my 250 t/shock wont start i fitted a new carb and it wouldnt run right. i have put the old carb back on now it wont start.it gets fuel and gets a good spark carb has been cleaned out.

Not a lot of info to work on. First we need to know what "new" carb you fitted and what the jetting is. Is the auto lube still connected? or are you running premix ?

I'll assume the new carb is a Mikuni VM26 which is ideal for these bikes. The plug should be NGK B7ES set to 22thou. Point gap at 15thou and the TY has fixed stator timing unless it has been altered.

If you have a Mikuni VM26 it needs a 150-160 main jet and about a 35 pilot jet. I'll also assume you have an in-line fuel filter ? If as you suspect its the carb causing the problems a good blow out with compressed air should solve most problems. First blow through the choke/enrichment circuit by depressing the choke lever and applying air. You can see through the main jet and see daylight. The pilot jet to the rear of the main can also be seen through when clean even though there is a "S" shaped wire in it. Normally if it won't start its the choke circuit blocked, if it runs on choke but falters and dies when the choke is taken off its a blocked pilot jet. When running and warm you can adjust the Airscrew for best pick up starting around 1.5 turn from fully in.

Check your carb and jettings and let us know

Tony

Stevie

Have you fitted electronic ignition ? Quite a few breaking down, 4 alone at Highland 2 day trial.

Ross

hi it was the vm 26 but its back on the carb that i used all year. will need to have a look at the choke it looked ok.electronic ignition fitted if that packed in i wouldnt get a spark?

Spark came and went on the bike I had borrowed (TD's) I thought it was fuel to and had the carb off 3 times.

The replacement ignition has now also failed.

Might well be carb, but worth considering ignition.

I assume you have tried a new sparkplug. I have seen some plugs that showed spark but woiuld not fire when installed in the engine.

Did you remove the reed cage and intake when you changed carbs? Perhpoas a vacuum leak from missing or bad gasket?

hi yes even had the plug in another bike to warm it up.will check more tomorrow.

a long shot but try another plug cap,i had a similar problem,good spark,fuel etc changed the plug cap and that sorted it

Spark came and went on the bike I had borrowed (TD's) I thought it was fuel to and had the carb off 3 times.

The replacement ignition has now also failed.

Might well be carb, but worth considering ignition.

Which brand of ignition would that be, thinking of fitting an electrex world 1 to mine seeing as John Cane isn't listing them anymore

Edited December 29, 201213 yr by tony27

I think a TY Yam is one bike where it isnt really much help to have electronic ignition,the original points setup is so reliable I cant see any point in changing it.Replacement points still seem to be of decent quality,unlike say modern Lucas car ones.The points and condensor in my TY250 have been changed once since 2006 - but only because I felt the need to do "something" to it,not because it wasnt running right.It still starts 1st/2nd kick,pulls cleanly and revs out well - what more could I want ?

got the bike started today will give it a try tomorrow if it starts i hope to ride it on the 2nd.not got a clue why it wouldnt start.

Did you look inside the side cover where the points are? I had a TY175 that ran great in the dry. When it got wet it would not run. It turned out to be a bad seal aroiund the side cover. When I pulled the cover there was a lot of white powdery substance for water and oxidation of the aluminum. A good cleaning of the residue and points, good sealing of the cover with new gasket and silicone seal and it worked great after that.

left the bike for a few weeks thought i would start it non starter again gave up and put a electrex world kit on it started 1st kick.