Jetting Report Part 3

[Anonymous]

Well, I installed the 140 mains and it cleared up more of the stumble at full throttle @ 6000rpm. In the lower gears it will pull through this area at 3/4 throttle with only a slight roughness, pulling hard. At full throttle it still does stumble, however. Not as bad, but still there. I am now pondering raising the needles one more notch to see if it cleans out more or trying 142.5 mains. I am loathe to mess with the needles, though, because it is running really well below 1/2 throttle with easy starts (<1min of choke in the morning, then ride away), great response and lots of power. The transition from pilot to needles is seamless regardless how fast or slow the throttle is opened. The only issue remaining is the stumble @ 6000rpm. Plugs are now showing a very pleasing shade of medium light tan on the insulators so I am going to leave my pilot circuit alone from here on out. The current specs are:

Kerker 4-1 pipe
Pod filters
Needles on second groove from bottom (5 grooves total)
Mixture screws 3 turns out
Stock pilot jets (47.5)
140 Main jets

I am waiting on a set of GSXR coils bought off E-bay to see if they also clean up some of the 6000rpm stumble issue. For the recent discussions on mileage with pods, it looks like I got about 38mpg (Imperial gallons, remember) from my first tank. This is very poor by my standards, but it was also done with several test rides in there, using lots of full throttle roll-ons trying to sort my jetting out. The current tank is looking much better, with about 165km and showing a bit less than half on the guage. Judging from that first tank, I would think I should be getting mid 40's in mixed riding while commuting to work. For comparison, my ZX-9 returns about 51-52mpg during commuting duty.


Mark

 

[Craig]

My friend: Go to Precision Auto & Cycle and let them do a dyno. I have a 83 GS 1100 with ++ mods, and they worked magic on my bike. Mike is great. It may set you back a few bucks, but you will be very happy. Tell him Craig sent you, and he will charge you double 8O

Kind regards..Craig Hollingshead (Red Deer)

 

[mike J]

Mark, can you tell me what kit, if any, you put in your carbs? You sound like your having the same problems I have with my 1150 w/ a DynoJet stg III kit. Mike J

 

[Mr. Jiggles]

I used to have a stumble at around 5000rpm/5th gear that cleared up after I tightened the blade connectors on the coils.

 

[Anonymous]

My friend: Go to Precision Auto & Cycle and let them do a dyno. I have a 83 GS 1100 with ++ mods, and they worked magic on my bike. Mike is great. It may set you back a few bucks, but you will be very happy.

Hey Craig, I am holding that in reserve if I need it. There are a couple of shops that will dyno tune older bikes for not insane amounts of $$$. But I hate to admit defeat like that...

We need to get together for an Alberta GS chapter group ride. I think I can round up about 5-6 guys here so far.

Mark, can you tell me what kit, if any, you put in your carbs? You sound like your having the same problems I have with my 1150 w/ a DynoJet stg III kit. Mike J

Mike, I have no kit in mine. The Canadian model still had adjustable needles in 82, so I have been using them. I am trying to avoid putting in a Dynojet kit because they:
1)cost money
2)are usually very rich in the mid-range
3)don't seem to be any closer to perfection than I am at right now.

I used to have a stumble at around 5000rpm/5th gear that cleared up after I tightened the blade connectors on the coils.

Interesting. I have not really had a look at the electrics yet because it seems to charge OK and most stuff works. I do have some issues to sort, but they are not stopping me riding the bike, so they can wait. Our weather is going completely in the toilet for the next several days, so maybe I will spend some quality time out in the garage with some emery cloth and contact cleaner. I do feel that some of the stumble is ignition related, so I guess now is a good time to check all my connections, etc. while I can't ride.

On the weekend I did try raising the needles to the bottom notch. It made everything worse, so I put them back at the second from bottom notch. It would appear that I am going rich at the stumble, so at least now I know what is happening. The big question now is whether the stumble is because it is rich at the end of the needle circuit or as the mains take over. The way it ran with the smaller mains would indicate it is not really that rich on the mains at the moment, however. When our weather clears I am going to try it back on the #3 notch with the 140 mains and mixture screws at 3 turns out to see if leaning the needle solves the stumble or not. I don't think it will, but it wouldn't be the first time I was wrong about something... When I get a chance to try the needles on #3 I will report back with the results.

Thanks for the comments and suggestions,

Mark