What's on your bench today?

[div_h]

I'm enjoying an empty bench. Sort of.

 

Need to start a new thread. Maybe what's in your workshop but too big for the bench thread, thread.....

 

 

Today I have. Replaced the hitch on a Massey 35x, old one was seized solid.

 

Serviced a daewoo 13t 360.

 

Repaired a split hose on a kabota 3t, nice and not so easy job, why they thought they needed that many bolts to hold the floor pans in I will never know.

 

Took delivery of a new project. Renault b120 four wheel drive, look very much like a unimog. Hydraulic winch. Hydraulic services. Air run boxes.

 

I'm really thinking about doing mobile plant now. Might get a transit and kit it out. I like working on the bigger stuff.

 

I was thinking of plant or truck mechanic and get away from cars. Was told by many it's easier than cars it's better! But when I looked into it money etc.... I'm sticking where I am lol:thumbup: think my boss has been over paying me for years. Good luck

[Rich2484]

I was thinking of plant or truck mechanic and get away from cars. Was told by many it's easier than cars it's better! But when I looked into it money etc.... I'm sticking where I am lol:thumbup: think my boss has been over paying me for years. Good luck

 

Yeah. It is easier tho. But the gear is more expensive. The amount needed is unreal. All the big tools. Plus a compressor and welder is essential.

[Dinosaw]

Hi guys, on dino's bench today is an 038 super. Comp. at 110 so fitted new rings as bearings appeared to be ok. No change. However it's really difficult to measure the squish as the pot has no squish band except a millimetre ridge around the inside of the pot. Guessing, I removed the gasket, about 0.8mm thick and turning over manually there is no TDC contact. Am putting back together with just HT silicone gasket. Is this a good idea? Your thorts please....

[Dan Forsh]

Hi guys, on dino's bench today is an 038 super. Comp. at 110 so fitted new rings as bearings appeared to be ok. No change. However it's really difficult to measure the squish as the pot has no squish band except a millimetre ridge around the inside of the pot. Guessing, I removed the gasket, about 0.8mm thick and turning over manually there is no TDC contact. Am putting back together with just HT silicone gasket. Is this a good idea? Your thorts please....

 

I'll jump in here based only on what you have said.

 

First question is: are you sure your comp tester is reading correctly?

 

2nd question: Does the saw have a decomp valve and if it does, is it okay? If in doubt remove, replace with a blanking bolt for testing and re-test the comp.

 

After that:

The squish band as I've always understood it, isn't an actual 'thing', it's just the measurement between the piston crown and the top of the cylinder.

I've never done this but my understanding of typical squish is that it is usually <1mm so the standard method of measurement is to take a piece of solder, bend it into an 'L' shape and put it in through the plug hole and pull the saw over so that it is 'squished' by the piston against the top of the cylinder bore. Remove it and measure the thickness of the now squished solder with verniers to determine the squish band. Approximate squish with the base gasket removed is simply measured squish, minus thickness of base gasket; or just remove the gasket and do the solder thing again. If you have already removed the gasket and found no issues with things hitting each other, then I'm assuming that you might be good to go, but measure the comp again (assuming your gauge is accurate).

 

Reducing squish should only really be considered as a customisation or modification though; if you have to do this to a saw with new rings fitted (btw compression has nothing to do with the state of the bearings) to get the compression up, I'd really be questioning the accuracy of your comp tester.

[Daniël Bos]

No contact at TDC does not mean no contact once the saw I'd starting to warm up, unevenly as they do....

I unintentionally found this out in an expensive way before now.

 

A safe minimum measurement would be

.5mm of squish.

[spudulike]

The squish band is a machined band around the outside of the cylinder and is there to control combustion and reduce detonation.

 

Rover is correct with his minimum dimension.

 

Dan is correct with his measurement method.

 

If a bearing has failed or the gudgeon pin has worn the seat down, it will effect compression and have seen faulty crank bearings and worn piston gudgeon pin holes reduce compression.

 

At 110psi I would suspect the gauge isn't reading correctly unless the piston/bore are in really bad shape - is the plating ok and is the piston to bore a good fit?

 

Worth checking that the piston crown hasnt been damaged by using a solid metal piston stop.

[Dinosaw]

Hi Dan, Comp tester newish, hasn't been a problem before. What I meant was that the Husky 254 I also have in bits for a new little end bearing has an actual horizontal band about 5mm wide machined into the combustion chamber in the same plane as the top of the piston so squish measurement easy peasy. However, on the 038 no such band exists and the dome of the chamber begins virtually at the edge of the combustion chamber, making it much more difficult to measure. By bearings I meant little and big end, any wear in these would contribute to a false reading. Thanks Rover, I'm aware of the vital .5mm!!

[Dinosaw]

Hi Spud, Piston and bore in very good nick, no gouges in piston or ally pickup on cylinder. New rings fitted due to 110psi reading with no change after fitting, old ones looked and measured ok. Took out 0.8 mm gasket and couldn't get piston to touch top so have re-assembled with silicone gasket and now waiting for it to go off before retest. On the Stihl 038 s there is no machined squish band. Thanks all for your input!

[Eddy_t]

Hyway cylinder arrived today, porting looks pretty good to start with! Who ever thought of doing this is a genius! The 56cc cylinder could outcut a 560, I wonder how good this will be

 

 

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[Dan Forsh]

The squish band is a machined band around the outside of the cylinder and is there to control combustion and reduce detonation.

 

If a bearing has failed or the gudgeon pin has worn the seat down, it will effect compression and have seen faulty crank bearings and worn piston gudgeon pin holes reduce compression.

 

Thanks, I'm still learning obviously. I'm still not too sure what this is though, if I'm understanding correctly, are you saying it it a wider diameter section at the top of the cylinder then? I always thought that when someone said they were cutting the squish band, they just meant that they were reducing the clearance gap.

 

By bearings I meant little and big end, any wear in these would contribute to a false reading.

 

I get what you both mean on the contribution that worn bearings or pin might make to compression. It makes sense now that you've said it. Just how bad would they need to be to make a significant difference; just worn or really bad?

 

Thanks for the info both.