Neotec 070 clone carb problem

[Mike in Montana]

Hi everyone, first post. Seems like a lot of knowledge here.

Several searches didn't turn up anything useful so I'll outline my situation followed by a question.


I bought a Neotec 070 clone as a project/milling saw. Stock it ran OK but was sluggish and seemed like it wasn't revving 100%. I know they are low rpm saws but still...

It had .050" squish so I deleted the base gasket and tried again. It definitely improved the torque and response but it started popping under load. Lean or detonation? I couldn't tune it out...

I pulled it apart to inspect the piston and cylinder. They looked fine other than the piston had very black carbon like it was rich.

While it was apart I cleaned up the ports, raised the exhaust 2 degrees(106 to 104) and cut 2 degrees off the piston skirt increasing the duration to 152. I also pulled the carb apart and blew everything out and checked the meter lever. I adjusted the meter lever to richer and buttoned the saw up.

Again the saw improved on the bottom and would rev up but just start to cut and bog out like it is starving for fuel. Again, I can't tune it out. I've pulled the carb several times and adjusted the meter lever both ways and adjusted the high and low as rich as possible but it pops and bogs just after reaching the powerband. It is so rich on the bottom it barely idles but acts lean on top...
If I over richen the high and lean it out again it responds but then bogs like it's starving.

The carb has a Tillotson part number on it but I can only assume...

I don't have a pop-off pressure tester, could it be the meter lever spring?

What am I missing? Is their any performance tricks for these carbs? High jet/nozzle to small?? Should I swap it for some other carb? The 090 has the same carb so someone has to know something about them?

If I can get this figured out, I have an 090 top end to play with next.

Any advice for the carb or 070/ 090 performance is greatly appreciated!

 

[Motorka]

governor ? It s limits max rpm. gogle stihl 070 governor

 

[Mike in Montana]

Right, forgot to mention I disabled the governor.

 

[Motorka]

A workshop manual.

 

[lehman live edge slab]

Wouldn’t personally spin that china clone to hard, an oem 070/090 was limited to around 9000rpms while you can turn them faster unless a race saw I’d leave it lower. Milling doesn’t require high rpm’s just torque and a good chain.

 

[kneedeepinsaws]

If you can’t tune it out it very well could be an intermittent coil issue.

 

[Mike in Montana]

Wouldn’t personally spin that china clone to hard, an oem 070/090 was limited to around 9000rpms while you can turn them faster unless a race saw I’d leave it lower. Milling doesn’t require high rpm’s just torque and a good chain.

I agree, I'm just trying to see what it will do.

 

[Mike in Montana]

If you can’t tune it out it very well could be an intermittent coil issue.

That crossed my mind, I may have to put a tach on it.

 

[Mike in Montana]

Find a Workshop Manual hope it help.

Thanks but I can't open or download it?
I'll try to copy n paste it in search bar.

 

[lehman live edge slab]

I could take pictures of the 070/090 repair manual if you can’t get it to download

 

[Mike in Montana]

Hmm...still can't open it...

 

[Motorka]

hope this works

 

[Mike in Montana]

hope this works

That worked, I was able to download it. Thanks.

So using this info, I put a timing light on the saw. Then I put a dial indicator on the piston and compared using a degree wheel. It turns out it is firing 29 degrees BTDC which is exactly what the manual specs.

By deleting the base gasket, I 've effectivley advanced the timing by lowering the cylinder .025". I'm wondering if I should advance the timing now that it is higher compression?...or should I retard it to closer to what stock was?

Adjusting for .025" would put the timing at 32 degrees BTDC. Trial and error I suppose...

 

[lehman live edge slab]

I’d leave it alone and run it asl long as you measured the squish with small soft solder. Will probably want 25 thousandths on a 106 cc engine

 

[srcarr52]

That worked, I was able to download it. Thanks.

So using this info, I put a timing light on the saw. Then I put a dial indicator on the piston and compared using a degree wheel. It turns out it is firing 29 degrees BTDC which is exactly what the manual specs.

By deleting the base gasket, I 've effectivley advanced the timing by lowering the cylinder .025". I'm wondering if I should advance the timing now that it is higher compression?...or should I retard it to closer to what stock was?

