few yars lol . All best , Greg Richardson Quote Link to comment Share on other sites More sharing options...
john collins Posted October 20, 2007 Report Share Posted October 20, 2007 Right Greg - I always tend to try to go back to standard - and often when new non standard bits are fitted this may lead to a problem - so yes I suspect carb as well. But first. 1) You say you have replaced LT coil. Colours that come from original Bultaco LT coil are as follows Black - goes to HT Coil Green - goes to earth - I always use bolt that hold HT coil to frame. Red - on later models is for Brake light only - leave disconnected. Tape up. Leave any cut out wires off at present ( they will later just be a T of the black) The light coil you have removed - not needed would have had a yellow wire from it. So first - just change over the wiring from what you have - to what is correct. 2) Did the machine run OK with this carb before - or have you bought it as non runner ? Quote Link to comment Share on other sites More sharing options...
swooshdave Posted October 20, 2007 Report Share Posted October 20, 2007 I believe he already mentioned the previous owner couldn't get it running either. What is so infuriating about these engines is that they are so simple that it makes no sense when they don't run. The wiring has got me more than once. Fortunately, once everything is sorted, they tend to run just fine. Quote Link to comment Share on other sites More sharing options...
gregr Posted October 20, 2007 Author Report Share Posted October 20, 2007 Right Greg - I always tend to try to go back to standard - and often when new non standard bits are fitted this may lead to a problem - so yes I suspect carb as well.But first. 1) You say you have replaced LT coil. Colours that come from original Bultaco LT coil are as follows Black - goes to HT Coil Green - goes to earth - I always use bolt that hold HT coil to frame. Red - on later models is for Brake light only - leave disconnected. Tape up. Leave any cut out wires off at present ( they will later just be a T of the black) The light coil you have removed - not needed would have had a yellow wire from it. So first - just change over the wiring from what you have - to what is correct. The replacement coil [from a good source] had the Black wire acting as a ground for the kill switch , as I found out when I first wired the thing [as per standard spec] and had NO spark at all ... at least now I have a great spark , even though the colours are wrong to the Bultaco Std. 2) Did the machine run OK with this carb before - or have you bought it as non runner ? The bike ran for a few seconds then fowled the plug major league , but when the crank is full of clutch oil & petrol thats not surprising [crank case seals in wrong way & totally shot] ... so me being foolish believed the "its the old petrol" excuse #310 and bought it as a runner when clearly it was not ... big big leason learnt here , make sure the bike runs for a minimum of 10 mins , you get a proper test ride to check all gears and dont believe anything your told ...even if it is your DREAM bike ! When I got it home , it ran for another few mins [major smoke] and after that it came appart ! ,,,, am so convinced its the carb , as nothing & i mean nothing ties in with the spec for a VM26 taken from the pro-flow.com chart ! which is why in a depressed state i ordered a new VM26-74 from the US .... this time next week and i hope to be posting a different thread ! Guys , thanks for all the help , like you say this is such a basic engine and should be easy to problem solve BUT only if the parts are good to start with ! All best Greg Quote Link to comment Share on other sites More sharing options...
gregr Posted October 20, 2007 Author Report Share Posted October 20, 2007 Quick question John , how would the kill switch been wired using the standard colour system ...just incase i have mine ass about face ....and is the voltage coming off the black wire [to ht] the same as the red wire [rear brake light] ? Cheers again , Greg Quote Link to comment Share on other sites More sharing options...
john collins Posted October 21, 2007 Report Share Posted October 21, 2007 Hi Gregr Regardless of what you intend to do carb wise - you realy do need to sort your ifgnition out correctly first. The red wire - was just some windings put into the LT coil in order to produce some voltage for a brake light ( normal lights worked off the other coil which you discarded) Your LT current needs to come from Black wire - so wire the whole thing as I have described. If you eventually need a cut out , and it is always best when sorting out problems to leave it off as it is one less complication - but when you need it - just T into the black wire you have taken to HT coil. You are probably using a plastic junction box - or terminal blocks to connect your black wire from engine to black wire to HT coil - just run an additional black wire from the black connections at junction box to cut out button - which when you press will just actually earth out the black to ground ie handebar. Once you have wired corectly as I have said - try to start again. If no joy - please do final ignition test - BEFORE - you start playing with carb: Dis -connect all the wires from engine at your junction box. I think you have already stated you have saet points to 15 thou - you should have done this by loosly assembling flywheel - but making sure it is home on shaft/keyway. Turn flywheel clockwise - until points can be seen through 2nd window - check with 15 thou gauge. I use a filed down one ( in width not thickness!) so it fits easily through flywheel window. If points not correct adust until they are. Next - as I have said dis-connect all wires from engine. You now need a continuity tester / or bulb battery home made job - anything as long as you can determine by light going out - or needle of meter swinging - that points are actually braking the circuit( this will not work unless you have dis-connected all wires at junct box) If bulb is not going out completely ie you are not getting clean " break" at points - you must sort this out. Now is the time to also check ignition timing ( although unless a mile out will not stop a Bultaco from starting. Using a plug depth gauge you can determine exact time point are opening etc. The re-connect wires and try Quote Link to comment Share on other sites More sharing options...
