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What are the basics to adjusting Two Cycle Walbro Crabs?

Posted by loger (My Page) on
Fri, Jan 13, 12 at 20:13

1. What are the basics to adjusting Two Cycle Walbro Crabs? I feel my old method of starting one turn off the seats might be outdated. On-Line (at the address below w/o a date) I found the basics to be two turns from lightly seating initially. Adjust high speed screw from there to get a smooth constant Wide Open Throttle (WOT) run. Any high speed hesitation is corrected with the low speed screw's tweaking.

2. I started with my old school one turn from a light seating and starved both for fuel. Then tweaked for smoothness and instant acceleration vs any hesitation. Ending about 1.5 turn from seating on both, Plus about 1/8th toward richness (to avoid any leanness) could be about the same. The starting point and starving (which might be harder to start and might fall dead leaning/starving) could be the major difference.

3. BUT! At constant WOT with no hesitation I got a high but an uneven high-end w/o a load after 10-15 secs. Was this OK or should it hold the WOT constant longer? I hate to run WOT period without a load. The saw showed no signs of lack of power or uneven power cutting (which is usually my goal).

I also wondered if I was (Slipping or Rusty) mixing my old Two-Cycle Carb Basics with Old Four-Cycle Basics (since they are not used as often? loger

Follow-Up Postings:

RE: What are the basics to adjusting Two Cycle Walbro Crabs?

Walbro and Zamma have excellent web site on how to adjust, tune, rebuild, and assemble their products. I would try to goggle. If I remember I think they start out a 1 1/4 to 1 1/2 turns and go from there. I think it should 4 cycle at WOT. I with you I never hold mine at WOT very long really not need IMO. As long as it got good power when you sink it in log.

RE: What are the basics to adjusting Two Cycle Walbro Crabs?

Loger: Ensure all your hose fittings are tight along with carb flange fasteners. Ensure your fuel filter is new or very clean , same with the air filter and spark plug . Then you must have at least a 3/4 full even better full fuel tank with fresh fuel and proper mixture.
Then Start tuning with the Low speed adjustment , usually 1-1/4 to 1-1/2 from seated. Adjust so there is no hesitation . Then go to the High speed jet and adjust the same turns out. Once you achieve max engine rpm at WOT turn the needle out to richen until the saw diesels then turn it back in until it clears itself. This will put you in the safe (rich) zone . Once the saw is let idle for a few seconds adjust the idle screw until the chain begins to move and then back out until it stops rotating . Thats all there is to it Bro ! Even works on Older Tillitson and Keihien carbs accordingly . Happy cutting :)

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