tobster Posted November 21, 2005 Report Share Posted November 21, 2005 why doesn't anyone use silkolene in their gas gas? Also, how much of a difference to the fuel mixture (in terms of rich/lean) does using different fuel:oil ratios make? I'm currently using 70:1 (silkolene pro) with a TXT80 and the bike runs rich & the mixture screw has no effect upon adjustment - presumably using more oil will lean it out slightly or should/can I just increase the float height to say 16.5mm? The bike starts fine from cold with no choke even in this weather, but stall it hot, and it's a beast to start - bump starting works, then it runs fine - what is going on? Quote Link to comment Share on other sites More sharing options...
gasgas Posted November 21, 2005 Report Share Posted November 21, 2005 What about silkolene that is so special that i shld use it? Starting a bike cold without the choke tells you enough, i wld say. It tells you either to much fuel in the carbbowl or to big a pilotjet. If the float is oke, leave it, since altering infects the whole throttle range. Do you leave the petcock on, while transporting yr bike, maybe yr floatneedle is worn. Anyway you have to go tru all the variables to solve it. succes. Quote Link to comment Share on other sites More sharing options...
jtt Posted November 21, 2005 Report Share Posted November 21, 2005 I agree with gasgas, check your pilot and float needle. Sounds very rich to me. Changing mix ratios will not make a big enough difference in your air/fuel mixture to be effective. Best to stick with the fuel/oil ratios you've always run and work around the carb jetting. Quote Link to comment Share on other sites More sharing options...
tobster Posted November 21, 2005 Author Report Share Posted November 21, 2005 indeed there may be nothing special about silkolene, it's just i've been advised by gas gas UK to steer clear of it with gas gas. It seems to work well enough in my Pinky though I'm more than happy to try another brand providing I can hold of it easily. We've only just got the bike and it came starting badly. I've put in a new NGK BPR5ES & since checked and changed the pilot jet (50). i've done plug chops at the various throttle openings and all seems well, though it is probably on the rich side, especially at small throttle openings. I've increased the float level to just over 16mm, trying to lean off the whole carburation. Fuel is switched off at end of ride. Float needle seems to work, though I only gauged this by blowing throught the fuel line. As I understand it, the mixture screw on the TXT80 is a fuel screw (as it's in the front of the carb), so I don't undestand why screwing it fully in i.e. reducing the amount of fuel, doesn't cause the engine to stop. Clearly the engine is getting fuel from somewhere else. The needle is in the fully lean position i.e clip in top position. What's going on? Quote Link to comment Share on other sites More sharing options...
gasgas Posted November 21, 2005 Report Share Posted November 21, 2005 (edited) I assume that a txt80 works with a Dellorto phbl carburateur? Turning in the fuelscrew must give you signs of leaniness, if not, yr pilotjet is way too big. You state that you use a 50 pilotjet? Can somebody tell us whether that is oke? edit edit: i just found out that we are talking a airscrew here. So turning the screw in means richer and out is leaner. maybe here is the culprit. Check this website: http://www.gasgas.com/Pages/Technical/Snel...ting-specs.html Edited November 21, 2005 by gasgas Quote Link to comment Share on other sites More sharing options...
tobster Posted November 21, 2005 Author Report Share Posted November 21, 2005 hi it's actually a PHBG 21DS which may be similar to the PHBL (I'm not sure). According to the Dellorto agents (Eurocarb), it has a fuel screw and NOT an air screw. Apparently the rule is that if the offending screw is nearer the engine than the air box, then it is a fuel screw, and an air screw vica versa. Sooo, turning it in (clockwise) will restrict the fuel flow, making it leaner. Of course this all contradicts that gas gas USA spec sheet, but I would tend to believe a carb specialist over a general bike specialist. That article also recommends richening up the needle, when it is certainly not lean at the moment. Hence loads of conflicting advice...... Incidentally I have set the screw at 1 1/2 turns out though it had no effect on the way out from completely in to completely out. Surely an indication of richness?? Help Quote Link to comment Share on other sites More sharing options...
steve shakeshaft Posted November 21, 2005 Report Share Posted November 21, 2005 A little off topic, but for my take on Silkolene lube oils please see the "Mechanical" section. Quote Link to comment Share on other sites More sharing options...
tobster Posted November 21, 2005 Author Report Share Posted November 21, 2005 thanks Steve for the input - an interesting topic. Unfortunately I don't think I can fairly blame the Silkolene oil (yet) as not only has this bike only had about 2 tanks of Silkolene, but when I bought the bike it was already running badly (very reluctant to start resulting in good price haggle), and he was using a general 2 stroke oil at 50:1. Quote Link to comment Share on other sites More sharing options...
steve shakeshaft Posted November 21, 2005 Report Share Posted November 21, 2005 (edited) Thanks. Use Silkolene oil or any other modern, quality two stroke oil with complete confidence. You never know where the last batch of your favourite was bottled nor do you know where the next batch will be bottled. Silkolene always comes from the Fuchs plant in stoke though. Oil's a commodity and brands will shop around for the cheapest commodity. Just like us buying tins of beans I guess. Actually, the stuff I'm running cost me 99p for 500ml in Morrisons last week. Edited November 21, 2005 by Steve Shakeshaft Quote Link to comment Share on other sites More sharing options...
jtt Posted November 25, 2005 Report Share Posted November 25, 2005 I'm not that familiar with this particular carb, but a 50 pilot sounds very rich to me. If the mixture screw is having no effect, it is most likely very rich. I'd try a couple of sizes down on the pilot. Never mind the needle or the main, those don't come into significant play until the throttle is opened more. And yes, as a general rule if the mixture screw is closest to the cylinder it is most likely a fuel metering screw. Might want to have a look and make sure the tip of this metering screw is not damaged or broken too. Quote Link to comment Share on other sites More sharing options...
tobster Posted November 25, 2005 Author Report Share Posted November 25, 2005 I'm getting the feeling that mixture may not be the only problem as the plug is quite wet - to me this points towards a failing wet side crankshaft oil seal. Whether this would screw up the carburation I don't know, especially relating the lack of adjustability of the fuel screw. Good idea - I'll have a look at the condition of the fuel screw tip tonight. Quote Link to comment Share on other sites More sharing options...
tobster Posted November 26, 2005 Author Report Share Posted November 26, 2005 getting a little excited as I (with your help) may have sorted the problem. One ride and all is still well. Guess what it was?...give up - well here's a clue - it costs about Quote Link to comment Share on other sites More sharing options...
gasgas Posted November 26, 2005 Report Share Posted November 26, 2005 Quote Link to comment Share on other sites More sharing options...
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