Another Jerk asking the SAME Carb Questions

ok, i realize that this is probably the most asked question on this site and that there are at least 5,000 posts already pertaining to this subject. I also own an dog-eared copy of the Haynes manual.

Forgive me.

I have cleaned my carbs by taking apart every assembly except the air/fuel mixture screw assembly and cleaned everything and now have reassembled. However, i have done nothing to sync my carbs. Before i started i found some great posts about bench-syncing with playing cards or paperclips but for the life of me I cannot find them now.

Can someone please tell me what to do next? My manual says i need several early 80's aerospace vacuum gizmos that i probably cannot find outside of the Smithsonian. Certainly you guys can tell me how to go about this better than the manual or point me to a post on this site.

oh yeah, its an '81 650 maxim.

Your collective infinite patience with dumb questions from beginners is humbling.

Thanks,

Mike

 

If you haven't removed the mixture screws they're not clean. Trust me, take them back off and do it right.

Carburetors are still synchronized the way they were in the '80s. Get yourself a vacuum gauge or a set if funds allow.

 

The, How to bench sync you carbs, by Gamaru, is about half way down on the first page of the FAQ suggestion forum. That will tell you how to do the bench synch. I assume the vac gizzmos you are talking about is the manometer for synching the carbs. You can make a 2 bottle system you self, that how to is also on the first page of the FAQ suggestion forum.
1. Be sure you have the little plugs over the mixture screws removed b4 installing carbs, or you will be pulling them again.
2. Make sure you have the enrichment well & little passages clean & can spray carb cleaner in one hole & shoot a stream about 10 ft out of the other. (watch your eyes).
3. Turn your mixture screw down till they bottom out softly, DO NOT TURN THEM DOWN TIGHT. Be sure you count how many turns it takes on each carb to get to the soft stop & record for each carb.
4. After reaching the soft stop on each carb turn each screw out 2.5 to 3 full turns out. This is a starting point not the end point.
5. Fire her up & let her get nice & warmed up before any more adjusting.
6. Set your idle at about 1050-1100 RPMs
At this point you wil need the 2 bottle sync setup to synch your carbs.
7. To synch you will start with 3 & 4 as 3 is the master & not adjustable, so your are synching 4 to 3. Then you move the hoses & synch 1 & 2 then synch 2 to 3. This should have you in the ball park.

Do some plug chops to make sure your are not lean, ge a nice even tan on the white insulators. If a plug is white your turn that mxture screw out about 1 degree not 1/4 turn, go small. If plug is black you turn the screw in the same amount. Keep notes on each carb how much you have turned each screw in or out. Once you have the nice tan color you will probably need to recheck your synch with the 2 bottle system & then you should be golden.

Hope this helps & if I have anything out of order one of the gurus will chime in.
Good luck & hope this helps.
Gregg

 

http://www.focusfanatics.com/forum/show ... p?t=214603

Vac guage for $30 being sold by a friend on the Focus Fanatics forums.

 

so i guess i DO need a vac gauge. i will try to pick one up at Advanced Auto tomorrow (or buy this one on the focus site). i didnt touch the mixture screws because my book told me not to. But clearly that is the way to go, so i will start on that tomorrow as well. thanks for pointing me in the right direction guys.

i suppose i will need this yics tool as well....? also, what is the best way to adjust/measure float height, or is that what the vacuum gauge is all about?

Thanks again,

Mike

 

Here’s the bench synch link.
It’s in the FAQ Suggestions section.

http://xjbikes.com/Forums/viewtopic/t=6366.html

Works great, thanks Gamuru.

ab

 

Mike; You only need the YICS tool if you have a YICS-motored bike.

As long as you record the positions of the mixture screws, and use those as a reference point when you put it back together you'll be fine. I said "reference point" because the perfect state of tune for your bike NOW is probably NOT going to be achieved with the original factory settings.

Float heights are best checked WET, using gas and the "clear tube method" that is described in your manual. It's better to do it with the rack off the bike however, since any adjustment necessitates removal of the carb bowl.

 

My fave el-cheapo carb sync tool

http://faq.ninja250.org/index.php/Is_th ... nc_tool%3F

 

Fitz,

does the 81 650 Maxim come equipped with the YICS engine? is there something i should look for to tell me for sure?

thanks guys, got the vacuum gauge and i am about to pull the mixture screws now.

Mike

 

wow. mixture screws at 2 &3/4 turns, 3, 4, 3 &1/2. no wonder this bike won't run. i am going to teardown the carbs again to be sure that i have the mixture screw channels appropriately cleaned.

thanks again-

 

The YICS motor says YICS all over it; on the left (ignition) and right crankcase covers and cast into the valve cover. If your valve cover just says "Yamaha" on it then it's not a YICS motor.

YICS motor:




NON-YICS motor:

 

Manuals tell you not to touch the mixture screws to satisfy the EPA in the 80's. In some cases they covered them. They didn't want people playing with the mixtures and making more pollution, and these bikes came from the factory a little lean. It's a good thing you didn't have any trouble getting them out (there are more threads on that one, in fact I think Rickomatic wrote one in the FAQ, as you do not want to strip the heads of the soft brass screws).

 

Wow, sorry for to ask the obvious. mine is definately YICS. I will contact Chacal about one of those tools. My mixture screws came out easy but were filthy (i guess you guys new that already). Back to the bench...

By the way, Fitz, your engine in the top picture looks amazing!