Adjusting for .025" would put the timing at 32 degrees BTDC. Trial and error I suppose...

TDC is TDC no matter what your squish clearance is. You haven't changed the timing at all.

If you can almost shut the high side needle off and it's still drowning in fuel up top you have insufficient pop off pressure. Try cutting little shim disks to put under the spring in the carb body, an aluminum can works well.

 

[Mike in Montana]

TDC is TDC no matter what your squish clearance is. You haven't changed the timing at all.

If you can almost shut the high side needle off and it's still drowning in fuel up top you have insufficient pop off pressure. Try cutting little shim disks to put under the spring in the carb body, an aluminum can works well.

You"re right, I was still thinking like port timing.

I have it as rich as it will run but it's acting lean on top like it's starving for fuel. Could that be to much spring pressure thus to high pop off?

 

[srcarr52]

You"re right, I was still thinking like port timing.

I have it as rich as it will run but it's acting lean on top like it's starving for fuel. Could that be to much spring pressure thus to high pop off?

If it’s fine for a few seconds and then goes lean that is usually too much pop off and it’s not opening the needle far enough to flow enough fuel.

 

[Mike in Montana]

I may have to buy a tester.

Yesterday I retarded and advanced the timing by moving the ignition plate just to see. Same thing.
I went through the carb again and the only thing I could find was the high orifice in the carb body was partially blocked by the orifice in the nozzle being misaligned. I drilled the nozzle orifice and it didn't fix it...so I bought another carb...

This saw wants to run so bad! It's snappy and torquey on the bottom but falls on its face as soon as I put it in the wood.

If a new Tilly doesn't fix it, I may be looking at a snowmobile carb or something. At this point, I've milled enough slabs the saw has paid for itself so if it continues to misbehave, I may start punishing it.

 

[Mike in Montana]

So I put the new carb on the saw and it improved slightly but the issue still persisted, the only thing left was timing, so I began digging.

I thought the saw had electronic ignition but it has points. Under a timing light the timing was all over at idle and revving it up.
I also found the woodruff key was too tall so the flywheel was off axis causing an oblong rotation to the coil.

I bought the Farmertec electronic ignition plate and installed it. It took some messing with to get it timed right. It advances the timing enough it wouldn't run until it was very retarded compared to the stock ignition position. This left the timing still advanced a few degrees from stock and automatically advances with RPM's.

THIS FIXED THE SAW! Now it REALLY runs!! I haven't put it in the mill yet due to weather but I expect good things now.

FYI...I would not buy this saw again though. If anyone is wondering, for what it's worth, don't.
The issues so far...
Hard to find a long bar. The Stihl 59" 880 bar fits perfect and is fair priced and available.
Flywheel/key issue described above.
Problem with points, saw wouldn't run right new.
Pop off was low, wouldn't idle until low was half turn out, I stretched the spring and slightly adjusted the meter lever and it seems to fuel right now.
I had to disassemble and debur every edge and inside the pull rope wheel. It's cast aluminum and the casting seams were sharp enough it was tearing up the pull rope.
The air filter isn't even close to sealed. I ran a bead of RTV around the sealing edges and let it tack up to about 90%, then I put it together and let it set over night. This formed a molded seal around the carb and top cover. Now it keeps the fines out.
The carb was severely restricted by gasket intrusion of the 3 intake gaskets.
After 3 times R&R the flywheel (out of probably 40)I had to buy a new flywheel nut as the factory one is so soft the threads began pulling out.
The oiler case gasket leaks.
The manual oiler plunger leaks, BAD.
The dogs are rounded off instead of being sharp.
The clutch is so so, slips easy enough unless its clean clean.
It's also just plain heavy for the performance.

As is, it's a 105cc 070. Unless you plan on putting a 66mm jug on it. Just buy the 660. There are more and better parts for it. All in all...you get what you pay for...

Thanks everyone for offering knowledge on this. If you guys are interested, I'll keep posting on how it does as I keep modding the saw and milling with it. After the using the 070 a while, I have a 66mm jug for it.