MAC 4-1 jetting for GS1100E?

[KEITH KRAUSE]

I'm not sure what's going on with your bike Steve. You say that 115 mains give poor top end and white plug reads, but 120 mains create a bog? You didn't take a plug read with the 120's but I'm assuming the bog was at full throttle? The bog would be a rich condition and the plugs would be dark. One full size up, (115 to 120) would not cause such a drastic change, in my opinion.
You have just mentioned that you suspect the motor is tired and is using a lot of oil? This could cause your problem of course. Oil in the mixture will compromise combustion. Less than optimum combustion will lower the top end performance for sure.
I have to say again I find it odd that you've had to raise the jet needle 2 positions for just a pipe mod, and in my opinion, the Mac's don't flow that well. Even if it was a Kerker or V&H pipe, 2 positions richer is odd.

 

[Jethro]

Plug reads are too hard for me. How do you test the main jet circuit? A couple of miles? I don't know if I can bring myself to ride at WOT for a few miles- guess I could use the highway at 3:00 in the morning and hope I don't get arrested! That's at least 130mph for me.

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.

Just for reference Steve, my 81 1100E would pull at about 125mph max when I was neck and neck with my buddy who actually had a speedo that went over 85mph. That was when the bike was in excellent running condition and stock gearing and jetting.

 

[Hoomgar]

Plug reads are too hard for me. How do you test the main jet circuit? A couple of miles? I don't know if I can bring myself to ride at WOT for a few miles- guess I could use the highway at 3:00 in the morning and hope I don't get arrested! That's at least 130mph for me.

You really need a Dyno if you can find one. That's the ticket.

 

[KEITH KRAUSE]

Plug reads are too hard for me. How do you test the main jet circuit? A couple of miles? I don't know if I can bring myself to ride at WOT for a few miles- guess I could use the highway at 3:00 in the morning and hope I don't get arrested! That's at least 130mph for me.

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.

Just for reference Steve, my 81 1100E would pull at about 125mph max when I was neck and neck with my buddy who actually had a speedo that went over 85mph. That was when the bike was in excellent running condition and stock gearing and jetting.

At least your speeds are more believable and I'm sure, truthful.
There is a lot of exaggeration here me thinks. I've ridden a few of the models and they were good running bikes that simply couldn't go as fast as some here say, at least not on level ground. Maybe down a steep grade. The only thing wrong with this bragging is it makes others think something's wrong with their bike. A few mph is nothing. We all know there's some difference between bikes, even good running ones. But saying your bike will go 138 or whatever when it's probably good for only 125 is just BS.
I won't brag up my lightly modified '79 1000's top speed, but I will say for its mod's, (1085/pipe/pods) in its class, I have one of the best running 1000's on this planet. Over 26 years, I've gotten into a lot of little "trophy dashes" and done well. It runs strong and I fool a lot of people on our rides. But I can only go about 125 on level ground, if you believe the speedo, which seems about as accurate as the guys next to me. I can't get to redline in 5th gear either, but I seriously doubt there's something wrong with my bike. But to read some of the claimed top speeds here, you would think there's something wrong.

 

[Anonymous]

This is helping me out here guys. I have the same kind of issue with my 81 GS1100E. Although the motor has only 17k of baby ridden miles, V&H pipe and pods on stock carbs, it has some running issues I'm dealing with. I'm learning about the jets and needle info pretty fast just with this topic. Make this topic sticky or archive it

 

[Anonymous]

I finally got the bike out again and was able to do pretty good with the airbox cover on. It was raining out and I couldn't see very well so I didn't do a 5th gear run but 3rd or 4th was pretty good. I was getting surging at the top end but it could have been a slipping rear wheel or something.

That's it for tuning for this year. The bike is running a bit rich (no black plugs today but dark dark brown) and I'll have to live with that. I haven't ridden nearly enough this year partly because of the time I've been spending fooling with the carbs.

Maybe I'll restart this thread next year and make it a 3 year saga. 8O

Thank you for all the help, Steve

 

[KEITH KRAUSE]

OK Steve. When you're ready, let us know if you want more help.
There's still some adjustments you haven't made that can make it right.
If it's rich from just puttin' around town, maybe a turn in on the mixture screws will help for the time being?
By the way, this topic is effected by that "no posts exist for this topic" message. When I click my e-mail topic notification, that's the message I got. So I had to get here the long way. So others may not have sent replies for this reason. Enjoy the rest of your summer!

 

[Jontheguru]

Mac Header reconstruction

Mac Header reconstruction

I'm in the process of finishing the immediate modifications to my 83 1100E. I purchased what I believe is a mac header, it looks almost identical to the ones for sale in dennis kirk. The baffle is nothing more than a squished pipe leading into a chamber than exiting out the end in an "s" shaped flow. I opened up the filter end of the air box so there is no restriction while still maintaining the integrity of the box immediate to the carbs. I have a stock replacement K&N filter for high flow into the latter chamber. I installed a dynojet jet kit as instructed. I tried various main jets and ended up with 127.5. It would not accept the 132's. The mid range was a punch, very strong, but the bottom end was non existant and would not run. I put in the 160 air jet to lean out the bottom end, better but still ran like crap. I pulled the baffle out of the pipe and was stunned to see the wacked configuration of the system. It was a risk especially when considering the complexity of pipe design but I had to try something. Out of space, will finish on next reply. Jon.

 

[Jontheguru]

Mac Header reconstruction

Mac Header reconstruction

As I was saying, I cut the two pipes out of the two round baffle plates and welded in the same diameter pipe, except I ran it straight through. I than drilled holes in the newly installed pipe and wrapped packing around it and reinstalled. It looks very close to the design of the kerker header my brother has on his 86' GSXR. Most oldschool performance pipes have straight through baffles, just like I made. It tool only a few carb adjustments and now it runs smooth and comfortable, even on the bottom end. The needles are on the 4th from the top and the air screw is out to 4 turns. I'm not sure how much of a difference it made on the top end because it wasn't dialed in before I made the change. The mid range doesn't seem as strong but that could be due to the drastic punch that was made from a non existant bottom end to a powerful mid. The true difference is that it actually runs pretty darn good on the bottom end and overall. In retrospect, I wish I dialed it in before the change so I could properly gage the difference, oh well, It's got plenty of power and is quite smooth. If anyone has any comments please let me know. p.s. I'm at sea level here in Portland OR.