Carb butterfly seals and carb set-up after disassemble??

[XS650D]

Hi Folks
Just picked up a 77D,relly nice but needed carb work,so pulled the BS38,s off and pulled apart to clean cheak floats ect,found butterfly seals shot and got some new ones BUT after pullin the originals cant remember if the open end or flange on the seals faces in or out also how do i line everything back up,unfortunately i dident really pay attention to were each butterfly plate is set ,is there a set point.Had a buddy helpin me and and he backed out the balance screw in the centre to be able to fit the hinge back in but now both carbs are set differently,totally lost now,plus the balance screw is now facing down in stead off up after springs r connected,is there a step by step process in getting thease carbs balance again.Thx warren

 

[gggGary]

First rule of working on something you are not familiar with; take apart ONE at a time.
The seals are shaped like a U, the opening faces out. With the carb upright looking in from the engine side, the lettering on the butterfly should be visible and upright.

The shaft has to be turned so the balance screw head is up.

This should help.



get everything back together like the picture, shaft springs and all. Have the butterfly screws snug but not tight. With the idle screw backed out and the synch adjusted so both butterflies are fully closed, snap the throttle open and closed a couple of times, then tighten the screws and stake them. now tighten the idle screw so the LH b-fly just starts to open, adjust the synch screw so the RH matches. looking into a bright light with the tiniest sliver of light visible helps get them very close. Finish on a running engine.

Too bad you didn't read the carb guide in tech that explains all this.

 

[XS650D]

Thx thats great,quick question regarding base jetting,the prev owner has installed Mixes xs pods and pipes from a BSA (pea shooters) with very little baffle,i noticed that jetting is stock for a 77D, 25 pilot, needle on middle clip and 125 mains,fuel screws out 2.5 turns,based on the way it runs and plugs its running lean,what would be a good base start.It hesitates off the line and again at approx 5000 rpm and up.No rust in tank,new plugs and wires,valves timing and cam chain set to spec.thx warren

 

[XSLeo]

Throw out those crappy XS pods and get good filters, Uni-Filters.
Then step up one on the pilots. Your up one on the mains already, might try another size up.
gggGary hinted that you should read the carb guide, I recommend it too. It has a section on tuning.
Leo

 

[5twins]

While most of the 650 carb sets do OK with one or two up on the mains, the '76-'77 set is different. It came stock with a 122.5 main, the smallest ever put in the 650. It usually needs mains in the low to mid 130s for mods. I would start with a 132.5, then try 130s and 135s to verify what works best. You will probably need to lean the needles a step as well.

 

[XS650D]

Thx,Got a range of main jets from 125 thru 132 and pilot jets next 2 sizes larger cant remember now,cleaned the carbs good,reset floats ect.Should i start with jet needle in middle,or could i go 1 clip richer (raised needle) and go from there with mains and pilots.
Thx,Great site by the way ps just set the valves to 0002 on intake and 005 exhaust with the procedure i saw on u tube were u adjust based on the largest tolerance that u can find by turnin the crank and cheakin the gap then adjust from there,guy apparently worked for Yamy thru out the 70s and 80,s and thats how they taught him the procedure.Pretty easy that way,he also states that u can go to 004 on exhaust side using this method on ALL 650,s regardless off year and it will run great,any thoughts on this.

 

[5twins]

I think .002" is too tight for the intakes. I'd go .003". Personally, I run .004" but I have the elephants foot adjuster screws installed which run quieter. Run too tight and not much oil will get in there to keep the parts lubed.

If anything, set your needle clip one step leaner, not richer.

 

[XS650D]

Am i ok with .005 on exhaust valve then,and go back to -003 on intakes thx 5twins

 

[5twins]

The exhaust spec for most years was .006". It's accepted practice to use .006" on the exhausts and .003" for the intakes on pretty much all the years. An exception would be if you had an aftermarket hot cam that came with instructions to set clearances differently.

 

[CDNTX650]

Did you get rid of those junky pleated pods yet? They will make tuning a nightmare.

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[XS650D]

Still got em,just tryin to get it to rum rite now and then start upgrading,they cant be that bad ,says on his site there bench tested and tuned ect ect,but will get the uni pods eventually as ther pretty cheap

 

[5twins]

Your first mistake is believing the bullshit on the MikesXS site. Before these, they sold the really, really shit ones and claimed they were good too, lol. They still sell carb rebuild kits with all the wrong jet sizes in them. Really, they're only in business to make money. They don't really care if the parts fit properly, work right, or fall apart in 2 weeks. Once they have your money, that's all that matters to them.

Even if you get your junk pods to not block the air passageways, the pleated element design just doesn't work best on a CV carb. It disrupts the air flow and you'll never get your carbs tuned as well as they could be if you choose to run this type of filter.