MAC 4-1 jetting for GS1100E?

[Anonymous]

The 115s aren't scary enough, I'll have to go bigger. 5th gear roll-ons are actually pretty weak. Atleast I've got one black plug now, I've never had that before. Does anybody remember which way you turn the pilots to get them to richen up? I've got them at 3.5 turns as per the manual but #2,3,4 are white. I synched the carbs at 3000 RPM with the middle ones a bit lower.

Thanks, Steve

 

[Anonymous]

I went for another ride so there's a bit of an update.

First, When I'm WOT in 3rd at 8-9 grand the bike surges. I tried looking up the term "surging" but it's used too often. It's like the bike doesn't want to go into the red area anymore. What do you guys think this is indicating?

Second, I turned the pilots back in one turn. The popping when I snap the throttle closed has come back. Does this mean I need different pilots?

Thanks, Steve

 

[Anonymous]

The saga continues... I dropped the clips down to the bottom (1 notch) and I'm getting better midrange. I turned the screws in 1/2 to 3 turns out and I'm getting a better start but now I'm getting a quick sputter when I'm open the throttle for a roll on. Once that passes I'm running better than before. Still can't do much better than 7000 RPM in 5th, I had it up to 7500 for a touch tonight. The 115 mains seem to be better but I've got 120s on the way. Ah well, the engine should be cool enough to get in there and check the plugs as well as turn the screws in another half turn.

Steve

 

[KEITH KRAUSE]

Are you re-jetting for a pipe only? Stock airbox with the lid still on?
As a general rule with your carbs, you can go to about 4 turns out on the mixture screws. If the results are still too lean, you go up a step on the pilot jets.
I test and get plug reads for the jet needle at 1/3 throttle. Get some tape and mark the grip and housing to be sure. Chop the bike off for the most accurate reads. Take a piece of hose and a rag with you to help you remove/install the hot plugs. After the needle circuit looks good, I then install the largest main jet I can that doesn't create any bogging during a full throttle roll on in 5th gear at 60 mph or close. The bike should pull strong. Some bikes won't redline in top gear on level ground.
I'm assuming all other work has been done correctly, carbs clean, floats adjusted, synch, ignition timing, good spark at all 4 plugs, valve clearances...

 

[Anonymous]

Hi Keith,
My bike is running the stock airbox with an OEM style EMGO paper air filter. The cover is still in place as I do not have the desire to do a complete rejet of the bike. The 4 into 1 still has the baffle in it too. My goal is to get the most fuel possible through this setup.

I have synched the carbs a couple days ago but I need to do that again since I've changed a lot of different things. The valves are within spec as I checked that when I had to inspect the cams last week. The floats should be okay, you explained to me how to check them last year. The advance has not been checked, I don't have a strobe. It looks like my cam chain is stretching though as my cams notches are out of alignment just a touch. Plugs and caps are about 5K km old.

I think my problem is the mains at this point. I get the impression that I am not burning enough fuel to get past 9000 RPM in 4th or 7500 RPM in 5th. Yep, I can't accelerate in 5th when I upshift so I suspect I need more fuel. Does this make sense?

Cheers, Steve

 

[KEITH KRAUSE]

I don't know what you mean by "I can't accelerate in 5th when I upshift so I suspect I need more fuel".
I wonder if you've got good fuel flow? 5/16" fuel line? New vacuum line? Clean petcock?
I find it unusual you have had to raise the jet needle 2 positions just for a baffled Mac pipe. This too could be a sign of poor fuel flow. I'd like to know what the plugs say at 1/3 throttle now.
The mixture screws at 3-4 turns out could be considered normal.
I would guess 2 full sizes up on the mains (117.5) or close.
I wonder why #4 is running rich if it's been subject to the same maintenance/tuning procedures? Good spark and solid/clean connections? Same vacuum as the other cylinders?
Some 1/3, full throttle and minimum throttle plug reads would be nice.

 

[Detman101]

For a MAC 4-into-1 pipe with the standard baffle you will be running 115s or 117.5s for the mains.

The 115s will be a tad on the leaner side if you are using the EMGO pods.
The only way to compensate for it would be to have your needles in the highest position.

The 117.5s will be perfect if you're running EMGO pods and have stock needles. For adjustable needles you would have them 2 notches from being raised to the highest position.

But that is just my experience. I'm running 115s in my cv carbs and the bike goes perfectly at WOT with them. However, using the 115s I'm at the highest adjustable notch on my needles.
I believe that if I went to 117.5s and lowered my needles two notches it would give me more adjustability should I ever want to swap exhaust cans on the MAC header.


