cb350sg Posted February 16, 2012 Share Posted February 16, 2012 Hey guys. I'm slightly baffled. Well, completely. My bike started on the button, every time. It's an old bike. 1986 Honda CB350SG. I'm off on a long journey soon and so I decided I'll replace the oil and filter. I've had a problem with a leak from the sump bolt, but as a result have ALWAYS checked the oil level and it's always been fine. However, I have fixed the leak now with some rubber washers. (Until I have the pan retapped or w/e).Having completed the oil change, I topped up the oil to the manuals specifications and let it settle, checked the dip stick, ran the engine for about 10minutes... Then the bike cut out and hasn't started since.Things I've tried in no particular order:Charged the batteryRemoved the carburettor, checked for dirt, sticking components, worn diaphragms.Removed the air filter, cleaned it out including the metal mesh separating the carbs from the filter. Did find some fuel residue which did seem a little dirty. but wiped it clean.Removed the spark plugs, checked for any fouling. I think they were a little dark. Quite black which suggests carbon build up? So running rich? I also noticed a pretty weak spark. I tried bump starting it off a local farmers quad. It tried to turn over. the exhaust was going as in it was actualy running but it wasn't running by itself. Soon as I brought in the clutch to give it some revs it didn't it was just dead again.My opinion is plugs and have ordered 2 new ones. Any ideas? I'm starting to try stupid desperate... pointless things now.. Thanks in advance! Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted February 16, 2012 Share Posted February 16, 2012 if the plugs were black after 10 mins of running did you have it on choke all that time as that would casue the plugs to foul up see how it is once you fit the new plugs Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 16, 2012 Author Share Posted February 16, 2012 Nah, I've never checked the plugs prior to the bike suddenly not running. So I'm guessing its been building up over time.Shall do, hoping they come quickly. Will let you guys know what happenes Quote Link to comment Share on other sites More sharing options...
Tango Posted February 17, 2012 Share Posted February 17, 2012 Could be plugs or coils. Have you got good compression? Turn it over with plugs out and stick your finger on the plug hole and see if it gets blown off. The plugs were Black...but were they wet? If you turned it over with no spark (or very weak spark) you'd expect the plugs to be wet from unburnt fuel. You are getting fuel through? Have you tried to start it with the tank filler cap open? Just in case the breather is blocked causing a vacuum in the tank. Float bowls on carbs full? Fuel tap in the correct place? Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 17, 2012 Author Share Posted February 17, 2012 I did a compression test with my thumb the other day to check it, it blew my thumb right off. so thats all good.Yeah the plugs were wetLoosened the drainage bolt on the carbs just now and they were flowing well, caught all the fuel from them in a glass and it looked really clean, so put that back in the tank.Not tried starting with the petrol cap off, i'll give that a shot tomorrow morning. thanks for the idea mate Quote Link to comment Share on other sites More sharing options...
Tango Posted February 17, 2012 Share Posted February 17, 2012 If the plugs were wet it would suggest that the problem is spark. New plugs may sort it. Blocked filler cap would cause fuel starvation.......so the plugs would have been dry.Other things to check are Plug caps....damp in the electrics.....CDI unit....etc. Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 17, 2012 Author Share Posted February 17, 2012 Hope the plugs do sort it. Hate not having transport!Will add these to my lists of things to try. I have been fiddling a lot with the electrics... I fitted some new indicators etc.Somebody suggested my oil filter wasn't in right? Could this cause it not to start? Quote Link to comment Share on other sites More sharing options...
Tango Posted February 17, 2012 Share Posted February 17, 2012 If the filter wasn't fitted correctly it could cause oil starvation which could cause a seizure or partial seizure....but from the sounds of it I wouldn't think that's what has happened here. Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 18, 2012 Author Share Posted February 18, 2012 Okay today i tried the following:I tried the filler cap open just because it was easy and worth a shotI cleaned the plugs with a wire brushTurned the oil filter the other way round, checked all the bolts in there were good and refitted it...Batterys on charge again now and I'm waiting for a mechanically minded friend to come round tomorrow and give me a hand. I think we're trying the timing chain and a 2nd opinion on all the stuff I've checked throughWould take it to a garage but theres no garage for 50+ miles. Debating towing it out and calling the AA... ha Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 18, 2012 Author Share Posted February 18, 2012 and I dont know how to check the CDI :S - The CDI decides when to fire? Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted February 18, 2012 Share Posted February 18, 2012 take spark plug out and rest it on the engine and turn engine over on starter button check out how well if at all it is sparking,also how well is it turning over on the battery when you are trying to start it Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 18, 2012 Author Share Posted February 18, 2012 take spark plug out and rest it on the engine and turn engine over on starter button check out how well if at all it is sparking,also how well is it turning over on the battery when you are trying to start it It's pretty weak tbh... I dont think it's as bright as it should be. I ordered myself a multimeter, handy thing to add to the tool box i figured Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 20, 2012 Author Share Posted February 20, 2012 Right, after a long long long day working over every possible thing I can think of on the bike.I've diagnosed the problem as a worn out timing chain that's slipped after the oil change and is now not firing at the right time. It's a pretty big job. I'm not sure whether I'll undertake it or just get shot of the bike. Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 20, 2012 Author Share Posted February 20, 2012 http://www.youtube.com/watch?v=BP1BOmfn ... e=youtu.beTheres a vid, anyone agree or think its something else? Quote Link to comment Share on other sites More sharing options...
