Hi, I think I've recently encountered a problem. I have '98 748 around 25k on the clock and my battery wouldn't charge from the bike, only the tender. So I parked it last year with a full tank of gas(unfortunately) in a climate controlled garage, and due to a death in the immediate family was not able to get around to it. I got to the bottom of the charging problem, there was burned wiring and connector between the stator and regulator so new wiring was spliced in. Bought a brand new battery, changed the oil and filter, topped off the coolant, and she fired right up. I forgot all about the gas sitting for so long. But I got on it, rode for a few days and even hammered it to 130 as all seemed fine. The gas light came on and I filled back up with a full tank. Now I rode as everything was normal for maybe 5-7 miles after filling up and parked it in the garage. Came back in about 6 hours fired it up and it was running kind of weak. I put it in gear and got maybe half a block and she cuts off. I thought it was the charging system again and I was running off battery but the battery is strong and doesn't seem to be dying out as it tries to start up every time I try(I've tried maybe one time too many). Sometimes it wont start, and sometimes it will start and run for about 3-5 seconds. Giving it gas only makes it die out. I'm going to start with the fuel filter, just waiting on it to get here. I siphoned the gas out of the tank and didn't see anything that would cause build up or blockage in the lines but i will check all the lines when i replace the filter. Are there any other suggestions? I think I read somewhere about a crank shaft sensor. I've been searching for a while and these seem to be the only two things to come up so far. Any help appreciated, Thanks.
so many things of course from symptoms but I think you are starting in right direction and while you are in there check that the pressurised hoses are not split as this is a common fault that occurs after a few years. The symptoms are similar to what you describe although not usually that bad i.e. - from what you have said hose would have to be almost totally ruptured almost right through rather than an initial split.
If it runs for a while then it would tend to suggest you have some sort of fuel problem. A 1998 tank should have the sealant protection sprayed into it from new, they then tend to only rust around the filler cap area and at the back where the bracket is welded on to allow the tank to be bolted to the frame. So there shouldn't be that much rust in the tank. Modern fuels only have a very limited shelf life, I believe about 6 weeks, you could have problems with gumming up and possibly even water in the system. I would suggest you start off by taking out the fuel pump and also the filter and start checking from there going through the whole system. Cutting the fuel filter in half, if you are replacing it, will give you an idea of rust or contamination, they can get quite clogged. I had one once that was full of all sorts of dirt etc to the point where it wouldn't filter at all, the previous owner had never changed it ever. Does the pump pressurise the fuel system? you can hear it whirring when you turn the ignition on. On the electrical side the pump relay could be playing up and after that then you are in to checking all the other wiring etc. Crankshaft sensors do go on occasion and really the only quick way to check that is by substitution.The air gap has to be correct also but it shouldn't make too much difference.
From experience I wouldnt think the fuel being 1 year old would cause this. Ive just recently got my R1 back on the road after it sitting in the garage for 3 years. It still had some old fuel in the tank and it fired up & ran fine. Im now on the 2nd tank of new fuel and still running well. On the other hand. My VFR, I left fuel in that and can safely say after 8 years the old fuel does turn into something which resembles treacle and gums up all your (on the VFR) carbs and completely messes it all up. Ive now got to strip the whole thing down and try and clean it out. So I think the fuel only starts causing problems after 3 or 4 years. In the past ive actually put diesel in a motorbike (basically i sythoned all the petrol out into a can whilst i did an engine swap, then my dad helpfully stuck diesel in the same can without telling me..... sigh). It ran like a bag of the brown stuff, misfiring & cutting out. I just drained it out, stuck new fuel in, swapped spark plugs for new ones and hey presto all was back running nicely again.
I'm no expert but i recently had a 'no start' problem with my 749s that I later diagnosed to be faulty fuel pump connection. It would be worth firing up the ignition and sensing with your hands and ears if you fuel pump is correctly priming. My wasn't and because I laid up the bike over winter, I had forgotten how much clatter the pump makes when priming. Other than the hassle of taking the filter out (assuming the 748 f/filter is similarly mounted in the tank) I changed mine in just a few hours, a new one costing me nearly £20 from Baines at Silverstone. Good luck, please keep us posted....