gregr Posted October 22, 2007 Author Report Share Posted October 22, 2007 Hi GregrRegardless of what you intend to do carb wise - you realy do need to sort your ifgnition out correctly first. The red wire - was just some windings put into the LT coil in order to produce some voltage for a brake light ( normal lights worked off the other coil which you discarded) Your LT current needs to come from Black wire - so wire the whole thing as I have described. If you eventually need a cut out , and it is always best when sorting out problems to leave it off as it is one less complication - but when you need it - just T into the black wire you have taken to HT coil. You are probably using a plastic junction box - or terminal blocks to connect your black wire from engine to black wire to HT coil - just run an additional black wire from the black connections at junction box to cut out button - which when you press will just actually earth out the black to ground ie handebar. Once you have wired corectly as I have said - try to start again. If no joy - please do final ignition test - BEFORE - you start playing with carb: Dis -connect all the wires from engine at your junction box. I think you have already stated you have saet points to 15 thou - you should have done this by loosly assembling flywheel - but making sure it is home on shaft/keyway. Turn flywheel clockwise - until points can be seen through 2nd window - check with 15 thou gauge. I use a filed down one ( in width not thickness!) so it fits easily through flywheel window. If points not correct adust until they are. Next - as I have said dis-connect all wires from engine. You now need a continuity tester / or bulb battery home made job - anything as long as you can determine by light going out - or needle of meter swinging - that points are actually braking the circuit( this will not work unless you have dis-connected all wires at junct box) If bulb is not going out completely ie you are not getting clean " break" at points - you must sort this out. Now is the time to also check ignition timing ( although unless a mile out will not stop a Bultaco from starting. Using a plug depth gauge you can determine exact time point are opening etc. The re-connect wires and try Thanks John , right on it this week , daft question but i presume when the buld goes out that when it should be 2.5-2.7mm BTDC ? ..yes ! All best & thanks a lot ! Greg Quote Link to comment Share on other sites More sharing options...
gregr Posted October 23, 2007 Author Report Share Posted October 23, 2007 Ok John , going by theeeee book and your kind words .... If I connect the black wire to the LT side of the HT Coil , I get a weak spark ! If I connect the red wire to the LT side of the HT Coil , I get a better spark than the above ! Odviously this is not correct and now I have a new "wont start" suspect , the already replaced LT coil or something else in the electrical system , but nearly all of it has been replaced ,,, appart from the HT coil . Jesss will it ever end ! All best Greg I know it should make NO difference but how many people have gone over to a digital system ? Quote Link to comment Share on other sites More sharing options...
swooshdave Posted October 23, 2007 Report Share Posted October 23, 2007 If you really want to get this resolved quickly... post a picture of the current configuration. A picture is worth a thousand words and by now I'm sure you are tired of typing. Pull off the side cover and take a picture. Then of the junction block and wires going to the coil. More than likely someone will be able to quickly spot the issue. Quote Link to comment Share on other sites More sharing options...
gregr Posted October 23, 2007 Author Report Share Posted October 23, 2007 Hi Dave Its ok I have a cunning plan , am going to enter the next meeting and at the start [when the bike wont start] ask for assistance from as many Bultaco riders there lol ........ hopefully by the end of the event I'll have a working machine As for posting a pic , lovely idea but there really is'nt much to post .... just done the "check the spark in the dark" test & confirmed my previous post ... Ta Greg Quote Link to comment Share on other sites More sharing options...
john collins Posted October 23, 2007 Report Share Posted October 23, 2007 Yes I agree a picture would help - as I am starting to wonder what you have got there. When you did as I asked last time - ie remove all wires and connect to tester/bulb& battery - did the light go out ( or needle swing) when you turned flywheel and the points opened? - I mean completely out ? Also - you have changed LT coil - where did you get this ? The wire colours you quoted originally were same as Bultaco genuine ie Black, Red, Green and Red If you have used a re- wound coil however these may be different - although most re-wound coils I have seen have not used the same windings as genuine eg have missed out the brake light part. If you have a rewound LT coil - we may have to go back to step1! Connections inside flywheel for genuine coil are - black going to points and to condenser - and up to HT coil. Green - from LT coil - up to ground. Red - going nowhere Quote Link to comment Share on other sites More sharing options...
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