stuessenhigh Posted March 16, 2009 Report Share Posted March 16, 2009 Hi all, OK..I've had some problems with my old 2002 Beta recently. It starts fine, ticks over lovely, and runs OK...UNTILL you get to about 1 quarter throttle, and then it blubbs really badly. Tried cleaning carb, airbox etc., several times, and didnt make any difference. SO..started to look a bit further, and on taking out the reed 'block' I noticed the upper reed valves, and the metal springy bit that kind of holds them in was all scorched. Do any of you have any idea what would have caused that, and do you think it could also be the cause of my blubbing...(the bike blubbs, not me!) THanks in advance for all your wisdom. Quote Link to comment Share on other sites More sharing options...
toofasttim Posted March 16, 2009 Report Share Posted March 16, 2009 Hi all,OK..I've had some problems with my old 2002 Beta recently. It starts fine, ticks over lovely, and runs OK...UNTILL you get to about 1 quarter throttle, and then it blubbs really badly. Tried cleaning carb, airbox etc., several times, and didnt make any difference. SO..started to look a bit further, and on taking out the reed 'block' I noticed the upper reed valves, and the metal springy bit that kind of holds them in was all scorched. Do any of you have any idea what would have caused that, and do you think it could also be the cause of my blubbing...(the bike blubbs, not me!) THanks in advance for all your wisdom. Is that with or without onions? Sounds normal Stu. It's the reason the valves are there, to stop the flame front going back into the carb. Have you checked your coil? Quote Link to comment Share on other sites More sharing options...
dan williams Posted March 16, 2009 Report Share Posted March 16, 2009 (edited) Huh? No the reeds should not look scorched. There should be no flame front going back to the carb. If there is your timing is waaaay off. Even then I'm not sure it's possible as the mixture is under very little pressure when the transfer ports are open. OK first things first. If the bike runs good at low RPM that's where the reeds are working. At higher RPM the reeds just stick open so it isn't a reed problem. Look for a blockage in the main or needle jet. If they're clean you may have a blockage in the exhaust system. Barring that it may be a high resistance breakdown in the ignition that only occurs when the engine spins up and can generate a high enough voltage to break down a dielectric but that's very unlikely but try a new plug and make sure your wires are not resting against the head or frame. You need four things. Ignition, fuel, air, compression. If it's running at low RPM you have compression. If it keeps running, though badly, you have ignition and the only question there is do you have the right timing? You say your airbox is good so that just leaves breathing out the other end. Most likely culprit is fuel. Blocked jets, blocked fuel tank vent, bad fuel, blocked float bowl vents, bad float/valve, blocked fuel filter. I'm still leaning towards blocked main/needle jet. Remember just because the jet looks clean it doesn't mean the bleed air passages in the body are clear. Get in there and blow them out with compressed air. Edited March 17, 2009 by Dan Williams Quote Link to comment Share on other sites More sharing options...
stuessenhigh Posted March 17, 2009 Author Report Share Posted March 17, 2009 Thanks both, and especially Dan for your thorough comments. I will do as you've said Dan and try again. Although, I've been pretty thorough with the compressor blowing out all bits of the carb before. I have heard people say that sometimes the needle jet can be worn, but doesnt look any different to the eye. Maybe its worth getting a new one? Also Dan, going back to the original post, do you have any idea why that scorching is there...(even if the valves aren't going to give the symptoms I'm experiencing, it would be good to have an idea why that scorching is there) THanks in advance. STU Quote Link to comment Share on other sites More sharing options...
lowbrow Posted March 17, 2009 Report Share Posted March 17, 2009 Are you sure its scorching Stu and not just a build up of varnish? Any chance you could post a photo of the charred remains? Quote Link to comment Share on other sites More sharing options...
paul w Posted March 17, 2009 Report Share Posted March 17, 2009 if the reeds are burnt, that would mean that there has been some ignition of the fuel in the crankcases, wouldn't it? the more probable fault is within the carb itself. its best to disassemble the carb and remove all the jets prior to a full clean like this. inspect by eye that all the small holes are clear. also check the clip on the needle, if this has broken the needle may be droping down in the slide. let us know how you get on paul Quote Link to comment Share on other sites More sharing options...
