Ms 462 repair on a budget

[sean donato]

LOL. The one we got from Stihl doesn't read anything, as in zero. Bad valve I'm sure.

Anyway, If you need a gauge you need to work on more saws.

No, if your primary source of income is working on engines with more then once cylinder, compression gauges and leak down testers become mandatory. Then like a dump shite you loan them out and end up buying another because that guy didn't bring it back. Also nearly every engine has a water limit spec for compression psi. I'll give you a hint, it's not how fast it falls when you hang it by the starter.

 

[bwalker]

So, you are thinking that excess oil will not blacken a piston. Curious logic.

Not curious at all if you have any sort of knowledge on the subject..

 

[ZeroJunk]

No, if your primary source of income is working on engines with more then once cylinder, compression gauges and leak down testers become mandatory. Then like a dump shite you loan them out and end up buying another because that guy didn't bring it back. Also nearly every engine has a water limit spec for compression psi. I'll give you a hint, it's not how fast it falls when you hang it by the starter.

I can pull it one thump and tell you whether it has enough compression to run. That is my job. They come in with the complaint being that it will not start. If it does not feel right I pull the muffler. All takes likely less than a minute. If it does feel OK I look at the plug to see if it is wet or dry. If it is wet I put it on high idle, pull it tell it starts and put flooded on the ticket. If it is dry I choke it til it starts and if it does just say they didn't try hard enough. If it doesn't I check for fire. If it has fire and compression I pour a thimble full of mix down the throat and see if it will light that. If it does I put a new carb on it. If not I check to see if the key is sheared or whatever. And, chase it down.

Long and short, if the saw has enough compression to sit and idle indefinitely it has plenty of compression to use. Past that, I don't care.

Here lately I do about 20 saws a week, and that doesn't count umpteen weedeaters, blowers, trimmers....

I'm damn good at it and I'm fast. And, I never use a compression gauge, ever.

 

[numnutz6383]

Didn't think this would become such a contentious topic.

Anyhoo...it just came to my attention that the ms462 takes a different thread size plbug than the typical chainsaw. It's an M10x1, not m14x1.25. Sav-a-thread comes M14x1.25 only from what I see, so it looks like that option is out.

Could I just retap it to fit M14x1.25 and run a comparable plug to the specified NGK CMR6H? Or will I have to send it out to @srcarr52 to weld, drill, retap to M10x1.

 

[bwalker]

>

Didn't think this would become such a contentious topic.

Anyhoo...it just came to my attention that the ms462 takes a different thread size plbug than the typical chainsaw. It's an M10x1, not m14x1.25. Sav-a-thread comes M14x1.25 only from what I see, so it looks like that option is out.

Could I just retap it to fit M14x1.25 and run a comparable plug to the specified NGK CMR6H? Or will I have to send it out to @srcarr52 to weld, drill, retap to M10x1.

You probably could run the bigger diameter plug.

 

[huskihl]

You might need a longer plug. They are designed so the bottom of the plug is flush with the dome. A regular plug would be a little short. Probably be fine though as long as there is enough flat surface area on top already for the larger washer to seat.

 

[huskihl]

 

[ericm979]

Can you explain to me "blow by"?

Combustion gasses that get past the rings. There's always some. Yours might have excess blow by, or just crappy oil.
You're probably going to replace the rings anyhow, so if it's blow by from worn rings you'll be fixing it.

What would cause flashing off at too low of a temperature? Too much compression? Wrong plug heat range?

The composition of the oil. Lower quality oils will vaporize at lower temps.

 

[numnutz6383]

You might need a longer plug. They are designed so the bottom of the plug is flush with the dome. A regular plug would be a little short. Probably be fine though as long as there is enough flat surface area on top already for the larger washer to seat.

Yes you're right based on my reading, appears the CMR6H is 12.7 mm reach vs. a 9.5 mm reach of a BPMR7Y that's specified for a 461.

I found this useful reverse engineering tool that NGK has on their site that will help my search tremendously.

https://www.sparkplugs.com/search/reverseengineer?ptid=8

 

[chipper1]

This thread sucks, no actual pictures and you're still not done with it .

I'm joking of course, but I do like pictures.
Not sure if this is the right one, but it could save a lot of messing around.
https://www.arboristsite.com/threads/ms462-cylinder.366354/#post-7954362

 

[mudrat2]

Heli-coil is certified as a repair option on aircraft engines. Done right, it is not a problem.

If it is good enough for aircraft it is certainly good enough for a chainsaw.....

Easy way to tap the hole without taking the jug off is to connect air line to intake or exhaust, plug the other one, and run low pressure air into the cylinder while drilling out and tapping the hole. No grease needed, lube with neatsfoot oil.

 

[cookies]

pull the cylinder off, take the head to a local machine shop with the plug and have it repaired if it looks good and be done with it. With the head off change the rings and locktite the bolts that hold the windage baffle to the case under the piston. stick a carb kit in the carb and go to work!

 

[singinwoodwackr]

Seafoam!

 

[numnutz6383]

windage baffle to the case under the piston.

At the risk of sounding like a complete moron, what is a windage baffle and how do I find it in the service manual?

 

[dboyd351]

Any chance you can use a threadchaser to restore the existing spark plug threads to serviceable condition?

 

[numnutz6383]

This thread sucks, no actual pictures and you're still not done with it .

I'm joking of course, but I do like pictures.
Not sure if this is the right one, but it could save a lot of messing around.
https://www.arboristsite.com/threads/ms462-cylinder.366354/#post-7954362

My bad. Two jobs and three toddlers don't leave a lot of time for me to play with my hobby.

I reached out and, your won't believe it, he withdrew the cylinder because, I **** you not, he realized the threads were stripped.

 

[Stihl Learning]

Seafoam!

Exactly, put a cap full in a full tank and it will clean up the piston and muffler!

 

[bwalker]

Exactly, put a cap full in a full tank and it will clean up the piston and muffler!

Seafoam has never done a damn thing for me.

 

[ZeroJunk]

Exactly, put a cap full in a full tank and it will clean up the piston and muffler!

Nah, just rev it up and spray a little water in the carb.

 

[ZeroJunk]

Something to think about Focke Wulf 190

"The third prototype, V54, introduced the MW 50 boost system. This used a mixture of methanol, water and anti-corrosives that could be injected into the supercharger for up to ten minutes at a time, boosting power from 1,750hp to over 2,200hp and raising the top speed to 426mph from 360mph."