WTF? I'm so tired of this game....

[dtkid]

Agreed............let me just add this:

No one that has not worked on these machines can trully appreciate just how ultra-sensitive the air/fuel mixture is.

My buddies that race Chevys thought that I was stupid or just over-stating the facts...until I proved it to them. These machines simply won't run without the correct mixture. They ain't like a truck; where you can take off the air-breather or filter or make large adjustments on the mixture screw (to pass a Vehicle Emissions Test).

These babies are super senistive to air-fuel ratios.

[Joe Guilbeau]

Not always. As he's said, his plugs looked good. MY plugs looked good in my 1100G. But it still wasnt quite running right at high speed roll ons. Smokin, give the adjustments i suggested a shot. See if it works for you. At your elevation, you MAY want to try the outer cylinders screws at 2.25 turns out and the inner at 2.5 out, since you'll naturally be just a tad richer than me.

I got my experience and info from Sudsco/Mikuni 4th Edition tuning manuals.

http://www.lambretta.net/shop/shopexd.asp?id=3996

Here is a Mikuni tuning guide for the VM Series

http://www.mikuni.com/pdf/vmmanual.pdf

A quick how to guide for the Mikuni CV Series

http://vmaxoutlaw.com/tech/cv_carb_tuning.htm

Here is a write up on the ST series of Mikuni carbs, go to the thread with all the pictures...

http://www.gixxer.com/forums/showthread.php?t=159718

In any case, there seem to be a lot of opinions on how to get something done.

Hope some of this helps in getting ya'lls jetting straight...

[TheCafeKid]

I got my experience and info from Sudsco/Mikuni 4th Edition tuning manuals.

http://www.lambretta.net/shop/shopexd.asp?id=3996

Here is a Mikuni tuning guide for the VM Series

http://www.mikuni.com/pdf/vmmanual.pdf

A quick how to guide for the Mikuni CV Series

http://vmaxoutlaw.com/tech/cv_carb_tuning.htm

Here is a write up on the ST series of Mikuni carbs, go to the thread with all the pictures...

http://www.gixxer.com/forums/showthread.php?t=159718

In any case, there seem to be a lot of opinions on how to get something done.

Hope some of this helps in getting ya'lls jetting straight...

While I do appreciate your experience, there is one thing that *I* have learned about thes guides. They are just that. Guides. We could put the same model bike next to eachother. Same miles, same valve clearance, same modifications such as pods and pipes and the EXACT jetting settings would be different, and sometimes VASTLY. What may work for me, may not work for his bike, even if it were the same. Also some peoples perspective of what a perfect running bike is, is subjective. These guides are great for getting you in the ballpark, but the fine tuning can only be done by the person who has to turn the miles on it. Mind you, i dont have nearly the experience on tuning and jetting that alot of these guys have, but i have listened intently, and studdied, and tinkered untill my eyes were red. There are a few basic rules of thumb that i follow that i have been taught by a few people here, and i pass that knowlege along. There ARE varrying opinions on how to do this, but the bottom line is ultimately its up to him to decide, based on however many suggestions he can gather, and tinker with, what feels BEST to him. Get it in the ball park. Tweek it to suit from there. As long as you're not overly rich, and not lean, what feels good to you is best. What opened the flood gate for me was actually gathering an understanding of HOW and WHY the carbs work the way they do. What affects what, what circuits are in use at any given point in the throttle. I still have a lot to learn, but i simply passed on some settings that i found worked for me for him to try.

[Joe Guilbeau]

I wholeheartedly agree with you, my original comment was addressed at the altitude thing.

I just added the links to help others decide, not to bolster any position I have, as a matter of fact a perusal of the various links will expouse differing tuning stratagies.

Rodger Baldridge a Ford service manager out in Oracle AZ schooled me on the carb thing for the bikes. Guy is amazing in overall breadth of knowledge.

In any case, I am sure that with some patience and skill and perservance the jetting will be fine.

Heck, it MIGHT even be a intermittent spark issue... who really knows?

Hugs and kisses all around, eh?

[Smokinapankake]

Thanks guys for all the help, I've clearly got a lot of learning to do. My patience right now is at about its lowest point and so I'll step away for a few days to regain some composure.
I will look at the valves as I've never done that, but the floats are all set. I'll check them again.
Maybe go up one on the main jet size?
Raise the needles and set air screws to 2.5/2.75.
But not today.

[terry]

Well considering the collective experience here, this is probably a silly question, but when you reinstalled the OEM air box, did you refit the OEM filter? CV carbs are super sensitive and while the bike will idle fine and rev out on the center stand with no air filter installed, under load it'll run like crap.

I installed a new foam filter in my GS1000S airbox (I don't know why people use pods, it must just be for looks, the OEM airbox flows plenty of air) and it ran way, way too lean, until I coated it in lots of foam filter oil, which reduces air flow considerably.

