1982 XJ650 Rejetting after changing exhuast

After rebuilding my 82 650 maxim I replaced the old rusted out stock exhaust with a MAC 4-1 exhaust (http://www.nichecycle.com/ncs/categ...50-900-seca-maxim-blk-by-mac-performance.html), the intake is still stock. I left the pilot jets stock and increased the mains to #112. I synced them and tuned using a colortune. This winter I replaced the 4-1 with a MAC 2-1 (https://www.amazon.com/gp/product/B0716X1N4Z/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) and it seems like it has a loss of power since changing them. I haven't started tuning the carbs for the new exhaust yet, but from looking at the plugs, they seem a little too clean and I'm thinking its a bit too lean. After about half throttle, there doesn't seem to be any increase in power. I'm not getting any deceleration popping and the chrome isn't changing color so I don't think it's excessively lean. Should I go up to #114 before I start tuning or should a pilot adjustment and sync be sufficient?

 

when you get the the point where 1/2 throttle is flat, just touch the choke. better if your lean or worse if rich

 

Ok, I will try that. I think since its easy enough, and I have all my stuff out from helping a buddy with his Fazer, I'll do a carb synch first and just see if that helps.

 

I ended up doing a full sync, colortune, sync routine and found that my pilots were actually running a hair rich, about a half turn or less on each cylinder. The sync was a little off but not crazy. My low end power improved but mid to full is still flat. I tried adding a little bit of choke, just barely cracked, and the engine just sputtered and ran pretty rough, I think I still have some gunk in the starter jets. On the highway at fifth gear I opened it up to full throttle and had very little acceleration also felt like it was surging. Seeing as my pilots were rich, I'm now unsure if my main jets need to go up or down. I know surging is a sign of lean and the plugs are still indicating lean so I think I need to up the mains.

 

if you want to keep trying easy things, stretch some t-shirt material over the airbox intake, that's going to get you richer.
think about a hot engine likes leaner, a cold one likes richer. so if you can tell a change as it warms up, that's a clue
changing jets isn't that bad but if you need to change them back, that really sucks

 

Sorry to bump old thread, but did this ever get solved? I'm having same issues, waiting on jets to show in mail! I hope they fix this!!

 

Plese start a thread for your machine.

 

Getting ready for the upcoming season and revisiting this issue. I ended up bumping my main jets from #112 to #114 and retuning. My lower end throttle response improved slightly but I was still getting little to no power past half throttle. The plug insulators were a nice browned marshmallow color vs the clean white they were before so there was an improvement there. Decided to say good enough and left it that way till winter.
Before it gets too nice outside, I want to iron this issue out. I'm thinking I may need to go back to the stock #110 mains, since most people here running stock intakes and 2-1 exhausts don't to change jets in the first place. Any thoughts on this?
Also, for those who use a colortune, what is the optimal color you're looking for? I usually will richen the pilot until I see some yellow and then lean it back slowly to the point the yellow goes away.

 

bunsen blue
you are doing it correctly

 

Bigger jets didn't fix my 5000~6000RPM sputter or lower throttle. Went back to stock jets (pilot/main) tried everything from re synching carbs to colortune and checking everything it could be. Come to find out we have valve clearance issues. So if you haven't checked clearances do it now. Thanks and sorry to butt in.

 

valve shim is the first thing everyone should do. followed by a compression test.
then check everything on the scheduled maintaince list.
the motorcycle is a collection of systems which all join together to make the bike run.
just like when you clean carbs, dont forget to clean/rebuild gas cap. clean out the tank and add a filter to the fuel line.
check to see if ignition system components are all in spec. clean all connecters that go to the ignition system
check to see if the charging system components are in spec. clean all connectors that go into the charging system. dont forhet all the ground points

 

Followed by a good old self flagellation session...
Personally I would check valve clearances, then the obvious and easy - apply some logic to it. But hey, we're all different.

 

I know :'( That should have been the first thing we did and I'm kicking myself right in the ass for it now that we didnt. But the bike ran so good we didn't think we needed to until we tried to put this header on and it unveiled some tiny underlying issues which made sense on some of the other tiny underlying issues I was having. So now I'm waiting on shims. Hopefully it clears up some of the hiccups. There's a reason why you guys are professionals. Thanks!

 

Okay I'm seriously hijacking this but I feel like I could help. So, I purchased a mac 4-1 with the help of some awesome people on this forum and I was excited as hell. But after installing the header my bike began to experience some weird issues (hidden underlying issues) hence me commenting on this post. To be short about my issues, the bike would stumble throughout the rev range and especially when the yics system really wanted to sing and it was super lean in WOT. Tried everything to fix the problem, 116 Jets, 42 pilots, stock filter, washer needle method, multiple synchs, but we couldn't get anything to show a change regardless of what we did. Did the valve clearances and it really helped!! Everything we did to the bike after made a change in the way it ran so from here it was real trial and error!! We ended up running 112 mains, 40 pilots, K&N air filter but still had a slight stumble off takeoff and to about 4000 rpm and we about drove ourselves mad trying to figure this out. Super mad!! But I just got my Y-13 needles today from Len in the mail and installed them and the bike runs perfectly! No stumble throughout the entire rev range and has plenty of power! Our findings on this was the Y-10s were too rich too early from the taper on the needle almost mid way causing issues within the rev range, the Y-13s have a much more even taper allowing smooth transition of fuel and rev range. So just for an update and maybe I can help a few out on here that have similar problems! Thank you so much Len and all who are on the forum lending a helping hand and watching out for one another! Ride safe out there!

 

just a note some of the xjs dont run well on a k&n air filter when people switched back to the oem style problems went away . just suggesting it would be cheaper to try this first before changing needles.