Swelled Cylinder ?

[Fish]

Yes some folks here contend that diagnosing and repairing two cycle equipment is so simple..........

I forgot about those folks that spend a whole lot of hours thanklessly helping folks fix this simple ****.......

Their thousands of posts have countless pic/diagrams of parts lists, pictorial threads of how to dis assemble/fix etc.....

 

[struggle]

Something is swelling and its the dealers bank account from the sounds of it:hmm3grin2orange:

 

[slipknot]

Ive seen cylinders that have become "out of round" trying to sand the remaining alum transfer the acid wouldnt get because it was more less impregnated.(i know....when they get that bad you are spinning your wheels) Swelling...heck I don't think it would have to get up to 1200 degrees I wouldn't think. I work at a forging plant that makes all of Honda's crankshafts going in vehicles except the v8. When we run our steel billets into the induction heater our target temp is 1240 degrees in order for it to become smash-able in a 5000 ton hydro press (any less we break $20k dies. If the steel gets above 1300 degrees it starts to liquify and the billets stick together and you can stab them with a steel rod if you can get close enough. I know exhaust gasses get that hot but actual metal temp, aluminum melts at 660 degrees. Not sure what the surface temp would be during a scoring of the piston on strait gas...I bet whoever owns the strait gassed equipment could be equally hot......in the head :mad2:. I would be. I'd want to beat someone up

 

[Fish]

Just out of curiosity what are PE techs making these days. When I graduate motorcycle Mechanic school I went from 14 to 28 by the time I was 25. Now the current kids are getting 12-14 an hour. Once I reached 28 there was no way to get any higher whether I was 25 or 65...

So you earn $28 an hour as what kind of tech? Motorcycle?

 

[watsonr]

660 C or 1220 F for aluminum and 865-1240F for aluminum alloy. Either way, it be darn hot!

 

[Fish]

What is funny on this site is someone with 30,000 posts......Or a lot more.....................................

This guy must really help folks!!!!!!!

 

[Fish]

tapatalk?

 

[Racerboy832]

Yes as a motorcycle mechanic. Now a days it nearly impossible for shops keep anyone past their 20's. They all seem to move onto union work where the bosses aren't shoving everything down their throat.

 

[cedarshark]

I put a compression guage on the blower and it wont do any better than 90 psi so I dont even bother putting gas in it. I pull the muffler and no scoring on the cylinder and light scoring on the top edge(exhaust side) of the piston. You can still see the machine marks on the remainder of the piston. Not nearly what you would expect from a saw that was supposed to be straight gassed. I pull the blower down all the way and take the jug off. Very light scuffing above exhaust port..not bad. I dont have much experience with worn rings but that's what it looks like. Can anyone let me know what the end gap should be on good rings when they are compressed ? Thanks for the help.

 

[cedarshark]

Forgot to mention....I pulled the rings off, cleaned the grooves and reinstalled the rings. When you compress the rings with your fingers, they actually sit below the edge of the piston. Doesn't seem normal but I don't know how to recognize a ring worn to the point where it would affect compression to this degree. Are there specs on a new ring that I can compare the old one with after measuring it with a micrometer ?

 

[1982dancbx]

Yes as a motorcycle mechanic. Now a days it nearly impossible for shops keep anyone past their 20's. They all seem to move onto union work where the bosses aren't shoving everything down their throat.

Right! I belong to the CBX owners association, I have heard many stories when a guy would bring a CBX to the shop, the kid (mechanic) says says wow!!! I didn't even know they made those.... yikes. And this was probably 15 years ago......

 

[dozerdan]

What is funny on this site is someone with 30,000 posts......Or a lot more.....................................

This guy must really help folks!!!!!!!

I agree. I could post one liners and get my post count up but why would I want to?

How many of those posts had any useful information in them.

Later
Dan

 

[Moparmyway]

I put a compression guage on the blower and it wont do any better than 90 psi so I dont even bother putting gas in it. I pull the muffler and no scoring on the cylinder and light scoring on the top edge(exhaust side) of the piston. You can still see the machine marks on the remainder of the piston. Not nearly what you would expect from a saw that was supposed to be straight gassed. I pull the blower down all the way and take the jug off. Very light scuffing above exhaust port..not bad. I dont have much experience with worn rings but that's what it looks like. Can anyone let me know what the end gap should be on good rings when they are compressed ? Thanks for the help.

