Carby question- sensitive idle.

[wayne]

After 10,000 klm of perfect running, my M model carby developed a problem. I was coming back from a long ride and as I got back into the traffic I noticed the bike reluctant to idle and stalling while sitting at lights.

This is sometimes a symptom of a failing plug and this one was well used.

I put in a new plug and even tried two different heat ranges to no avail.

Lots of fiddling with the brass screw and idle stop and now I've got it so it will idle but it's still sensitive.

For example, it will sit idling happily but if I very rapidly pull it upright from the sidestand it will stall. If I have the clutch in and am rolling to a stop but brake too heavily, it will stall.

As far as I can tell NOTHING has changed and it literally did 10,000K with no problems. It still runs perfectly otherwise with no hesitation etc. Just this idle thing.

My original carby from 10 years ago used to do this. Then I got another carby and it started and idled so well that I kept it on.

Does this "inertial sensitivity" trigger any "seen this before" from our mechanics ?

Thanks, Wayne

[Al Corelli]

Float level?

Restriction in fuel line.

How is it on the road?

[bdalameda]

I have found that many times when the engine stalls after sitting on the sidestand - the cause is the small checkvalve on the accelerator pump is leaking. Fuel will collect in the intake tract and when the bike is leveled the fuel is fed into the intake causing a stall. Sometimes too high of float level can cause this as well.

Dan

[wayne]

Al, the bike as mentioned is perfect on the road. No hesitation no bad anything. Just this issue. Float level is what first occured to me but as mentioned this problem just started one afternoon after not touching this carby for years and years.

Forgot to mention, float valve set very carefully with a micrometer when it was done.

Dan- thanks, I was hoping this might trigger a past experience. I'll have a look, it might have a bit of crud blocking the valve. As mentioned, float height set years ago and top hasn't been off carby for 5+ years. The valve thing could also explain the sudden appearance of the problem. I looked carefully at the book idle circuit but didn't think of this possibility.

Will report back.

[ziggystardust]

Hi Wayne, back to basics, have you tried cleaning and resetting the points?

Lee

[wayne]

Thanks Lee. As a matter of a fact, and by pure coincidence, I did recently reset the points and that was after this issue started. That came about with the whole dynamic/static timing thing. I was so pleased with the spark plug method I did all three bikes. I didn't clean them per se so I'll give them a wipe this afternoon and see what happens.

There is another symptom associated with this issue. I used to be able to start this bike on full choke, return to half choke within seconds of it starting and not long after remove choke altogether. Coincident with this idle problem is that the start has returned to what my old carby used to do......full choke to start and you cannot remove it from full choke for minutes lest it stall.

This aspect seemed to point to a blockage in the idle circuit but I was hoping with the other symptoms someone may be able to point to something very specific.

[goandy]

It does seem to point to the bike running leaner now so possibly a partial blockage somewhere- before needed little choke = richer, now needs lots of choke = leaner ??

Time for an ultrasonic clean and reset of the carby?

[koolstrike]

I will toss one item into this thread as a side note.

Last year I bought one of the electronic ignition set from Jess at Rotary Recycle. That electronic ignition gets gets rid of the points and the CDI box. I have found the ignition set to be very reliable and the bike starts right up and runs great with it.

So if you are sitting on the fence deciding if you you upgrade the ignition to electronic ignition, I would say "GO FOR IT".

Just one more way to make the bike reliable.

[wayne]

Has taken me a while to get back to you but I finally sorted it.

Lee I tried cleaning the points to no avail but worth doing......it would have been an easy fix.

I started out just intending to remove the float bowl and clean the pilot air and fuel jet but there was so much crud in the bottom of the bowl I pulled the whole thing off. I do use an additional inline filter but it is mesh design and the crud was extremely fine.

Pulling this carb off has filled me with fear for years. It took me so long to get rid of the hesitation on this one, I was too scared to touch it.

Carby off, thorough clean (without ultrasound) but compressed air and liquid cleaners. Double checked the float, am adept at removing carby rear casing without disturbing cables and locknuts. Back together with Jess's new float bowl gasket and new intake gaskets etc.

Idle problem solved, doesn't stall when raised rapidly from sidestand and doesn't stall when rolling to a stop at intersections.

Big plus, runs even better than before. Still is hesitation free (thank you Lord !) and much more linear in acceleration.

Thanks Al, Dan, Lee, Andy and Koolstrike. I do have Jess's electronic ignition and it will go on my A model. This one I like to keep stock in ignition while experimenting elsewhere (AM shocks, 530 chain etc- braced swingarm coming up).