southwestbiker Posted June 21, 2009 Report Share Posted June 21, 2009 Hi, im having problems with my bike and was wondering if anyone else had come accross this before and knew how to fix it. I have a 1996 SRAD 750 carb model, and when i start the bike, it runs fine, but as soon as i run it at full throttle it starts to stutter and then cut out, as though it was runnning out of fuel. It then wont start for 2-3 min after, and then once it does start, it runs fine unless i open her right up again! I can ride her all day with the throttle open just a bit, so im confused! Ive been thinking this could be a vacum/fuel issue, but have checked all the pipes and they seem fine, and have added a little bit of reddex to the fuel to try and get any gunk off the carbs, but this doesnt seem to have done anything. Each time it cuts out i take the lid of the fuel to check any air suck noise. but theres nothing. Any ideas? Any thoughts would be much appreciated, Cheers, Adam Link to comment Share on other sites More sharing options...
cagimaha Posted June 21, 2009 Report Share Posted June 21, 2009 If you're sure that the vacuum lines are all ok then I would check the filter in the petrol tap then the floats in the carbs next. When it starts to "stutter" at full chat does it sound like its only one of two cylinders cutting out or does it stutter a couple of times then just drop off? If its cutting out dead then its more likely to be the fuel filter, if juct one cylinder drops off then it is more likely to be the needle valve in the carb thats blocked/jammed. I have recently had this problem on one of my bikes but found it was because I was putting premix fuel through a very fine filter. It definitely sounds fuel starvation related though because it starts up again once you leave it for a little while. Check the filter and floats then let us know how you get on. Hope this helps, Ben. Link to comment Share on other sites More sharing options...
southwestbiker Posted June 21, 2009 Author Report Share Posted June 21, 2009 Nice one cheers buddy! When i say ive checked the vacuum pipes, all i have done is check to see if they are all attached and dont have any noticable tears or leaks anywhere, and that the ends arent all bunged up. Took it out again a minute ago to try and narrow down when the problem happens, and it only did it once this time, but i had it att full throttle for a moment, then rolled off, and it seemed to die, i knocked it down through the gears, but there was just nothing happening, much like if you were to have hit the kill switch. When i get it going again, it sounds lumpy for a moment, as though its running on 3 cylinders, then it clears itself, and its back running on 4. Im gunna wait till ive exhausted all the fuel in the tank and pop the fuel pump out and check the filter, hopefully this is it! Link to comment Share on other sites More sharing options...
cagimaha Posted June 21, 2009 Report Share Posted June 21, 2009 No worries, there may be a filter for the pump as well as the tap. If it is just the filter then its an easy fix just clean it out. Normally if the vac hoses look to be in good nick (that is to say they're not cracked or perished and still seem rubbery and not hard and brittle) then they are usually ok. If all the filters seem clear and the problem is still there then it could also be that the fuel pump can't deliver enough fuel at full revs but I'd check the filters and floats first because they're easier and cheaper to sort. Link to comment Share on other sites More sharing options...
southwestbiker Posted June 21, 2009 Author Report Share Posted June 21, 2009 Nice one mate, just been out getting rid of the last bit of fuel in the tank, and i think its low enough to start taking the tank apart. Fingers crossed in a couple of hours, ill know! Cheers Link to comment Share on other sites More sharing options...
southwestbiker Posted June 21, 2009 Author Report Share Posted June 21, 2009 Think ive found the answer! Took the tank off and took the fuel pump out, and found a layer of orange gunk on the bottom of the pump. Should of probably mentioned that this bike had been stood for at least a year before i bought it! The little brass tea bag type filter is a nasty black and orange colour, and i popped it off its little rubber mount and couldnt even blow through it! I think it was allowing a small amount of fuel through - enough to ride round on a partially opened throttle - but when i cracked it open, it drained the bowls and cut out. Does this sound right? I hope so! Gunna pop to the bike shop tomorrow and see if they can organise me a new filter tommorow, fingers crossed this cures it! Link to comment Share on other sites More sharing options...
cagimaha Posted June 21, 2009 Report Share Posted June 21, 2009 Yeah sounds spot on. I had the same problem except I was pre-mixing 40 weight oil at a ratio of 20:1 so the fuel was a fair bit thicker than normal and it had the same effect. It just wouldnt get through the strainer thing. Fine when bimbling about but as soon as it hit the powerband you had about 4 seconds of fuel. The plus side is that at least it wasnt only slightly blocked because then it might allow just enough petrol through for the engine to keep running but would cause it to get dangerously lean. More of a problem on a pre-mix 2 stroke but I dont imagine it would do a 4 stroke any good. Hope that cures it, Ben. Link to comment Share on other sites More sharing options...
