TS400 Intellicarb?

[lblac36315]

New TS400, maybe 5 hours. When started will idle ok?, but will run extremely rich (solid smoke plume) when throttle is given, even to the point of dying (flooding out). I have done alot of 2 needle carbs, but never been into one of these. I don't know what testing procedures are for the intellicarb to even start to diagnose problem. Will someone tell me how it works? Please Help. Thanks, Lee

 

[Simonizer]

New TS400, maybe 5 hours. When started will idle ok?, but will run extremely rich (solid smoke plume) when throttle is given, even to the point of dying (flooding out). I have done alot of 2 needle carbs, but never been into one of these. I don't know what testing procedures are for the intellicarb to even start to diagnose problem. Will someone tell me how it works? Please Help. Thanks, Lee

This is a chainsaw forum, not cut-off saw. I will attempt to help never-the-less. First the obvious, this machine has a separate 3-position choke control on the lower left of the handle. Make sure your choke is open.

 

[lblac36315]

It's where all the knowlege is!

I know it's chainsaw forum, but I knew somwone here could help. Been reading this forum for about 4 yrs. and here learned more from this forum than I have anywhere. I have 6 saws in the shop, with most modded with info given to me from these members. I'm a mechanic for a rental store, so I now have to fix cut-offs, rather work on saws! I've gone over all the basics, fuel line, impulse line, filters, carb boot leaks & gasket air leaks. Pretty sure its within the carb. Just looking for some advice. Sorry if I offended by posting in saw forum.

 

[Lakeside53]

Yes this is a chainsaw forum, but it's not like we don't digress, and it's an interesting topic and technology that may well end up in saws (hopefully not).

Cutoff saws are hard to diagnose by conventional observation. The electronic ignition will limit the max speed of the saw by skipping sparks to the point where you may only be sparking a few times a second at full rpm and light load. This happens almost immediately you rev the saw up and tries to exceed the max rpm. A tach is useless as it get a bad reading as soon as the ignition limits. Skipping sparks means you aren't igniting the gas, so it blows though very rich. Look at the big black soot plume across the blade cover on all TS400 saws. The "problem" is MUCH worse if you are running a composite cutoff blades instead of a steel diamond blade as they are much lighter and the saw peaks instantly. The ONLY way to figure out if they are running correctly is to bury them into concrete or steel. If they idle fine and run fine under load, they are fine.

Just as a note, the "intelligent carb" just senses the pressure inside the filter instead of the atmosphere, and as such adjusts the mixture slightly for blockage of filters. This is on almost all Stihl chainsaws in current production.

For tuning, DO NOT chase the high end around with the H screw. All you'll do is burn up the engine. Set it (assuming you have the adjustable carb) to exactly one turn out and leave it. The ignition module will do the rest.

On the older generation saws like the TS350/360 (uses the TS08 engine), the ignition fires per stroke and carb has a valve that by engine vibration at max rpm massively enriches the gas. The first time I met one of these I was dead sure the carb was bad - the saw barely appeared to run when not deep in the cut, and impossible to tune by conventional means.


Why do I think it's heading toward saws, possible the lower end consumer saws? Stilh latest series of 4-mix engines on the weed wackers has the exact same electronic limit in the coil... If your string is too short, the engine can no longer rev beyond the design limit. Seems like Stihl (or their lawyers) is trying to protect us from ourselves...

I wonder how this all factors in their EPA testing....?

 

[NevadaWalrus]

The intelicarb shouldn't be confused for making any different settings. As lakeside stated, the main diaphragm is vented to the air filter, as the filters clog up, more vacuum is created in the air box. This extra vacuum vented to the backside of the diaphragm limits its ability to fluctuate causing the needle to open less and lean the fuel, in theory to match the reduced air intake. This keeps the fuelmix more accurate as the filters get dirty. Any carb adjustments should be done with clean filters and as stated due to the ignition rpm limiter the high jet has to be set at spec and left alone.

You say you work on rentals I think, suggest if you have another TS400 available to pull the coil and put it in this unit. They use a slope advance and sometimes pop the control diode and become stuck on start up retard. They won't rev and sound rich. They spark to all get out so any spark test will show they're good, the only way to check for advance working is stick in a known good coil.

 

[Lakeside53]

Nevada brings up a good point. It's VERY easy to get mislead by a bad multi-stage coil. I had an HS45 (stihl hedge trimmer)that "obviously" has a bad carb, so I rebuilt it.. hmmm.... still ran apparently really rich and would'nt pull more then 6500rpm (should limit at about 9500). Coil was bad.

Testing the condition: Seems to me that on a TS400, a timing light would be a great test. The coil/flywheel side cover can be taken off as the winder is on the clutch side (mutter mutter....). You should be able to see the multistage stage spark advance quite clearly. Maybe it's worth testing a "known to be good" saw, then the bad saw for an immediate comparison. Let me know if you do this - I've aways wanted too, but never had time in our busy shop. You are going to have to be VERY carefull with the throttle - under light load (not in concrete) only tiny amounts of gas are required to get the saw rpm to the ignition limit point, so maybe use the "LA" screw instead of the main throttle. you may have to use a small 12 volt battery to power the timing light, depending on the type.

On swapping coils, there are two types: a three screw mount and a two screw mount. Yours should be 3 screw if it's only 5 months old. Use Loctite 242 or 241 when you put back in the screws.

 

[lblac36315]

Thanks Guys...

Didn't get a chance to swap coils today, will try it on Monday. What you are describing with hit/miss rev limiter is exactly what its doing...will not make any revs like other units that I have. I found out today that the owner is going to sell all of our MS440 Mag saws soon, too much saw to rent to homeowners. I suggested that they be replaced with MS260 Pro's. He ordered them today. None of the 440's are more than 40-60 hours old and some with as little as 4 hrs. All will be sold with 20" ES bars and RM chain(s) some will be new bars & chain. I think for around $500?. May list some on ebay. Again thanks for the info & I will post the results of ignition swap. Thanks, Lee