Ring end gaps : 0.002-0.004 inches per inch of bore - unless otherwise noted by manufacturer ( example: gapless rings)
Check ring gap : install ring in cylinder and push it down with the piston, into the bore to ensure the ring sits level all of the way around and check the gap with a feeler gauge.


Most top rings in normally aspirated engines run around 600 deg F, second rings are usually about 300 deg F .............

 

[cedarshark]

Ring end gaps : 0.002-0.004 inches per inch of bore - unless otherwise noted by manufacturer ( example: gapless rings)
Check ring gap : install ring in cylinder and push it down with the piston, into the bore to ensure the ring sits level all of the way around and check the gap with a feeler gauge.


Most top rings in normally aspirated engines run around 600 deg F, second rings are usually about 300 deg F .............

Thanks but i am a little confused. Does your explanation for checking ring gap mean: Slide the ring down the bore 1 inch at a time (with the piston) and check every inch to ensure the ring gap is between .002-.004 ?

 

[3000 FPS]

Thanks but i am a little confused. Does your explanation for checking ring gap mean: Slide the ring down the bore 1 inch at a time (with the piston) and check every inch to ensure the ring gap is between .002-.004 ?

It means that if the bore is 3" diameter then it is .002 to .004" per inch of the that 3". In other words. .002 X 3= .006 end gap.

 

[cedarshark]

It means that if the bore is 3" diameter then it is .002 to .004" per inch of the that 3". In other words. .002 X 3= .006 end gap.

Ah....thanks ! Explanation greatly appreciated. I will check the old rings for correct end gap. I have already ordered a set a set of Cabers, but I am curious.

 

[qbilder]

I put a compression guage on the blower and it wont do any better than 90 psi so I dont even bother putting gas in it. I pull the muffler and no scoring on the cylinder and light scoring on the top edge(exhaust side) of the piston. You can still see the machine marks on the remainder of the piston. Not nearly what you would expect from a saw that was supposed to be straight gassed. I pull the blower down all the way and take the jug off. Very light scuffing above exhaust port..not bad. I dont have much experience with worn rings but that's what it looks like. Can anyone let me know what the end gap should be on good rings when they are compressed ? Thanks for the help.

Rings are a cheap fix if that does it. But don't be surprised if the cylinder warped if it got warm enough. I suspect that's what the tech meant when he used the term "swelled". If that's the case, then rings won't help. Rings are cheap though so give it a shop. Most likely the rings wore away rapidly without having oil in the mix to keep them lubed, and a new set will fix the issue. The tech is getting a bad rap for what was most likely a brain fart in using the wrong word. If he had said warp instead of swell then he wouldn't sound so off base, IMO.

 

[cedarshark]

The Stihl IPL for the BG 55, essentially the same blower as the BG 56, says the piston rings are 34mm x 1.5mm. Can I not measure the ring thickness(1.5mm) and accomplish the same result as an end gap test ? Or, is the end gap test used to measure possible cylinder wear as well ?:msp_confused:

 

[cedarshark]

It means that if the bore is 3" diameter then it is .002 to .004" per inch of the that 3". In other words. .002 X 3= .006 end gap.

Here are my measurements:
1) Cylinder diameter= 1.33 inches(I know..it's a monster)
2) Ring end gap measured w/ ring level in cylinder = .012 inches.

3) .012 x 1.33 = .01596(rounded to .016)

4) Acceptable ring gap: .002 x 1.33 = .0026
(or)
.004 x 1.33 = .0053

Leading me to believe my measured ring gap of .016 is more than 3 times the acceptable gap indicating severe ring wear. I'm not very good at math...am I doing this right ? This is the first time I have dealt with ring wear so it's a great education for me. Thanks for your insight.

 

[tpope]

Yep, your ring is worn and should be replaced. Your methods and results seem correct too.