Carb Differences

[james64]

What is the difference between the Walbro 48 vs Walbro 65? Ive got a super 2 that came with a Walbro 65 and I am not having any luck getting it to run let alone start. Ive got several Walbro 48 cabs and thought I'd try one of those but I don't want to damage the motor. Also, is it normal for these little saws to accumulate a bunch of oil inside the case after its run?

[charliec]

Hi,

It is more about proper sizing based upon the saw's size. All the Walbro HDC series carbs were for saws ranging from about 30CC through about the mid 50's. I don't think Walbro really even documented the differences between the carbs within the same series (e.g., HDC, SDC, etc.). Basically, if the saw came with an HDC you can put any HDC in it. If I remember correctly, the main difference between these specific carbs was that the model 48 had only a Low side adjustment needle with a fixed High setting (i.e., no adjustment needle) while the 65 came with both a Low and a High adjustment needle. In my opinion, since many of the people buying the XL family of saws (not including the XL - 12, 15 or any of the SXL variants) were homeowners/average joe with not a lot of chainsaw knowledge/experience. Therefore, not providing a High side needle probably saved a lot of saws from being scorched (i.e. running too lean on full throttle). This is not to say experienced chainsaw operators did not own these saws as they are great for small limbs/cleanup.
The link below is to the limited information Walbro now publishes on their website for the old school HDC carbs. If you have standing fuel/oil mix in the muffler and/or crankcase after you run the saw, I would say there is a 80+% chance you are running it way too rich. If you are referring to bar oil in the storage case, then before you put it away release the inline pressure by loosening the oil cap. The oiler is run via pressure at about 6 psi so oil will continue to pour out the bar oiling hole till the pressure has dissipated (i.e., oil mess in the storage case). The current documentation from Walbro (see the link below) states to start the H/L needles at 1 turn open each then fine tune. I start at 1.25 turns on the High and 1 turn on the low. Once it is warmed up, I start by fine tuning the Low side then the High until you have it dialed in. I have no doubt others have a slightly different process but this works for me. I believe this process is very similar to Leon's process. I prefer to start a little rich and then lean it out especially if you have a new ring installed in your Super 2. In addition, Leon has many, many videos about the Walbro HDC series of carbs for your review.

www.walbro.com/wp-content/uploads/2016/01/HDCseries.pdf

Charlie

[charliec]

OOOps, I forgot to mention, while the main body of the HDC carb will swap out easy you may have to contend with a choke shaft/rod swap out. For example, the VI Super 2 HDC carb configuration has a different choke rod assembly than the plain Jane Super 2.

[james64]

I was thinking perhaps the jetting was different but from I can see, they appear to be about the same with the exception to the Hi/low screws. As far as the oil in the case goes, its bar oil leaking to the inside of the case. The saw I'm working on right now has the diaphram oiler and it really leaks alot of oil inside the case as well as out the port to the bar so I'm a little confused as to how the oil is getting inside the case.

[charliec]

Hi,
Okay so you mean the exterior of the engine "case" (i.e., cylinder, power head, clutch, drum, etc.). Given that scenario I can only think of two things: 1) One of the oil hoses has a leak or is not sealing properly around one of the fittings. 2) The seal between the engine body and the oil pump cover is not correct/sealing. I have seen this a few times due to one or more of the following; Someone attempted to put the oil pump cover back on with the drum removed but the "S" clutch still in place/on. This technically can be done but it tends to lead to misalignment of one or more of the components and/or the diaphragm/gasket(s) getting a fold/wrinkle in it at the bottom causing a leak. Another scenario is the gaskets are no good/damaged. There should be two gaskets, one on each side of the diaphragm. It is also possible that either the cover plate or engine body mounting area is damaged/warped. I like to deck (i.e., lightly file/sand) the cover plate on a flat surface prior to installation with 320 grit wet/dry sandpaper. I then feel the engine mounting surface to determine if there is any irregularity or remaining old gasket material. Please note, you don't need to crank on the three small mounting screws but they do need to be firmly secured. If you are using the manilla color paper style gaskets (i.e., material known as Karropak) this material will expand slightly when the oil saturates it creating an improved seal. The black rubber gaskets require a little more pressure as it does not expand in my opinion.

[blythkd]

Another possible leak path is a hole in the oil tank. I've replaced a few. We used to keep them in stock.

[james64]

Ive checked the tank and there are no leaks. Im building a test stand so I can run carbs without having to put them in the case. Right now my test motor has a real weak spark so once I fix that, I should be able to take the motor out of the case and run it so I can see where the oil is coming from.