Carboned-up 2-stroke, how to clean?

[Spazdog]

Originally Posted By: boraticus
...I also pulled apart two RD350 engines that were in excellent shape for being 36 years old. Some discolouration on the piston crowns and cylinder heads but no carbon build up. Even the exhaust ports were clean.


My RD350 had substantial carbon build up in the exhaust port and OE pipes. But I wasn't the original owner. For all I know, the original owner was running pre-mix and the cheapest marine 2-cyle in the injector tank that he could find and lugging it around at 3000 rpm.

After the rejet, elimination of the autolube, and adding expansion pipes, carbon ceased to be an issue. (yes, I eliminated the autolube. The shop that did the rejet insisted that I would have to

)

Bardahl was the "good" 2-cycle oil when I was 15. It probably wouldn't even rank at the bottom of 2 cycle oils now. (yes,15. my license was only for a 125, but the cops were apparently so impressed with seeing a 15 y.o. with a class M license and insurance that they ignored the 125cc restriction code. They never bugged me once seeing my license.)

In my defense, I did admit that oils were probably better now and might be the sole reason why my Chi-com POS is still so clean where my RD was so carbon choked.

 

[Texan4Life]

When I had my HF generator apart I used Hoppe's no. 9 gun cleaning solvent and a scotch brite pad to clean the top of the piston.

And I cleaned the head outside so I went to town with break cleaner and scotch brite.

 

[SOHCman]

Originally Posted By: Texan4Life
When I had my HF generator apart I used Hoppe's no. 9 gun cleaning solvent and a scotch brite pad to clean the top of the piston.

And I cleaned the head outside so I went to town with break cleaner and scotch brite.


I have also used a scotch brite pad before on a piston crown, it worked quite well but after the fact I wondered if I had done something bad by slightly roughing up the crown surface, giving the new carbon something to grab on to.

Would it have been better to polish the crown as well, or did I do no harm?

 

[boraticus]

This RD350 has a few modifications that keep it running clean. State of the art programmable digital ignition, modified carbs, heads machined to remove the squish band, a bit of port work and expansion chambers.

The oil injection on these things is bullet proof. I thought of removing it but after doing some research, I changed my mind. Glad I did.

I've been running this set up for over 1000 miles. Pulled the plugs yesterday and they're perfect. I put 50 miles on it today. Light, quick and agile. Lots of fun!

 

[Johnny]

That is one good looking RD350. Very nice.

 

[hate2work]

Originally Posted By: Johnny
Lawn Boy use to make a plastic tool for scraping carbon. You don't want to use anything made of metal as you run the risk of scratching the piston.


I've been using a metal scraper for 32 years now, no problems to report. I've never seen a plastic/wooden scraper that works as well as any of the metal ones I use.

It's all in being careful, of course.

 

[boraticus]

Originally Posted By: hate2work
Originally Posted By: Johnny
Lawn Boy use to make a plastic tool for scraping carbon. You don't want to use anything made of metal as you run the risk of scratching the piston.


I've been using a metal scraper for 32 years now, no problems to report. I've never seen a plastic/wooden scraper that works as well as any of the metal ones I use.

It's all in being careful, of course.


I'm sure that if you use copper or aluminum or even a mild steel, you could clear the ports of carbon if the piston is well below the exhaust port.

I've never really seen enough carbon build up on an exhaust port to chip off. Most of what I've seen has accumulated in the muffler. It's usually baked, dry and crumbly. That stuff scrapes off very easily.

 

[boraticus]

Originally Posted By: Johnny
That is one good looking RD350. Very nice.


Thanks Johnny.

To me, these old RDs are the equivalent of Lawn Boy mowers. Simple, effective, well built and very reliable even when modified to race level.

I had a collection of five of these old Yamaha two strokes. I had three 350s but fixed one up and gave it to a nephew. I'm working on an RD200 to sell to a friend. I have an RD400 restored and modified similar to the yellow 350. All that will be left to do is a '72 R5 which is similar to the RDs but with 5 speed transmission and no reed valves.

It's cold here today. I'll probably find a sunny spot in the garage and go over the three old LB mowers I picked up last night. Got all three for $40.00. They look rough but the engines look good and sound and the decks/wheels are rock solid. Once I get the serial number and spec them out, I'll post what year they are.

 

[hate2work]

Originally Posted By: 660mag
You can get edta from a Stihl dealer. It's called "Engine De-Carbonizer".


This stuff might work well, but it works too slow IMO. I don't have 24 hours to sit around waiting for this stuff to work, especially if the unit is being used commercially. PF FTW

 

[boraticus]

Originally Posted By: hate2work
Originally Posted By: 660mag
You can get edta from a Stihl dealer. It's called "Engine De-Carbonizer".


This stuff might work well, but it works too slow IMO. I don't have 24 hours to sit around waiting for this stuff to work, especially if the unit is being used commercially. PF FTW

Sounds like you need a back-up machine. Find yourself a nice used $25.00 Lawn Boy or Toro for short term replacement of the mower in for maintenance.

 

[660mag]

Originally Posted By: boraticus
Originally Posted By: hate2work
Originally Posted By: 660mag
You can get edta from a Stihl dealer. It's called "Engine De-Carbonizer".


