Idles but won't accelerate?

[Ken Talbot]

The jets just screw in and out - no adjustment. Be sure your screwdriver is in good condition and fits the slot absolutely properly. I would also use an impact driver the first time I was removing a jet that had been in place for a while - then you can be sure the screwdriver will not slip in the slot or twist off part of the soft brass head. The little buggers are pretty easy to damage, and although an impact driver sounds extreme, it is actually the safest way to go - just don't use your biggest hammer...

[Bill__Woods]

Hi Warlock,
Tighten all the jets. The only one that need turned out is the idle mixture screws, and they have springs around them to keep them where you set them.

[warlock60]

Bill, I spent two days tearing down and cleaning every mm of them carbs. All jets and screws came out, though some of the brass ones seemed to be brittle and chip a little in the slot head.

Anyho, now for the confession: I was adjusting the idle screw, on the second on with just two to go before I could claim victory, and the darn tip broke off as I turned it in while counting turns. Oops.

Do I need to get a new needle? Where would be the next question.

I think I may be all thumbs

[nashville_bill]

Yes, and try www.motorcyclecarbs.com as they list them on the web site.

[xssiveone]

Originally posted by warlock60
Anyho, now for the confession: I was adjusting the idle screw, on the second on with just two to go before I could claim victory, and the darn tip broke off as I turned it in while counting turns. Oops.

Do I need to get a new needle? Where would be the next question.

The idle screws are usually repairable. Clamp the broken screw in a drill press and then use a file to reshape the tip,(use one of the other screws to try and duplicate the angle) followed by some emory cloth, followed by come fine sand paper to take all the file marks out.

Bill says you can still get them, but one day they will no longer be available so don't throw the broken one away.

[Snow]

The idle mixture adjustment screws are indeed still available from Yamaha, at least for the 78 carbs. Does anyone know if the idle screws that go in a 78 will fit and work in 79-81? Just curious. Btw, the screws are about $14 from bikebandit.

Also, just got my carb kits from motorcyclecarbs.com and they include the idle mixture screws along with jet needle, gasket, float valve, float seat, main jet, pilot jet, and some other type of jet that I haven't identified yet...prolly some type of air jet. They also include new c-clips for the jet needles.

Total for my 78 carbs: $115

I'm putting the kits in today hopefully

[warlock60]

Thanks for the advice.

I cleaned the carbs two times. Second time actually removing the jets and such. Broke the idle mixture needle in one carb, but got a replacement from a place for $8 in PA http://64.30.217.113/speedandsportinc/index.html . And one for $14.95 from http://www.motorcyclecarbs.com/, just in case ('cause I am all thumbs).

While I had the bike apart I replaced the coils with Dyna 2-1s for $108 from http://www.mpsracing.com/products/Dyna/ig01aa.asp.

Replaced a couple of dry rotten fuel lines. Pulled one pitcock off the fuel tank, drained and flushed the tank.

Bleed the brakes. For S and Giggles.

Finally put it all back together this afternoon and with a single push of the start button it purred like a kitten.

It idles like before at 1200rpm, but for now that's Ok. Maybe this weekend I'll try to adjust. I've got a synchonizer, but no "colortune" gadget. I put the new idle needle jet(pilot valve) in at 2 1/2 turns and it seems to sound ok.

Again, I appreciate all your advice and help. Now if I can just get ahead of the corrosion

Ray
Savannah, Ga

[warlock60]

One small PS concerning the broken idle needle screw:

bought a set of tempered spring steel jewelers screwdrivers (about $6) and with a dremel shaved the smallest one down. Cut it off at a 1/2 inch and while holding it over the needle hole on the inside of the carb body with a pair of needle nose pliers another guy placed a large screwdriver over the top and smacked it with an adjustable. (not very technical, but it worked) Out popped the broken needle valve without dinging up the port.

Just thought I'd pass it along.