dynojet question, still running lean

[kpotter16]

I've been having the same problem with my 83 GS750es. i just installed a Dynojet stage 3 and its been bogging down or something similar to that effect between 1/4 to 1/2 throttle position. i was told by CafeKid that it was the position of the needle jet clip needed to be moved. i did install the cheap pods though...could that really be a part of the issue?

 

[jordraatt]

I've been having the same problem with my 83 GS750es. i just installed a Dynojet stage 3 and its been bogging down or something similar to that effect between 1/4 to 1/2 throttle position. i was told by CafeKid that it was the position of the needle jet clip needed to be moved. i did install the cheap pods though...could that really be a part of the issue?

well, i've read some threads around here, and it seems that cheap pods might be a part of the issue yes.. we seem to be in the same position here my friend, so let's figure it out..

the cheap pods are letting in a lot more air than for example K&N filters.. i've heard people talking about major differences in air flow, just by running with/without oil in the filter, so i guess this is pretty sensitive..

as i said, i am going to install K&N pods as soon as i get them now.. when i do, i'll get back to this thread and tell you about the results.. meanwhile, maybe you can experiment by moving the needle jet clip?? because this is the midrange sector of the carb tuning.. jets are the high rpm, and float height is the low rpm

 

[kpotter16]

i haven't done this yet but i am planning to move the needle jet clip down one more position to make it run a little more rich and it should help alleviate some of the problem, but i was actually just talking to someone who said that the problem is that with the pods on a stage three kit the jets are not big enough to compensate for the increase in air flow. if we were to go up one size to larger main jets it could clear the problem up. He said to first try adjusting the needle clip position again first though and if it didn't work to clear it up to try that.

 

[EvilEnfield]

First move the needle jet down one notch, towards the tip, if that doesn't help then get yourself some of these;

http://www.ebay.com/itm/20-PC-MICRO...ultDomain_0&hash=item2a1e14285b#ht_500wt_1180

http://www.ebay.com/itm/4PC-Hollow-...delKits_JN&hash=item5d33b3fb62#ht_5191wt_1163

Then you can drill out the jets which you know are too small to see if it helps.

 

[jordraatt]

First move the needle jet down one notch, towards the tip, if that doesn't help then get yourself some of these;

http://www.ebay.com/itm/20-PC-MICRO...ultDomain_0&hash=item2a1e14285b#ht_500wt_1180

http://www.ebay.com/itm/4PC-Hollow-...delKits_JN&hash=item5d33b3fb62#ht_5191wt_1163

Then you can drill out the jets which you know are too small to see if it helps.

to drill the holes bigger or change the main jets will probably work if the problem is in the upper rpm area.. but both of us are struggling with lower/mid rpm area.. that means changing needle position and/or adjusting float height

 

[jordraatt]

i haven't done this yet but i am planning to move the needle jet clip down one more position to make it run a little more rich and it should help alleviate some of the problem, but i was actually just talking to someone who said that the problem is that with the pods on a stage three kit the jets are not big enough to compensate for the increase in air flow. if we were to go up one size to larger main jets it could clear the problem up. He said to first try adjusting the needle clip position again first though and if it didn't work to clear it up to try that.

i have already tried bigger main jets, but that is for the high rpm area.. we are struggling with the low/mid rpm area.. the problems here might be the needle clip position, the needle size or the float height.. looking forward to try with the new K&N pods though, to see if that helps

 

[blowerbike]

simple...
ride the bike with no filters.
it will run the same as if it had K&N's on it.

FYI
the problem with the emgo's isn't that there letting to much air in..
its that there shape is small and restrictive and makes the in coming air do strange things.
emgo's on CV carbs are crap and cause problems but they seem to work ok on the small say 26/28mm mechanical VM's.

 

[jordraatt]

simple...
ride the bike with no filters.
it will run the same as if it had K&N's on it.


FYI
the problem with the emgo's isn't that there letting to much air in..
its that there shape is small and restrictive and makes the in coming air do strange things.
emgo's on CV carbs are crap and cause problems but they seem to work ok on the small say 26/28mm mechanical VM's.

