slide drilling

[briyenkieth]

to start with I've done a couple of searches already. Search button is my friend! That said I have a couple of ?'s about this. First how big do I drill the hole in the slide? Second, do you drill the carb body as well? Referring to the port on the filter side of carb throat.

Useful info:'78 gs400, carbs dipped n ringed, new intake boots n rings, new plugs and points, emgo pods(new), jcwhittney reverse meg mufflers w/ crossover retained,oil change, everything but the valve adjustment. Which they seem fine, starts fine and no excessive noise or any of the valve adjustment symptoms I'm used to.

I'm currently dialing in my carbs(still), since I finally recieved my jets and figured while I'm in there. I've had a slight response problem since I installed the pods.

[Steve]

Your VM carbs do not need to be drilled.

Drilling a slide is only necessary on CV-type carbs to enable the slides to lift a bit quicker after the installation of pods.
Your slides are lifted mechanically, so no drilling is necessary.

.

[almarconi]

First how big do I drill the hole in the slide?

This is usually done in some applications when installing a jet kit. I checked and dynojet does not make a kit for your bike. I would be real hesitant to drill the slides without knowing what you are doing because you could easily screw up your carbs.

You may want to try to find some adjustable needles for your carbs and try going up in size on your mains. See how that runs before drilling anything. I'm no expert on rejetting but this seems to me to be a more sane approach than drilling the carbs.

[almarconi]

If you must drill, then a #30 drill should be appropriate for CV slides.

[almarconi]

I would not drill the carb body. You may want to consider shortening the diaphragm springs in addition to drilling the slides. Are you running the stock pilots? It may be worthwhile to go up one size on these also. Do one mod at a time to see the effect.

[almarconi]

How does it rev off idle? Do the rpms go up and down at the same rate or does the rpm hang before returning to idle?

Where are the mixture screws set now? Did you set them for highest idle?
If you have some popping off idle, richen them up a tad. If the engine responds quickly and no backfiring through the carburetor, you have your idle mixture right. If backfiring occurs through the carburetor then adjust the idle mixture screw out another 1/8 to 1/4 turn. Under normal circumstances, the idle mixture screw should be between 2 and 3 turns out.

To test the main jetting, put bike in fourth or fifth gear and running fairly high RPM 4000 then open the throttle all the way to the throttle stop, noting the feel of the bike. Immediately let off the throttle about 1/8 turn and note the feel of the bike. If it seems to accelerate some when you let off the 1/8, your main jet is too lean. If it hesitates or the top speed is poor (i.e. less than 80 MPH) you are too rich. Adjust your main jetting accordingly by increasing or decreasing the jet size


Tuning for pods and a pipe takes some trial and error. It would probably be helpful to take some notes of your settings. Try to change one thing at a time and make a note of your changes.

[Commodus]

I don't know if this has been mentioned yet...

It's a very bad idea to modify your carbs without solving the problems you're having with them first. You don't want to add yet more unknowables to your situation.

You've deviated very far from stock when you went to pods. You have to learn how to jet your carbs now. It will be a long and frustrating process (this you already know), but if you take it slow and use a methodical approach you will end up with a good motorcycle, and not writing a craigslist ad like, "I'm pretty sure all it needs is some carb work..."

One thing, I've myself been frustrated with Emgo pods. I've always found it much easier to tune K&N pods, I don't know why. Something to think about.

[almarconi]

Not sure where to start but at the leanest point, I.E. smallest jets I got and highest notch I guess.

Why would you do that? You know your going to have to go up on the mains and richen the needles since your running pods and a pipe.

Hears an idea..why not put the stock airbox and stock pipe on, return the carbs to stock jetting and RIDE the bike

[posplayr]

Either do as almarconi suggests....

Hears an idea..why not put the stock airbox and stock pipe on, return the carbs to stock jetting and RIDE the bike

Or read there instructions and see if you can get past step #1

Once you get past #1 then on to #2, and so on. Dont mess with #4 and #2 when you don't have #1 yet.

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,lower_rpm_engines.html

Pos

[almarconi]

Or read there instructions and see if you can get past step #1

http://www.factorypro.com/tech_tunin...m_engines.html

Thanks for the link..just added it to my favorites..very interesting read.

[Nessism]

You realize of course that drilling the slide will not fix a steady state fuel mixture problem, it will only change the throttle response when wacking open the throttle.

Regarding one plug looking white and the other dark, this obviously indicates a fault somewhere, not jetting related. Common problems include dumping fuel down the petcock vacuum line or float needles that are not sealing properly. Could also be weak spark. I suggest fixing this problem before moving up to jetting.

Good luck

[Steve]

I know I should be running a better filter but it's hard to rationalize $120 for filters when I paid $100 for the bike.

I just love that line.

I was given an 850 for free. Does that mean I should feel bad about having to pay for anything that it takes to fix it?

I have always adopted the view that there are certain things that are necessary for a bike to run well.
Depending on what's wrong with the bike, it's going to take XX amount of money to fix it.
Darn good thing I didn't have to pay much, I now have that much more money available for parts.

By the way, you pay the $120 for K&N filters now, you get to keep them for life.
You pay less money for lesser filters, when they get dirty, you throw them away and get new ones.
How many filter changes do you anticipate?

.

[Nessism]

Lots of people run those Emgo pods with fine results. I wouldn't expect them to flow like K&N's, but maybe they will filter better which would be a plus.

[hp1000s]

Lots of people run those Emgo pods with fine results. I wouldn't expect them to flow like K&N's, but maybe they will filter better which would be a plus.

...plus, doesn't APE offer high-quality pods for less than K&N?

[almarconi]

ness,steve do you guys read the entire thread before you talk $hit or do you guys just dive in?

I think thats a bit harsh, I've talked to both these guys and they are genuinely helpful people. You must admit that you are not always forthcoming when you ask a question. I've noted on a couple occasions that you have left out rather pertinent information . For instance, your bike is listed as a 78 GS400 but yet it has bs34 cv carbs and a hard tail. Someone trying to help you (wrongfully assumes you have a stock bike) and offers advice. Its also hard to diagnose a problem through a computer screen. You can't hear or see what the problem is, only give a list of possibles. It's not like I'm standing next to you in the garage listening to what your listening to.