MAC 4-1 jetting for GS1100E?

[Anonymous]

Hey guys, I'm trying to dial in my 1100. I've got a MAC 4 into 1 with a removable baffle and the bike's been running really hot and popping like a son of a gun since I bought it. What I've done so far is set the pilots between 2 and 2.25 turns and raise the needles 1 notch. The bike's carbs still have the stock jets and came with the notched needles in Canada. They were origionally in the middle position of the 5 slots so now I'm 1 from the bottom.

Up until now I have not been able to read the plugs. After a ride they'd come out the same as new. What does this mean? I do have a problem with the charging system so I'm running close to a full loss system but I don't see how it would effect the plugs this much.

Thanks for the help, Steve

 

[Anonymous]

Have the carbs been cleaned recently? If its popping on a cruise condition there could be some crud plugging up some of the orfices on 1 or all of the pilot jets, had that one happen to me alot until I switched tanks. Do you have an airbox or open filters? The air bleed will be too big if its stock and open filters are on it. Maybe you'll be looking at a jet kit, but it could be something simple also. More info would give me a better idea of whats going on, but there are guys here that may solve it for you right off the hop. Good luck Steve.

 

[scotty]

How was the plug coloUr before you put the pipe on??
electronic ignitions are sensative to low voltage. Do a plug test after a short ride but have the battery fully charged first.

 

[Mr. Jiggles]

I have a '82 1100E with stock air box/OEM filter and a 4-1 header (not sure of the make). When I put in the dynojet kit I went with one of the lower mains (115 I think) and raised the needle all the way up (C-clip is on the lowest notch). The plugs look just OK. This morning I forgot to shut off the choke after warm-up leaving it roughly at 1/2 to 1/3 choke - enough to raise the idle to about 2K. I noticed that it had more power and ran cooler.

I was considering increasing the mains to the next size in the kit, #130 I think, and lowering the needle.

Jeff

 

[RacingJake]

Drop the bowls and check what size the main jets are. Most likely you'll need to go biggers.

I bet you got 110's in there.

 

[Anonymous]

According to my notes from when I cleaned the carbs last year the jets are 107.5, 140, and 45. I'm not sure which numbers go with which jets but that's what I wrote down. :lol:

The bike came with this exhaust on it so I don't know how it was running previously. The popping is caused during heavy engine braking. It takes a bit of choke to get the bike started (1/2 choke perhaps?) so I suspect the idle is lean too. After raising the needles 1 position is seems to me that the bike has a touch of a hesitation when going from idle to wide open.

Steve

 

[Detman101]

It sounds like it is running a bit lean.
Perhaps going with mains in the 120 range will dial you in right.
I've got a mac 4-into-1 on my gs750L and i use 122.5 mikuni mains.
I believe that is like a 128 dynojet main if I am looking at my conversion chart correctly.

Dm of mD

 

[Anonymous]

The popping is caused during heavy engine braking. It takes a bit of choke to get the bike started (1/2 choke perhaps?) so I suspect the idle is lean too. After raising the needles 1 position is seems to me that the bike has a touch of a hesitation when going from idle to wide open.

If it is popping on deceleration, it is lean on the idle circuit. I would try either the next size up pilot jet or maybe give your mixture screws another 1/4 turn to see if that helps it. I wouldn't touch the main jet until you sort the idle, because the main has no effect on the idle, but the idle circuit does affect the main jet performance. Try running it with a bit of choke left on. Does that improve everything? If so, it is definitely lean and a bit of tweaking will sort that out.

Mark

 

[Anonymous]

I tried slamming the throttle shut with the choke on and I get the same noise. Well, up until the point where I've got the choke on so far that it acts as a cruise control.

What really gets me is that the plugs aren't showing any colour at all. I thought all it took was a few minutes of riding for the deposits to turn up and I can't see how they could disappear.

Steve

 

[pano]

I have individual pod filters and a dynojet kit with a V&H supersport 4 to 1 on my 1100e. My needles are on the 5th notch from the top. The mains that came with the kit for using the individual pods are j138. I increased them to Mikuni 140's thinking they were slightly larger. The bike runs fine but i plan on reducing the mains back to the j138's due to poor highsppeed gas mileage. Plugs look fine too.

During my jetting process I started the needle setting on the 3rd notch from the top per the instructions. Like you I had clean plugs. I also had some midrange sputtering during acceleration just off idle and popping on deacceleration. Raising the needles had more of an effect than anything else except for a good carb sinc.

