Fuel Filter

I'm going to put a fuel filter on my 82 XJ650 Maxim and Len's catalog says that the 90 degree one he sells is the most popular. I'm thinking I'll go with that one. Does anyone have a picture of one of those installed? I've read about a number of people having air bubble and flow problems with fuel filters in general(not one type in particular) and want to make sure I know where in the line to put it to avoid that. Should it be placed as far down behind the carbs as possible? A picture would be great if anyone has one for the 90 degree filter.

Thanks,
Stacy

 

I use a Briggs & Stratton fuel filter (had 2 in my parts box new in package) they are red plastic small and easy to pop in.

 

I prefer paper element filters over the brass elements (and especially over simple screens) wherever possible because I feel they filter out finer material, but I have yet to find a 90* one for motorsickle applications. The brass ones do an OK job. The air bubbles don't really matter; I used to stress over that but I found that when I just ignored it, the bike(s) still ran fine and the bubbles eventually went away.

 

What I'm really wanting to know is if the 90 degree fuel filter can be mounted as shown in the picture below? This would be as viewed from the left side of the bike as if you are looking at the petcock. I'm thinking this should be mounted toward the rear of the carbs and as low as possible. I want to make sure there will be no air lock problem. I would really like to see how others, who don't have any problems, have mounted this filter. Thanks.

 

There wont be an air lock problem. That is how they (at least the one in the photo) are supposed to be connected, in regards to the inlet and outlet.

 

I know that I've got the inlet and outlet labeled correctly. I'm more concerned with the orientation of the filter. If it sits just as shown on the bike, will the air that is most likely going to collect in the upper cone be a problem?

 

That is the way they fit on the bike. Those fit well because there is so little room between the top of the carb rack and the bottom of the tank.

Here is one installed on tzkaz1's bike (though he really should have the upward fuel line routed inside of the upper rack bracket).



I use the 180º version of that type filter, and it also fits well in the available space.

 

Thanks, that's what I wanted to know. I know I'm being a little paranoid but just want to be sure. I want a good fuel filter on it but didn't want any air lock problems like I've read so much about. Thanks everybody!

 

Mine on my XJ700 is installed exactly as the one K-moe shows. I've had no problems at all with it. Remove the tank, install the fuel line vertically from the carb inlet, cut it to the correct height so that the fuel line from the tank is level or slightly descending and connect to the filter. Works great.

 

I've been running fuel filters for years and never found a bubble to cause a problem. An air lock is a different thing, of course.

 

As you can see the filter on my bike is also located as the one on t1's and tabaka's bikes.


Gary H.

 

Thanks. That's what I wanted to see.

 

I will tell you two things. The tip of the filter can run on the underside of the tank, and the plastic will become brittle with age. Make the fuel filter a part of your annual inspection routine.

 

Will do. Thanks.

 

Im currently using the tank filter AND the inline filter and I think I’m having fuel flow issues.

Is it recommended to remove the in tank standpipe filters once the inline filter is installed?

Thanks!

 

There is no reason to remove the tank/petcock filter. It helps keep crud out of your petcock for one thing. On my XJ700's it also determines the fuel level for the reserve fuel.

 

If you are having fuel flow problems you can remove the petcock and be sure that the inside stack filter is clean--but, as Huntchucks says, do not remove it. If that doesn't solve it, then you probably have a problem with the petcock and it may need attention. If you had no fuel flow problems before adding the inline filter, then that's probably where the problem is.

 

Can you post a pic of your filter setup?

 

I love this forum

I got the bike to where it would reliably run of the aux tank (bottle). It would fire right up. I have the carbs synced and partially color tuned. I was going to ride it to work to tune it the rest of the way.

I tried to run it off the bike tank and it wouldn’t. So I bought a new petcock off Amazon. https://www.amazon.com/dp/B08Z34VRBJ?psc=1&ref=ppx_yo2ov_dt_b_product_details

Once the new petcock arrived I tried again. It didn’t work. But now, the bike also won’t run off the bottle. I’m speculating that my 90* fuel filter is now plugged, so I have more on the way. I cleaned the heck out of my tank but I think a glob of Kreem may have gotten to my filter.

Pictures below of my new petcock and my fuel line to the filter. The fuel line is as low as I can get it, and the line is as short as I can get it (realistically it’s probably too short).

 

Disconnect line from petcock and attach a longer one to run to a container. Turn petcock on and observe if fuel is flowing freely. If so, remove sintered filter and connect it to long line, repeat test.

 

I had problems with filters as follows.
The vertical height between the top of the carbs to the bottom of the petcock is not much. So to avoid an upward run of fuel line that could cause a trapped bubble is very high.
If you get air in the line, the vacuum to pull the fuel down has to overcome the force to move the fuel up and over the bubble hump. If you don't have good flow through a filter, it can resist that.
I found a rock filter like you have shown there chis, to not work well for several reasons.
The way you have that there lends itself to trap air. If you see that the filter is not 100% filled with gas, and there is air trapped at the top, then that portion of the rock filter that has air around it is not participating in filtering or flow.
Second, those rock filters don't have much surface area and can clog up IMO much faster than a larger paper filter that is pleated.
My rock filter lasted only 300 miles before I started to have fuel issue. I blame the contamination on fine particles that remained in the tank after de- rusting it.

