Dynojet advice

[glib]

I called Dynojet to get advice on the following: 83 GS1100E with stage 3 kit, pods and 4-1 runs amazing all the way to redline if you twist from idle to full throttle slowly (1-1.5 seconds) but if you just open it, the engine will stumble at around 5,000rpm and not recover until you back off for a moment and then hit it again after which it will accelerate strongly to redline.

The guy at Dynojet said they think it is rich at the stumble and to raise the needle. We talk mostly about lean conditions here so it never occurred to me that it might be rich. I don't know if I've read anyone describe the behavior of a rich GS other than black exhaust.

Anyone able to advise on this?

[gustovh]

Do a plug chop when it stumbles and see if you are running rich or not, that should give you better direction than a guess.

V

[stain]

You can also run your choke slightly on, if it gets better you are lean, worse you are rich

[Carter Turk]

If it is rich where they say, then raising the needle will make it richer. Is it a Mac pipe?

[geol]

Does the pipe have a baffle of any sort? Flat spots in mid-range are typically due to lack of any back pressure without knowing more info.

[ShadowFocus603]

Do a plug chop when it stumbles and see if you are running rich or not, that should give you better direction than a guess.

V

+1 this. Plug chop will tell you everything you need to know.

[glib]

If it is rich where they say, then raising the needle will make it richer. Is it a Mac pipe?

You are right of course. I meant to say that they said to raise the clip.

It is a Vance and Hines.

You can also run your choke slightly on, if it gets better you are lean, worse you are rich

I thought this sounded good but it didn't make any difference in the stumble.

[glib]

Does the pipe have a baffle of any sort? Flat spots in mid-range are typically due to lack of any back pressure without knowing more info.

It does have a baffle.

[glib]

This is a new plug after a plug chop test. I hit the kill switch in the middle of the "stumble" and pulled the plug and this is what is looked like.

[OldVet66]

I would run it around a bit more until the plugs color up some before doing another plug chop and check all the plugs. The one you show looks dead lean if it's firing at all. A plug chop should burn off all excess richness from idling and show you what is really happening at full throttle where excessive leanness could melt a hole in your piston. Where is your antisease for the plug threads or is that camera angle?

[glib]

I would run it around a bit more until the plugs color up some before doing another plug chop and check all the plugs. The one you show looks dead lean if it's firing at all. A plug chop should burn off all excess richness from idling and show you what is really happening at full throttle where excessive leanness could melt a hole in your piston. Where is your antisease for the plug threads or is that camera angle?

Good eye. No anti-seize on this plug. I think the plug does show what you describe. It has burned off any excess richness from idling and is indeed showing a lean condition during the full throttle mid-rpm stumble. Before I make any adjustments however, I am going to look at the coil relay mod idea and check my voltage at the coils since low voltage at the coils apparently can cause similar behavior.

[glib]

Voltage to the coils is good. Same as the voltage at the battery so back to the carbs. I dropped the clips to the fourth position. Still getting some stumble but may be a bit better. Guess I'll try the next position. PITA.

[glib]

Pod people?

I raised the needle again but still get the mid-range stumble. In first gear this morning it pushed through the stumble and pulled the front wheel off the ground. Startled me a bit.

The "stumble" occurs at a higher rpm in each gear...for what it's worth.

I guess I'll try the plug chop again. I wish I could test at a track. The neighborhood is not a great testing environment.

In my 700ES the dynojet kit went in and performed perfectly from the start so this is pretty frustrating.

[Carter Turk]

Are all the carb internal o-rings original? Might be causing a rich/lean condition somewhere.
What about the air/jets they provide in the kit, did they say to use them?

[glib]

Are all the carb internal o-rings original? Might be causing a rich/lean condition somewhere.
What about the air/jets they provide in the kit, did they say to use them?

The kit was installed in another "E" that I bought with a broke motor so I checked the main jets which are the only ones they say to change and installed them and the needles in this bike. I had completely dipped the carbs and installed new o-rings prior to installing the kit. I have moved the needles up and down so much for so little notable change that I am beginning to wonder if it could be something else but I have no idea what. Could it be that internal engine modifications are necessitating a different main jet? I don't know what has been done to this motor but my ES won't pull the front wheel off the ground by just twisting the throttle.