For a MAC 4-into-1 pipe with the RACING baffle you will be running 120s or 122.5s for the mains.

Good luck.

 

[Anonymous]

Hi Keith,
I'll get back to you on the plug readings some time during the weekend. I'm going to be working a few evening shifts so I won't be able to ride during daylight. How far should I travel at each throttle position before killing the engine? The last two plug reads after normal shutdowns showed that all of the plugs were black. The one black plug previously may have been airbox related, I found that the two outer carb tubes going into the airbox were not sealing properly.

As for fuel flow, I put in a new petcock with smaller pick-up tubes (that you advised against). You can see a photo of it in the Tips and Tricks section. The bike has not shown any difference in performance and the petcock is meant for Harleys up to about 1300 CCs.

What I was trying to say before about upshifting is that my maximum roadspeed is the same in 4th and 5th gear.

Current carb settings:
Mains - 115 Mikuni
Adjustable needle - raised all the way, stock was middle
Float level - stock
Vent tubes - gone, tees still in place
Pilot screws - 2.5
Float needles - new
Other jets - stock

Cheers, Steve

 

[KEITH KRAUSE]

I usually go a couple miles for each circuit read, though the pilot circuit can be difficult and the reads fluctuate some.
Back on the 23rd you had 1 black plug at #1 and 3 white plugs. That could have been a poor carb synch, maybe. But since then you said you raised the needles one more position, which is as rich as the stock needle can go. Though you say the performance seems OK, all the plugs are now black. Regarding the needles, I still need to know what the 1/3 throttle position reads will say and the carbs MUST be synched to get accurate reads. I think your black plugs will probably not improve much at 1/3 position. As I said before, I think 2 positions richer on the needle is too much for just a pipe. Just my opinion. Do the 1/3 test and we'll know. Mark your throttle and housing to be sure. As I tell everyone, I can do these tests where I live. It may not be as safe for you. Be careful.
I like to get the needle right first, then I simply install the largest mains I can without creating any bogging at 5th gear/60 mph roll ons. Works for me. If we lower the needles 1 position and the plugs look acceptable, and then the mains are determined as I said, the bike should run well at higher speeds.
I'm not sure if your model with stock gearing will redline in 5th gear/level ground. Some bikes won't. My bike runs well but won't redline in 5th. It'll go about 7,700 rpm's according to my tach and may possibly hit 8,000 but I don't want to push it (8,500 is redline). Maybe your model does, but I'm just mentioning it in case you're expecting too much. I do know your bike will go faster in 5th than in 4th though. I still don't trust the "aftermarket" fuel valve you're using. I hope it's not causing a problem. Re jetting can be difficult enough without trouble shooting being mixed in.

 

[Anonymous]

It was my impression that these bikes could go 240 km/hr stock which is 9000 RPM in 5th gear. It would be a real dissapointment to find out otherwise. Up until now I have not been giving roadspeed numbers because my speedo is far less accurate than my tach. Anyway, I just did some number crunching with GearCalc and it's showing my top speed to date has been 119 MPH (191.7 km/hr). I think that's pretty slow considering the speeds some members have been bragging about achieving.

Steve

 

[gspaul]

My bike will do nearly 200kph( Speedo reading), that's in theory of course.I allway's observe the speed limit.( Well I can see it, but it's a blur)
So I can not see a reason you won't be faster!

 

[KEITH KRAUSE]

What's redline on your bike Steve?
I don't know about top speeds, but I'm just saying that some models won't redline in 5th gear. And yes, a lot of top speeds you see/hear is bragging.

 

[mark m]

It was my impression that these bikes could go 240 km/hr stock which is 9000 RPM in 5th gear.

That works out to 149mph, Steve. Which is significantly higher than the 135mph or so that I have seen in magazine tests from that era. My 1100 will easily pull an indicated 9500 in 5th and that is showing a bit over 210kmh at that point. It was still pulling hard and would have easily made 10,000rpm if I hadn't backed off. I believe my tach is reading a bit high, though, and a disassembly and clean up is in order, but I just haven't got to it yet. When I get that done, hopefully I will have some more accurate info on this.


Mark

 

[KEITH KRAUSE]

Just another quick though Steve...when you bench synched the carbs, did you adjust the throttle plates for the fully open position correctly? You can adjust them "too open" and possibly cause your top end complaint.

 

[Anonymous]

I should be able to run the bike on Saturday. I told my boss to work me like a government mule until the GSR Convention and she took me seriously. :lol:

Cheers, Steve

 

[Anonymous]

Keith: I finally got it done!