TheFlymo Posted June 22, 2009 Report Share Posted June 22, 2009 Hmmm. If it's a carbed model then the fuel pump wouldn't have such an immediate effect with respect to throttle position. The float bowls on the carbs contain more than enough fuel to run the bike on full throttle for a fair amount of time, assuming the floats aren't jammed up. Since the fuel pump strainer is orange, I'd assume the tank is rusty- the finer rust has probably made it's way through the pump and has clogged up the carbs. Best bet is strip the carbs and clean them. If the rust in the tank is bad, get that treated (POR15 is worth a try if you do it DIY, I did it to a tank on my TL once), or alternatively if you've got a common colour, look out for a cheap tank on Ebay- far less hassle! Link to comment Share on other sites More sharing options...
RonniB Posted June 22, 2009 Report Share Posted June 22, 2009 clogged tank breather?!? Link to comment Share on other sites More sharing options...
southwestbiker Posted June 22, 2009 Author Report Share Posted June 22, 2009 Ordered the new filter today, and that should be here tomorrow, so ill pop it on tommorow and have a try. Ive looked in the tank as best i could armed with a little torch, and it all looks silver as far as i can tell, though the metal pipes look a bit orange. I swilled a little fuel round and got rid of the las few dregs, so i think before i start taking the carbs off ( bit dubious as i have never done that ever before ) im going to take it for a spin and see if it is any better. Bloody well hope so, im meant to be taking it to pembrey next weekend............. Link to comment Share on other sites More sharing options...
southwestbiker Posted June 23, 2009 Author Report Share Posted June 23, 2009 Right. now i think im in trouble! Fitted the new filter, and the pump. Put key in ignition, and the fuel pump kicks in - as per usuall! Then i hit the thumb start, and ............... theres a fairly loud "click" and nothing!!!!!!!!!!!!!!!! Any ideas, im bloody stumped now and startying to panic! Link to comment Share on other sites More sharing options...
cagimaha Posted June 23, 2009 Report Share Posted June 23, 2009 Does the click sound like the starter relay? Not a big clang or anything just a click? If so then that means the relay is working ok. What else have you disturbed under the tank? Anything in the region of the starter motor? Link to comment Share on other sites More sharing options...
southwestbiker Posted June 23, 2009 Author Report Share Posted June 23, 2009 Yeah, theres a definate click, and i just popped the cover off the relay to check the fuse and thats fine. Dont think i've been anywhere near the started motor - im not entirely sure where it is, but ive only had the airbox and tank off. Could it be possible that if i got a hose on the wrong way round i could have done something? Is there anything i can do to check the starter? If i removed it and wired it up to a battery directly, would that work? edit: Do you think if i popped it in gear and gently rocked it back and forward it could free the starter. Link to comment Share on other sites More sharing options...
cagimaha Posted June 24, 2009 Report Share Posted June 24, 2009 Hmm minefield! Right 1st off you can't turn the starter using the engine if you see what I mean cos they usually have a bendix gear on them so they only engage in one direction. I don't think that the starter itself will have siezed or anything. Its more likely that you have inadvertantly disturbed an electrical connection somewhere. Even if you had none of the hoses connected in the carb/airbox region the starter should still turn the motor over even if the engine won't actually start. Have you got a multimeter? If so then check if there is any voltage getting to the starter motor when the starter button is pressed. If there is a voltage here then the motor is at fault. If not then the problem lies somewhere with the relay or in the wiring further along. One more thought. The bike hasn't had an alarm/immobiliser fitted at any point has it? If so then it could have been only half removed and you have disturbed the immobilisation which is why it won't turn over. Can you bump start it? If so then its not an immobiliser playing up. Hope this helps, Ben. Link to comment Share on other sites More sharing options...