If you haven't re-installed your OEM filter yet, do so, and I bet all will be well. Cheers, Terry.

[PAULYBOY]

Okay, so reading this thread, and accessing a couple of the links therein, has me wondering (riddle me this) some mention turning the screws out to richen the mixture, some mention turning them in. It can't be both, so which is it? I thought turning the screws clockwise (IN) meant more fuel to less air, and turning them out (counterclockwise, or anti clockwise for the Europeans among us) meant more air in the mix.

[Nessism]

Okay, so reading this thread, and accessing a couple of the links therein, has me wondering (riddle me this) some mention turning the screws out to richen the mixture, some mention turning them in. It can't be both, so which is it? I thought turning the screws clockwise (IN) meant more fuel to less air, and turning them out (counterclockwise, or anti clockwise for the Europeans among us) meant more air in the mix.

For BS/CV carbs, the pilot screws control how much gas/air emulsion enters the engine - out is richer. This is not to be confused with VM carbs which have separate fuel screws and air screws.

My advice for the OP is to verify everything in the intake system is stock: jets, properly sealed airbox (foam needs to be intact), filter in place, etc. Running a stock bike at 4500 will richen up the mixture which should be close to perfect since the bike was set up quite lean from stock.

If you still get the lean surging, try playing with the needle height; lowering the clip raises the needle which will richen up the mixture. Move a couple of notches and see how it goes.

Good luck.

[C.V.]

I got my experience and info from Sudsco/Mikuni 4th Edition tuning manuals.

http://www.lambretta.net/shop/shopexd.asp?id=3996

Here is a Mikuni tuning guide for the VM Series

http://www.mikuni.com/pdf/vmmanual.pdf

A quick how to guide for the Mikuni CV Series

http://vmaxoutlaw.com/tech/cv_carb_tuning.htm

Here is a write up on the ST series of Mikuni carbs, go to the thread with all the pictures...

http://www.gixxer.com/forums/showthread.php?t=159718

In any case, there seem to be a lot of opinions on how to get something done.

Hope some of this helps in getting ya'lls jetting straight...

Great links! These should be posted up here permanently, the mikuni guide really offers a lot of insight into how carbs work, very usefull.
Lambretta Huh? You an old scooter guy? My first ever solo ride, and subsequent first crash, was on an Vespa primavera 125. Started a long career of scooter crashes!

[flyingace]

I'm confused about what the poster is trying to do at this point. Going back to stock makes sense. To me, that means going back to exact stock settings, not trying to rejet for altitiude and continue to get frustrated when it doesn't work. Remember, the airbox, filter, manifolds and carbs were designed and set to work as a unit.

I'd go back to box stock carb settings and see how it runs. At 4500', there may be no altitude effect. My bike ran fine stock at 6000'.

[Smokinapankake]

Thanks for all the replies folks, this is what makes this forum so great.
I wanted to return to stock because 1: It's stock - this gives a solid baseline to make assumptions from, i.e., It will run, because the factory designed it to. 2: I had the same line of thinking - airbox, filter, manifolds, carbs and exhaust were designed to run as a unit with little trouble. Eliminating as many variables as possible. See reason 1.
3: Stock looks way prettier (to me anyway) than some bastardized 4-1 with noisy pods. Because that's what it would have to be since virtually no one makes a decent 4-2 replacement pipeset for this motorcycle (excepting the UK).

Thanks for the tip Terry, I don't know how but the air filter completely slipped my mind. I'll put it in and see what happens.

BTW, I have verified through the forum at www.katanacentral.co.uk that my carb settings are factory. See thread topic 2900.

[terry]

Thanks for the tip Terry, I don't know how but the air filter completely slipped my mind. I'll put it in and see what happens.

No worries mate, I hope that fixes your problem, it certainly did for me! Cheers, Terry.

[jetta90]

Smokinapankake - Ive been doing some carb work on my 1984 GS 750E lately myself.
Privious owners had a 4 into 1 and pods. When i bought it came with original exhaust and foam filter in stock air box.
Someone else metioned this before - the CV Mikuni carbs are EXTREMELY sensitive.
If your going back to stock make sure your foam element is in good shape and not overly oiled and that the air box is totally sealed.
This is what i've got running now but I don't think I'm there yet..................
Main jet - 120
Needle jet - Y7
Jet needle - 5D10
Pilot jets - 40
My fuel/air mixture screws are ONLY turned out 1/2 turn and not the usual 2 turns plus. Note that my pilot jets are 40's and not 37.5's like the factory, this probably is why it is running fine at 1/2 turn out.
The above gives you an idea where you could need to be.
No two ways about it ................... make sure your valves are adjusted. Don't go any further until you are sure your valves aare adjusted to spec.