Before jetting with the individual pods I had the stock air box on with cover removed. The mains I took out were 122.5's and I think I was running just on the leans side. The original jetting was done at a Suzuki shop back in the 80's

 

[mcycle-nut]

According to my notes from when I cleaned the carbs last year the jets are 107.5, 140, and 45. I'm not sure which numbers go with which jets but that's what I wrote down. :lol:

Steve

According to the Suzuki manual I have, 107.5 is the main jet, 140 is pilot air jet, and 45 is the pilot jet. These are stock. 8)

 

[Anonymous]

Thanks for the confirmation, I figured they were stock. Now that fiddling with the pilot screws and needles hasn't done anything I am going to pull airbox out. I want to use black RTV on the carb inlet tubes just to make sure they are sealing well enough. I just don't know who's going to help me get them back on.

Steve

 

[mcycle-nut]

Thanks for the confirmation, I figured they were stock. Now that fiddling with the pilot screws and needles hasn't done anything I am going to pull airbox out. I want to use black RTV on the carb inlet tubes just to make sure they are sealing well enough. I just don't know who's going to help me get them back on.

Steve

I dunno if that's such a good idea. Doesn't gas eat that stuff? :-k As far as putting the carbs etc on, I just loosened the airbox an pushed it back as far as it will go, put the inlet tubes on the engine, and then put the carbs on. It's really not that difficult, then again, I have an '83, not an '81. Still, it's harder to do than my 750 with pods! Oh yeah, REMEMBER TO INSTALL THE THROTTLE AND CHOKE CABLES BEFORE YOU PUT THE CARBS ON! Otherwise, you will be kicking you ass around the block! #-o Believe me, I know.

 

[Anonymous]

I'm not sure if it's a good idea either but when I had the air box off the last time it was easy to turn the inlet pipes around inside of the first of TWO airboxes on the 1100. Maybe they are supposed to be a little loose? It makes me think the bike is running lean because of the fit and the bike sounds like it's running pods when I crack the throttle open.

Steve

 

[saaz]

Some of the popping may be due to air getting into the exhaust. There may be a leak around the exhaust gasket. If the bolts seem firm enough, don't try and do them too tight!, replacing the gaskets may help.

At the moment I have to clean out my carbs as I am getting backfiring etc. Some junk in the system so time to fix it properly.

 

[Anonymous]

I went ahead and tightened the exhaust the other day. While some of the bolts were a little loose there wasn't any change in the noise BUT the next day the exhaust baffle broke loose and got sucked 1/2 inch deeper into the cannister. Today I pulled the baffle out and drilled another hole in it so I could bolt it back on and the result? The bike is running kinda bad...hopefully when I check the plugs I will find that it's running rich.


Steve

 

[Anonymous]

Hehe, 5000 km later and I'm still riding around with the bike running lean. Atleast I understand the problem a bit better now. One issue is that the slip-on is leaking a bit so I will have to cut off the cheezy MAC clamp and get a band clamp to cover up the slots. I'll fix that up on Monday. Since posting last year I've changed the manifold gaskets and shimmed the air filter to fit better in the box. My petcock is messed up so I've started running it on prime and I've blocked off the vacuum lines. The vent lines are not on the carbs but the T fittings are still in place.

Now back to the jetting. When I'm cruising down the highway at 4000 RPM in 5th (roughly 110 km/hr with stock gearing I think) the bike is running well. All it takes to maintain this speed is the lightest of pressure on the throttle. If I actually turn the throttle I will speed up. I can burry the tach in the first 4 gears but I haven't got enough power to burry 5th.

Do you guys still think jumping from 107.5 up to 120ish Mikunis is the way to go? I was at the dealer today and they said they had lots of Mikuni jets for snowmobiles. Will these be the same as for our bikes?

Thanks, Steve

 

[Dink]

Mikuni jets are even easier than that, there are two types one is the nut type, the other is flat, our bikes with CV carbs take the flat ones.
BTW I believe 115 would be worth a try before 120.
Dink

 

[Anonymous]

Thanks Dink. I went to Mikuni school today searching for some mains. There are only two more places in the city to check but nobody seems to have enough of each size or the correct type. Turns out there are big and small round jets and hex jets. Supposedly the small jets will replace the big jets but I'm not sure if they'd be able to hold the washer in place on our bikes. The best thing is that jets are cheap. 3 to 5 bucks a piece from what I've seen.

Steve

 

[Anonymous]

The small ones do fit! Now if only I had a chain on my bike to test them out. :x

Steve