Strange Carburation Issues... need ideas

[81xsproject]

I've been on your side of the argument on this same issue were some JA swore that bench synching was good enough and everyone was politely telling him he was an idiot. I do feel I have a very good bench synch method that has never failed me. The carbs never run perfect without the final synch, but these carbs are experiencing problems that SEEMs out of the scope of the final synch. However, today when I put the carbs back on, if they are still screwed up, I will synch them to rule it out. Thanks for the jab of encouragement.

[Rasputin]

I, for one am very interested in finding out what you find wrong in the end. We did my bike on a dyno with a sniffer etc, and had to drop the jetting to 132.5 from the stockers to get the readings correct. It runs great but the plugs seem very light colored. It acts like it is too lean with WOT as well. I have never really liked the way it performed since we dropped the jet sizes. I am hoping that when you find your problem it will shed light on my setup. Then I can correct mine. Good luck

[Ivan]

I, for one am very interested in finding out what you find wrong in the end. We did my bike on a dyno with a sniffer etc, and had to drop the jetting to 132.5 from the stockers to get the readings correct. It runs great but the plugs seem very light colored. It acts like it is too lean with WOT as well. I have never really liked the way it performed since we dropped the jet sizes. I am hoping that when you find your problem it will shed light on my setup. Then I can correct mine. Good luck

If you are looking to get the EPA recommended 14.7:1 fuel to air ratio, I'd bet the bike will always feel lean on the top end. The best power comes in at somewhere around 12:1 and best economy is closer to 18:1. If your sniffer is looking for the right co and o2 levels to get 14.7, as you can see, top end will be flat. The EPA even allows different mixtures at Wide Open Throttle, since they figure most cars won't run there for any extended period of time. On a scan tool, GM cars (back when I was wrenching them) would show what ratio the ECM was commanding, and above 80% throttle it changed to 12:1.

This write up has helped me immensely in tuning. Also, reading what the very knowledgeable Dan Hodges writes is invaluable.

[renegade_xs11g]

Just to let you know, I only last year, built my own sync tool...

Yes, I too, used to think a bench synch was good enuf' but then I had a problem similar to yours,
ran fine, until I stopped, then wouldn't drop til dragged down, then start all over, drove me nuts, built a tool, WOW, what a diff

[petejw]

just another thought,
have u checked that the slides are all sitting equally
and bottoming.
i cleaned mine several times and hadnt noticed the slides
sitting unevenly with only 1 sitting at the bottom.

[81xsproject]

Issue resolved

Well, I went with my gut feelings and swapped out the innards. All that was in them from the kit was the #42 pilot (yes, it says 42 instead of 42.5). On further inspection, I noticed that these jets had 8 holes in the side instead of the 6 that genuine Mikuni's have. I also swapped out the emulsion tubes for SAG's because I was told that other in bowl parts were heavily corroded. I didn't notice any corrosion, but I figured I would trade them out anyway. Long story short, they started right up and ran like a champ on the test ride. I would be willing to bet it was the kit pilot jets letting all the extra fuel in.

There is one more point I would like to make. If properly done, a bench synch IS good enough to run carbs with no problems. This doesn't mean that I don't condone synchronizing your carbs (it's Colortuning I think is a sham), just the opposite in fact. But, if you do a good job on the bench synch, the bike should run great. The genuine on bike synchronization should just be a SWEET sugar coating to an already okay running engine. Once the idle mixture screws were all at their sweet spots, I turned the idle down to around 700 rpm and it was steady and smooth, all on a bench synch.

I think TC did a write-up on how to do a good bench synch. Thank you EVERYONE (including Renegade )for your help, ideas, and input. This was the first time after an ulra'clean, rebuild, and bench synch that any set didn't just fire right up and run like hell.

[devilschld]

i wish to say thank you for the carb work. i understand what was the first thing i did wrong now was trying to save money and ordering the carb rebuild kits off ebay. if anyone else has carb problems i would be glad to tell u he does great work. i must tell he is a very polite person to deal with.

[Larrym]

Off brand carb kit??

Congrats on this one as it definitely merits another notch made on the workbench.

I have yet to need a carb rebuild kit with all the jets/floats/etc. Some threads have mentioned that members have had difficulties with some "kits" while others say they haven't had any problems with them. (???)

Just for the record here, can you tell me who makes/sells the kit which provided you and the owner with such a delightful carb rebuild "experience?" Was it sold as the right kit for an XS1100?? Who knows? One day I may want to have just as much fun as you did.

[81xsproject]

These were the ones

[DGXSER]

These are for an 80 LH?

Are the carbs from an 80 LH? It seems I gathered from the thread the bike was an 80 model. I have an 81SH and the genuine Mikuni 42.5 pilot jets that were in it had only 6 holes. When I ordered my kits I was told it was a different kit for the 80SG and the 81SH.

Just tryin to resotre piece of mind in my kits. They were not from that store or that brand.

[Larrym]

picture perfect kit

Thanks for the link. I've bookmarked the page and will be sure to look at it before I get out my credit card for a new carb kit. I guess sometimes Less is More.

[81xsproject]

I've said it before and I will say it agian, Kits are not only garbage, but they are a waist of money. The only parts that need to be replaced are the bowl gaskets and the float valves. Everything else can be clean and re-used 98% of the time. On the odd chance that you do need to replace something, get genuine Miki' parts or order what you need from Mikes or crc or one of the other trusted vendors often mentioned here on the site. Not only will it work, but it is usually way cheaper.

[Ivan]

I ahve also found that genuine mikuni jets are available at all the motorsports retailers here in my area. So they shouldn't be that hard to come by. Shop around though, the price varies quite a bit around here too.