New carbs for '77

brasco18 · Posted: November 13, 2007, 2:07 pm Post subject: New carbs for '77

I am considering getting new carbs for my '77 650. Is it worth it? What carbs should I go with? Where can I get them? the reason why is I cannot seem to figure out my current carbs. I am consistently getting only 30 mpg right now and it actually makes it more worth while to drive me car!

grizld1 · Posted: November 13, 2007, 6:23 pm Post subject: Re: New carbs for '77

Don't know how many times I've posted this, but the bottom line is that if you can't figure out the OEM carbs, you're not likely to install and tune custom carbs successfully. There's a lot more involved than just bolting them on.
It's a bit pricy, but motorcyclecarbs.com offers a complete remanufacturing job on the OEM units. You might consider that approach.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Amen, Griz. In my opinion, the '76-'77 stock carbs were the best ever fitted to the 650. If you can't figure them out ..... well then Good Luck with VMs. There's about a bazillion different jets available for them but if you don't know anything about carbs, you'll never sort them out.

brasco18 · Posted: November 14, 2007, 2:24 pm Post subject: Re: New carbs for '77

I have just heard a lot of bad press about the OEM CV carbs. I have also heard that upgrading to something like 34mm round slide Mukuni carbs takes a lot of the headache out of tuning the carbs. I understand how to tune the carbs. They just seem so freakin' touchy that I am considering getting something that may be better designed, therefore easier to tune.

kingwj · Posted: November 14, 2007, 4:21 pm Post subject: Re: New carbs for '77

I too was bad mouthing the stock carbs until I raised the needles and it is a totally different bike. Mine was very cold blooded but now will go off choke in about 5 seconds on a nice day. And it pulls smoothly from idle to redline. The plugs are a nice toast color where before the bike was extremely lean. I'd make every effort to maximize the stock before sinking money into replacements.

Retiredgentleman · Posted: November 15, 2007, 3:40 am Post subject: Re: New carbs for '77

From my experience Mikuni CV carbs work great. Had them on my 1976 XS500 back in the 70's and 80's and they worked perfect.
When I bought my present 78 XS650, this past year, I read all the posts and expected to have problems with carbs.
But guess what...........no carb problems. Bike starts and runs really well.
The key things..............no rust in tank, use a fuel filter, get a re-build kit, clean out your carb checking each jet and each air passage way is in pristine condition,use a clear plastic tube from the bowl drain plug to be sure your float levels are set correctly.

brasco18 · Posted: November 19, 2007, 2:08 pm Post subject: Re: New carbs for '77

I have cleaned the carbs super a lot. I gave the a chemical bath to really clean them out. I used rebuild kits on both of them. I have set them to OEM specifications. The bike starts on choke when cold, usually goes off choke after about 20 sec. It has great acceleration. It tends to idle a bit high sometimes because the butterfly valve on the left is not aligned perfectly, meaning when close it is not perfectly flush with the housing (it will idle at 1500 rpms instead of 1200 rpms). It never backfires, even when I role off the throttle going downhill. The bike runs great and is fun to ride. The plugs are always black. I can't get it to lean out. the mileage is about 30mpg.

royfisk · Posted: November 19, 2007, 3:43 pm Post subject: Re: New carbs for '77

I dont know but I thought stock carburators were bs carburators? I thought cv carburators were made by kehin??? The stock bs carburators do work good when there rebuilt correctly and in good working order. I have seen that the now 30 plus year old diaphrams have weakend and are not what they once were. replacement cost of these isnt cheap. Personally I like the vm mikuni 36mm carburators, there isnt any rubber diaphram in there to go bad, and air isnt controled by vacume. When you twist the throttle open the slide goes up imediately. not a butterfly opening up and then the slide off from vacume. But most of the people who by kits from 650 central will tell you there 100% satisfied with the kit right out of the box, and 10 or 20 years down the road when the carbs need a rebuild they will be happy to know there easier to rebuild. You dont have to worry about the diaphram getting chemicals onto it and swelling up like a woman about to give birth, and not fitting anymore. adjustments are easy, main jet just take off the plug in the bottom of the bowl screw out the jet and screw in the new jet and re screw in the plug done. air screw readily accessable.

busrider · Full Member Joined: Nov 20, 2006 Posts: 40

hey im with you on this i have a set of 34s and love them

xs1961 · Posted: November 19, 2007, 8:55 pm Post subject: Re: New carbs for '77

Yep, 34mm roundslides,I luv em..got 3 sets in use on 650 through to 840.. piece of piss to set-up,less parts to wear & cheap jets/parts available...

