Let's Talk 262 Timing and Performance

[shorthunter]

for the most part it is caused by poor fuel burning too slow. it's called coking

Poor fuel is all too common today

 

[shorthunter]

But when?

During Gordon Blairs simulation of a chainsaw, he found that,

"The pressure at the cylinder end of the transfer duct exhibits a backflow during the first 10° of transfer port opening, as the cylinder pressure exceeds the crankcase pressure at that juncture during blowdown. The consequences of the backflow on the local purity and temperature can be found in Figs. 5.17 and 5.18. In Fig. 5.17, the purity at the cylinder end of the transfer duct drops temporarily from 0.95 to below 0.90 and, in Fig. 5.18, the temperature rises from 180°C to 280°C. When scavenging actually commences, it is with gas which is both hotter and less pure than it might otherwise be."

 

[drf256]

I see no carbon deposit at all on my hybrid jug. I pulled it today and was gunna give some feedback on the transfer theory but nothing but oil.
View attachment 11941

What keeps the rings in the piston on that jug as it nears BDC?

 

[Deets066]

What keeps the rings in the piston on that jug as it nears BDC?

Smoke and mirrors

 

[drf256]

Smoke and mirrors

The smoke that runs down the transfers?

 

[Deets066]

No carbon in the combustion chamber or exhaust port either. I'd say it hasn't been run enough since your build.

At least 15 tanks, possibly more

 

[Deets066]

The smoke that runs down the transfers?

Exactly

 

[drf256]

Motul800=No Carbon

 

[mdavlee]

Load a saw on a mill with 800 and you'll have carbon. Piston is backwards in that hybrid I would guess.[emoji6]

 

[huskihl]

I would also think that the more the muffler was opened up, the less exhaust would be forced back down the transfers

 

[lmbrman]

I see no carbon deposit at all on my hybrid jug. I pulled it today and was gunna give some feedback on the transfer theory but nothing but oil.
View attachment 11941

I have never seen any carbon in my 262 transfers, but was curious based on comments above.
-dave

 

[Bjorn]

Hi. To avoid backflo in the transferports you need to put on an pipe- expensioncamber to the engine. Best is to calculate one on computer so it matches the engine. And you can gain up to 20% of power With the right pipe

 

[Billy Currie]

I have just recently ran across a 262 that looks like it has ridden in the back of a truck under a pile of saws for the last 20 years. Starter housing has several cracks, the plastic starter spring retainer is broken in multiple spots, the metal rope guide in the starter is worn and cuts the rope, the fuel tank leaks from thrown chains (just fixed), side cover cracked, top cover cracked, well you get the idea......pulled it apart and the cylinder, piston, and crank appear to be in near excellent condition. I replaced the ring, rebuilt the carb, threw some filters at it and it runs great! I was very impressed how this saw runs stock. All I want to do now is fix the starter so its more reliable. I figure if it looks this rough no one will want to steal it.

 

[drf256]

View attachment 199187 I have just recently ran across a 262 that looks like it has ridden in the back of a truck under a pile of saws for the last 20 years. Starter housing has several cracks, the plastic starter spring retainer is broken in multiple spots, the metal rope guide in the starter is worn and cuts the rope, the fuel tank leaks from thrown chains (just fixed), side cover cracked, top cover cracked, well you get the idea......pulled it apart and the cylinder, piston, and crank appear to be in near excellent condition. I replaced the ring, rebuilt the carb, threw some filters at it and it runs great! I was very impressed how this saw runs stock. All I want to do now is fix the starter so its more reliable. I figure if it looks this rough no one will want to steal it.

The starter plastic is still available new for a reasonable price. You’ll have to swap the guts into it.