megawatt Posted February 21, 2012 Share Posted February 21, 2012 I have never heard of a timing chain jumping the sprockets during or after an oil change. You have tested the compression and said it was good? Easy enough to check though? Think you're barking up the wrong tree , unless something catastrophic happened after you tried to start it??? Can you get pix of timing marks and slack in cam chain(there shouldn't be any!!!) with rocker cover removed? Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted February 21, 2012 Share Posted February 21, 2012 got to agree with mega on this one i have never heard of chain jumping due to oil change if you have aprtial seized it then that could be the problem you need to do a proper compression test on it,but it does sound like it has compression as it is knocking starter out after few turns.if you have not fitted new plugs thats what i would do as cleaning the old ones up doesnt always work a sthey could be tracking through the ceramic section of the plug and not firing properly Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 21, 2012 Author Share Posted February 21, 2012 I have never heard of a timing chain jumping the sprockets during or after an oil change. You have tested the compression and said it was good? Easy enough to check though? Think you're barking up the wrong tree , unless something catastrophic happened after you tried to start it??? Can you get pix of timing marks and slack in cam chain(there shouldn't be any!!!) with rocker cover removed? Hey, my diagnosis proved to be wrong. I took the cover off last night to have a look inside the engine, the chain seemed absolutely fine. nice and snugly fit. Wouldnt got pics if i had read this post first. got to agree with mega on this one i have never heard of chain jumping due to oil change if you have aprtial seized it then that could be the problem you need to do a proper compression test on it,but it does sound like it has compression as it is knocking starter out after few turns.if you have not fitted new plugs thats what i would do as cleaning the old ones up doesnt always work a sthey could be tracking through the ceramic section of the plug and not firing properly I fitted new plugs etc. and compression seemed okay when i held my thumb over the plug holes.OKAY! SO! Today, I've phoned around pretty much every mechanic around this area and they all say they don't do motorbikes. So I just casually explained my problem and they all gave a diagnosis over the phone which I then tried. and it's not helped.So... I phoned the AA up today as I'm already a member. I explained my situation and i've now added home start and garage repair to my existing policy, only £22 extra to what I already pay. I pay like £7 a month I think. So that was a really good deal I thought. It takes 24hrs to take effect so tomorrow I can get them out to come and help me. If they can't do it then they'll in theory take me to my nearest garage which is 50miles away. Also, they'll help me with repair costs, win win so long as all goes according to plan Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 22, 2012 Author Share Posted February 22, 2012 AA has picked up my motorbike, it's now off to the garage for repair. Hope it doesn't cost much... if anything! Quote Link to comment Share on other sites More sharing options...
giocast Posted February 22, 2012 Share Posted February 22, 2012 i'm too late!! - was going to suggest you try 'Easy start' to try and prove if it's fuel related. If i'm stumped it's an easy test to do to save time (if you're careful). To add to all the other suggestions it could be a small amount of water in the carb float bowls. Tends to happen when bike hasn't been used for some time. Another idea - did the engine oil you drained out smell of petrol? I won't bother to explain why i'm asking now you've taken it in - just a thought. Quote Link to comment Share on other sites More sharing options...
cb350sg Posted February 23, 2012 Author Share Posted February 23, 2012 I do want some easy start. looks pretty useful stuff! I did try pouring a little fuel into the spark plug holes and warming the plugs to see if it was fuel problem. A mechanic told me to try that over the phone, just a heads up for anyone else. I thought it was a good idea.So the garage got back to me. They were so confused... But they did eventually come to a conclusion. It's the ignition coil which is crazy hard to find. But I think I've located one off of somebody on ebay so thats all good. Getting that sent to me hopefully tomorrow. Then that should be me!oh yeah, the garage asked for my service manual, that's how confused they were haha Quote Link to comment Share on other sites More sharing options...
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