"Pod filters"

[Anonymous]

I have a 79 GS750 with an 844 Wiseco piston kit installed (and a 4-1 pipe of course). The air filter box does not have the rubber snorkel to provide laminar flow to the carbs and a replacement unit will be about 30% of the entire cost of the bike (bought 2nd hand and thoroughly rebuilt). I am therefore considering pod filters.

I have been warned by several local dealers not to even think about pod filters, mostly because the carbs become virtually impossible to tune, lots of fiddling with jets etc.

Searching this site, I am left with the impression that pods filters are generally a good idea but that there is a fair amount of tuning required to achieve decent results. I am quite prepared to invest whatever time it takes to re-jet and re-tune the carbs but only if there is a definite positive outcome. I would also appreciate any comments about jetting for such a configuration. I have 102.5 main jets (new) and new needles. but the bike appears to run fairly lean.

Any informed comments would be most welcome.

thanks

Rob

 

[Anonymous]

I'm a big fan of pod filters for 2 reasons and they are 1) increased performance and 2)It's so much easier to work on the bike without an airbox.

True they're a little harder to tune but once you get your carbs dialed in, there is definitely an increase in performance. With the increased airflow you're generally going to be able to run main jets that are 30-50 % larger than stock. I do find the increase to be mostly top end but altogether better throttle response throughout the entire range.

Just my $.02

 

[KEITH KRAUSE]

Re: "Pod filters"

I have a 79 GS750 with an 844 Wiseco piston kit installed (and a 4-1 pipe of course). The air filter box does not have the rubber snorkel to provide laminar flow to the carbs and a replacement unit will be about 30% of the entire cost of the bike (bought 2nd hand and thoroughly rebuilt). I am therefore considering pod filters.

I have been warned by several local dealers not to even think about pod filters, mostly because the carbs become virtually impossible to tune, lots of fiddling with jets etc.

Searching this site, I am left with the impression that pods filters are generally a good idea but that there is a fair amount of tuning required to achieve decent results. I am quite prepared to invest whatever time it takes to re-jet and re-tune the carbs but only if there is a definite positive outcome. I would also appreciate any comments about jetting for such a configuration. I have 102.5 main jets (new) and new needles. but the bike appears to run fairly lean.

Any informed comments would be most welcome.

thanks

Rob

The VM carbs can be tricky sometimes. I recommend a Dynojet jet kit. You may still experience what is termed "driveability" issues after your final jetting. If you do the job right, these issues will be minor, if at all, and you can realistically pick up 10HP with filters/pipe alone. You can also try to adjust the stock needle and replace the pilot/main jets with larger ones. It's up to you but I have had good/easier to achieve results with jet kits. You can end up buying several sizes of jets and what you saved by not buying a jet kit can quickly be lost, not to mention your time.
If you get a kit, follow their advice and let us know if we can help.
If you try re-jetting with Mikuni jets, I'll take a stab at it to get you started.
First, the other parts of the bike must be working correctly. Valve clearances, compression, ignition, manifolds and their o-rings, the carbs must be clean inside, good o-rings, correct float level...
I would try 130 or 132.5 mains, raise the jet-needles by placing the needle clip 2 grooves LOWER than where they are now, if you can.
Go up 1/2 size on your pilot jets. Leave your pilot fuel screws(underneath) alone, unless plug reads tell you they need adjusting.
Adjust your side air screws for the highest rpm possible. Warm up the motor and then turn the air screws "2 at a time" in or out in 1/2 turn increments and listen for the highest rpm's. Do this for all 4 screws and re-set the idle with the idle screwknob.
Then sinc' your carbs CAREFULLY. These carbs will give you mixture problems if they are not set closely. Get all 4 levels (mercury) within a 1/2" of each other at about 3500 rpm.
Do what testing and the plugs tell you to. When testing, at idle you are on the pilot circuit. Just above idle to 1/5 throttle you are overlapping the pilot and needle circuits. Above this you are on the needle circuit. At about 3/4 throttle, the mains take over.

 

[Anonymous]

How do the pod filters hold up to rain? The water whips around the engine of my 400 and heads right to the front of the airbox. I would think that this would cause some problems if I was running pods.

Steve

 

[Anonymous]

How do the pod filters hold up to rain? The water whips around the engine of my 400 and heads right to the front of the airbox. I would think that this would cause some problems if I was running pods.

Steve

I've never had any problems running pods in the rain. I wouldn't want to let the bike sit out in the rain for a very long time. I think the K&N's probably deal with the water a little better since they oiled foam filters where the paper element non oiled EMGO's wouldn't hold up as well.

 

[Anonymous]

I've never had any problems running pods in the rain.

I'll second that. I ran pods on an 86 GSXR 750 for years and never had rain issues. Of course, I tried not to ride much in the rain, but it never seemed to be an issue. Once the engine is running and warm, it can suck in some water and nothing much happens. I noticed more weirdness with cross winds than water. If I got into just the right wind, it would cause the engine to run unevenly, but it was not very sensitive to this. It just happened a few times in years of riding that bike.

