Author Topic: carburetor confusion  (Read 316 times)

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Offline the husqvarna kid

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carburetor confusion
« on: May 23, 2014, 05:05:49 pm »
I have a Husqvarna 365 with air injection that I got recently. I purchased a big bore kit for it which increases the power of the saw by 20%! I adjusted the saw to what I thought was proper running order but in less than an hour I seized the motor. I purchased another bore kit for the saw but was asking around and have heard that I would need to buy a new carb that can handle the fuel needed! my question is does anybody know where to buy one of these carbs or know what I can do to the one it has to run the bigger motor properly?

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Offline 660magnum

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Re: carburetor confusion
« Reply #1 on: May 23, 2014, 05:18:58 pm »
Someone told you wrong?  The original carb handles the big bore kit just fine. You need to open the needle valves to let in more fuel.

A likely problem with your 365 spec is that it has a crankcase air leak is the reason the cylinder seized up? Either crankshaft seals, intake boot, or other source? You need to do a crankcase pressure check?
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Offline the husqvarna kid

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Re: carburetor confusion
« Reply #2 on: May 23, 2014, 05:41:18 pm »
alright thank you for clearing that up for me! but how do I do a crankcase pressure check ive never had to do this so I don't know how! is it different from a regular cylinder pressure test? also I was looking to purchase a stihl 660 magnum for big trees! do u know anywhere I can get a new or a used one in good condition for cheap money?

Offline 660magnum

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Re: carburetor confusion
« Reply #3 on: May 23, 2014, 08:02:50 pm »
I can mail you a service manual for the 365 Special? The crankcase pressure test is described in the manual. It is not like the cylinder pressure test.

The 066/660 Stihl come up for sale all the time. Look on Craig's list or the swap sections of the forums? It might take you a year to find the one you want?
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Offline 660magnum

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Re: carburetor confusion
« Reply #4 on: May 23, 2014, 08:06:38 pm »
Look in Yahoo mail for the manual?
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Offline SawTroll

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Re: carburetor confusion
« Reply #5 on: May 24, 2014, 07:11:00 am »
An aftermarket "BB" top end doesn't necessarily increase the power of a 365 - it depends on the exact kit, and what carb is on the 365.

Anyway, if it blew up, there likely is something else wrong with the saw, like an air leak  - or with the top end, like the rings catching the ports.

Offline KilliansRedLeo

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Re: carburetor confusion
« Reply #6 on: May 24, 2014, 08:37:37 am »
Both 660 and Troll are giving you good advice. What exact model saw do you have? Was the saw running when you got it? Did you buy the BB kit to repair the saw? Either way you don't need a bigger carb the stock carb will do just fine.
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Offline KilliansRedLeo

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Re: carburetor confusion
« Reply #7 on: May 24, 2014, 10:56:00 am »
Quote
but how do I do a crankcase pressure check ive never had to do this so I don't know how! is it different from a regular cylinder pressure test?

A pressure/vacuum test is easy to perform if you have the tools. It differs from a compression test in that it tests the entire saw for leaks in the case, cylinder to case joint, intake tract, exhaust tract, decompression valve and both the crankcase seals all at once. If you are thinking of a compression test where you screw a hose into the spark plug hole, this will not do because it does not test the entire saw. Two stroke engines cannot leak air from any of the above areas or the engine will self destruct!

The pressure/vacuum test is a timed leak-down pass/fail situation. HVA specifies that you put 80kPa of pressure into the motor, wait 30 seconds. If at the end of the 30 seconds the remaining pressure in the saw is above 60kPa you are good to go. The vacuum test is the same sort of thing, you place the saw under a certain amount of vacuum, wait a specified time and check the indicated remaining vacuum in the saw, if above a certain number you are good to go. Can't recall the vacuum numbers or time limit but they are in the Workshop Manual 660Magnum sent you.

The first thing you must do is to seal off the pulse tube, exhaust, intake and spark plug holes. You can use an old bicycle inner tube and make blocking plates for the exhaust and intake tract. You then connect you gauge and pump to the pulse tube. I happen to use this device to do the tests it will do both pressure and vacuum with a single tool. http://www.ebay.com/itm/MIGHTY-VAC-PRESSURE-VACUUM-TESTER-TEST-BRAKE-BLEEDER-DIAGNOSTIC-ENGINE-TOOL-KIT-/251216512533?pt=US_Hand_Tools&hash=item3a7dabc615 but you can find others that will do the job at your local auto parts store you may even be able to borrow one from the auto parts store.

Failing to do these tests will result in the same thing happening to your saw. OBTW I quoted HVA numbers here because you have a Husqvarna saw but the process is the same and required for ALL brands!
"When the people fear the government...you have tyranny....When the government fears the people....you have liberty"

Thomas Jefferson
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