Walbro WJ-69 on an 066 Big Bore

[Johndirt82]

Not sure where I saw it but , I could have swore I saw a thread about 066 jets about .72mmsize. What size main jet should I be running on a ported 066 Bigbore with a walkerized style muffled mod? My main jet is .62mm and the saw runs ok but lacks a little and Im affraid its too lean. I just don't want to blow the thing up.

 

[timberwolf]

??? You have a fixed high speed jet on WJ69?, just never ran into that combo up here. I would certainly hunt down a carb with adjustable HS. I don't think it is possible to say what jet size would be ideal as it will depend on too many variables and would take some small changes and testing to work it out.

If you have adjustable jets then nothing inside the carb needs to be changed to accomodate porting or the BB.

 

[Johndirt82]

I will definately have to do some more reading and maybe some testing. I am kinda new to the small engine world and am trying to learn all I can, although I have been a marine diesel mechanic for the NAVY for 10 years, chainsaws are a whole different animal. Thanks for the info.

 

[timberwolf]

Yeh, they both have pistons, conecting rods and cranks, after that there is more different than the same.

Are there two small ajustment screws and on large idle stop adjustment on your carb? if so the small one towards the filter needs a slight turn counter clockwise to richen the high speed mixture. The small on closer to the engine is the low speed mixture depending on the style there can be limiter caps that will prevent you turning the needle as far as you would like. Very easy to pull them out with a small pick or even a screw.

 

[troutfisher]

I have used a exacto knife or sheetrock knife and trimmed the limiters off right on the saw. I cut the tabs off only, the red and white caps were still on the skrews, only now they can be turned.

 

[Johndirt82]

Its an older style with no limit caps its fully adjustable. I just wasn't sure if the jet sizing played into the mix somewhere. I know it can on other performance engines . Another quick question , is it me or do the rings that come with the baileys 066 BB arn't of the greatest quality? I just ordered a set of the caber F-cast one's are they any better?

 

[Johndirt82]

I think I may have figured it out. According to the 066 ipl, the .62 mm fixed jet was for a high altitude set up, .64 for low i suppose and .74 was for the wj-76 that supposedly came on an 066 model. Anyone know anything about a wj-76?

 

[FrankHgh]

walbro WJ 69 carb

greeting, where can i locate the diagrams for a WJ 69 carb?

 

[Johndirt82]

They should be on an 066/660 IPL.

 

[Tzed250]

Not sure where I saw it but , I could have swore I saw a thread about 066 jets about .72mmsize. What size main jet should I be running on a ported 066 Bigbore with a walkerized style muffled mod? My main jet is .62mm and the saw runs ok but lacks a little and Im affraid its too lean. I just don't want to blow the thing up.

You might have been thinking of this thread:

.

A few weeks back there was a discussion about the high speed jet, called the fixed jet in a Stihl IPL, and its role in tuning the carburetor.

A little research shows that the US bound MS660s are equipped with a Walbro WJ-69 carb. The IPLs that I have show a .64 jet as standard, with a .62 jet optional for high altitude operation. After porting my 660 I found that the H needle needed to be 1.25 turns out to get the saw to four-stroke. I figured a new jet was needed. I ordered the 1122 121 5607 .74 fixed jet from the dealer. This jet is found in the WJ-76 carbs found on saws not headed for North America.

When I disassemled the carb I found a somewhat unpleasant surprise. The saw had been shipped with a .62 jet. EPA strikes again.

I thought I would share a quick how-to for replacing this jet.


1. Remove the carb and orient the top toward you.


top by zweitakt250, on Flickr

2. Remove the top cover. This will expose the fixed jet. It is the slotted brass part below the lever.


62 by zweitakt250, on Flickr

3. Remove the fixed jet. Be sure to use the correct size screwdriver as brass is soft and unforgiving.


driver by zweitakt250, on Flickr


4. This is the new jet to install. The jet number is stamped on top.



new by zweitakt250, on Flickr

5. The new jet in place. Reassemble the saw then tune as usual.


74 by zweitakt250, on Flickr




After the .74 jet was installed my 660 now four-strokes with the H needle 7/8 of a turn out. That is how it should be.


Thanks for looking!


.

 

[Johndirt82]

I saw this post a while back. My dealer tried to tell me they couldn't get the bigger jets. So I just let it go. Have you noticed any improvements since you changed it to the 74 ?

 

[Tzed250]

I saw this post a while back. My dealer tried to tell me they couldn't get the bigger jets. So I just let it go. Have you noticed any improvements since you changed it to the 74 ?

The saw doesn't run any different, but the H needle is much more useable now.

Just order part # 1122 121 5607

 

[Meadow Beaver]

Tzed, how did you get a .074" jet for your 660? I went to my dealer a few months back to order one and I was told they don't make them anymore. :msp_mad:

Nevermind, found the 0.074" at Bailey's.

 

[singinwoodwackr]

I have a later '066 with a WJ 48 F5 that has the same .062 jet. The manual I have for my older ('85) 066 Mag lists a .068 and .064 jet for reg and hi-alt.
I recently replaced the pist/cyl on the older saw with a big bore so may look into the .074 jet

 

[Chippa]

Hey guys, new member and I am rebuilding a 066 magnum for my father. I found this old thread because my carb is a WJ 48 L5 with the .62 jet and I don't want the saw to run too lean. My altitude is 800 ft and I ordered a dual port Stihl muffler with the Stihl cylinder and piston. Should I order at .64 jet or .74 jet? Thanks!

 

[spindrift7mm]

Check your hi adj, as long as you can richen up and make your saw 4 stroke your fine, but many want their adjustment range to be somewhat centered. Changing jet size will change your tuning range but you still need to tune properly.

 

[redoakneck]

It is more complicated than being able to turn the screw out further, get the 74 if you muffler mod or want a sweet spot at 3/4-1.25 turns out. It is cheap.

U won't notice a difference unless u put saw under high load

 

[Chippa]

Thanks a lot for the input. I ordered a .64 and .72 today. This site is great. Very informative!

 

[tree_chomper]

Thanks a lot for the input. I ordered a .64 and .72 today. This site is great. Very informative!

Send the .64 back... .72 or .74 should be good for you