Hard to idle at 1050rpms

Hi

I rebuilt carbs and replaced throttle shaft seals, diaphrams, needles etc

I also bench synced the carbs too.

Put them on the bike and ran it, tried to set the idle lower than 1500rpms, but if I get lower to the 1050rpms it will just die.

Do I still need to balance the carbs with carbtune or something?

I havn't done my valves yet either

Can any one shed some light?

Daz

 

Yes you still need to balance the carbs while its running and the pilot screws. Bench synching gets you close but not close enough, do the valve shims first would be ideal, at least check them they will most likely need doing. Do the carbs pass the clunk test?

 

Clunk test - yes they pass

The valve shims and balancing carbs, not sure whether I want to do it or I should pay a dealer to do it as I don't have the tools.

I know it would be cheaper if I do it and learn more...but don't want to mess it up.

Daz

 

Get a manual if you havnt,....float levels?.. you can make a bottle or tube synch gauge , search the forums for a good how to by bigfitz for doing the shims, I think its called "airhead valve adjustment' and some form of yics tool makes things easier. In fact its all there for your searching. And I'm gonna have to learn how to put in a link. Goodluck.

 

first, before you worry about the idle, get it fully warmed up by driving it for 15 minutes or so.... come home and set the idle.
see if it will then

when you bring it home and if you cant get it to idle, see what it does with the choke on. will it idle then? if it does, you havent cleaned the pilot passages well enough.

 

You can probably buy the tools from Chacal cheaper than the dealer will do the job. You then have them for future work. Don't know what shipping would be but he can tell you. Len is a whole world of resources.

There are many good instructions on the threads that can guide you through the different procedures. There is also information on how to build a serviceable manometer setup to sync the carbs.

Also check the idle speed for your bike. My 550 idles at 1200 according to the manual. It also states not to use the bikes tach. It apparently isn't accurate at low speed. Don't know if the 650 is the same.

 

Assuming your local stealership would even TOUCH your bike (none around me will. Not even to do the tires.) you'd pay a FORTUNE to have them do your carbs. One shop in Indianapolis (couple hour drive from me) quoted me 300 to do the carbs when I first got mine, and I can practically guarantee they wouldn't do anywhere near as good a job as you would.

 

Hi

Float levels checked measured to 17.5mm

Thanks, I can borrow a carb balancer from a mate, the yics tool I'll do some research about that.

Regards

Daz

 

Hi

Got to work and it was racing like hell I'd been riding it for 10 mins, parked up and adjusted the idle and it calmed down and sat at 1500 but I could have adjusted it further, I noticed the rev cable to the engine was loose and shaking, that damn thing keeps coming loose so i'll put some grease on it so it doesn't come free.

I'll keep you posted

Thanks

Daz

 

The cables are originally sealed with some RTV silicone to hold them from backing off. I can't see grease being effective as a sealant.

 

when adjusting anything on these bikes, it must be at normal operating temp.
drive it home from work and try to adjust it 1050 then.
If the cable is shaking, then you have too much slack in the cable. how much play do you have in the throttle? it should have some play, but not a lot.

 

After cleaning my carbs and riding for a couple hundred KM, my idle became irratic. I think that some varnish had broken free from the tank and got into the carbs. Ran a couple of SeaFoam treatments in the fuel in the next two fillups. Problem went away. A lot easier than pulling the carbs again.

 

I sealed the tank 3 months ago, so its fresh as a new tank.


Daz

 

Hi There


I meant the rev cable to the engine not the throttle, the throttle is fine.

Thanks
Daz

 

Daz....

I just posted about my purchasing experience from Chacal..... I mentioned how his prices considerably lower than the local Yamaha dealers here......

As for checking your shims..... i also thought it would be something better left for an experienced bike mechanic, however, I started researching here and found numerous posts on the topic (thanks everyone), i soon realized that it is not rocket science and that after talking to one parts dealer here about prices and the sound of confusion in his voice was enough for me to do it myself...... i know there is a special tool for holding down the valve seat, however, i read about how someone here using a zip tie, i used a plastic coated wire coat hanger and bent the end as needed, it worked perfectly.... take your time and you too will see that these engines are relatively easy to work on, i changed out 7/8 shims in a couple of hours (my first time)....

sorry for the winded response, i guess i get a little excited sometimes...

 

Hi

Labradorian
Thanks for your response, ok I'll email Len and give him a list of tools I need, I'll also ask him about carb tunning tools too, you guys give me confidence when I'm low, It's taken me blood sweat and tears to get this far, my bike almost finished and , at the moment the bike is running rough at low rpms but higher than 2000rpm its fine ish!. So I'm not gonna ride it until I sort my valves and Carbs, just hope that sorts it?.

My local dealer is cool but they said they would charge me £200 at least to do the valves and carb tunning, so saving money and learning more motivates me.

I'll keep you all posted with my efforts.

Daz

 

Daz,
first, you need to reset your idle screws to 2.5 turns out and see how it idles then.
these little screws make a huge difference.
if it still wont idle, you may have something plugging the pilots up
at idle, use a misting bottle of water and spray the headers... see if any are cool or cooler than the the others....
that is a great place to start.

 

Hi Helmet

Can you instruct me on how to measure 2.5 turns out please.

Daz

 

on the engine side of your carbs, where the intake boots meet your carbs, you will see a small straight-headed screw. sometimes they are covered with a "plug", but they can be removed. there are 1 per carb.
turn the screw clockwise until it softly bottoms out, and then count half-turn increments as you turn counter-clockwise until you get to 2.5 turns.

 

Daz....
when adjusting the pilot screws, add a couple of drops of penetrating oil or lubricating oil untop of the screws to allow for the threads to move smoothly along, a friend of mine gave me this tip and when i cleaned and rebuilt my carbs i tried his tip and the screws moved quite smoothly..... you never know the last time those screws were moved....