Hello,

Hope someone can help me out with a tech problem,

I have a 1978 TY250 which starts from cold ok the bike will run for 30 seconds or so then starts to die as if petrol not getting through then stops and wont restart for an hour or two when the pattern is repeated.

I have a good spark, petrol is getting into the carb, i have cleaned the carb and blown out all the jets,

Any ideas ?

Cheers,

Frankie,

check plenty fuel is coming out the fuel tap at the tank .sometimes theres a filter there that can choke

Make sure your carb tube vents are clear, especially the one's that run towards the skid plate, an old tip was to slice the ends diagonally to prevent fluid stops.

The old TY's had some routed towards the skid plate, where any bit of bog could plug it

Check the fuel filler cap vent isn't blocked too - try running without the cap on...

Paul MAc

From what you describe it sounds like some sort of blockage between the tank and the float bowl. Have you checked Fuel Tap, pipe, float valve for blockages/flow?

penno350 might have hit the nail on the head.

It sounds the float or the the float bowl valve is stuck.

When you leave the bike for a while it will slowly fill the bowl back up, but when started the motor will greedily empty the bowl in no time.

With the bowl off let the floats drop down and check that there is heaps of fuel pouring through.

Good luck

Edited April 1, 200818 yr by LesGamble

Cheers, Lad's for the advice i will try all the above tonight,

Frankie.

Frankie,

Sounds like fuel starvation, caused by corrosion or petrol gumming up. Take the tube off the petcock and see if you get a "good" flow on normal and/or reserve. If that is good check after your in line filter. If still good then take off the bowl and blow through the fuel passage way. Finally take out the float rod and let the valve drop in your palm. Lightly emery the the valve and replace and check it moves up and down. Most likely stuck in the up position and a little fuel is seeping past to allow you to start.

Tony

Hello,

Hope someone can help me out with a tech problem,

I have a 1978 TY250 which starts from cold ok the bike will run for 30 seconds or so then starts to die as if petrol not getting through then stops and wont restart for an hour or two when the pattern is repeated.

I have a good spark, petrol is getting into the carb, i have cleaned the carb and blown out all the jets,

Any ideas ?

Cheers,

Frankie,

I purchased my TY a few weeks ago and had the identical problem. Would fire first or second kick with full choke, but then die in about 30 seconds, would not accept any throttle. After spending 30 minutes kicking (good exercise) to finally get it running, and deciding it was a poor form of entertainment, I replaced valve float needle and holder (JK Hirst has these) and main jet, disassembled and cleaned the carb. Checked my hoses and none blocked (nasty looking though!).

The other thing I did was to simply put the mixture screw back to the factory setting (having got a .pdf of the workshop manual) - fully in and then back out 1 and 3/4 turns. Starting it on those settings it revved like a ******* and I had to adjust it out bring the idle down. I'm used to modern CVs and four strokes where the idle speed adjuster actually does something, but it seems on these stone age items fiddling with the mixture screw is critical.

Now, since then, I've had no further problems with starting. If you've taken the carb apart and cleaned it already, maybe also check your mixture setting? I just noticed that you didn't specify that you'd tried adjusting it.