TY175 restoration

[TYYamFan]

Hi all,

the closer I get to finishing this project, the more money it seems to consume! I'm 99% there, just need new shockies to finish. However..... I ran this bike for the first time last week, mechanically it's all sweet as a nut (should be, as just about everything has been replaced) but it doesn't run too well from say tickover to maybe 30% throttle. It idles nicely and goes very well above 30% but seems to be lethargic off the bottom, lots of intake roar and no go. It is a little better if I apply a bit choke. I have replaced the main jet (240), pilot (25) and needle 4L6, centre notch. Slide is No.3 with no wear marks, nozzle is O-0. I have set the timing as near as I could.
My question is, where do I start to troubleshoot, ignition timing or carby?

Thanks - Mark

[Starky]

Rule of thumb is the easy things first.

My TY175 is particularly sensitive about the position of the clip on the needle. When it is too high it wil die just off idle, then works fine in the higher rev range. Put it on the factory setting and there is no problem. Mine is set at second slot from the pointy end ( very technical discription)

New points and condensor worked wonders also.

Starky

[David Lahey]

Sounds like the pilot jet is blocked or part blocked.

[TYYamFan]

Spot on David, the pilot was blocked, it's almost right now but it's still not as responsive right off the bottom as I'd like, maybe I should try a 27.5 or 30 pilot jet?

Thanks - Mark

[David Lahey]

I'm assuming you have a standard airbox arrangement and end muffler for the 525 model. The 1N4 model has a rubber silencer on the air box lid and a more restrictive muffler which will affect the jetting if you have the carby setup for the 525 model. It doesn't matter really which setup you use but the carby jetting has to match the muffler and the airbox lid and your jetting numbers sound right for the 525 model.
Other possible causes:
Too big a sparkplug gap. They go best off the bottom with the recommended (0.3 to 0.4mm) sparkplug gap.
Ignition being slightly too far advanced can also cause a problem off the bottom.
Idle mixture set too lean likewise.
If you can't get the motor to idle right with the air screw in the range 1/2 turn to 1 1/2 turns and a 25 pilot jet, there is either still something wrong with the pilot circuit or air is leaking in somewhere downstream of the carby.

[TYYamFan]

Hey David,

spot on again! The unused autolube inlet on the carby has never been sealed, thus air leaking in downstream of the carby.
Are you sure the plug gap should be 0.3 - 0.4mm? My manual states 0.5 - 0.6mm

Thanks - Mark

[David Lahey]

Yes you are right about the spark plug gap. I was thinking of the points gap. Good to hear you have it going well.
David