Husqvarna big bore issues...help

[dohcsvt]

I have a Husqvarna 340 that I purchased the big bore kit from farmer tech for. I did some mild porting on the exhaust and transfers and re-assembled. Got it to idle great and then I went to set the high speed circuit I have some issues. I can get it to go to about 14,200 rpm, but it will only stay there for a half second or so and want to drop off.

It seems that the highest RPM I can get it set to that it likes is about 11,400. These numbers are before I start to richen it up a little to prevent damage.

The original 340 engine I had muffler modded and I tuned the carb to about 13,800. As of right now I am displeased with the big bore kit (MORE THAN LIKELY NOT THE MANUFACTURERS FAULT SINCE I PORTED IT) and am about ready to reassemble the factory set up.

The porting that I did was gasket matched the exhaust and tapered it into the cylinder and only widened it, did not raise or lower the port.

Also ported the upper transfers, again only widened, did not raise or lower.
However, I tried to blend all the ports that I touched into the cylinder wall (including the tops and bottoms of the ports). I did this because on the exhaust port there was a small thin piece of casting material on the port where it entered the cylinder, so just blended all of them to make sure there was nothing for the rings to catch on.

I didn't think I messed with the timing but very well may have while doing the blending.

Do you guys think the blending is the issue or do I have to start more than 2 turns out on the carb since the displacement is increased by 25%. Just looking for input before I tear it back down.
Thanks,
Ottis

 

[cus_deluxe]

Limited coil?

 

[cus_deluxe]

Pull starter and look at color of the coil. If its blue its rev limited, if its black its unlimited.

 

[cus_deluxe]

And i think they used the same zama el32 carb on that whole family of saws, at least for a while so it should be able to handle 50ccs

 

[dohcsvt]

The coil is not a limited one (it is black) and as I noted the factory set up was tuned to 13,800.
Also, I just did some research (should do that before a project) and figured out that it only takes a couple thousandths of an inch to start affecting timing.

I am pretty sure that I screwed this up with the blending.

DAMMIT

 

[cus_deluxe]

Got any pics of ports?

 

[Cease232]

Only way to tell for sure is to put a wheel on it and check the timing. Check it against your OEM jug. I'd be willing to bet the timing on that aftermarket kit was not great to begin with.


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[dohcsvt]

Got any pics of ports?

No, I do not have a camera cellphone.

Did you match the intake port to the exhaust,

No, I did not touch the intake at all

Only way to tell for sure is to put a wheel on it and check the timing. Check it against your OEM jug. I'd be willing to bet the timing on that aftermarket kit was not great to begin with.
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You know the ****** part, I bought a wheel just for this purpose. Then life happened and the disassembled saw sat on my work bench for two months. I finally had time to work on it, and just rushed through it. I guess I will use the degree wheel after all.

 

[Cease232]

Was there something wrong with the OEM jug or were you just looking for more power?


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[dohcsvt]

I'm one of those guys that can't leave anything alone. Stock set up was running like champ, but I needed more power... why, because I can... or at least thought I could

 

[Cease232]

I'm one of those guys that can't leave anything alone. Stock set up was running like champ, but I needed more power... why, because I can... or at least thought I could

Now that you've practiced port that Stock jug and you'll be good to go.


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[dohcsvt]

That's a damn good idea. I will research what exactly to do as I am sure this has been covered before. I appreciate the feed back.

 

[grizz55chev]

I'd try and rule out any fuel- carb related problems before giving up on the AM setup. All else fails, as suggested earlier you can go back to the OEM. Most people will tell you that's the best option anyway. Check that you don't have a fuel line leak where it exits the tank, telltale signs are dust caked around the area. Also check the fuel line inside the tank, maybe soft and collapsing. There is also a screen on the pump side of the carb that gets plugged with debri from old failing fuel filter in the tank, good luck!

 

[thefarmboy21]

I did a Hutzl/Farmertec big bore kit on a model 50. Biggest issue I ran into was that the air injection holes didn't line up right....actually almost not at all. After some dremel work with an 1/8" burr it was taken care of. Other than that, the gasket they sent me was like .030+ thick....without the gasket at all, I had .020 or .025 squish at the lowest point? It wasn't consistent all the way around...point is tho, had I used the gasket I'd have had like .050-.060 squish and had lousey compression. So if it were me I'd start by:

1. Do a compression test and/or solder squish test. If you haven't yet.
2. Check the alignment of the air port in the bottom of the cylinder where it meets the case.

 

[dohcsvt]

Yes, I already did a squish, without the base gasket it was about 38, which is high. SO I used motoseal and left the base gasket out.

As for the airport, I am not familiar with that, I will have to research AND it sounds like disassemble it to check. Thanks for the input.

 

[dohcsvt]

Can anyone point me towards 340 porting information? I have scoured the web and found almost nothing. Definitely did not find any instruction type items.
Thanks.

 

[dohcsvt]

So I did some research and determined that a 340 and a 350 have the same stroke but different bores, so it seems that timing numbers that work on the 350 should also work on the 340...any input. TI found the below info in another thread, what do you think

Port timing on this saw was as follows.

Exhaust 104°
Transfers 125°
Intake 70°

I left the exhaust and transfers alone. I didn't want to lower the intake floor that much. That would likely take it down into the impulse area. So I trimmed the intake piston skirt to get it to 80°