brucey Posted January 23, 2013 Report Share Posted January 23, 2013 Having put my Gas Gas up for sale I thought I'd check it over as I hadn't started it for 3 months. It starts o.k but will not idle and once warm is slow to return to idling speeds. The sypmtoms point towards an air leak somewhere and I have done the following: Removed the carb and jets and cleaned everything (it was all pretty clean anyway). Can someone confirm the round bit of the floats face upwards? Cleaned and inspected the rubber inlet manifold. I also squirted carb cleaner around this area with the engine running but it didn't speed up. Removed Magneto Cover and squirted carb cleaner around with the engine running. Engine still didn't speed up. Changed Magneto Side Crank Case Seal anyway as it seemed the most likely cause. There was no signs of oil around the old seal and problem is still there. Adjusted mixture screw (was about 3 turns open at start) but it makes very little difference where it is set. If I put the choke on with the engine warm, it just speeds up. When I removed the carb, I did notice one end of the Crank Case Breather Pipe is free. Should this be connected to something? I'm assuming it's a timed breather and just sticks up in the air. My next job will be to replace the Clutch Side Crank Case Seal (because I've already bought it!) but I don't think it's this because the bike doesn't smoke. I did replace the Water Pump Shaft and Seal about a year ago and wondered if this may have damaged the RH Crank Case Seal in some way. I should also mix some new fuel up but again, I think this is clutching at straws as it wouldn't cause these symptoms. I'm running out of ideas fast. The engine is quite, has good compression and doesn't smoke. Maybe it just wants to stay with me! Any help would be appreciated. Brucey. Quote Link to comment Share on other sites More sharing options...
copemech Posted January 23, 2013 Report Share Posted January 23, 2013 Well, it sounds to me that you do have a good general grasp of the situation. There are a couple things I may throw out to you as suggestions. Insure the pilot jet is totally clean by finding a fine wire to pass through it. After sitting, they may develop what seems a skum layer within and without, if it had turned green especially. . Use the carby spray to insure flow throuth the two small passages in the carb bore as well. If one is indeed sucking air through the crank side seal, then blocking the tranny vent tubs should stop that, as a vacume develops.. As these are normally at atmospheric pressure, one may install a small clear hose just to see if the thing will suck water up out of a cup. Break the carby over a clear glass or plastic vial to catch the fuel. Finding water droplets in your stored fuel / tank is not unusual, and does not set well with the pilot jet. One suggested insuring the o-ring on the slide cap is intact, good thought on an older bike me thinks See how you get on, Cheers Quote Link to comment Share on other sites More sharing options...
brucey Posted January 23, 2013 Author Report Share Posted January 23, 2013 Thanks for your helpful sugestions Copemech. 24 hour support can't be bad! I think I may need to double check a couple of things before draining all the fluids and attacking the RH Crank Case Seal. I had convinced myself it was the LH Crank Case Seal and was dissapointed to say the least when replacing it didn't solve the problem. I've had pilot jet issues on my Tiger Cub in the past and the symptoms were totaly different. I really can't remember seeing the Crank Case Breather Pipe end 'floating' around on any of the other Gas Gas's I've owned but there is no obvious place to attatch it to and the end is chamfered. When I replaced the Spark Plug as a matter of course, the old one looked pretty normal to me. Brucey Quote Link to comment Share on other sites More sharing options...
jse Posted January 23, 2013 Report Share Posted January 23, 2013 Well, it sounds to me that you do have a good general grasp of the situation. There are a couple things I may throw out to you as suggestions. Insure the pilot jet is totally clean by finding a fine wire to pass through it. After sitting, they may develop what seems a skum layer within and without, if it had turned green especially. . Use the carby spray to insure flow throuth the two small passages in the carb bore as well. If one is indeed sucking air through the crank side seal, then blocking the tranny vent tubs should stop that, as a vacume develops.. As these are normally at atmospheric pressure, one may install a small clear hose just to see if the thing will suck water up out of a cup. Break the carby over a clear glass or plastic vial to catch the fuel. Finding water droplets in your stored fuel / tank is not unusual, and does not set well with the pilot jet. One suggested insuring the o-ring on the slide cap is intact, good thought on an older bike me thinks See how you get on, Cheers Good advice, Copey. The pilots in Trials bikes are very sensitive to ambient moisture corrosion when the bike is put away for any length of time(often after a wash). The green corrosion (brass/water) will stop up a pilot quite easily as they usually are only an orifice of .014" (#36 or .36mm). I replaced a pilot for a friend at last week's Trial as he had run into the same problem. Even if the pilot jet is cleaned with a wire (use copper wire, not steel) the jet is damaged by the corrosion and will never be "correct". Jon Quote Link to comment Share on other sites More sharing options...
