GS1100E performance

[headsbikesmopars]

I believe you have a high gear leanout. Poping and cracking (missing) is classic leanout symptoms. Just put some 117.5/120 mikuni mains in it and go.

[rasndas]

There is no popping or missing at high speed. That happened with the previously installed jets ( dyna jets) and they were too rich.

[Nicholaschase29]

The jets per my shop manual are 112.5 ( which is what I installed) and ran leaner than the dynojets. At least the missing stopped.

I would say 115 dynojet is LEANER than a 112.5 mikuni - so the stock ran lean but OK and the dynojet ran really lean.

DynoJets are leaner than mikuni jets with the same size stamped number in that range. put in Mikuni jets that are a few sizes that what the stock ones were. or put in dyna jets that are corrected for the flow difference.

DynoJet jets are marked according to the diameter of the hole in the
jet .. ie: DJ150 = 1.5mm and DJ175 = 1.75mm.
This is not true for Mikuni or most other OEM equivalent jets. This size
Mikuni jet, (N102.221 Super BN), is marked according to its' flow rate,
ie: 150 = a rating of 150 cc of fuel per minute.

[rasndas]

I am saying the dynajets were too rich because I ran the bike wide open and it would start to miss about 6000 RPM. I then took a piece of duct tape and closed off about 1/3 of the airbox opening. The missing then started about 3000 RPM. I then removed the tape and the top of the airbox and the missing stopped. I assumed after doing this that it was a problem of the jets being too rich. The dyna jets installed were labled as 115 but I have no idea if they had been drilled or messed with in any way by the previous owner. Thats when I installed the 112.5 Mikuni's.

[RacingJake]

Sorry if this has been covered before but I couldn't find a thread using the searh function. I have a stock 1983 GS1100E with the exception of a old vance and hines 4 into 1 exhaust.

Get some real jets like Mikuni 140's then come back and post the speeding ticket for 140 mph plus

The best mod I ever did was to get rid of the dyno jets and needle's cause they will have you chasing your tail trying to fix a lean condition. Stick with Mikuni jets, go big for big power.

[headsbikesmopars]

When you block off part of the airbox with tape you are changing the flow rate of the airbox, how it was designed to flow air to the carbs. That creates turbulence in the airbox which will reduce flow. Turbulence is resistance to flow. That can create all kinds of fuel distribution problems. Why not just install some Mikuni jets above what you have tried and work down from there. Try the easy stuff first. Good luck and keep us posted.

Terry

[headsbikesmopars]

Get some real jets like Mikuni 140's then come back and post the speeding ticket for 140 mph plus

The best mod I ever did was to get rid of the dyno jets and needle's cause they will have you chasing your tail trying to fix a lean condition. Stick with Mikuni jets, go big for big power.

What he said..

[rasndas]

Weather cooperated and I had a chace to do a plug chop on the current setup. Did test as follows. Rode out to my testing spot. Put in new plugs and then did a full throttle pass through all the gears. Power seemed to start to fall off above 7000 RPM. Pulled clutch killed engine and coasted to a stop. What is probably no surprise to anyone here but me is the plugs were pure white. No color at all. You guys are right; high speed lean condition. Need to get some richer jets. Not sure how I got wrapped up in thinking the Dynojets were too rich. Right now I have 112.5 Mikuni's. I'm thinking of ordering up a set of 120's and 125's to try. Sound right?

[rapidray]

That should get you closer. Ray.

[headsbikesmopars]

RASNDAS,
I have 125 mains in my '81 GS1100EX with a nice street head , '83 cams with stock pipes and airbox without lid and k&N filter , 34 CV's . Runs super.

[rasndas]

Thanks for the replies guy's. I ordered both sizes yesterday and hopefully they will be here this weekend. I was truly shocked at how white those plugs were after the plug chop. I will also check the petcock to make sure there is no restriction there. I enjoyed the post on the Wards machine. Thanks

[headsbikesmopars]

Rasndas, Good idea to always start rich and jet down because plugs are cheaper and a WHOLE lot easier to change than pistons. LOL. Yes you were WAY too lean I hope you didn't burn the pistons. If run very lean long enough it can burn pits in the domes of the pistons. You are probably good if you didn't run it long like that. ALWAYS start on the rich side when working out a new combo. Fouled plugs are an easy fix. Good luck and let us know how it is coming along.

Terry

[rasndas]

I have never run the bike hard much. Most of the time just crusing it down country roads so I hope you are right about the pistons. It has never given me any trouble at all so I'm thinking for the most part it's OK. Have no idea how the PO ran it. I am still amazed that the factory jetting is that lean. Hard to believe the V&H header would make all that much difference. I will keep you guy's appraised of what the jetting changes do.

[headsbikesmopars]

The GS's were on the lean side from the factory (EPA), and a good scavaging pipe will lean it out even more. If it was running ok then you are good I am sure. If you had any holes in your pistons you would know it by now. Ever see bikes that had aftermarket exhaust systems and the head pipes are very blue ? Blue is hot and that means the mix is too lean. I see this a whole lot with the V twin bikes. A goldish color is much better , richer is cooler. Chrome will turn blue when it gets too hot. Looks like you are on the right track with your project.

Terry

[rasndas]

Jets came in and I decided to try the rich ones first ( mikuni125). Power was greatly improved on the top end. I ran another plug chop and the plugs are still white. I am assuming with brand new plugs a full throttle 1/4 mile blast is enough to put some color in them. If this is the case it looks like I will have to go even richer. I really thought that 125s would be plenty.