I'm running w/o a filter now and looking to just get ugly and run a paper filter along the outside of the carbs. I'm running that same yellow fuel safe fuel line and its a godsend for being able to see what is going on.

 

I really appreciate this information. Knowing that others have had similar issues helps a lot.

I do get fuel through the 90 degree filters, but it seems like it’s not enough. I haven’t tried running the bike on just the in tank filter yet because I’m paranoid that I’ll plug the fuel screens in the carbs.

Maybe I’ll get some pleated filters and try them out.

Thanks!

 

I remove those screens and fit a main filter. It's easy to drain the bowls when necessary, but if you ever get stuck at the side of the road because your little bitty carb filters are plugged, you're screwed. Nothing you can do.

 

That’s a good point. Maybe I will remove them on my other bike.

In the second post of this thread, Jetfixer referenced little red Lawnmower filters. Are these the style?:
https://www.amazon.com/gp/product/B07LCKTDFM/ref=ox_sc_act_title_3?smid=A3062TSEQWAA1I&psc=1

 

That's the kind of thing, but when choosing one I do a flow test before using it. Most lawnmower gravity filters are ok.

 

Got it.

what is the minimum acceptable flow?

 

Its interesting and I thought about this when I had flow problems due to a clogged rock filter.
Lets say your bike gets 30mpg during hard acceleration going 60mph.
That means your at that moment your pulling 2 gallons per hour. 60 M / G x G/30 m
If you can dump 1 gallon in 30 minutes, that's the flow you need.
Lets say I'm off by a factor of 2 (15mpg @ 60mph) , then 1 gallon in 15 minutes would be the answer to keep the bowls filling back up.
In my case, the new rock filter was great and dumped 1 gallon in about 5 minutes I recall. When it eventually clogged it was tricking so slow I knew something was wrong and pulled it off.
The problem is not always how well it flows when new, but how easy that filter is to clog and then what will it be like then.
All the boat outboards I've own had very large pleated paper filters. If you can keep your gas and tank clean, not a big deal w/ a rock filter. I just had some resedue floating around after the de rusting.
For me on any filter, I'm looking at surface area and what it is (rock, fine screen, paper) .

 

I work on 1/2lb / hp / hour, which is what most engines consume.
Divvy that to get lbs/min.
Basically, any filter that can flow a pint per minute will outflow nearly any sub-1000cc bike engine in common use.
If it can flow 0.3L in a minute, that will do.

 

One other aspect to consider regarding these fuel filters is the micron rating.

Google says the finest grade of sand is 125 micron, a human hair is 70 micron (diameter), and the naked eye visibility threshold is 40 micron.

The small red lawnmower filters I bought have a 150 micron rating.

It would be nice to know what the factory petcock filter mesh specification is.

Do you guys think the 150 micron lawnmower filter is acceptable?

 

I go with a "Pro line" filter from my local auto parts store. They don't get brittle or yellow from all the ethanol in our fuel here in the Midwest. Just how bad is the gas tank and why are you worried about supper high micron rating? I would think you would only be worried about the sand getting into the jets and plugging up the carb?

If the gas tank is that bad, think of cleaning it and treating it. At least that way if any sand or left over bits will hopefully be covered by the tank sealer and must less filter worry. Still run a filter but much less bits flowing to the carb and engine.

Looks like this but is around $9 US.
https://www.amazon.com/K-N-81-0221-...MI_Ie8kPffgwMV69XCBB3xMQNZEAQYCCABEgJSBvD_BwE

 

Good question. I'm really just interested in matching the OEM micron rating. No more, no less.

I have cleaned the heck out of my tank (with your help via PM!). But shortly after I began having fuel delivery problems and I think my sintered filters (two of them) plugged. I think some residual Kreem tank liner may have gotten to the filters, but I'm not sure.

I bought the little red "briggs & Stratton" type filters on another members recommendation.

 

Best you can do is drain the tank (again) and have a look to see what is going on with the liner. I was the one the said "Kreem"? As I don't use that tank sealer anymore. I either use POR 15 or Golden tank sealer as both of them can handle ethanol gas and I an not too sure kreem can make that statement.

The after market in-line filter will be better then the ones in your petcock. Not too sure how you plugged the hole in the gas tank where the petcock goes, but more sure it is open and not plugged by the sealer. Taking compress air to the petcock to make sure it is all cleaned out as well. The screens are flexible plastic and can be cleaned a few ways. Using compressed air to so the finish job on them will make sure they are all clean, and more or less dry.

Look into the tank and make sure the liner took. move it around with a good light source and maybe even put some compressed air in, a small pressure to make sure the sealer is all afflicted to the tank.