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Steady Progress, but not there yet. Jets & Pods

  • Thread starter Thread starter Scudder
  • Start date Start date
S

Scudder

Guest
I have a 1978 gs750. I've been going through the normal tweekings and adjustments involved with air pods and jetting. This is what I've done and I am hoping that someone can give me some ideas. Am I heading in the right direction? It seems like it.

1st go around
Uni Pods
air mixture 1/2 turn out
Fuel mixture 1 turn out
main jet: 107.5
Topped out speed 70 mph, with the throttle twisted all the way.

2nd go around
Uni Pods
air mixture 1/2 turn out
Fuel mixture 1 turn out
main jet: 120
Topped out speed 85 mph, with the throttle twisted all the way.

Do the adjustments below seems to be appropriate for the 3rd go around. I hope to make them this weekend after I get some ideas.
Uni Pods
air mixture 1/2 turn out
Fuel mixture 1 turn out
main jet: 125
Topped out speed ______, with the throttle twisted all the way.

Please feel free to give me any suggestions. I feel like I'm close, but I need some expert advice.

Thanks

scudder
 
Why people continue to get Pods after so many threads about how hard they are to tune and how little gain you get is beyond me.
 
Especially people who don't know how carburetors work. Kind of like the ones who don't know Jack about electricity cutting into their electrical systems and then asking for help. Oh well, more parts bikes for the rest of us.
So Scudder, is it too rich or too lean now?
It's hard to tell from here.
 
Thought I'd take a stab at you guys for advice. I probably don't know enough to ask the question. This is my last go around before returning to stock. The bike, has be an odyessy in many other ways than just the pod, jetting thing. However, far from a parts bike. Preciate it.

scudder
 
Again, is it too rich or too lean? If you don't know this, put the airbox back on.
 
Hi,

As I understand the VM carb operation, you're supposed to have the air screw out at about double the fuel screw, then adjust from there. Start with fuel screw 3/4 or 7/8 out and the air screw about 1 1/2 or 1 3/4 turns out. Plug chops at each throttle opening will tell you what the different carb circuits are doing; pilot jet, needle jet, jet needle, main jet, etc. Read your plugs. You'll find links to carb tuning tips on my little website.


Thank you for your indulgence,

BassCliff
 
Too lean, I'm thinkin'. I think I'll just put the box back on like you said, and start over. What concerns me, is the bike had some of the same tendencies before I took off the box, and started down this slippery slope of pod and jets. When I got the bike stock it wouldn't run over 50mph full throttle. Thanks for the advice.

scudder
 
tkent02 said:
Especially people who don't know how carburetors work. Kind of like the ones who don't know Jack about electricity cutting into their electrical systems and then asking for help. Oh well, more parts bikes for the rest of us.
So Scudder, is it too rich or too lean now?
It's hard to tell from here.
Click to expand...

I know how carbs work, but I'm going back to stock airbox

Why?

Simple answer: IM BROKE & CHEAP AND DJ KIT IS NOT WORTH THE DECREASE IN MPG TO GET MY BIKE TO RUN RIGHT!

Cost too much damn money for what its worth.
 
I just got done rebuilding and tweaking a GS1000 and had headache after headache with it. Be smart.....Go back to your Mega Welcome and take a look at the most common issue's section. Go through your bike one by one and verify that everything on that list is good on your bike. Once you have it running right, stock, then you can start modifying it. If you dont get it running correctly in stock form, you will just end up chasing your tail around.

Simple checks:

Rust in your tank
Petcock is fully operational
Airbox is sealing correctly
Intake boots and IB O'rings are still good
Getting healthy spark on all four plugs
After rejetting, make sure your plugs arent fouled out. Replace them if they are

Most important thing when messing with jetting........READ YOUR PLUGS. Plugs are an easy way to see how the motor is doing.

This isnt hard and it isnt rocket science. Break down the mechanics of everything and research. If you cant afford to do research and teach yourself this stuff, your better off taking your bike to a mechanic who already knows what he is doing. Theres a trade off to wrenching on your own stuff.
 
Scudder said:
I have a 1978 gs750.
Click to expand...
What exhaust is on it?

125's might be in the ball park with a 4 to 1 exhaust and pods. WAY too big for pods alone.


50 mph top speed in stock form? fix what's wrong with your bike first! it should do at least 110 in stock form.
 
Exhaust is 4 to1 with a modified muffler made out of an exhaust tip. The muffler is more free flowing that the old beat up 4 to 1 muffler.

I now realize that I should have gotten everything figured out stock before modifying anything. Too late for that, unless I retrace my steps now.
 
Scudder said:
Too late for that, unless I retrace my steps now.
Click to expand...
No it's not...


check/adjust valve clearances.
compression test
check point gap(s)
measure voltage at the coils
measure coil secondary resistance; plug cap to plug cap.
measure fuel levels with external tubing.


did you raise the needle height in the carbs?
 
With that kind of loss of power are you sure you're firing on all 4 cylinders?
 
I raised the needle when I first started this process, and if I remember right it was running way to rich. That was many adjustments ago. I'm pretty sure I returned the needles to the stock setting, but I'll make sure this weekend. All 4 pipes are hot after riding. That would indicate that all 4 cylinders are firing...right?

I checked the value clearance a month or two ago. Some were way off, and I switched the shims around and got them pretty close. I haven't rechecked the clearance. I know there were a couple gaps that were too big. I've got the correct size shims now, but I haven't installed them yet.

scudder
 
Scudder said:
All 4 pipes are hot after riding. That would indicate that all 4 cylinders are firing...right?

scudder
Click to expand...

Not necessarily... Everything there conducts heat really well so a cylinder that isn't firing will still get quite hot.

A quick test is to turn it on and a minute later spray some water on the pipes, it should turn to steam pretty much on contact.
 
Thanks Adler. The second exhaust pipe was not hot, therefore cylinder # 2 is not firing or working. Now... what is my next step. I don't want to get in to deep. May have to seek professional help.

scudder
 
sounds like it's time to do a full dip and rebuild of the carbs with orings and all
 
First, Pull all your plugs and look at them. What color are they right now? White is lean. Black is rich. Brown is the right color.

For your cyl #2 problem, Grab an extra spark plug that you have laying around that you know is good and pull the plug wire off of all 4 plugs in the motor. Now, take that extra plug you have and go down the line, 1-4 and install the plug in the plug wire. You should have a plug wire with a spark plug attached to it now. Now, hold the plug against the head to ground it out and try starting the bike. Your looking for a nice strong spark on the spark plug. If you dont see a spark, you have an electrical problem. If you see a good spark coming from all 4 plug wires, then you *should* be alright in that department.

If its your #2 cyl that your having issues with, check your petcock. Is it a vaccuum type petcock or a On, Off, Pri style? If its a vac style, fuel could be going down the vac line and flooding out your #2 cyl.

While some could say that putting it back to stock is back tracking, in the long run, it will take less time to put it back to stock and get it running correctly in mechanically stock form.

Every engine needs 3 things to run: air, fuel, and spark. Trouble shoot the electrical first(spark), then look at air (pods/Stock air box), and then fuel.

If you need some help, PM me and Ill give you my phone number so you can call and we can talk about it. The biggest issue with bikes of our vintage is trying to find someone that will work on them. You cant just drop it of at the Suzuki Dealership and tell them to call you when its fixed. The mechanics of a bike is easy, you can fix this and we can help. I built a bike from the ground up using this forum, a Factory Service Manual, and some common sense. PM me if need be, I took this whole week off from work so I could ride now that the weather is in the 70's here; Ill be around. Somwhere.
 
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