Zama RB-K89 vs Walbro WYC-9

[Merkava_4]

Which is the better carburetor ?

This is why I ask:

Echo SRM-266S = Zama RB-K89
Echo SRM-2620 = Walbro WYC-9

Both are 25.4 cc trimmers.
Both have sold steel drive shafts.
SRM-2620 is the newer model.

[bgsengine]

they wont interchange either - the 2620 is also more emissions compliant - the cc's dont matter - it has more power than the 266 despite the same displacement. I like the zama carbs better (they are a bit cheaper) over the walbro's Echo has several new designs (and patents) for rings, cylinder design (porting, etc) and ignition (electronically controlled) so the carb's will have different flow rates and through-put

I have tried many times to explain to someone that the CC displacement don't matter any more when it comes to the power output and performance - I have seen personally a modern 58-ish cc chainsaw out-cut an older 64cc chainsaw by a mile and yet for some reason the guy thought his 64cc's was "better" somehow..

I give up trying to explain it and try to not even talk in cc's any more but rather compare power output (kw) and torque which matters much more than cc displacement

[Merkava_4]

bsgengine, did the first half of your post go missing ? Did you say the 2620 is more powerful than the 260 ?

[bgsengine]

bsgengine, did the first half of your post go missing ? Did you say the 2660 is more powerful than the 260 ?

The SRM-2620 is more powerful and lighter in weight (about a pound lighter) than the SRM-266, yes - also with the gearbox re-design . SRM-2620 trimmer has more torque as well.

But as noted I'd rather have seen the 2620 come with Zama carburetor..

[Merkava_4]

The SRM-2620 is more powerful and lighter in weight (about a pound lighter) than the SRM-266, yes - also with the gearbox re-design . SRM-2620 trimmer has more torque as well.

But as noted I'd rather have seen the 2620 come with Zama carburetor..

Why is the 2620 more powerful than the 260 ?

Also, I noticed they went back to having two piston rings with the 2620 instead of just one like on the 260.

[KE4AVB]

Different transfer port timing, different ignition advance timing, decrease piston blow-by plus other engineering improvements.

It is like when I rebuilt my small 79 Chevy V-8 changing the cam from stock to mild race cam, added variable duration lifters, change the 350 trans to a 350 with lock-up torque convertor and changed the exhaust over to a turbo version. It greatly improved my average fuel mileage from 16 to 22, increased takeoff torque all while being quieter and the same CI. And with me driving up to 50K a year at that time it really paid for itself in fuel savings. There was one improvement that I had planned later but I sold the car later as it had around 300k on the body. That was to change the 350 lock-up to a 200R4 metric transmission, this one was an overdrive with lock-up and would even increase my fuel mileage more while maintaining low speed drive-ability; just didn't have the time at that time.

There are pros that modify chainsaws for a living to improve their performance doing much the same things as first mention plus they even increase the compression ratio by reducing the squish of the cylinder though that can be a little risky as too little will cause things to hit each other.

[Merkava_4]

bgsengine
KE4AVB

Would you guys recommend the SRM-2620 trimmer ? It doesn't have a solid steel drive shaft like the previous model SRM-266S. I always thought a shaft drive was better than a flex cable. I'm still trying to decide whether I could put up with a two-stroke engine. They're noisy, belch out smoke, and make you smell like 2-stroke exhaust at the end of the day. The Honda trimmers are quiet, run clean, and don't need 2-stroke oil mix. But they're heavy.

[bgsengine]

I have run and sold both models (the SRM-2620 is new this season) and after trying out the SRM-2620 I have to say I'd much prefer it over the SRM-266S given the choice between the two. Due to their new design and emissions compliance they actually run really clan and hardly can smell (or see) any 2-stroke smoke at all, *IF* you are using an approved high quality certified oil (better yet use Echo's Red Armor or PowerBlend oil ) mixed properly.

[Merkava_4]

bgsengine, why did Echo go with a flex shaft instead of a solid steel drive shaft in the SRM-2620 ?

[bgsengine]

bgsengine, why did Echo go with a flex shaft instead of a solid steel drive shaft in the SRM-2620 ?

weight savings and durability - flex shaft is a little more forgiving of sudden load and torque changes, lighter weight as well, you'll be less likely to experience vibration and flex shaft will run cooler.
At least in the USA Echo has a lifetime warranty on drive shafts and ignition modules (parts only after 5 years) so if they ever do break and not from abuse or neglect Echo will cover them.