My GS850L falls asleep over 5K, help!

[bison head]

some test results...

-compression 135psi
-back pressure in exhaust around 3psi peak revving the snot out of it on both exhaust banks
-No intake leaks of any kind checked all properly, running
-ignition mech. advance free, all in by spec in manual
-No fuel flow problems, went through whole system
-plug readings - idle and cruising, dark tan\
- problem revs - turning white
-Carbs all clean, soaked in solution completely stripped cleaned jets and replaced needles and seats. main jets are #115's, all diaphragms perfect and aligned.
-stock airbox and filter
-stock exhaust except intermediate muffler

-symptom, no power over 5k rpm, adversely - wicked torque and smooth idle in the low end.

I read in the "real" suzuki manual that causes could be incorrect cam timing or possible plug gap too narrow so I'll check both of those and get back to everybody sooner or later. I appreciate all the suggestions and help. how do these bikes usually run? I read somewhere that these bike wake up at 6000 rpm, in the forum. And I know i'm a newbie here and I just can't figure out what does LOL stand for?

[robinjo]

LOL stands for Laughing Out Loud, it is followed by LMAO. :-D

Did you try taking the two breather hoses of the carbs?
And did you manually check if the throttle slides can open completely?
And how and why do you do a backpressure test?

[flyingace]

In light of the plugs reading leaner at higher RPM, I would consider forcing the bike to run rich temporarily to see if that solves the high RPM problem. I haven't made mods to my carbs, but I guess you need a jet kit. Maybe you can just larger mains? Experts...?

Another issue is again the exhaust. If balancing piece was rotted before you took it out, it wasn't doing its job before removal either. Try to find a functional one - that would be my first move.

[bwringer]

115 is the stock main jet size on an 850, so you could go up a few sizes to see what happens.

No one can write out a prescription for this because your exhaust is a totally unknown factor.

[bison head]

Hopefully you can learn from my mistakes...

I have no idea how many hours and lunch breaks and nights i've spent learning and fiddling for the greater good of my GS but I now have learned some stuff that I hope that all of you can learn from. I have no faith in plug readings. I was misfiring rich and the plugs were white? I dont know how long it takes to to get an accurate reading but I have seen my boss who is an avid plug reader get burned in the automotive world with engine problems giving false indicators and I won't try to diagnose with this system any more. Leave it to the pros... The key that helped me unlock the power on my GS is a dynojet troubleshooting sheet that came with my father in-law's roadstar kit. It had an illustration that showed where all of the different sections of the carb worked and a list of symptoms to try to help the customer. It said that usually a bog in midrange is a rich problem and caused by needle placement. I tried leaning the needles out and got better results but my GS was not fixed yet. I was still desperately trying to get my GS to run right and was talking to a guy at a bike wrecker and he told me another thing that got me thinking, "it sounds like it's starving for air in the midrange" Eureka! This got me thinking on a whole new level. Then I thought what if the whole system was starving for air? Now we are getting to the good part. I took out my air cleaner (SGP brand new) and thought maybe I over oiled it. I rinsed it out with gas and voila bike is running way better under load! Although it still was hesitating a little, Hmmm? Next I tried removing the side door from my Aircleaner box and now, WOW this thing pulls pretty hard, no bogs. Now I guess that maybe it could be rejetted and needled so the airbox could remain stock but I am cheap and so is this bike therefore I will cut holes in the airbox for better flow in an inconspicuous place. By the way all of you guys have commented on my exhaust mod, I took out the I-muffler which is barely anything other than a glorified crossover. The mufflers are stock and the system should theoretically retain the same backpressure as stock in it's present configuration. I noticed my bike was sold originally at a place around sea level and where I live is at around 900 metres above sea level. Does that sound like where my losses of air came from???

[49er]

It's all part of the learning curve. Ask questions/pick brains, do your assessment and acknowledge good advice.
Altitude has a hugh effect on air density and jetting. Just ask any pre-fuel injected Pikes Peak Hillclimbers who tried keeping fuel air ratios correct over the duration of the hillclimb.
Enjoy your 850 at 8000+
Cheers

[HobieSun]

I have modified the petcock so the vacuum isn't needed for fuel, so I know it doesn't have a fuel flow problem. I have everything apart for fuel today and re checked it. The mufflers are stock and it ran the same before I took out the intermediate muffler but I thought I just needed to clean out the fuel system. As for jets, the mains are 115's and torque and power are great at W.O.T. until around 4500 - 5000rpm.

How would you go about doing this(petcock modification) and what would be the downfalls of doing this? I have a slight suspect that mine is messing up. I have an 80GS750L and it is going to 6krpm and bogging down. Everything is stock.

[chef1366]

Hobiesun, here's what I did about the pos 80 petcock.

http://cgi.ebay.com/ebaymotors/1980-GS550-GS750-GS850-GS1000-GS1100-PETCOCK_W0QQitemZ180009831577QQihZ008QQcategoryZ35597QQssPageNameZWDVWQQrdZ1QQcmdZViewItem