This stuff might work well, but it works too slow IMO. I don't have 24 hours to sit around waiting for this stuff to work, especially if the unit is being used commercially. PF FTW

Sounds like you need a back-up machine. Find yourself a nice used $25.00 Lawn Boy or Toro for short term replacement of the mower in for maintenance.


Couldn't have put is better myself.
Most com guys cant afford anything "extra" around these parts due to the fact they only collect 18$ a cut.
I charged more that that when I was 12 years old.

 

[Hokiefyd]

Me too. I had a steady lawn job in the neighborhood and it was 20 bucks. I used a good ol' 1991 Lawn-Boy 2-cycle and slogged through the fast-growing fescue every Saturday for a few years.

 

[morris]

LOTS of MMO.

 

[Mamala Bay]

Originally Posted By: 660mag
Low rpm, rich fuel, and poor fuel are without a doubt the main cause in 2 stroke ope. Stihl started using edta out of necessity in there 4-mix engines. The manual states the decard/vale adjustment as regular maintenance around the 130 hour mark. It was a tricky engine with new challenges. A 4 stroke engine that delivers the oil through the fuel system. If any of the running conditions you mentioned are there the interval is shortened considerably. The carbon is not an issue in the port of the 4mix but the exhaust valve itself. You would set the piston at tdc and turn the rocker nut so the exhaust valve was deep in the cylinder, fill the cylinder with edta and 24 hrs later readjust the valves dump it out and run it at wot of 5min. Carbon comes out in sparks and random clouds of black powdery smoke. That engine without a spark arrest screen would be a fire starter for sure.


The 4 stroke hybrid has design flaw .. not sure with Stihl but to state to DISREGARD valve adjustment after 130 hours? Valve adjustment on the Shindaiwa 4 stroke??? hmmm it was a joke never was the problem.

The Stihl EDTA is an excuse assuring consumers this is the remedy for the 4 stroke hybrid. Sorry the product probably is awesome I have no idea since I've never used it but if you state this a potent product I'll take your word.

 

[660mag]

Not clear on every thing your post is trying to say. Mine may have not explained it well enough. The valve adjustment is not something the has anything to do with the carbon issue, but is grouped with the 130hr decarb service for timing reasons. Shindaiwa has the exact same carbon issue in there 4mix, but may have had some things going for it in the way of design that extended the interval in which it needed to be done. Sthil throttle cables on the fs and fc setups needs adjustment monthly under commercial use. When it's off the air fuel mix is rich. Low rpm use with a fouled air filter, and [censored] for fuel well... how does an oem help that. Shindaiwa also has a valve adjustment in there book of regular things to do.

 

[Mamala Bay]

In hard long commercial usage the 4 stroke hybrid may lack proper lubrication resulting in costly engine repairs...I just don't believe the new design is 100% bullet proof as of yet. What I'm saying it can happen as I've talk to dealers that sold the Shindaiwa 4 stroke hybrid. http://www.hybrid4engine.com/animation.asp

 

[mva]

Originally Posted By: SOHCman
Originally Posted By: Texan4Life
When I had my HF generator apart I used Hoppe's no. 9 gun cleaning solvent and a scotch brite pad to clean the top of the piston.

And I cleaned the head outside so I went to town with break cleaner and scotch brite.


I have also used a scotch brite pad before on a piston crown, it worked quite well but after the fact I wondered if I had done something bad by slightly roughing up the crown surface, giving the new carbon something to grab on to.

Would it have been better to polish the crown as well, or did I do no harm?


NEVER use scotch brite on an engine! This is something I learned on this site thanks to bbobynski:

"Scotchbrite seems so benign but it is death to engines. Scotchbrite pads are nylon fibers with 40 micron particles of aluminum oxide in them. Scotchbrite dust leaves behind all those 40 micron particles hidden everywhere. Aluminum oxide is an extremely aggressive abrasive. It imbeds in the bearings and eats the crank....and other things."

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=563163

 

[sciphi]

I got a can of PB Blaster Lawn Mower Tuneup (Google it), cleaned/oiled the air filter, and got a gallon of 93 octane gas with 50:1 TC-W3 and 2 ounces of MMO mixed in. The 93 octane and 50:1 TC-W3 are per the owner's manual. The MMO and Mower Tuneup are since MMO and PB Blaster products have never let me down before.

The air filter was nasty with oil/gas. It went from brown to its pristine green again.

I'll also take off the muffler again and hit it and the exhaust port with the Mower Tuneup right before cutting the grass again to burn that crud off. Worst case it makes a nice smoke show while killing any early-rising mosquitoes.

 

[sciphi]

Update: I cleaned out the carbon from the exhaust port again, added the fresh gas, and used the Blaster Lawnmower Tuneup per the package directions. It's a purple liquid that does not smell. Starting the lawnmower gave a nice smoke show. The engine ran roughly for the first few minutes, and got smoother as I was going. By the end of cutting the lawn it was not smoking any smoke visible in sunlight and was roaring right along. I'm declaring victory and letting it be for the season.

 

[OilNerd]

Thanks for the update. It's always nice to hear a happy ending!