29r Posted March 17, 2009 Report Share Posted March 17, 2009 Might want to take a peek and see if there's blowby past the rings whilst yer' at it . Quote Link to comment Share on other sites More sharing options...
dan williams Posted March 17, 2009 Report Share Posted March 17, 2009 I put carbon fiber reeds in my bikes now so I have a set of the stock reeds and cage rattling around in my truck somewhere. I'll try to find them and have a look but I seem to remember in the back of my little mind that there was what looked like overspray of black paint on mine to some extent. On the old piston port MX bikes and certainly highly tuned road race bikes a back fire through the carb was possible but the port timing on a trials bike is so conservative that I'm not sure it's even possible and if the timing was off that much it's a pretty safe bet the thing wouldn't run at all. I've seen a lot of things but I can't think of anything that would cause the reeds to be scorched in a trials engine. Then again I'm always learning new things. Maybe if the engine was getting super hot because it was lean from a blocked jet or something but it would have to be spinning over very fast with a light load to sustain combustion. Odds are it would seize very quickly. I keep running it over in my head but I'm drawing a blank. Wish I had your reeds here to throw under a microscope. Did you buy the bike new or second hand? Quote Link to comment Share on other sites More sharing options...
tilertrialler Posted March 17, 2009 Report Share Posted March 17, 2009 treat yourself when you put it back together and fit some boyesen reeds best Quote Link to comment Share on other sites More sharing options...
stuessenhigh Posted March 17, 2009 Author Report Share Posted March 17, 2009 Thanks again everyone for your very usefull comments. Lowbrow...here is a couple of pics..HOPEFULLY, if I can manage to post them properly. One of the clean (lower reed valves),..and one of the scorched upper reed valves. Hopefully the pics might bring up some more ideas of the cause and maybe if it is connected to might bike blubbing very badly at about quarter throttle. THanks in advance everyone...keep the ideas coming. Uh-oh..just tried adding an image to this and just dont have a clue how to do it. Last time I did it...couple of years back, it was easy...now it just seems to ask me to enter an url of where the image is???... AAARRRGGHHH..had some good pics for you all too. Quote Link to comment Share on other sites More sharing options...
stuessenhigh Posted March 17, 2009 Author Report Share Posted March 17, 2009 Will check the clip on the needle paul..thanks for that. Probably will be Saturday till I can do any more work on the bike, but will let you all know what happens. No pics sorry...it appears one has to post them on Photobucket first, to be able to put them on here. SOrry guys, but cant be bothered with all that. More soon. Cheers. STU Quote Link to comment Share on other sites More sharing options...
subanator Posted March 18, 2009 Report Share Posted March 18, 2009 (edited) I would be firstly checking the colour of the plug, its the main indicator to how the bike is running. Look for too wet, too lean, too black etc tell tails. I then would see if its got a good spark. Change plug if you havent already. Then I would check ignition timing, and set it to standard if its not already. Other than that: Other possible probs as mentioned carb etc and CDI electrics. I do know of some bikes that had a partial breakdown in the stator causing the CDI to perform badly. Crank seals? Another possible prob. Exhaust muffler packing done recently? Somethings here to consider if you get to here with no change. Edited March 18, 2009 by subanator Quote Link to comment Share on other sites More sharing options...
dan williams Posted March 18, 2009 Report Share Posted March 18, 2009 Helping out Stu with posting pictures. a bit odd for sure. What kind of oil is used in the bike at what ratio? Did it sit unused for a long time? The reeds on one side definately look more abused then the other. What does the inside of the cage look look like? It almost looks like one side isn't opening so it isn't getting cooled by the incoming mixture. Quote Link to comment Share on other sites More sharing options...
lowbrow Posted March 19, 2009 Report Share Posted March 19, 2009 Well done Dan, what's the secret for posting pic's then? There's nothing wrong with those reeds. Do you expect them to look brand new after 6 years? The discolouration is just a build up of varnish. The bottom reed has a sheltered existence but the top reed is closer to the action, that's all. Quote Link to comment Share on other sites More sharing options...
dan williams Posted March 19, 2009 Report Share Posted March 19, 2009 No big secret. I own the website for newenglandtrials.org so I have my own server space. Once Stu EMAIL'd the pics to me I FTP'd them to my server and put a pointer here to the pics. The pointer is basically a set of HTML tags that say "<img> picture address here </img>". The tags tell your browser that the address points to a graphic so treat it as such and the picture address is the file location on the web accessable server. Essentially the pictures have to be on a computer somewhere the internet can access them. A "server". When you put them up on flicker or some other picture server you're throwing them up on a server that is open to the internet. I don't know if Andy has any setup for uploading to his servers. It's a real pain to maintain if it is and I can understand limiting the access. Disk space can be eaten up fast by photos and there are serious consequences if a server you're responsible for gets loaded with, er... shall we say questionable material. Best to just rely on the photo sharing sites to hold content as they are equipped to handle such issues. Quote Link to comment Share on other sites More sharing options...
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