staldantes Posted October 10, 2012 Report Share Posted October 10, 2012 Having nothing to compare it to, but how many seconds should the engine return to idle after giving it a good throttle action? Should it be immediate, or is there a little lag? Mine seems to rev well now after a little tweeking of the fuel screw and idle screw (having previously stripped and cleaned the carbs). But after a quick twist of the wrist from idle it takes about 3 seconds before it returns to full idle revolutions. Is that normal, or what might be the culprit? I´m thinking maybe the engine is a little starved of air, maybe a new filter? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
ham2 Posted October 10, 2012 Report Share Posted October 10, 2012 3 seconds sounds like a lot if you're on standard factory ignition timing, I've heard some of the experts on bikes with advanced timing and their revs rise and fall instantly like a strimmer...how are your main bearing seals? They may be leaking? I reckon you have a standard flywheel fitted so hopefully it's just a carburation problem (less ££ for you to sort). You can't add a flywheel weight to a 2000 Gassser, can you? Quote Link to comment Share on other sites More sharing options...
sting32 Posted October 10, 2012 Report Share Posted October 10, 2012 (edited) Having nothing to compare it to, but how many seconds should the engine return to idle after giving it a good throttle action? Should it be immediate, or is there a little lag? Mine seems to rev well now after a little tweeking of the fuel screw and idle screw (having previously stripped and cleaned the carbs). But after a quick twist of the wrist from idle it takes about 3 seconds before it returns to full idle revolutions. Is that normal, or what might be the culprit? I´m thinking maybe the engine is a little starved of air, maybe a new filter? Thanks in advance. Stal, The lack of air you were "thinking" IN MY HUMBLE EXPERIENCE, seems to me it would probably return to idle faster, Lean conditions cause the bike to carry on, same in cars and other engines. So you are going to have to troubleshoot this, make sure since we're not able to hear your bike unless you post up a video, that we're not making a mountain of a molehill... There are a few things to think about, how high you are revving for one (how high?), if it has an added fly wheel weight. if it is coming back down, at a pretty linear seeming speed, or is it as if you don't really let off the throttle, although you did? When it 'seems to carry on' after throttle is closed, then it sounds to me like a LEAN condition. Oh I Just thought of this, make sure your Carb's slide and the grip throttle are working right (twist n let off, the grip should very quickly return to closed, and when engine is off the slide will make a pretty audible "click or clank" when it bottoms out (closes). Damaged cable can hang your throttle you know. Back to probably Lean, this can happen of course with wrong jets sizing, or carb is plugged in the jets (very common), fuel from tank not getting INTO the carb, like floats are bent or not right, or harder to find - air is seeping into the intake path. For troubleshooting purpose, lets cover a basic... a leak in the intake path area we're talking about, is BETWEEN the carb, up to where the spark plug resides in the cylinder in my troubleshooting working idea, at least, OK? Most common areas of the intake path where a leak might happen is the boot from carb to crankcase, there is a gasket I believe where the reed block goes into the crankcase, if anyone has had that out, and didnt put i t back correctly sealed... Then there is the base gasket (under the cylinder), a bad seal on the flywheel side of crank case. Lastly, but I doubt it is a head (o'ring), but it could be. But, with head gasket/orings usually you have radiator spewing water out whenever the engine is running warm or cold, or the usuall symptoms or water in the transmission oil which makes foam. To trouble shoot here on the farm, since I keep a can of starting fluid, for all the engines that get run once a year, I'll start the engine, spray the boot around the carb (with the carb all hooked up to air filter of course). carefull not to spray towards airbox air inlet opening, as this would void the test... if the engine speeds up, that is where the leaks is. you can try soapy water to check for bubbles around base and head gaskets. I haven't had a crank seal ever go bad, on any of my Gas Gas's yet, so not sure how I would test this, I think I would try a quick squirt of ether with flywheel COVER off, or call it the process of eliminating all other possibilities First. going from a 38 to 40 jet (not actual values, I cannot seem to recall what mine are to less than 1000ft elevation) OR maybe changing the needle height, or even float level, can change how the bike returns to idle, I like my bikes running with bigger "fatter mixture of fuel" jets usually, makes it easier to start as well. Good luck, surely more "mechanically experienced" members will help on this one, my expereince is just from years of riding and working on older project bikes and being a farmer who had to work on a helluva lot of things as I grew up... Edited October 10, 2012 by sting32 Quote Link to comment Share on other sites More sharing options...
staldantes Posted October 13, 2012 Author Report Share Posted October 13, 2012 (edited) Had a good run out today; on the way back she was behaving very dog-idly (i.e. badly). So before my next run out I thought I better give her a check-up. Long story short fine clay particles were getting past my filter and had crudded up the carb. Problem discovered. However whilst giving the carb a thorough clean I discovered that my D36 needle was in the fourth slot down, and I'm thinking maybe it should be in the 2nd down (as most jetting info suggests). Could this be a reason for slow return to idle? Pretty sure the filter is partly the culprit. Will order a new filter, but plan to place some rubber sheet along the underside of the rear mudguard to prevent other dust build-up in the air intake gap (I think that maybe my second-hand bike was missing this). By the way, thanks Sting32 for your suggestions. I had the altitude problems once on a XTZ750 going over the Pyrenees, I knew immediately why the bike wasn't responding as normal. And I am also a keen collector of older bike projects (GSX1100F, ZXR750, Cagiva Elefant 650, all on the operating tables; they are all stable, could just do with throwing some money at them). Edited October 13, 2012 by staldantes Quote Link to comment Share on other sites More sharing options...
