Shindaiwa 488 Rebuild Woes

[eric4]

Howdy y'all! I picked up a 'parts' shindaiwa 488 a while back, as it was a nearly complete machine. All it was missing was the air filter + cover setup. The saw originally seemed to have gone down due to the rings seizing up in the piston, from ingestion perhaps?

I gave the saw a near-full disassembly, soaked the case, installed new rings, cleaned up the cylinder, base gasket delete, and muffler mod. The carb had dual adjustable jets, so I rebuilt it. When she was ready to fire up the first time, I got no spark. Verified I wasn't using a 'resistor' plug, then purchased a new ignition.

Finally after installing the new ignition system, the saw fired up! Ran erratically so I pressure tested, and it passed with 10lbs holding vac and pressure. I had figured it was my tuning, so I rebuilt the carb again, and tried to retune. Got the idle settled in, but once I give it full throttle, it can't find idle again and takes off on its own.

What would y'all start diagnosing next? Some things I'm considering are tank vent, bad fuel line, crank seals? A little stumped on where to go next, and the last thing I want to do is score up my newly cleaned combustion chamber.

It's a sweet lil saw that I hope to get running soon.

 

[Woodwackr]

Howdy y'all! I picked up a 'parts' shindaiwa 488 a while back, as it was a nearly complete machine. All it was missing was the air filter + cover setup. The saw originally seemed to have gone down due to the rings seizing up in the piston, from ingestion perhaps?

I gave the saw a near-full disassembly, soaked the case, installed new rings, cleaned up the cylinder, base gasket delete, and muffler mod. The carb had dual adjustable jets, so I rebuilt it. When she was ready to fire up the first time, I got no spark. Verified I wasn't using a 'resistor' plug, then purchased a new ignition.

Finally after installing the new ignition system, the saw fired up! Ran erratically so I pressure tested, and it passed with 10lbs holding vac and pressure. I had figured it was my tuning, so I rebuilt the carb again, and tried to retune. Got the idle settled in, but once I give it full throttle, it can't find idle again and takes off on its own.

What would y'all start diagnosing next? Some things I'm considering are tank vent, bad fuel line, crank seals? A little stumped on where to go next, and the last thing I want to do is score up my newly cleaned combustion chamber.

It's a sweet lil saw that I hope to get running soon.

View attachment 445059

Vac and pressure test?
I have a fair amount of parts for these.
And, a runner I picked up cheap that has yet to be rebuilt

 

[eric4]

Vac and pressure test?
I have a fair amount of parts for these.
And, a runner I picked up cheap that has yet to be rebuilt

Done it a few times, plugging muffler and intake, and testing thru the impulse line. It's held pressure and vac just fine, which is stumping me. I wondered if maybe the crank seals are on their way out, and losing pressure once there's some friction added...?

I'm converting it to a 488P, and have all the parts needed except the black plastic elbow after the carb.

 

[Woodwackr]

This?

 

[Woodwackr]

Done it a few times, plugging muffler and intake, and testing thru the impulse line. It's held pressure and vac just fine, which is stumping me. I wondered if maybe the crank seals are on their way out, and losing pressure once there's some friction added...?

I'm converting it to a 488P, and have all the parts needed except the black plastic elbow after the carb.

Intake boot torn?

 

[eric4]

Intake boot torn?

The pressure test includes the intake boot, as my stop-gasket is between the boot and carb... So I don't think it's the boot.

The air filter elbow I need is different, since I'm going for the HD air filter. I've got an order put in, and it's expected in a few weeks. Hopefully it's not discontinued...

 

[Woodwackr]

The pressure test includes the intake boot, as my stop-gasket is between the boot and carb... So I don't think it's the boot.

The air filter elbow I need is different, since I'm going for the HD air filter. I've got an order put in, and it's expected in a few weeks. Hopefully it's not discontinued...

Ah, cool. Didn't know they had a different filter available. That elbow has 22157 so my not be for a 488 (22160) anyway

What about a bad carb? I assume you rebuilt it.

 

[eric4]

Ah, cool. Didn't know they had a different filter available. That elbow has 22157 so my not be for a 488 (22160) anyway

What about a bad carb? I assume you rebuilt it.

I'm pretty sure the one you pictured is for a 488, just the standard low-top model. The 488p is full on Quasimodo with a tumor of an air filter, but it's an impressive three-stage setup!

Could be the carb. I'll dabble with a pressure test on the carburetor, as well as another ultrasonic bath...

 

[Woodwackr]

I'm pretty sure the one you pictured is for a 488, just the standard low-top model. The 488p is full on Quasimodo with a tumor of an air filter, but it's an impressive three-stage setup!