Minimal Throttle gives me two flat black plugs and two slightly blacker plugs. (2.5 turns out on pilot)

1/3 Throttle gave me 4 flat black plugs indicating rich but not really really rich were you'd see they are fluffy and thickly covered. (lowest notch on needles)

Full Throttle gave me 4 white plugs. I dyno'd my bike yesterday and got a reading of 83.67 HP so I'm short on power as you'd expect from the plugs. (Edit 115, not 117.5 Mikuni small round main jets)

The bike hasn't been sync'd after the last pilot or needle clip adjustments so I believe that's why my idle colours are a little different.

What do you think I should do next? Move the clip back up a notch and get bigger mains? I think I'd prefer to try different mains before trying another petcock.

Thanks, Steve

 

[KEITH KRAUSE]

Keith: I finally got it done!

Minimal Throttle gives me two flat black plugs and two slightly blacker plugs. (2.5 turns out on pilot)

1/3 Throttle gave me 4 flat black plugs indicating rich but not really really rich were you'd see they are fluffy and thickly covered. (lowest notch on needles)

Full Throttle gave me 4 white plugs. I dyno'd my bike yesterday and got a reading of 83.67 HP so I'm short on power as you'd expect from the plugs. (117.5 Mikuni small round main jets)

The bike hasn't been sync'd after the last pilot or needle clip adjustments so I believe that's why my idle colours are a little different.

What do you think I should do next? Move the clip back up a notch and get bigger mains? I think I'd prefer to try different mains before trying another petcock.

Thanks, Steve

Hi Steve. Looking back at previous posts, the jet needles were too lean at position 4. Though you didn't do a 1/3 throttle test at that time, I think your performance description suggested the needles were lean then. Now your tests show on the rich side with the needle at position 5. So it's obvious, if the stock needle is to work, you need to try position 4 1/2. That means adding a jetting spacer directly on top of the e-clip, leaving the clip in the 5th position. Spacers are about .022" thick.
For the main, you're getting pretty good flow increase for just a pipe. If 117.5 is as lean as you say (white), then I'd try a full size up, 122.5.
For the lower throttle/pilot circuit tests, I believe by lowering the needle 1/2 position, you'll see some needle overlap effect and that will lighten the plug reads some. Leave the mixture screws where they are and wait to see what the needle adjustment does for the minimal throttle position reads. Remember, a vacuum synch is critical for accurate reads for the needle/pilot circuits. It must be done. Besides uneven reads, how can you really know which levels to go by? The "higher ones" or the "lower ones"? They must all be uniform.
Hope the main jet suggestion works. I don't want you wasting your money on my suggestions only. It's trial and error. Some shops will swap the jets if you didn't damage them at all. Another reason I like jet kits.
PS: I sure hope that fuel valve isn't causing the lack of top end. We'll see what the larger mains do. Good luck!

 

[Anonymous]

Oh so close, I went from 115 (thought they were 117.5 in the last post but I corrected it) to 120 mains and the bike wouldn't redline in any gear. It would bog down. I removed the airbox cover and it was running just like the 115s with the cover on. I may have picked up 250 RPM in 5th gear but perhaps I'm just getting bolder and braking later. :twisted: I didn't get any plug reads tonight because I was passing cars before every run and there was also an airport cop watching me. I didn't feel too safe stopping. :lol:

I'll have to decide what to do now...if I can get a partial refund on my 115s or 107.5s I'll swap them from 117.5 If I can't do that I'll try to swap with a member here and run without the airbox cover (assuming it shows better WOT plugs) until then.

I won't have another day off for atleast a week so testing is going to be at a standstill again...I do plan on putting in half thickness washers.

Steve

 

[wayne cooper]

Quick thought

Quick thought

All the talk about max speed leads me to one thought-Wheel bearings. I know they will not effect your MPH but a speed wobble can seriously effect your future. 8O My one front was shot with only 32k on it. About $15 per side at bearing supplier. Seems a lot of people overlook the little devils. If nothing else this little note might be read by someone who hasn't checked theirs. Ok a little question- can the non-adj. needles be swapped out for adjustable needles or would I have to get the complete unit?

 

[Anonymous]

Hi Wayne,
If your bike was origionally sold in Canada it will have adjustable needles. I hear that the jet kit needles have a different taper. Keith has also told me you can shim non-adjsutable needles. Thanks for the tip about the wheel bearings too. I check that stuff once in a while but not on a daily basis. My bike is getting ready to roll 86K and it had OEM bearings when I put on the tires last year.

I'm starting to think that the engine is worn out. It has good compression but it sure is burning a lot of oil. I think I've been topping it up after every second tank this year! I missed a shift while going down hill today and pegged the tach at 12 grand so the engine seems to be mechanically sound even if it's a little loose. :lol:

Steve