brucey Posted January 23, 2013 Author Report Share Posted January 23, 2013 (edited) Just stripped carb again and double checked inlet manifold and jets. All appear to be fine. Just off to get some fresh fuel to try. If that doesn't work then I guess I'll strip and replace RH Crank Seal although I think I'm clutching at straws now! It has to be something pretty obvious. Pinching the crank case breather pipe slows the idle speed a fraction but doesn't really improve idle response time. Brucey Edited January 23, 2013 by brucey Quote Link to comment Share on other sites More sharing options...
thats_a_five Posted January 23, 2013 Report Share Posted January 23, 2013 Your description does sound like vacuum leam but.... At the risk of sounding silly, you did check for smooth operation of the throttle cable and throttle tube on the bars, right? Quote Link to comment Share on other sites More sharing options...
brucey Posted January 23, 2013 Author Report Share Posted January 23, 2013 O.k., I need to eat a bit of humble pie here! At 54 years old, I still don't always follow my own advice and do the obvious things first. After spending 2 days and £50 trying to sort the problem out, I finally purchased some more 2 stroke oil and 10l of BP's finest premium grade unleaded. I drained the tank and float bowl, mixed up a litre of fresh fuel and ran it until the fan came on. I then adjusted the idle screw and pilot screws (unsuprisingly back to where they were originally) and hey preso, I now have a bike the revs up and then slows down to a nice steady tick over. Looking on the bright side, at least I (and the next owner) knows all the other bits have been cleaned and checked! Thanks for your help. Does anyone want 41/2 litres of stale 2 stroke fuel? Maybe I'll keep it for cleaning the Cub chain. Brucey. Quote Link to comment Share on other sites More sharing options...
zippy Posted January 23, 2013 Report Share Posted January 23, 2013 Does anyone want 41/2 litres of stale 2 stroke fuel? Maybe I'll keep it for cleaning the Cub chain. Brucey. I pour old fuel into my truck, it gets mixed into 20 gals of good stuff and it don't know the difference........................ come to think of it the fuel mileage of my truck is so low it sits in the driveway more than anything else.........Probably have a tank full of stale fuel now. HMMMMM maybe I should go start the truck, if I do that I may as well load the Gas Gas into the bed and go for a ride!!! OOOHH I like that. Thanks Brucey for the idea of going for a ride! Now I have to convince the that I "need" to go for a ride. Quote Link to comment Share on other sites More sharing options...
copemech Posted January 24, 2013 Report Share Posted January 24, 2013 O.k., I need to eat a bit of humble pie here! At 54 years old, I still don't always follow my own advice and do the obvious things first. After spending 2 days and £50 trying to sort the problem out, I finally purchased some more 2 stroke oil and 10l of BP's finest premium grade unleaded. I drained the tank and float bowl, mixed up a litre of fresh fuel and ran it until the fan came on. I then adjusted the idle screw and pilot screws (unsuprisingly back to where they were originally) and hey preso, I now have a bike the revs up and then slows down to a nice steady tick over. Looking on the bright side, at least I (and the next owner) knows all the other bits have been cleaned and checked! Thanks for your help. Does anyone want 41/2 litres of stale 2 stroke fuel? Maybe I'll keep it for cleaning the Cub chain. Brucey. Well at least you are honest! You prolly don' follow ours either, so I doubt you caught any of that dribble in the clear vial to see what was init! Finding these culprits is like panning for gold at times, but you may be shocked to see just what settles out of a tank of old fuel, specially with the alcohol. I usuly just cut open a clear 2L pop bottle. Of course, one needs to ck the cans as well periodically! Just saying! 1 Quote Link to comment Share on other sites More sharing options...
nig1956c Posted February 4, 2013 Report Share Posted February 4, 2013 Just have the same problem. The only thing is that when I spray carb cleaner on to the inlet manifold it speeds up. So I am assuming the manifold has a leak. I am having a job to find a replacement. Are there gaskets between the manifold & spacer / reed block? I will try to get it off tomorrow. Quote Link to comment Share on other sites More sharing options...
thats_a_five Posted February 4, 2013 Report Share Posted February 4, 2013 Yup, sounds like you found the problem. A bad gasket will do that. If you can't find a new gasket, you should be able to buy plain gasket paper and cut your own. Quote Link to comment Share on other sites More sharing options...
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