Felt Fuel Filter Pickups?

[SteveSr]

Hello,

Both Zama (now owned by Stihl) and Walbro a big customer of Stihl both make several varieties of felt based fuel filter pickups. At one time Stihl actually used the Walbro felt filters. I don't know about Zama.

For some reason Stihl stopped using this technology quite a while ago. Were any of you around when this switch occurred and remembers why? I am looking for decent AM fuel filters to avoid the high cost ($10) of the current OEM Stihl product? But I also don't want to start using the felt filters if there was valid reason for abandoning them.

I believe that Kufner in Germany makes the current line of Stihl fuel filter pickups:
https://www.kuefner-filter.com/en/fields-of-application/power-tools.html

Do any of you know if there is an AM source for the Kufner filters?

Thanks,
Steve

 

[heimannm]

One benefit of a felt filter is that the felt will absorb and hold any water in the fuel. Limited usefulness for the small filters on the end of a fuel line but very effective if you have a large felt wick in the fuel tank.



Mark

 

[Little Al]

There are listed on Fleabay .com 10 non felt filters for around 12$ S&H free

 

[SteveSr]

One benefit of a felt filter is that the felt will absorb and hold any water in the fuel. Limited usefulness for the small filters on the end of a fuel line but very effective if you have a large felt wick in the fuel tank.
Mark

Interesting advert. Water is not an issue any more since the ethanol in the gas will absorb it and allow it to be burned with the fuel.

 

[s sidewall]

Ethe is the problem now. Felt filters are a lot better filter because it filter more than what is used now, carb don't get a lot of gunk buildup either. I have a few saws that have the felt filter and they don't have any buildup on the inlet screen compared to the ones with a regular filter.


Steve

 

[SteveSr]

Ethe is the problem now. Felt filters are a lot better filter because it filter more than what is used now, carb don't get a lot of gunk buildup either. I have a few saws that have the felt filter and they don't have any buildup on the inlet screen compared to the ones with a regular filter.

Interesting that you are finding gunk on the screens of carbs with the non-felt filters. Any idea what that gunk is?

The felt technology is probably 40-50 years old or older. Both Walbro and Zama still make these filters yet, they are no longer used by Stihl. I am wondering if they tend to clog up too easily leading to lean/fuel starved issues. I did notice that the Walbro filters won't accommodate the larger nipple diameter for the Stihl molded hoses. I'll attach the datasheets that I found for both.

 

[s sidewall]

A few that i have torn down look like blue paste, thought it was gas brand or oil so that was changed to different brand and still done it. Possible our winter blend we get. Never have problems in summer.

Steve

 

[SteveSr]

A few that i have torn down look like blue paste, thought it was gas brand or oil so that was changed to different brand and still done it. Possible our winter blend we get. Never have problems in summer.

Steve

Interesting. I wouldn't think that our winter blend here in NC would be much different than yours in GA. The next time that you find this it might be interesting to see if it it will all burn up with a torch. If not it probably contains glass fibers from the tank housing.

 

[SteveSr]

Ethe is the problem now. Felt filters are a lot better filter because it filter more than what is used now, carb don't get a lot of gunk buildup either. I have a few saws that have the felt filter and they don't have any buildup on the inlet screen compared to the ones with a regular filter.
Steve

This may be one of Stihl's reasons for abandoning the felt filters. Crud from the tank is only an issue if it is big enough to clog the orifices in the carb. If it isn't it just gets burned with the gas and spit out the exhaust. This may be why the current Stihl filters are a little on the "coarse" side compared to felt. They would rather have a little dirtier fuel than risk fuel starvation/lean seizure with a felt filter that is "overkill".

I imagine that the felt filters will clog up slowly so that a user might not notice any issues until after damage is done to the engine. I recently experienced a clogged carb screen:

http://www.arboristsite.com/community/threads/light-gray-powder-residue-on-carb-screen.306709/page-2

My only clue was that the saw would only burble at WOT for a couple of seconds before the RPMs would start to climb. Once I confirmed this it was time to go home and pull the carb apart.

 

[s sidewall]

When the filters start to clog, saw won't have the power as it should, that when someone will try to adjust out a lean problem rather than inspect a fuel flow problem. I like the felt filter cause I don't have near the carb problems as I do with the ones without it.

Steve

 

[s sidewall]

Read your post, i have seen that happen before, mine was the aluminum weight on the filter, was starting to deteriate causing the screen to clog, replaced filter, cleaned the whole fuel system and has no more problems.

Steve

 

[SteveSr]

Read your post, i have seen that happen before, mine was the aluminum weight on the filter, was starting to deteriate causing the screen to clog, replaced filter, cleaned the whole fuel system and has no more problems.

Steve

I can see the weights corroding but mine didn't have a weight... Just an old OEM filter.

 

[SteveSr]

When the filters start to clog, saw won't have the power as it should, that when someone will try to adjust out a lean problem rather than inspect a fuel flow problem.

Steve

I think you nailed it. Especially with "H" fixed jet carbs. Stihl would rather have sufficient but dirtier fuel rather than suffer lean/fuel starvation damage with clean fuel.