DJ Stage 3 Jet Kit on GS850G - Removal of "float bowl vent tubes"???

[Darin Jordan]

More Testing...

First, I wanted to make sure the exhaust system was clear and flowing. I pulled the baffle out of the muffler and found this:

Looks pretty restrictive to me, not to mention pretty beat up. Will have to replace this here shortly.

However, Even riding the bike without the baffle in the muffler, the bike does the same thing. WOT, hits 6500 and acts like a rev-limiter kicks in.

If I roll up to 6500 at around 1/2 to 2/3rd throttle, it'll pull right on through.

New plugs, 4500RPM long steady 3rd gear run, then quick shutdown... They look damn lean to me still.

I suppose I should put a vaccuum gauge on it to see if it's losing vaccuum at WOT to the point where it shuts down the fuel flow through the petcock. Maybe I can run it on Prime to test this??

Everything is pointing to this simply having way too lean of main jets? Maybe they aren't factory cams? I have no way to really tell. The cam covers have been off at one time, but with 21000 miles on it, that's not surprising. I'll be doing the valve adjustment shortly so maybe I can tell then.

EVERYTHING I'm seeing points to this being too lean on the mains. I'm about ready to say the heck with it and start just tuning to the bike. Try some larger mains until it gets rich and see where we end up.

Is there ANYTHING you guys can think of that I haven't already checked and double checked?? I will be going over the ignition to verify it's operating properely, but I don't think that's the issue, since it works fine when NOT at WOT and above 6500... A bad ignition would make the plugs look too rich, anyhow... which isn't the case.

ANY advice/suggestions would be appreciated. I'm NOT beaten yet and will keep working at it!

 

[mike-s]

Amongst the other headaches i have, I am getting something similar happening when i am in a gear above third. in 3rd i can get the bike most of the way towards redline, and can get it easily to go to redline in 1st & 2nd.

 

[Darin Jordan]

Threw the baffle back into the muffler after cleaning up the leading end a bit.

Sounds better... and draws a lot less attention from the neighbors

Bike still acts the same way, only it happens lower in the RPM range... around 5800-6000. Seems worse that with the open pipe.

Plugs look about the same, though a little blacker around the outside. Still look really lean.

 

[Darin Jordan]

Talked to DJ tech again today.

I can't think of anything further to check in the intake tract at this point that should be an issue. Fuel delivery is fine... No airleaks... all jets correct and in the right places... float levels AND fuel levels in float bowls (using clear tubing) all double-checked and good... New plugs... exhaust good... etc...

I keep second guessing myself on the carb rebuilds, but I've had them back apart twice now, and it all looks perfect and is all new. Besides, what are the chances that, if let's say a passage was plugged or blocked still, that ALL FOUR would have the exact same random piece of debris in them?? This isn't a single carb issue... they are all running the same way and all appear to be working as designed.

I'm turning my attention to the cam timing for the moment. Only other thing I could think of that would be causing the system to run lean. Need to research how to go over this part on this bike (done it many times in Japanese and American and British racing cars, so I'm generally familiar with the process)...

Tech told me that if the came timing was off a tooth, it could cause something like this. I suppose it's possible that this bike has other than stock cames, but the tech suggested that they'd have to be REALLY a lot bigger to cause this kind of condition.


If I don't find a problem here, I'm going to start throwing richer mains at it until I get it to run right, or find a point where it is obviously too rich.

If the cams check out, I'm not sure what other choice I would have.

OH, and Yes, I did verify that it IS a GS850 motor, by visually inspecting the part number on the case... though, that doesn't mean someone maybe didn't put a V&H big-bore kit on it or ??? Judging from the general lack of other goodies the bike came with (It just looked stock, with a fairing), I wouldn't think that would be the case.

 

[Darin Jordan]

Oh, one more thing I want to verify is the carb sync. I bench sync'd them and all looks good... I doubt this is the issue either, but just to be completely thorough...

 

[Darin Jordan]

Just a quick theoretical question:

Is it possible for the cam timing to be off by any amount, and have the bike still run well from Idle to 6500 or so? I wouldn't think so, but figured I'd ask, as having the cam timing off "could" make the bike run lean, I suppose....

 

[tkent02]

Just a quick theoretical question:

Is it possible for the cam timing to be off by any amount, and have the bike still run well from Idle to 6500 or so? I wouldn't think so, but figured I'd ask, as having the cam timing off "could" make the bike run lean, I suppose....

I have had a few bikes that were "off" one tooth, they ran OK at some RPM ranges.

 

[Darin Jordan]

I have had a few bikes that were "off" one tooth, they ran OK at some RPM ranges.