1. mmm, i'm not so sure about that.. i've tried with and without a oiled up pod, very big difference in air flow..

2. the K&N's are designed in another way than cheap pods.. they are designed to eliminate this air-turbulence caused by cheap pods.. well, at least that's what i've read around.. so you are right about the air doing strange things with pods
here's a photo of the K&N filter: http://www.google.no/imgres?q=suzuki+k%26n+clamp+on&start=143&um=1&hl=no&sa=N&biw=1366&bih=643&tbm=isch&tbnid=GUGHxfzCVq816M:&imgrefurl=http://www.thefind.com/cars/info-vw-beetle-fuel-pump&docid=ue-u9glj-pTl7M&imgurl=http://i.tfcdn.com/img2/7Q4EFGAABcHBFcIgDABQnje36AIhHHpym0jTWhsCDyKZsjv5_2O5nyFTH-Fj1l6I7h4bdRvCFnMtmDfFNSW8QOGn5-Q-SCALlQZVYT_FuMOscg2ngxWmw5vZhOO3HX8*/fyVMtP8A&w=180&h=180&ei=qMLDT-CAJ8XP4QTTi4HlCQ&zoom=1&iact=hc&vpx=407&vpy=204&dur=100&hovh=144&hovw=144&tx=107&ty=86&sig=101961843915767771379&page=7&tbnh=141&tbnw=142&ndsp=24&ved=1t:429,r:7,s:143,i:128

 

[blowerbike]

1. mmm, i'm not so sure about that.. i've tried with and without a oiled up pod, very big difference in air flow..

2. the K&N's are designed in another way than cheap pods.. they are designed to eliminate this air-turbulence caused by cheap pods.. well, at least that's what i've read around.. so you are right about the air doing strange things with pods
here's a photo of the K&N filter: http://www.google.no/imgres?q=suzuki+k%26n+clamp+on&start=143&um=1&hl=no&sa=N&biw=1366&bih=643&tbm=isch&tbnid=GUGHxfzCVq816M:&imgrefurl=http://www.thefind.com/cars/info-vw-beetle-fuel-pump&docid=ue-u9glj-pTl7M&imgurl=http://i.tfcdn.com/img2/7Q4EFGAABcHBFcIgDABQnje36AIhHHpym0jTWhsCDyKZsjv5_2O5nyFTH-Fj1l6I7h4bdRvCFnMtmDfFNSW8QOGn5-Q-SCALlQZVYT_FuMOscg2ngxWmw5vZhOO3HX8*/fyVMtP8A&w=180&h=180&ei=qMLDT-CAJ8XP4QTTi4HlCQ&zoom=1&iact=hc&vpx=407&vpy=204&dur=100&hovh=144&hovw=144&tx=107&ty=86&sig=101961843915767771379&page=7&tbnh=141&tbnw=142&ndsp=24&ved=1t:429,r:7,s:143,i:128

i have never oiled my K&N's...most people oil them to much.
i don't live near a beach or down a gravel lane so i have never had any engine problems from the K&N's not being oiled.
the information i offer is from 20+ years of working on these GS turds.
do with it as you wish.

 

[EvilEnfield]

to drill the holes bigger or change the main jets will probably work if the problem is in the upper rpm area.. but both of us are struggling with lower/mid rpm area.. that means changing needle position and/or adjusting float height

What about pilot jet?

 

[jordraatt]

i have never oiled my K&N's...most people oil them to much.
i don't live near a beach or down a gravel lane so i have never had any engine problems from the K&N's not being oiled.
the information i offer is from 20+ years of working on these GS turds.
do with it as you wish.

i'm not an expert, so i'm thankful for all tips

 

[jordraatt]

What about pilot jet?

i've never heard anything of changing the pilot jets, only the main jets..

 

[EvilEnfield]

I'm no expert, but when I did mine I think I went up 3 or 4 sizes on the main jet, 1 on the pilot and 1 or 2 on the air and moved the needle down a notch. I think the pilot is part of the low to mid range system, there is a very helpful link on BassCliffs site.

