mike55

mickh, thanks for your interest, I've heard that the shell higher octane fuel can help so i'll try that first, the old stuff can go in the mower. I'll post the result as soon as I've done it regards, Mike.

Hello Plodder, thanks for all your advice, i will try to get my head around it. In the meantime I have stripped and cleaned the carb and made a note of the settings. The jet sizes seem to be wrong from what seems to be standard. The carb is a TK26 The main jet is a 135 The other jet is a 38 The bike is a 250mono S, 59n Are these correct or can any one tell me what they should be and could this be a source of my "knocking" problem? Also between the main jet and the bit it screws into (marked S10) there is a sort of washer, should it be there, I've never seen one before! thanks everyone, MIke.

Thanks everyone, I'm learning so much! Just goes to show that an old fart can still learn. I am quite looking forward to solving this little mystery now (negative into a positive and all that). As I don't need all the power of this bike would it be an idea to put on an additional base gasket anyway, especially if it makes it easier to kick over. If there is a head gasket, could the same result be had by adding another head gasket? Please keep your opinions coming, thanks again, MIke.

Thanks to everyone taking an interest in my problem. Can I just confirm that 50:1 is the correct fuel/oil ratio? Is there a particular make of oil that suits this engine, I think some are synthetic? Did I mention that I am a duffer when it comes to 2 strokes, especially when one opinion is that the squish may be too tight and another is that the squish may be too big, whatever squish is? I have remembered that the chap I bought it from said that he had recently had the middle exhaust box cut, re-packed and welded back up again. Could this have a bearing on things? thanks for your help, Mike.

Hello, I'm new to this and I posted this in the wrong place, so i'll try again. I have just bought an'85 TY250 mono and when the engine is warm either on overrun or light load, you know how they only fire or pop erratically well each time it "pops" there is a loud metallic knock. Is this normal because I thought something was going to let go! Any help would be much appreciated, thanks Mike.

Hello all, just bought my first trials bike although I'm far too old to be playing games. It's a Yamaha TY250 mono. All my off road riding has been on 4 strokes and as I don't bounce so well these days I've changed to trials although I should know better. My knowlege of two strokes is limited so I fully expect to become a real pain in the **** to you all. regards, Mike. I also have a noise from the engine but I will try and post it in the correct place.