Thank you for the response. That makes me feel more justified in giving this a double-check as a possible issue. Ordering Gaskets today!!

 

[Darin Jordan]

Cleaned up the starter relay and starter button tonight, and the OFF-RUN switch. LISTEN to the experts, guys... cleaning up the Electrical is an important step! The OFF-RUN switch was reading 12 Ohm... after cleanup, it only measured 0.4 Ohm...

I moved the needles down one slot tonight. On the stand, it seems to have a hessitation at about 1/4 throttle now, and then zipps right up after that. Will be interesting to give it a road test.

Someone in another thread mentioned that they had experienced the same problem with a very similar setup, and moving the needles down one slot fixed it. Figured it was worth a try while I'm waiting to do the valve adjustment. Hopefully will road test it tomorrow.

 

[Darin Jordan]

OK, so moving the needles down a slots and the 160 mains made it worse... Moved the stumble point down 500 RPM or so.

Went back to the 165 mains, and moved the needles UP and it's getting better. Was REALLY cold this morning, however, and I wasn't able to really test it out, so I'll ride around a bit in this configuration and see if I can feel it out a bit more. It feels, thus far however, like I'm heading in the right direction.

 

[Darin Jordan]

Been riding the bike a bit lately, and have some more observations...

Bike, with the choke on and cold, will start and idle, but "pops" occasionally. I don't leave the choke on that long, and it seems to go away once I take the choke off. It will "pop", or misfire, every now and then, when just idling, especially after revving the bike slightly.

When colder and riding, the "flutter" still occurs around 5000 or so. When the bike is warmer, it seems to get a little better, but it's still there.

For reference, mains are back to 165's and the needles are set one notch RICHER (needles moved UP) from where Dynojet recommends for the stage three kit.

The other thing I noticed was that it NEVER stumbles like this when revving in first gear, and it does seem to be less noticable in 2nd. Gets worse in the upper gears.

If I pull off the line and really go for it from 1st gear, shifting and keeping the RPMs over 6,000, it pulls like crazy through 4th... Haven't had enough room to try to pull all the way through 5th yet, but the point is that the "stumble" isn't there when running it hard right from the start.

I'm going to correct the exhaust system to fix the stinger (see pics above), before I worry about it too much more, to make sure this isn't contributing to the problem.

Bike generally feels really good up to 5,000 RPM and drives great around town. Might be a tad rich, but isn't fouling or blowing rich smoke or anything like that.

More to come...

 

[J Paster]

starving issues

starving issues

I have an 82 GS 750E beater bike that I am riding while turning my 78 GS550E into... something else. Got it for $500 on Craigslist, it needed the usual cleaning, etc. to get it running. I had a V&H 4:1 pipe, and decided to use it, following the handy V&H guide to rejetting certain listed Suzukis for their exhaust. 130 main, 42.5 pilot jet, pull the airbox cover per the recommendation. Everything seemed OK, but it lean stumbled ALOT around 3500 - 4k. I tried a 45 pilot, which really helped with the stumble, but then its as if the thing hit a rev limiter when the tach got to around 5k. Then it cut out pretty hard. Looking at plugs, which if anything looked a little lean when I expected rich, and thinking it through, I wondered if I was experiencing a fuel starvation issue with the fresh rebuilt, but OEM petcock. I then pulled the carbs again and tried raising the float level in the bowl. Got it so rich it bogged off idle at first, but after two more slight adjustments, I eliminated the cutting out altogether. As a side bonus, once I went back to the 42.5 pilots, the lean stumbling was greatly improved to the point where no further adjustments were required.

End adjustment worked out to about 2mm higher than recommended OEM. OR, you could go the smarter way and just hang a Pingel petcock on it...

 

[Darin Jordan]

After doing the updates to my exhaust system, the major part of which was to replace the broken up baffle in the megaphone with a new part and some proper exhaust packing, the stumble is GREATLY reduced... I need to ride it some more to figure out exactly what it's doing, but it felt a lot better today. I suspect it's running a tad rich at the moment, and when I'm just cruising at around 3-4K and just barely open throttle, it seems to have a stumble and pops from time to time. Also pops a lot on decell with the throttle closed.

Currently has everything back to exactly how Dynojet recommends... 165mains, Needles in the 3rd slot, but I have the idle screws turned in at 4 1/4 instead of 4 1/2.

Exhaust looks rich on the tailpipe.

Feels good to be getting closer, however.

 

[Guest]

Curious how this one worked out??

 

[bobgroger]

Not sure if he fixed this, but I had a very similar problem with my GS850 that had sat for years running well up to 5500 or 6000, then laying down. Turned out to be the ignition advance mechanism all rusted together. Some PB Blaster for a couple days and breaking it loose was a night and day difference....