Nowt wrong with mid 70's cv carbs though as long as diaphragms are ok & you can find a decent pair of aftermarket air filters to work with em..which is not easy in my experience..

busrider · Full Member Joined: Nov 20, 2006 Posts: 40

i changed mine because of the diapham thing and im really impressed with the difference

xsjohn · Posted: November 19, 2007, 10:16 pm Post subject: Re: New carbs for '77

Diaphragm and all the crap RANT.......The reason for the diaphragm technology was to "help" compensate for different altitudes "atmospheric pressure"...Pre map sensor technology...........tune your round slides for Daytona and stall half way up a mountain out west......poop....to rich too lean depending on altitude.....been there and done that....although the diaphragms won't fix all that it was a industry patch for the manufacturers that didn't know where their machines were going to end up and had no real idea how to fix it correctly.....for a pre epa guess it was better than nothing...along came the epa Yamaha panicked....hence the BS series...log the main needle and hope we pass.....screw the consumer......WW2 fighters used superchargers to compensate for altitude………most of us can’t do that……….map sensors and fuel injection…….not for my XS……suffer we will with all of it for sure………a happy medium might make the trip............with these old beasts........maybe not........depending on who is is doing the guessing........ethanol will goof it up even more....ha......

It's just like the gearing on these things......back and forth on a short strip in frontof the factory....boss this is good.....it halls ass.........the next week on the trip to Tokyo it worked good too boss........47 miles an hour......later the express happens....boss I didn't see that comming........Boss says dont worry.... they will never know the difference....they can just rev the hell out of it...... good idea boss...since these were designed by Germans they would have noticed the autobahn .....zing......zing.......zing........where's the exit............

when I first got my 80 ..10 years ago....I did make one exit........1 and 1/2 miles.....hair raising...to say the least...........zing zang wang...epa carbs clanking the engine and pulled off........next year raised the needles and increased the MJ......still zing .....ding....no more for me.....fixed that...........threw those epa fricken ass needles in the crapper and did it right......now the express is just another road........18/29..........

John

grizld1 · Posted: November 20, 2007, 12:44 am Post subject: Re: New carbs for '77

Mercy, John--if you want a tractor, get a Hardly! Just for yucks I dug out the owner's manual that came with my '68 Trunch Bonnie when I bought it 39 years ago. Stock gearing on the XS650 sits right in the middle between the Bonneville and the TR6, 17/32 puts you just a tad taller than stock Bonneville gearing.

One of the problems with early diaphragm carbs is the weight of the slides; newer designs are much more responsive. And right, the VM carbs are somewhat higher maintenance; but any given set of mains is good for for a range of about 2500 ft. of elevation, and swapping 'em out takes about 10 minutes. A more serious downside is that pod filters, fabric (K&N) or foam, block up when they get wet and create a severe rich condition real fast, running them under stock frame covers ain't a fix, and there's not a lot of room for a decent plenum without moving the battery and no very conveniently accessible spots to move the battery to, if you need to run one big enough to work the electric boot (which I need due to big bore, high compression and gimped right leg). I'm still working on a solution to that one.

