esteve Posted February 12, 2013 Report Share Posted February 12, 2013 (edited) I'm posting this in the event it might help somebody. At a trial last Sunday (10th Feb) my usually well behaved Honda TLR200 had a sticking carburettor slide problem. I've had the bike for 2 years and have never touched the carb or the manifold nuts apart from taking the float bowl off to inspect/clean it when I bought it and draining it after each post trial wash. It had behaved faultlessly during a run the week before when I warmed the engine up to change the oil. The ambient temperature was 4degC and I thought it might be carb icing. I took the top of the carb and pulled out the slide. With the slide free of the carb body the twistgrip action was normal so it wasn't the cable and I had already checked the cable run to see if there was a kink or pressure point. I removed the slide from the cable and inserted it into the carb body and there was resistance. Fortunately I had some stiff lockwire in my tool box as I had to form a hook on the end of some lockwire and insert it into the cable slot to remove the slide as it was quite firmly stuck. I wiped everything with a clean rag and sprayed everything with WD40 and put it back together and it was just about rideable despite it being a total mystery as to why the carb had gone from faultless performance to a mystery problem. I did most of the first lap until the bike was unrideable with the slide occasionally sticking in the open position. I returned to the paddock and I took the slide out again. Absolutely no dirt or gumming up (WD40 is a wax?) but the slide was still sticking. 10 out of 10 to anybody who has by now considered carb body distortion. When I considered it and slackened off the carb manifold nuts the slide freed up immediately. The bolts were then slack so I tore off some 1cm wide strips of duct tape and wrapped them around the flange joint in case of air entry (Duct tape actually being used to seal a duct; that must be a first), put the top back on the carb and finished the trial with no further problems. As i said above, I've never had the carb off and have never touched the manifold nuts. There is a physical explanation for the distortion that occurred in the carb body but what it is I don't know; perhaps it was ambient temperature related. There is the faintest evidence of a high spot in the carb body towards the front but until last Sunday i never had a problem. So, consider carb body distortion for a sticking slide, even if you haven't disturbed a carb that was behaving faultlessly. UPDATE 29/09/2013 I got around to removing the problem carburetor and have traced the problem to somebody replacing the o-ring between the carb and the manifold with an oversized replacement. The groove in the carb is 2mm deep and 3.4mm wide. The correct replacement o-ring is approx 2.5 mm diameter and when the carb is flanged up compression of the ~.5mm standing proud of the groove forms the seal and can expand into the 3.4mm wide groove when compressed. However, somebody replaced it with a 3.4/3.5mm o-ring so when the carb is flanged up with the manifold there is nowhere for the extra o-ring material to expand to and the flange will bow about the centre of the flange and the distortion will either have immediate effect or as in my case creep through the body of the carb and cause slide sticking much later. Carb flange with correct 2.5mm diameter o-ring: Carb with oversized o-ring completely filling the groove: Edited September 29, 2013 by esteve Quote Link to comment Share on other sites More sharing options...
j13me Posted February 13, 2013 Report Share Posted February 13, 2013 Hmmm, interesting, never heard of this. Sounds silly but have you tried it since? With a different temp? May be worth cleaning the slide up with a bit of fine grade sane paper and try it again if it has any gunk on at all? Quote Link to comment Share on other sites More sharing options...
wobblenorbed Posted February 13, 2013 Report Share Posted February 13, 2013 Scary stuff. Quote Link to comment Share on other sites More sharing options...
johnyboy Posted February 13, 2013 Report Share Posted February 13, 2013 Have experienced the exact same problem on an Rtl250,same solution slacken carb nuts Quote Link to comment Share on other sites More sharing options...
maxbikes Posted February 13, 2013 Report Share Posted February 13, 2013 this is common,take carb of,and o ring that goes on flange.get a piece of glass and sand paper,and rub till flange is flat.redrill 2 bolt holes.now wash out carb well,you dont want any sand to go in engine.the glass is a very flat surface.hope this should fix your problem without replacing carb. Quote Link to comment Share on other sites More sharing options...
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