atc70 points?

[hippyplz]

I am having a prob with my 70 and thought I would ask for some insight before I tore back into it. It has the tb88 piston, 20mm carb with uni filter, pk cam and pipe. It ran great after the rebuild but after a few weeks it was getting hard to start and would not idle for very long. I cleaned the carb and that didn't change anything so I just replaced the points. Starts first pull now, but would idle really high. Was able to get it to idle down buy turning the idle screw way out, but it is backfiring through the carb a little and the idle is hanging on it when i hit the gas, also seams to be running hot. It acts like its running lean, I have the point set where they are starting to open right when the F on the flywheel lines up with the mark on the case. will the point being off a little make it act like this?

[Dirtcrasher]

I'll tell ya. I have fixed everything under the sun and these 70's defeat me constantly so they are stored until I want to deal with them......

We changed to a CDI setup and even that was an issue.

All I can fix and I am a 70's idiot......

Kasey is really good at them as well as some members here.

[jb2wheels]

Did you replace the condenser, too?

Normally, I say points/condenser are the problems on 70s IF they are all stock. The stock carbs are very sensitive to changes.

But, that doesn't apply here...

Where did the carb come from? With pipe and Uni, easy to be lean. The Chinese carbs I've used have been grossly lean. For example, the carb on my Loncin 125 in the TRX had like a 30 Pilot and 74 main jet. It has a 38 pilot and 95 main now. I don't know what size or make but it's Chinese and uses same jets as my ATC 70 stock carbs. The carb that came with my 200CC Loncin in my 200X was really lean, too. Like 88 main. Needed a 110 to run. Was also a Chinese Keihin copy.

Also, check intake tract for leaks - between carb/intake manifold and also between intake manifold/head. Spray some carb cleaner or brake cleaner or WD40 around these spots. I had to "adapt" an intake for make the 125 fit right in the TRX frame because it has a top mount e-start. I had a leak between the carb and intake and had to make a gasket to fix it. Ran like until then - hard to start, coughing popping, would not idle right.

Good luck!