jimbobjames125 Posted October 16, 2012 Report Share Posted October 16, 2012 Check the float levels, common problem with rev3 's. My 125 sherco says 18.5mm from casting to top of float tabs if that's any help. Bumpy roads / tracks and big drop offs cause this. Quote Link to comment Share on other sites More sharing options...
sting32 Posted October 17, 2012 Report Share Posted October 17, 2012 (edited) That needle position is key in how much fuel gets mixed with air after ilde, to ( I dont have the knowledge to say "technically" where). so yeah lowing the needle (raising the clip "up") leans the fuel, what think you described or you saw was needle raised (more fuel sooner vs throttle position). I find it more deals with responiveness, once you get close with the correct jets. when looking at the needle remember the clip rings are at the top of the needle, so thats what I describe, lowering the clip to the ring below it, raises the needle, and vice versa. Plugged carb, then you cannot do anything until you get it clean, and it stays clean, then you (and only then) do you attempt adjustments... I'm no tuning expert, I get advice from others when I need it, you should as well, so Ill stand aside after this post of course. I know there was some 'not common to what I have heard" settings used at over 12000 ft in Nationals I heard about, and will try if I finally get to go to colorado someday to ride. I was under the impression you go smaller jets all around, but that was not the case. Guys that ride up that high, have it figured out, ask them. Edited October 17, 2012 by sting32 Quote Link to comment Share on other sites More sharing options...
staldantes Posted October 17, 2012 Author Report Share Posted October 17, 2012 Hi sting32/jimbob, Been busy with work, but looking forward to getting back in the saddle. So I have raised the cir-clip to the second notch down to see if this deals with the lean conditions that you suggested earlier. Float level seems fine, with no overflow and correct valve function. I was waiting to get the filter but my local supplier is waiting for a delivery of the original filters (the triangle shaped type), so I was considering the ´RQ´ filter they have in stock. I have never heard of this brand, but can I assume its an improvement? anyone use this type? I should also mention that my regulator was defective, but I don´t think this would interfere with engine timing (or does it?). New regulator on order too (it kept shorting bulbs). Quote Link to comment Share on other sites More sharing options...
staldantes Posted November 9, 2012 Author Report Share Posted November 9, 2012 Right, have tweeked as many elements as I can and still no real joy. I have repositioned the needle, checked/cleaned all jets, cleaned or removed the air filter, adjusted the fuel screw at different points and still the engine sounds like it slowly returns to idle, not on/off like the strimmer mentioned earlier. Should I start considering piston rings? the regulator has been changed as that was a dudd, but made no difference to engine revolutions, or could the exhaust result in some form of hinderance to a return to idle speed. Having said all this, I have never heard another trial bike run in comparison as I´m relatively new to the sport. Ta. Quote Link to comment Share on other sites More sharing options...
sting32 Posted November 12, 2012 Report Share Posted November 12, 2012 Staldantes, you stating the triangle filter, means pre PRO BIKE/engine, so must be 04 or older TXT engine. this engine has more mass that turns as well, so might not rev and return as fast as the newer high compression, less flywheel size/weight/diameter PRO model bikes. you need someone used to the bike you have see and hear it, you might just be chasing your tail because of unfair assumptions. Jetting is key, as well as air leaks and or something like clogged jet causes lean conditions, that seem to make an engine run on a bit, or at best, that can have you chasing your tail... We usually try to change rings often, I was told this can save wear on pistons, I dont know if that is exactly the truth, but it sounded like good advice to me... cheap too. Quote Link to comment Share on other sites More sharing options...
staldantes Posted November 12, 2012 Author Report Share Posted November 12, 2012 Cheers for all your input Sting32, I´ve had a lot of experience with carbs in the past, were I was used to blocked emulsion tubes, and floats jamming the fuel valve open, but this has beat me. Maybe I am starting to chase my tail. However at least I´ve ruled out certain components and that is a positive step forward. Having read other forum posts on idling, and garbelled throttle action at high revs I am starting to consider two things. Either the piston rings are badly worn and creating poor vacuum, and therefore weak intake of fuel/air mix, or maybe the reid valves are damaged hindering the complete fuel intake cycle. I think its one of these, so will check the valve first (though I´m new to reid valves). What should I be looking out for? and I assume its an easy swap for a new one. My bike is the 2000 model TXT, just before the PRO models incorporation. Does everything I want, but believe I should expect more from the motor, and when I have a safe excess of money in the bank would love to try a newer model (though I am an avid fan of the second hand by nature). Cheers for your advice. Quote Link to comment Share on other sites More sharing options...
sting32 Posted November 13, 2012 Report Share Posted November 13, 2012 Keep me updated, we're kind of alike, I like used or on many other "toys" versus new... however I am loving riding the 2011 Raga 300 Pro this year... But as luck would have it, Im just now starting to work on a 82-ish Fantic 200, that is definitely having fuel issues, might be close what you describe. my plan of attack is: 1. dad (whos done enough carb cleanings) took carb apart, cleaned it. we had to buy the rubber from engine to carb, now ready to do more. 2. reclean the carb, make sure nothing got back in jets or elsewhere. 3. going to use carb cleaner, and spray while engine is running without the flywheel side, if it picks up the carb cleaner usually idle will change, probably means crank seal is bad. 4. Luckily I have a nice running version of the same bike, I plan to check that carbs are set "EVERYWHERE" the same. 5 check and compare compression readings. 6 maybe you have an idea, when you said reeds, I have never had a bike with reed problems, I don't know if the Fantic even has reeds? unfortunately until I goto the shop I haven't any more ideas... except maybe the low compression like you are fighting could be another idea... Quote Link to comment Share on other sites More sharing options...
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