MAC 4-1 jetting for GS1100E?

[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

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

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.