plodder

P.S. You have the later carb on your bike & yes the washer is intende to be there on that model. Regards Plodder

Hello again, The TY250 59N model you have originally had a restrictive airbox lid & would of had the following jetting as standard : Tekei Y26P/1 carb Main Jet 110 , Needle Jet 2610,Jet Needle& clip position 5C95-3, Cutaway Slide 2.5, Pilot jet 48, Air jet 2.5mm ,Starter Jet 0,7, Airscrew 1 1/2 turns, Float Height 22mm , Spark plug NGK B7ES. Ign. Timing 2.8mm BTDC. Compression 7.6:1 TheTY250R Model number 38V/44J/44H differs in having a free flowing airbox lid & lighter flywheel. Carb specs for this model are: Tekei Y26/P1 Main Jet 140, Needle Jet S-00 , Jet Needle & clip position 5C95-3, Cutaway Slide 2.5, Pilot Jet 40, Air jet 2.5mm , Starter jet 0,7, Airscrew 2 1/4 turns,Float Height 22mm, Spark Plug Champion N-5G , Ign. Timing 2.8mm BTDC. Compression 7.8:1 The TY250R(last model ) 2AF 38V-010101 Different Piston to earlier models. Carb specs for this model Tekei Y26/P1 Main Jet 135, Needle Jet S-10,Jet Needle & clip position 5C99-3, Cutaway Slide 2.5, Pilot Jet 38, Air Jet 2.5mm , Starter jet 0,7 , Airscrew 1 1/2, Float Height 22mm , Spark Plug NGK BR6ES , Ign, Timing 2.8 BTDC , Compression 7.0:1 A few points to take into consideration: It's very easy to chase a jetting problem when the carb is worn, especially the slide, as this could be letting air past it.I put some new jets in & the bike was a lot easier to start.Also it's possible to have the carb settings correct , but be spoofed by a too rich pre-mixture (wrong oil ratio )or old fuel which will both give the symptom of weak carb settings. Hope this helps your situation, Regards Plodder.

Hi, i've been working on a TY250 Mono that knocks like yours does. The problems i've found are; The bike was designed with a very wide squish clearance , depending on which piston is fitted it can be as much as 2.4mm which is excessive. There are TY 250 pistons with conventional crowns (Piston top ) & Later pistons with two crown heights which have a lower crown height on either side to bleed the fuel/oil mixture into the cylinder earlier through the transfer ports. The upshot of all this "Jargon " to the layman is that the Squish clearance is to high . If you measure the suish clearance as mentioned in the previous posts & say it comes out at say 2.4mm then the fuel/oil mixture will not totally be burnt causing the "Knock " you mentioned ( if you remove your cylinder head & turn the engine over to TDC look at how near the piston is to the top of the barrel, there will be a soot line left by the carbon deposits ). Some people remove the head gasket ( measures 1mm thick ) & lap the head to the cylinder to close up the squish, but i would advise turning 1mm from the base of the barrel then raising the exhaust port 1mm to get you back to where it should be, The transfer & inlet ports will be o, the optimum squish clearance is 1.1mm to 1.4mm. Also the TY250S road model has a 28mm wide flywheel weight & the TY250R competition model has a 17.5mm wide flywheel so owners of the TY250S can get a more responsive bike by having the flwheel weight machined to the TY250R width. Other things to note are ; always use fresh fuel at 50:1 pre-mix( 100ML to 5 litres of Petrol ) with a good quality synthetic oil , Ignition timing static is 2.8mm BTDC but you can experiment slightly 0.2mm either way won't do any harm. Keep the exhaust clear & a good silencer fitted. The carburettors on these bikes are usually worn out and one of the biggest problems is leaving the bike with fuel in the tank for a while , then the float valve lets the fuel flow into the crankcase & this can lead to all sorts of running issues the next time you use the bike ( unburnt fuel sloshing around in the crankcases ) . So the number one thing on a TY250 mono is to remove the bash plate & you'll see a 6mm bolt with a fibre or copper washer under it , remove this bolt & see how much fuel pours out !! if it doesn't you can leave some fuel in your tank but personally i'd at least remove the fuel pipe from the tank. I hope this is of help . I'll do another post on the jetting when i've finshed this bike. Regards Plodder.