Mark

 

[moto_dan]

My experience is that rain and Pods(K & N's) don't get along well. The last hard rain I got caught in I did a little experimenting and found out that with conservative twisiting of the throttle(which one should do in the wet) all was well, contrasted to WOT and my bike would spit, sputter and lose power. But I still like pods for all the before mentioned reasons.

 

[Anonymous]

I've got some S&B pod filters (cheaper than K&N's) on a '77 GS750 and have had no problems in the rain. I use the bike to commute in to Central London all year round and it does rain a bit over here!

I fitted a 'Ledar' jet kit (cheaper than Dynojet!) but I don't think they make 'em anymore and I think they were made in the UK.

I couldn't honestly say that I notice an increase in performance though - I just like the look and that lovely intake noise!

Tony.

 

[robinjo]

Re: "Pod filters"

I have a 79 GS750 with an 844 Wiseco piston kit installed (and a 4-1 pipe of course). The air filter box does not have the rubber snorkel to provide laminar flow to the carbs and a replacement unit will be about 30% of the entire cost of the bike (bought 2nd hand and thoroughly rebuilt). I am therefore considering pod filters.

I have been warned by several local dealers not to even think about pod filters, mostly because the carbs become virtually impossible to tune, lots of fiddling with jets etc.

Searching this site, I am left with the impression that pods filters are generally a good idea but that there is a fair amount of tuning required to achieve decent results. I am quite prepared to invest whatever time it takes to re-jet and re-tune the carbs but only if there is a definite positive outcome. I would also appreciate any comments about jetting for such a configuration. I have 102.5 main jets (new) and new needles. but the bike appears to run fairly lean.

Any informed comments would be most welcome.

thanks

Rob

The VM carbs can be tricky sometimes. I recommend a Dynojet jet kit. You may still experience what is termed "driveability" issues after your final jetting. If you do the job right, these issues will be minor, if at all, and you can realistically pick up 10HP with filters/pipe alone. You can also try to adjust the stock needle and replace the pilot/main jets with larger ones. It's up to you but I have had good/easier to achieve results with jet kits. You can end up buying several sizes of jets and what you saved by not buying a jet kit can quickly be lost, not to mention your time.
If you get a kit, follow their advice and let us know if we can help.
If you try re-jetting with Mikuni jets, I'll take a stab at it to get you started.
First, the other parts of the bike must be working correctly. Valve clearances, compression, ignition, manifolds and their o-rings, the carbs must be clean inside, good o-rings, correct float level...
I would try 130 or 132.5 mains, raise the jet-needles by placing the needle clip 2 grooves LOWER than where they are now, if you can.
Go up 1/2 size on your pilot jets. Leave your pilot fuel screws(underneath) alone, unless plug reads tell you they need adjusting.
Adjust your side air screws for the highest rpm possible. Warm up the motor and then turn the air screws "2 at a time" in or out in 1/2 turn increments and listen for the highest rpm's. Do this for all 4 screws and re-set the idle with the idle screwknob.
Then sinc' your carbs CAREFULLY. These carbs will give you mixture problems if they are not set closely. Get all 4 levels (mercury) within a 1/2" of each other at about 3500 rpm.
Do what testing and the plugs tell you to. When testing, at idle you are on the pilot circuit. Just above idle to 1/5 throttle you are overlapping the pilot and needle circuits. Above this you are on the needle circuit. At about 3/4 throttle, the mains take over.

116 main jets worked well in mine, '79 750 too.

 

[Anonymous]

"pod filters"

"pod filters"

Thanks for all the constructive responses!

What I am intrigued by are the main jet sizes you folks are recommending:

"30% - 50% larger than standard"
"130 - 132.5"
"116 worked for me"

Given that the factory standard jets are 100s, does the addition of pod filters Really require such a large change in main jet size? I am an absolute beginner in the wonderful world of carburretion but I would have expected the engine to drown in raw fuel with such a large change from standard. I do have a set of 115s which fall into the lower range of the suggested sizes so i will give this a shot.

I look forward to some further education about all this.

thanks

rob

 

[robinjo]

Re: "pod filters"

Re: "pod filters"

Thanks for all the constructive responses!

What I am intrigued by are the main jet sizes you folks are recommending:

"30% - 50% larger than standard"
"130 - 132.5"
"116 worked for me"

Given that the factory standard jets are 100s, does the addition of pod filters Really require such a large change in main jet size? I am an absolute beginner in the wonderful world of carburretion but I would have expected the engine to drown in raw fuel with such a large change from standard. I do have a set of 115s which fall into the lower range of the suggested sizes so i will give this a shot.

I look forward to some further education about all this.

thanks

rob

Well my suggestion was based on my own experience with the same model bike for about 3000km, yours should be close at least. Unfortunately i don't have any other settings like jet needle or fuel screws for you since I had it done at a professional shop with a test bench.

Try the 115's and do a chop test and report back okay?