Could be the carb. I'll dabble with a pressure test on the carburetor, as well as another ultrasonic bath...

Yup, just checked the IPL
I have a carb if you want to try that.

Pics of this filter? I don’t see it on the schematics

 

[eric4]

Yup, just checked the IPL
I have a carb if you want to try that.

Pics of this filter? I don’t see it on the schematics

Here's a link to the 488P schematic. All the parts are seemingly available to make the conversion, but I'll let you know about that last part I'm waiting on.

I'll get some pics of the filter setup later, as they're all boxed up in my garage currently. I believe it was ~$100 for the filter setup...which ain't cheap, but I needed a filter and filter cover anyway, so it was only a $65 upgrade in that case.

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[jacob j.]

I would replace the seals for good measure. I've seen rare instances where the seals pass pressure/vac when everything is stationary, but fail when the crank is turning.

 

[eric4]

I would replace the seals for good measure. I've seen rare instances where the seals pass pressure/vac when everything is stationary, but fail when the crank is turning.

That's where my head is at too... I actually purchased seals and bearings for this saw, when I got my rings. But since it seemed to pressure test fine, as well as spin with ease, I didn't go down the path of splitting the case.

Is it hard to replace the seals without splitting the case?

 

[Woodwackr]

Here's a link to the 488P schematic. All the parts are seemingly available to make the conversion, but I'll let you know about that last part I'm waiting on.

I'll get some pics of the filter setup later, as they're all boxed up in my garage currently. I believe it was ~$100 for the filter setup...which ain't cheap, but I needed a filter and filter cover anyway, so it was only a $65 upgrade in that case.

PartsTree - Home of OEM Parts for Outdoor Power Equipment

Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.

www.partstree.com

Cool. I wonder if Benson has a newer IPL like that. All mine are ancient.

 

[Woodwackr]

That's where my head is at too... I actually purchased seals and bearings for this saw, when I got my rings. But since it seemed to pressure test fine, as well as spin with ease, I didn't go down the path of splitting the case.

Is it hard to replace the seals without splitting the case?

Do you have the shop manual?
Hm, nothing there on replacing seals

 

[jacob j.]

That's where my head is at too... I actually purchased seals and bearings for this saw, when I got my rings. But since it seemed to pressure test fine, as well as spin with ease, I didn't go down the path of splitting the case.

Is it hard to replace the seals without splitting the case?

It's pretty easy if you have a decent seal puller or can make one. I've made a variety of seal pulling tools with old flat head screwdrivers of different sizes. Hutzl also has an aftermarket puller that's essentially a copy of the Stihl seal puller - I've not used one though.

For installation - you'll need a sleeve for the crank so the inner lip doesn't roll. You can make a sleeve with a beer/pop can.

 

[eric4]

It's pretty easy if you have a decent seal puller or can make one. I've made a variety of seal pulling tools with old flat head screwdrivers of different sizes. Hutzl also has an aftermarket puller that's essentially a copy of the Stihl seal puller - I've not used one though.

For installation - you'll need a sleeve for the crank so the inner lip doesn't roll. You can make a sleeve with a beer/pop can.

Ok, the pop can makes sense, to keep the brass seal from catching an edge... Well, I reckon I'll give it a go tomorrow afternoon, and keep y'all posted.

Just watched a video of that Hutzl seal puller. Looks like a dandy tool. I can imagine how many curse words it'd save from making a DIY hooked screwdriver.

 

[Woodwackr]

Ok, the pop can makes sense, to keep the brass seal from catching an edge... Well, I reckon I'll give it a go tomorrow afternoon, and keep y'all posted.

Just watched a video of that Hutzl seal puller. Looks like a dandy tool. I can imagine how many curse words it'd save from making a DIY hooked screwdriver.

I’ve had one for a while. Works ok

 

[pbillyi69]

i would pressure test the carb......it cant hurt to pressure test the saw and pull it over a few times and see if it fails

 

[mrxlh]

Just to add to what others have already mentioned, try tweeking the saw like it’s being used. Treemonkey posted a video of a saw holding vac/pressure and pushing forward on the jug would allow the saw to leak down.

 

[Coupe]

I done a real old Dolmar for a guy a few years back and was doing the same thing right
from startup. Didn't need to touch the throttle it would just hit full revs. How it ever run I
do not know to this day. Both crank seals were completely shot, one was that bad it was spinning on the shaft.
I would still check for an air leak somewhere in the system. If you can leave the carby on test on the air filter side
and screw your two mixture jets right in plus count the turns.
To me I do not think there should be anything in the carb that should cause it to do that unless the throttle linkage
is jamming a bit. But revving up like that from startup sounds like an air leak to me.