stihl ts420's and husqvarna k760's and k750 total rebuilds. best parts to use for $ other than OEM?

[ginsenger]

there is a small bevel in the hole for the seal, it takes it down almost to the inner lower edge of the bevel. That's why I made the seal driver so it would stop at the 1mm below edge. With a driver that did NOT stop at the edge it would be near impossible to stop at a specific spot if the seal needed to be below the surface any at all. Hope I haven't screwed up on this..

I didnt blow directly in the holes of the carb but I should have held my finger on the fuel tubes on the outside. thanks though I will be even more careful in future.

 

[ginsenger]

Replacing the seal on the clutch side Mod. 650, 700 In order to gain access to the seal the washer which lies inside the clutch drum must also be dismantled. This has a forced fit on the shaft and may be difficult to dismantle without being damaged. Use two screwdrivers first to bend out the washer far enough so that extractor 504 90 90-02 can be used. Dismantle the seal with an extractor 504 91 40-01. Fit the new seal by means of drift 502 50 82-01. Remove and install the seal ring in the same way as described for changing the seal ring on the flywheel side.
NOTE! Press the seal in the crankcase until the plate shell is flush with crankcase.

so I may have screwed up dag gone it. This is all the info I could find when I first started studying this. I have a newer shop service manual that didn't say anything other than use tool bla bla xxx

 

[ginsenger]

You won't need to replace the carb gaskets, but you need to check for contamination, and put back together clean, then test it.
???
what do you mean here by test it. How do I test what??

 

[alexcagle]

A carb test:
Pump it up to 8psi.
Bump the carb lightly in a wood surface. It should not lose pressure.
Then put your palm on the back of the carb while pulling light vacuum with your mouth. Then watch the gauge. Short drops should stop and hold without bleeding on down. That's not in any manual...... lol

The seal depth
Sounds good.
It probably applies to any saw.

I got an early Partner K1200 behemoth in a tote with a new piston.

 

[ginsenger]

A carb test:
Pump it up to 8psi.
Bump the carb lightly in a wood surface. It should not lose pressure.
Then put your palm on the back of the carb while pulling light vacuum with your mouth. Then watch the gauge. Short drops should stop and hold without bleeding on down. That's not in any manual...... lol

The seal depth
Sounds good.
It probably applies to any saw.

I got an early Partner K1200 behemoth in a tote with a new piston.

**
Where do I hook up on carb to pump up the 8 psi?
Do I pull the vacuum with my mouth at the same place?
**
What is your method of determining if a crankshaft is bent?
**
Is there an exact measurement or way to know without guessing if a rod bearings is worn too much??
As a beginner I can't quite tell. I know if it has up and down play, any is too much. but the slight side rocking is more than I know. I haven't the experience with a bran new one to judge by it.
&
I really am grateful for your efforts to guide me. Art

 

[alexcagle]

8 psi at the 45° inlet barb.

With it under 8 psi pressure, and holds, pull vacuum on either end of the carb throat with palm sealing off the other end.

A bent crank can be detected by rotating the flywheel, and observing the clutch pulley while held still from spinning.
A dial indicator works too.
The flywheel can be seen wobbling while rotating the clutch as well, or with a drill on the crankshaft, like on the youtube video below.

 

[ginsenger]

8 psi at the 45° inlet barb.

With it under 8 psi pressure, and holds, pull vacuum on either end of the carb throat with palm sealing off the other end.

A bent crank can be detected by rotating the flywheel, and observing the clutch pulley while held still from spinning.
A dial indicator works too.
The flywheel can be seen wobbling while rotating the clutch as well, or with a drill on the crankshaft, like on the youtube video below.

Ok thanks. That won't work if the crank bearing is froze up. I guess if bearing is burned out and wont turn or anything that might have hurt the crank is found, after it is tore down, I should put it in the lathe and dial indicate it.
**
I used some green locktite on a bearing when installed. some must have gotten in the bearing and from the heat it setup and stuck. when it cooled down it was froze up. I got it freed but it still feels a little rough. What should I do???????????????? Never mind , I kept working it and wd40 and air, it finally cleaned up and turns smooth.

 

[ginsenger]

Alex I have two stihls ts420 that have broken blocks. Broken on opposite halves. im looking at using half from each saw and making a one out of the 2. ,,What do you think of that?,,, they were fairly new.
What should I look for as far as if to use one of the pistons and jugs over with new rings?? Or should I just buy a new piston and rings and use one of the jugs over??

 

[ginsenger]

I did a carb test. This is on a husky k760...8psi on inlet taped it on wood and the pressure dropped a little every time I tapped it??
when I did a palm test it dropped all the way.
** I did pressure test by a pdf service manual and it pumped up only to 18 psi and fell to 14psi. the other pressure tests seemed ok as best I could tell.
this saw is fresh built, it seemed to wallow just a little on a rev. Another one I just did revved better, smother right on up to top rpm. It just sounded better with more pep than this one.. that is why I pulled carb back off this one.

