redcota Posted December 8, 2010 Report Share Posted December 8, 2010 Hi all, I have a 1974 Tl 125. It run Quote Link to comment Share on other sites More sharing options...
1oldbanjo Posted December 8, 2010 Report Share Posted December 8, 2010 (edited) I have never owned a Honda Tl125 - but one cause of the problem you are describing is a lean condition that can occur on 4 stroke bikes when you just start to open the throttle. As the throttle opens the vacuum in the throat drops and the fuel flow from the carb doesn't increase when the vacuum drops. Accelerator pumps are used on some cars and motorcycles to correct this problem - others use the constant velocity carbs that have a throttle plate and a vacuum controlled needle and slide. On the accelerator pump carbs there is a little shot of fuel whenever you open the throttle quickly - and on the constant velocity carb when you open the throttle quickly it moves the butterfly and the slide and needle drop until the vacuum builds up enough to pull the slide and needle up. My thought would be to try setting the idle mixture just a bit richer and see if that helps. If that doesn't help - then clean the carb thoroughly and check the float level. It may also help to raise the slide needle by lowering the clip - but this will richen the mixture at all rpm's above idle. My thought on plugs.......as long as you have the right heat range and a good plug.....they really don't make much of a difference beyond extended life. If the plugs made a huge difference the original equipment manufacturers would use them. If the builder could improve the performance of their product by just putting in a better spark plug - they would as they are spending millions of dollars trying to improve the performance of their engines. Back in the old days we used to change spark plugs every 10,000 miles on cars as the tips would start to round off and performance was affected - but modern Platinum and other exotic metal tips have made spark plugs with 50,000 miles on them still work fine and look like new. When you have a single cylinder engine it really doesn't cost much to try exotic plugs......but for 4,6 & 8 cylinder cars it can get pretty expensive. You can get a much better spark plug today than you could in 1974 when your bike was built - but they will not help your bike run much better if it has other mechanical or fuel related problems. Edited December 8, 2010 by 1oldbanjo Quote Link to comment Share on other sites More sharing options...
kramit Posted December 8, 2010 Report Share Posted December 8, 2010 Hi all, I have a 1974 Tl 125. It run Quote Link to comment Share on other sites More sharing options...
stork955 Posted December 8, 2010 Report Share Posted December 8, 2010 Gday, an off idle hesitation is usually either lean pilot jet or the wrong slide cutaway. I can never remember which way to go with the slide - someone will chime in here... Cheers, Stork Quote Link to comment Share on other sites More sharing options...
redcota Posted December 8, 2010 Author Report Share Posted December 8, 2010 One thing that needs to be mentioned again. This burp only happens when I have been really working the bike and the motor is hotter than normal. Thanks for the time you all are spending on this problem of mine. Lots of things to try. john Quote Link to comment Share on other sites More sharing options...
mcman56 Posted December 9, 2010 Report Share Posted December 9, 2010 Off idle stumble is a known trait of the single cylinder Hondas......maybe all single cylinder 4 strokes. It i snot uncommon to see them go pop and stall in sections. I have a Reflex and a slightly larger pilot jet was the cure for it. Although, it will occasionally stall when the throttle is chopped. It requires a triple blip technique with the third blip to prevent the stall. I'm also in Nor Cal and when the motor gets really hot the idle speed will change but I don't get the stumble. I could not find a source for larger pilot jets so drilled out one the the 38s. Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 9, 2010 Report Share Posted December 9, 2010 Off idle stumble is a known trait of the single cylinder Hondas...... My experience to, do you have a heat shield on the carb ? Quote Link to comment Share on other sites More sharing options...
redcota Posted December 10, 2010 Author Report Share Posted December 10, 2010 No heat shield is installed. There is quite a gap between the carb and the exhaust pipe and alot of free air flow between both. Are you thinking about a vaper lock? Ha fellow PITS member, how did you finish up last season and what line do you ride? Are your initials jw? Thanks all for your input. john Quote Link to comment Share on other sites More sharing options...
b40rt Posted December 10, 2010 Report Share Posted December 10, 2010 A heat shield would help eliminate fuel overheating. Quote Link to comment Share on other sites More sharing options...
tlrider Posted December 11, 2010 Report Share Posted December 11, 2010 I agree with mcman56 and B40RT. Enlarge your pilot jet. I drilled mine but don't recall by what amount. Keep in mind you are dealing with area of a circle when enlarging the hole; for example an .020" hole enlarged by 25% or .005" changes your area from .0003 square inches to .0004 square inches or 34% if my math is correct. I.E. a small change in diameter is a larger change in fuel flow. The heat shield, which is probably broken off your carb insulator, is crucial in hot weather. The TL's had them stock but most were broken trying to remove the carb insulator from the head. I was riding the Ahrma Trial at Mid-Ohio a few years ago when it was very hot. I rode up to another TL rider who was having problems similar to yours but worse. He saw the heat shield on mine and asked what it was and I explained it's function was to prevent the gas from boiling in the float bowl. I saw him later with an aluminum foil heat shield and he was running again with no other changes. Over the summer I saw a TL rider who had done the most ingenious thing. He had a battey powered fan which ran off 4 C or D batteris and had a flexible arm; the battery pack was just the right size to drop into the front lower motor mount and the flex arm allowed aiming the fan at the cylinder. Brilliant! Said he got it at an outdooor store. Quote Link to comment Share on other sites More sharing options...
mcman56 Posted December 12, 2010 Report Share Posted December 12, 2010 No heat shield is installed. There is quite a gap between the carb and the exhaust pipe and alot of free air flow between both. Are you thinking about a vaper lock? Ha fellow PITS member, how did you finish up last season and what line do you ride? Are your initials jw? Thanks all for your input. john I usually ride a Sherco and had a good year but am not JW. Where could I find a picture of the TL heat shield? Quote Link to comment Share on other sites More sharing options...
redcota Posted December 13, 2010 Author Report Share Posted December 13, 2010 I second that, I'd like to see that picture and the one with the fan. Are there other than stock needles available and do these carbs have a pilot jet? Thanks all for the information. Quote Link to comment Share on other sites More sharing options...
jack85 Posted December 13, 2010 Report Share Posted December 13, 2010 Number 10 on the drawing. Unfortunately not avaiable now at cmsnl but you can try on ebay. Quote Link to comment Share on other sites More sharing options...
redcota Posted December 14, 2010 Author Report Share Posted December 14, 2010 (edited) One other thing I would like to find is a skid plate, or rock guard to protect the side cases. The stock one seems to protect the bottom ok, its just the side cases Im seeing damage on. Pictures would be great of your creations with a little commentary or sources of bolt ons would be appreciated. Thanks Edited December 14, 2010 by redcota Quote Link to comment Share on other sites More sharing options...
mcman56 Posted December 15, 2010 Report Share Posted December 15, 2010 There is a company on ebay that sells after market rebuild kits that include needles. They have numbers for the different needles but I don't know how to interpret them. I have an SL125 needle in my Reflex. It provides adjustment that the original Reflex needle did not. AFAIK only the original #38 pilot jets are readily available but you can drill them out with something like: http://www.use-enco.com/CGI/INSRIT?PMAKA=300-0019&PMPXNO=945609&PARTPG=INLMK32 Dan Quote Link to comment Share on other sites More sharing options...
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