394xp compression question

[Trent Curtis]

 

[71dart]

Just to be clear, as westcoaster90 mentioned, when you went through your carb did you hook the metering diaphragm onto the metering lever? If you simply set the diaphragm onto the carb body ( like you do on most carbs) that would cause the saw to run rich.

 

[Trent Curtis]

Just to be clear, as westcoaster90 mentioned, when you went through your carb did you hook the metering diaphragm onto the metering lever? If you simply set the diaphragm onto the carb body ( like you do on most carbs) that would cause the saw to run rich.

yes- the diaphram was hooked to the diaphram, and each time I pulled it apart it was still hooked properly.
W the mentoring lever set any higher than the dish top the saw floods. I finally set it slightly lower..... Still 11,000 max.

I set the mentoring lever so that when depressed w a straight edge to the top of the dish it makes contact but does NOT lift the needle valve.

 

[71dart]

Nice looking saw btw!!
Yamabond, hondabond, threebond 1194, dirko. There are a few good sealers out there just be sure they're fuel resistant.
When you say the 'dish top', I assume you don't mean the rim that the gasket and diaphragm set on. As a WJ metering lever needs to be set below that rim.
You probably already know all this but I'm just trying to make sure it's not something obvious.

 

[Trent Curtis]

Nice looking saw btw!!
Yamabond, hondabond, threebond 1194, dirko. There are a few good sealers out there just be sure they're fuel resistant.
When you say the 'dish top', I assume you don't mean the rim that the gasket and diaphragm set on. As a WJ metering lever needs to be set below that rim.
You probably already know all this but I'm just trying to make sure it's not something obvious.

I should have posted these from the beginning- see attached pictures. And I appreciate the input!!

 

[Trent Curtis]

Already ordered an OEM carb, rings, anti vibes and some new stickers.

Killing me waiting for it all to get here!!

 

[MGoBlue]

1. I was surprised to find that it already had a gasket delete done.... As it was only pulling 155 psi.

After deleting the base gasket on my '94 and breaking in the new piston/ring, I gave up after 185psi. It was too darn hard to keep the saw still to pull! I've used Motoseal for a while now with great success.

 

[Trent Curtis]

After deleting the base gasket on my '94 and breaking in the new piston/ring, I gave up after 185psi. It was too darn hard to keep the saw still to pull! I've used Motoseal for a while now with great success.

Thank goodness for compression reliefs eh?

 

[Big_Wood]

The main nozzle in the WJ39 is also a fixed jet. Even with the needles closed it will still flow fuel. Your metering chamber is being overfed by the needle. Most likely causes are gasket/diaphragm mixed up, diaphragm nipple not hooked on metering lever or metering lever not adjusted properly. Anything under 13.6 is rich for a 372. Even The limiter is 13.6 and the whole purpose of the limiter is to keep them from turning to many RPM's because they like to be tuned above that limiter.

 

[Trent Curtis]

The main nozzle in the WJ39 is also a fixed jet. Even with the needles closed it will still flow fuel. Your metering chamber is being overfed by the needle. Most likely causes are gasket/diaphragm mixed up, diaphragm nipple not hooked on metering lever or metering lever not adjusted properly. Anything under 13.6 is rich for a 372. Even The limiter is 13.6 and the whole purpose of the limiter is to keep them from turning to many RPM's because they like to be tuned above that limiter.

West coast- thanks for the input-

I agree with you on the metering lever.

I'm positive that the gaskets and diaphragms are correct, as well as the metering lever being hooked to the gasket properly.
The metering lever is set flush with the bowl using a straight edge.
I swapped out the needle as well-

Do you propose setting the metering lever even lower?

 

[Big_Wood]

If you have the lever set level with the bowl in the bottom of the chamber it is set right. This is not to be confused with the chamber itself. Many carbs have a metering lever set level with the gasket sealing surface of the carb body. If you do that with a WJ39 I'm surprised you could even get it to run. She'd be pretty well dumping fuel into the engine. Post a pic if you get a chance.

 

[Trent Curtis]

If you have the lever set level with the bowl in the bottom of the chamber it is set right. This is not to be confused with the chamber itself. Many carbs have a metering lever set level with the gasket sealing surface of the carb body. If you do that with a WJ39 I'm surprised you could even get it to run. She'd be pretty well dumping fuel into the engine. Post a pic if you get a chance.

 

[Trent Curtis]

westcoast- you are correct about the flooding though. When I initially installed the new carb kit I left the metering lever as it came. It was above the bottom of the bowl..... And it flooded the saw immediately.

when I get home next week I'll give one go at setting the needle lower than I currently have it before just installing the new carb.

But in all actuality I'm glad to have had this issue- it forced me to learn how the carb actually works. With help from y'all!

 

[Big_Wood]

yep, that lever's set right. did you remove that welch plug in the chamber? even if you didn't someone else in the past may have. give it a tap in the center flattening it out slightly. that'll tighten up the edges to the carb body then try run the saw again. the saw is pulling unmetered fuel from that chamber somehow.

 

[Trent Curtis]

yep, that lever's set right. did you remove that welch plug in the chamber? even if you didn't someone else in the past may have. give it a tap in the center flattening it out slightly. that'll tighten up the edges to the carb body then try run the saw again. the saw is pulling unmetered fuel from that chamber somehow.

I didn't mess with the plug- but I can try that next! Thanks!

 

[Trent Curtis]

Ooohhhhhh----- the wife me pics of saw parts waiting for me on the work bench!!!!!

Rings, new anti vibes, exhaust deflector for muff mod, carburetor and some new stickers.

 

[Trent Curtis]

Ok so new rings brought compression to 165.

New carb is working perfectly.... Able to bring the RPMs up and down as needed.

Put a duel port on the muffler as well.

Now I need your help with the tune- I'm terrified of burning this baby up, as the new cylinder coat almost as much as the saw is worth

These big bore saws are a lot harder for me to hear (not that I'm any good at it anyway) with their torque monster soundtrack.

See video-
Note:
So it's set to 2800 at idle..... And I walked it up slowly.
You can clearly hear the four stroke in the beginning, as well as the saw hitting "flat" spots at WOT. Is this is what they refer to as "missing" when four stroking?

Anyway- I ended the tune at 11,400-11,700 at WOT. It feels to me that any more and I'd be getting too lean.

Please give a rook some feedback!

 

[Trent Curtis]

Hmmmmm- video doesn't want to load. I'll have to find other means of loading.

 

[Trent Curtis]

Flat spots mean "too lean"-but I can't be too lean at 11,700 can I?

Here's a pic of the plug-

 

[HuskStihl]

Hmmmmm- video doesn't want to load. I'll have to find other means of loading.

You have to put them on youtube first.
Here's how a 394 should sound in the cut and letting off. 394's like to be a little rich