5twins · Full Member Joined: Aug 05, 2006 Posts: 1616

Yes, get one of the early 883 Sportsters, '86 or '87. Biggest slug on the planet. My buddy got one and let me ride it. He asked what I thought. Being honest, I told him it reminded me of the 350 Honda I had in high school. He was offended, don't know why. It really felt just like that.

royfisk · Posted: November 20, 2007, 11:59 pm Post subject: Re: New carbs for '77

Down with the great american rip off machine. They build them wrong right from the get go just to sell you more crap. Has anyone ever seen a harley that hasnt had something added to it ?? huh ?? Think we have troubles with these mikunis try making a bendix or zenith work right. But thats ok s&s will go right on and work. Personally I ran a mikuni vm on my sportster and it performed well for the piece of antique farm equipment it was.

xsjohn · Posted: November 21, 2007, 3:09 am Post subject: Re: New carbs for '77

It is a bit puzzling why America can't make a normal motorcycle that didn't cost 9 milloin dollars........the new Harleys I've been reading get so hot that....you figure out how to remap them or ride a stove.....dealers won't help....against the law.....how did we ever get into this mess.....how much can a motorcycle polute.....have we gone crazy to let these idiots run the show.....the answer to that I'm afraid is "yes"........two more years of tougher epa regs and that should about do it for Harley if not already..........

John

GOSTAZ · New Member Joined: Nov 20, 2007 Posts: 5

HD will kill themselves. The all fuelie lineup of bikes they are selling are horrific. I have an '06 StreetGlide... had to put an aftermarket closed loop fuel system on it.

Harley thinks, like most other poorly run American Companies, that they are special. They are not. They sell to mid-life crisis crowd. My crisis is over, I am back on Jap bikes more often, and much happier. If you buy a HD, buy a used carbed bike, throw an S&S on it, and enjoy.

uch easier to work on Jap bikes, and much less expensive. Who cares about the Tshirts....

xsjohn · Posted: November 21, 2007, 2:35 pm Post subject: Re: New carbs for '77

Keep in mind it's not really Harlley....it's the epa regs....harley knows how to richen their bikes but the govt won't let them....we are idiots for putting up with govt regs on these small things......lean don't get it on an air cooled engine........the govt would rater run a company into the ground than use common sense..they are actually traitors in suits and ties......my 80 XS suffered from the same epa crap.....and when it destroyed itself and I woke up.........I have the fix for them......

Bet they are not out at the airport leaning small airplane engines.....god....maybe they are........

John

xsjohn · Posted: November 21, 2007, 7:27 pm Post subject: Re: New carbs for '77

New figures with my new needle kit........
76 ambient today........

40 miles 65mph 3700 rpm geared 18/29
Right cylinder expressway 239 degrees
left cylinder expressway 237 degrees

backroads ridden medium hard
right 229 degrees
left 228 degrees

down 25-30 degrees from last year and flies.......50mpg.....

John

busrider · Full Member Joined: Nov 20, 2006 Posts: 40

hi john check out the adjustable jet device on tpi web site and tell me what you think

busrider · Full Member Joined: Nov 20, 2006 Posts: 40

sorry its www.thunderproducts.com

royfisk · Posted: November 22, 2007, 12:28 pm Post subject: Re: New carbs for '77

I have used the dial a jet on my kawasaki klr 600 and it does work and work well. And now that I think about it would probably work well with the 34mm carb issue, cause the first thing you do during installation is lean out the system. Makes elavation changes a snap for those going from la to the mts. WILL WORK WITH ALL MIKKUNIS AND HEHIN CARBS AND PROBABLY OTHERS. Man cant beleive I hadnt done this on the 34's yet. I must either be looseing my mind or haveing brain farts or something.

xsjohn · Posted: November 22, 2007, 12:46 pm Post subject: Re: New carbs for '77

80 dollars X-2.....lean the carb out....then richen it with that....has everyone gone mad..........maybe I should raise my price.......

John

cscarroll · Full Member Joined: Oct 08, 2006 Posts: 112

John,

I'm nearly done with the build-up on my '74 motor and am looking for the right stock carbs as I don't have the $$ or know-how for custom. the '76-'77s sound like they are the ticket if I'm going stock. Would you agree?

One note, with the 6th over pistons from Mikes, I'll be up to 680cc...

Thanks for the help, may very well be interested in a set of your needles when the time comes...

What Happened to 650rider.com?

Yamaha xs650