 

[Anonymous]

"pod filters"

"pod filters"

OK Robinjo thanks again.

Perhaps what I should have added is the fact that the bike in question is in the process of becoming a fully fledged rat bike (while maintaining mechanical perfection of course), and therefore has effectively NO exhaust pipe, just a few inches of beer can where the 4-1 canister used to be.

Apart from this, I don't understand why you suggest raising the needles by two notches (ie to the limit) as well as using such large jets. How is it that such a large change from standard jets and needle settings is required to compensate for pod filters, a slightly larger displacement motor and a 4-1 pipe?

Thanks

Rob

 

[Hoomgar]

I've run two differant kind of pods on my GS over the last 12 years and have ridden in rain, parked in rain then rode, etc... and have never had an issue.

 

[KEITH KRAUSE]

rloc, pod filters DO make a huge difference to the jetting. Jetting can be a lot of trial and error with so many variables. I personally like to start on the rich side and work my way back. If your needles are in their stock position, I recommend raising the needles 2 positions by lowering the clip.
You spend the most time riding on the needle circuit, so this part of the jetting is important. Jetting is not just changing main jets.
My experience with your kind of motor, with a piston kit, pipe, pods, VM carbs, has always been to go up several sizes on the mains, raise the needles AT LEAST 1 1/2 positions (by use of a jetting spacer) and either pilot jet changes or pilot screw adjustments. If you leave the needle alone, you'll have a lean and hot running motor.
You can try adjusting the needle and buying seperate jets, but I have had good luck with Dynojet jet kits.

 

[Anonymous]

Keith,

Where can you still get jet kits for these bikes? I have looked everywhere for a jet kit for my '79 750 and only have found stuff for 80's on up. Do they still make these?

 

[KEITH KRAUSE]

Keith,

Where can you still get jet kits for these bikes? I have looked everywhere for a jet kit for my '79 750 and only have found stuff for 80's on up. Do they still make these?

I did'nt see any at Dynojet, V&H, or Factory. Our bikes are too old. All you can do is look for an NOS kit on E-bay, etc. In the U.S., the 750 and 1000 both used the VM26mm carbs. They do have different jetting components but you could try to find out the exact differences and see if a combination of replacing the Mikuni jets and a 1000 jet kit might work for your 750?
Have you tried re-jetting with Mikuni jets and adjusting your needle?

 

[Anonymous]

So far i have only played with jet sizes and prob need to go a bit bigger. But i havent done anything with the needle yet. The reason for the jet kit is i would think the needle calibration would be slightly different with pods then with the stock air box. Otherwise i know i can get new jets and things. The jet kit would only be for the needle. If thats not an issue, then i will play alittle more.

 

[QuaiChangKane]

Re: "pod filters"

Re: "pod filters"

OK Robinjo thanks again.

Perhaps what I should have added is the fact that the bike in question is in the process of becoming a fully fledged rat bike (while maintaining mechanical perfection of course), and therefore has effectively NO exhaust pipe, just a few inches of beer can where the 4-1 canister used to be.

Apart from this, I don't understand why you suggest raising the needles by two notches (ie to the limit) as well as using such large jets. How is it that such a large change from standard jets and needle settings is required to compensate for pod filters, a slightly larger displacement motor and a 4-1 pipe?

Thanks

Rob

Rob - if you're seriously going the no-muffler route, then you'll definitely need incredibly larger jets. If you go with high-flowing pods on top of this (K&N as opposed to Emgo), it makes it more important.

The pods will decrease intake resistance, so you'll be sucking in more air and running lean. The same with the unrestricted pipe - there will be far less resistance to your exhaust gasses, which is going to cause you to run lean, as well.

With the piston kit on top of it, you're going to have some serious trial-and-error time when it comes to rejetting your carbs. But you'll be running so lean if you don't, that you run the risk of simply blowing the old girl up (if it runs at all!!).


The biggest benefit that new FI bikes have over ours is that they can simply throw their bike on a dyno after they've changed out their pipe and filter, and the dyno tech can re-map their bike to match the changes in equipment, and tune the power output to the rider's liking (within reason). You could do the same thing, but it would be far more expensive. I'd play with the jet sizes until it felt right, then run it on a dyno and see where the flat spots are to fine tune the adjustments.


It'll be a pain in the arse, but worth it in the long run.


Just my .03....


-Q!

 

[KEITH KRAUSE]

So far i have only played with jet sizes and prob need to go a bit bigger. But i havent done anything with the needle yet. The reason for the jet kit is i would think the needle calibration would be slightly different with pods then with the stock air box. Otherwise i know i can get new jets and things. The jet kit would only be for the needle. If thats not an issue, then i will play alittle more.

You're going to have to raise your needles. Right now your bike is running too lean from about 1/5 throttle to 3/4 throttle just because of the needle position. Needle adjustments will also have an overlap effect with the main when you roll on the throttle. Changing the mains alone will not work.

 

[Anonymous]

Not for the 77 to 79. Only 80 and up. I have looked. I do not have them in any of my parts books either.