***EDIT*** Lots of helpful links on BassCliffs site.

 

[MisterCinders]

I'm no expert, but when I did mine I think I went up 3 or 4 sizes on the main jet, 1 on the pilot and 1 or 2 on the air and moved the needle down a notch. I think the pilot is part of the low to mid range system, there is a very helpful link on BassCliffs site.

***EDIT*** Lots of helpful links on BassCliffs site.

The jet circuits affect different throttle positions. That's why you see everyone ask about throttle instead of RPMs for carb issues. RPMs mean nothing.

The jets and throttle relationships are:

Pilot = idle to 1/4 throttle
Needle = 1/4 to 3/4 throttle
Main = 3/4 to WoT

If you change to pods and pipe, you have more air at all circuits than originally contemplated by the designer. So you need to adjust the jetting to accommodate the extra air at every stage. The air increase has a bigger impact in the needle and main circuits, but the pilot circuit needs some love too.

The pilot circuit has the most margin, since they can be adjusted without new parts. Most people can tune the pilot for pods/pipe with changes to the screw setting or settings. If you are still lean/rich at the edge of the screw settings (e.g., idle screws set at the rich end, but plugs show lean), then you can change the pilot jet for a larger size.

 

[jordraatt]

The jet circuits affect different throttle positions. That's why you see everyone ask about throttle instead of RPMs for carb issues. RPMs mean nothing.

The jets and throttle relationships are:

Pilot = idle to 1/4 throttle
Needle = 1/4 to 3/4 throttle
Main = 3/4 to WoT

If you change to pods and pipe, you have more air at all circuits than originally contemplated by the designer. So you need to adjust the jetting to accommodate the extra air at every stage. The air increase has a bigger impact in the needle and main circuits, but the pilot circuit needs some love too.

The pilot circuit has the most margin, since they can be adjusted without new parts. Most people can tune the pilot for pods/pipe with changes to the screw setting or settings. If you are still lean/rich at the edge of the screw settings (e.g., idle screws set at the rich end, but plugs show lean), then you can change the pilot jet for a larger size.

okey, now i see.. but there's one thing. the dynajet stage 3 kit does NOT include any pilot jet, and in the instructions it says turn the mixture screw 2,5 turns out.. i guess this is the screw i'm supposed to experiment with??

 

[MisterCinders]

Yes, IIRC your bike has CV carbs which use a single screw to adjust the pilot mixture. Dyno is telling you to set that screw at 2.5 turns out, which I suspect is a bit richer than the stock setting.

If you end up too many turns out and are still lean, then you may have to increase the size of the pilot jet itself.

 

[NeyborDayfid]

On the VM carbs, IIRC, you have 2 mixture screws.

On the CV carbs, IIRC, you only have the one mixture screw right at
the front on top of the carb right before the intake boot. (to the engine)
Doesn't taking this out make it leaner, while turning it in makes it richer?
I thought opening this up allowed more air. I could surely be wrong though.

 

[jordraatt]

Yes, IIRC your bike has CV carbs which use a single screw to adjust the pilot mixture. Dyno is telling you to set that screw at 2.5 turns out, which I suspect is a bit richer than the stock setting.

If you end up too many turns out and are still lean, then you may have to increase the size of the pilot jet itself.

allright, thank you very much.. i'm going to experiment with this screw.. but what if i have to go up in jet pilot size?? where do i order??

 

[BigD_83]

The stock setting on the air/fuel mixture screw was 1.5 for the '83 650. That info is somewhere in a chart here. There is no listing for an '81

\\http://members.dslextreme.com/users/bikecliff/images/carbspec_float_height.html

 

[EvilEnfield]

allright, thank you very much.. i'm going to experiment with this screw.. but what if i have to go up in jet pilot size?? where do i order??

Drill it out yourself with a pin vice and micro bit, just twist it gently and it will nibble away at the soft brass.