 

[alexcagle]

The green only needs to be like two drops, and spread around the pocket.
I use it only on the TS420 because of the plastic rings not liking heat.
When I use long bolts to draw a crankcase together it lubricates too. - But make sure to lightly wedge something centered between the counter weights of the crank first, so it won't stress the point at which the crankshaft was heated and joined together at the factory.
*
Service manuals on the K760 carb say to have the lever just below the deck, but if the diaphragm is malformed slightly, or moves at an angle, it can cause it to leak when it when it's bumped. I usually have the fulcrum contact point set a little lower if it leaks when bumped.
At 8psi, pulling slight vacuum, try to make it drop 3psi and stop.
It should hold with no bleeddown after the three psi drop.
If it bleeds on down, either the diaphragm needs replaced, the needle spring is weak or incorrect.
If it fails this test, try removing the diaphragm and cover, and pump it up to 8psi, the lightly touch the fulcrum an see if it stops positive. If it does, then the diaphragm's center round aluminum contact may be wrong in thickness to work correctly. A carb kit must have a mated fulcrum and the center contact of the diaphragm design to work in the carburetor it was designed for.
Like these Tillotson and Walbro versions.

 

[alexcagle]

The best settings I've found on the K760 is just shy of 1-1/2 turns out on both high and low needles.
These saws have a rev limiter on the coil. That's why they miss at wot when under "no load" conditions.
At idle they normally sound like a cammed out race car.

 

[ginsenger]

The best settings I've found on the K760 is just shy of 1-1/2 turns out on both high and low needles.
These saws have a rev limiter on the coil. That's why they miss at wot when under "no load" conditions.
At idle they normally sound like a cammed out race car.

**
I took another carb from another saw , it passed the test, and used it. The benefits of them all belonging to the same person. I think I will get a kit and learn a little from putting it in while not feeling as much rush.. They needed saws now. I been slow trying to learn instead of saying I know it all and slamming them together and not knowing ****. So far i have done 4, One ( the first one) had a crank bearing go back out after 3 days. It shattered when I tried to pull it. I sold them a new crank. The rest of them have been running for a week or two and are doing good. Still got 4 in the floor. All of the first ones were leaking under the jug at the crankcase split when I checked them for leaks.. The hondabond 4 took care of that. The 328 EZ-tach+plus I got for rpms does not seem to do good for checking max rpm. It makes for a question rather than a sure thing.

 

[alexcagle]

The max rpm is limited, so there really isn't any reason to check them with a tach.
I use them on chainsaws, and to set idle speed & mix on TS420's that tune by setting highest lean dropoff at 3100 rpm, then bringing it back down to 2800 rpm with the "L" mixture screw.

 

[ginsenger]

The max rpm is limited, so there really isn't any reason to check them with a tach.
I use them on chainsaws, and to set idle speed & mix on TS420's that tune by setting highest lean dropoff at 3100 rpm, then bringing it back down to 2800 rpm with the "L" mixture screw.

**
If you reuse a jug, what do you cleanup, shine, the bore with?? using same piston with new rings

 

[alexcagle]

I use a small knot cup on a dril to clean out the carbon on the cylinder ceiling, and a Dremel rounded end cutter to clean the carbon out of exhaust port. This can occasionally can rough up the edges at the exhaust port.,
Then take a 502 or 503 Dremel flap wheel to remove any aluminum scoring transfer, and smooth out any roughness at the exhaust port edges, from the carbon removal step.
If you run your index finger around the cylinder wall, you'll feel any roughness that could scratch the piston.
Due to the accelerated wear of masonry dust, and how hard it can be to clean the
carbon out of the ring grooves, I would recommend always using a new piston kit. The reason for this is the ring grooves get excess clearance, which lets the rings move up and down too much, and can cause problems with rings breaking and ring locator pins that getting worn and letting the rings rotate and hang on a port.
Not to mention the ring ends wear a step in the sealing surface of the ring lands that may not seal well with new rings.
*
Stratified charge cylinder designs are not as susceptible to excessive intake skirt clearances causing "spitback" through the carburetor.
On conventionally designed piston ported engines, like the TS400, this "spit back" spray soaks the air filter, causing flooding conditions. If the machining marks are completely worn smooth on the piston intake skirt, or the bottom edge is shiny and rounded, then piston replacement is warranted.

 

[ginsenger]

What is the flywheel and clutch torque for stihl ts420?

 

[alexcagle]

What is the flywheel and clutch torque for stihl ts420?

 

[ginsenger]

View attachment 572214

what is the clutch ( the cast piece with the springs? or what are they calling it? iS IT THE DRIVER?

 

[alexcagle]

Yes.
Strange that they call it that.

 

[ginsenger]

Yes.
Strange that they call it that.

tHANKS A BUNCH