2 stroke will idle but no Full Throttle...

DeezilDennis

I recently got my old 2 Stroke yamaha Enduro 100cc out of 15 year storage and did all the specific steps to get it going.

I cleaned the tank. I also drained the tranny and installed new clutches and steels. I bled the Oil Injector and it seems to be working fine. I drained the carb before I put it away for storage.

The bike fired up after 2 kicks and settled into a nice idle after it warmed up and the choke was pushed in.

I can get about 1/4 throttle but thats about it. It just levels out and bogs a little it sounds like..
If I let it sit idling for a second I can rev fast and hit high rpms for a second and then it just goes back to what it was doing before. I pulled the carb and disassembled it and cleaned it. It looked fine. I adjusted the carb screws even though I had them to set to factory specs and nothing helped.

I put the carb back on and it still does the same thing.

Any Ideas

sr71cbx · Posted: Sun Aug 19, 2007 8:25 pm Post subject:

Mainjet is plugged or the mainjet air bleed hole is plugged. If it has a side type mainjet(screws in the side of the floatbowl), check the mainjet holder that screws into the needle jet(emulsion tube). The o-rings on these types of carbs can leak fuel if the o-ring is damaged or old and drown it in fuel.
Keep us posted!

DeezilDennis · Posted: Sun Aug 19, 2007 8:39 pm Post subject:

Im not sure but I'll check again. I cleaned everything out till it was spotless I ran needles and tiny rods through everything.
All rubber parts looked great..

I guess I should have got it running again before I spent a ton on tires, tubes and other goodies.... Sad

Biquetoast · Posted: Mon Aug 20, 2007 6:17 am Post subject:

That's odd timing. There was just an article about two-strokes and air leaks in the latest (August) VJMC magazine. Did you see that? They pressure-tested the engine with like 6 psi, and found there were some air leaks that caused the same symptom you're having.

Mind you, I know absolutely nothing about two-strokes, just thought I'd pass that along...

Cool

DeezilDennis · Posted: Mon Aug 20, 2007 4:40 pm Post subject:

Where would I find this article?

Biquetoast · Posted: Mon Aug 20, 2007 6:52 pm Post subject:

sr71cbx · Posted: Tue Aug 21, 2007 1:55 pm Post subject:

An air leak in a 2-stroke bottom end will usually manifest itself as a lean idle condition if it's that bad. Another tipoff is oil residue around the magneto/ignition case cover from seal seepage behind the ignition assembly, or heavy smoke out of the exhaust that really stinks BAD if it's the clutch side crank seal. I've even seen an instance where the crankcase pressurized the tranny/clutch area(seal had physically popped out of cases) and forced all the oil out of the tranny thru the oil seals and cover gasket.
Good replies, keep us posted! Cool

DeezilDennis · Posted: Tue Aug 21, 2007 3:58 pm Post subject:

Ok I went and checked the cases again and ran it. It does not smoke more than normal and the cases are dry other than the area by the front gear.
Magneto area is dry as well.

masterduke · Posted: Tue Aug 21, 2007 5:07 pm Post subject:

Could a weak ignigation coil be the problem?

Cyclebits · Posted: Fri Mar 28, 2008 12:37 pm Post subject:

Hi Ya,
Also keep a very close eye on the oil level. It must be kept as close to full as possible.
The oilburners build the fuel/oil mixture up to pressure in the crankcase.....
low oil level = low pressure mixture = VERY poor performance/power
Vern

jayel · Posted: Mon Apr 28, 2008 7:51 pm Post subject:

check the o-ring on the bottom of the main jet if its not sealing to the bowl it will run like you discribe

YD3 · Posted: Tue Apr 29, 2008 2:30 pm Post subject:

Have you checked the exhaust for a restriction? Either at the head or baffle? Does it have a battery? I have seen a weak battery do strange things.

Good luck