TheFlymo Posted June 24, 2009 Report Share Posted June 24, 2009 My only worry here is a stuck float and a cylinder full of petrol causing hydraulic lock. Horribly unlikely though. Put it in top gear and see if you can turn the motor by pushing the bike, or pull the oil filler cap and smell for petrol. Link to comment Share on other sites More sharing options...
lorenzo Posted June 24, 2009 Report Share Posted June 24, 2009 3 things; First, check for hydraulic lock, That's bad. Second thing, it's not a fuel starvation iussue unless you're finding it happening after about 40 seconds of running the bike at full throttle: your carbs will have enough fuel in them to run at full throttle for a good while before they run low. To demonstrate this, start your bike up, turn off the fuel at the tank and watch it run for about 3 minutes off the fuel in the carbs. Thirdly, your problem. You've got a flat battery. I'm guessing that you simply charged the battery up that's on the bike when you got it, and I guess that the battery's had it. I've had this on a couple of bikes in the past that the bike'd run fine at part throttle but not when it's wide open, and each time it's been the battery, I assume causing a weak spark. And, as the battery's fooked, it's not held its charge for the couple of days that you've waited for your bits to turn up. That said, what you've done so far is a good thing. If the little filtery bit was blocked, it was blocked and needed replacing. Now borrow a decent battery from somebody and see if that solves your problem, then go from there. Link to comment Share on other sites More sharing options...
lorenzo Posted June 24, 2009 Report Share Posted June 24, 2009 A haynes manual will tell you what the idle rpm charging voltage should be and what the max voltage should be. Although as a rule of thumb, you can expect about 12.5-13v at idle, then building up to about 14 at about 5000rpm, then stopping more or less dead flat, maybe an increase of 0.2v from there upwards in the rev range. If it goes anywhere above 15v then it is a problem. Link to comment Share on other sites More sharing options...
southwestbiker Posted June 25, 2009 Author Report Share Posted June 25, 2009 Right, got it sorted........ .......i'll tell you what i did if you promise you laugh...... After putting a new fuel filter in, i wanted to start the bike minus the tank so i could control the amount of carb cleaner i was putting in. So next step, get a funnel and attatch it to the fuel pipe and pour a little bit of fuel down - hopefully to fill the carbs and leave a bit in the pipe so i can get is started, then pour the cleaner down the funnel. So i started pouring the fluid down, little bit at a time, but couldnt get it to fill the tube. "Odd" I think, but try the starter anyway, and nothing, just the afforementioned click. Now for the breif summary of what i actually did:- Instead of pouring fuel down the fuel pipe as i thought i was, i poured it down the sodding vacuum pipe. Cue fuel ontop of the piston, so the starter couldnt turn the engine because it couldnt compress the fuel. Still, nice and easy to fix, just took the plugs out, popped it on the paddock stand, stuck it in second and turned the wheel by hand till the fuel spurted out the top. Put the plus back in and she fired straight away!!! Learnt my lesson now though, check to see WHERE the pipe goes, not just go for the one that you think it is. Cheers everyone though for all the advice, very much appreciated O yeah, had the bike out running and had about 100miles out of it including some prolonged "throttle to the stop" riding without so much as a stutter, think its actually sorted if the weather stays nice this weekend ill do a few more miles and see how it goes, but im optimistic Link to comment Share on other sites More sharing options...
cagimaha Posted June 25, 2009 Report Share Posted June 25, 2009 Awesome. Don't worry we have all had them moments where you look round and realise the sump plug is still on the windowsill and oil is now all over the carpet. Sounds like its sorted though. Link to comment Share on other sites More sharing options...
TheFlymo Posted June 25, 2009 Report Share Posted June 25, 2009 Good stuff. You might want to at least have a sniff of the oil- a significant amount may have got past the rings and into the crankcase. Link to comment Share on other sites More sharing options...
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