850 won't idle

My first post!

My 850 idles poorly, I can tell from the exhaust sound the left cylinder is weak, more of a popping sound than the right.

Here's the deal.

Head is good, rings are good, new carb bodies, I switched coils and no difference, it runs OK at speed, seems maybe a little down on power?

I just can't get a nice even idle like I used to have.

Is it possible for a Boyer to go weak on one side? Or do they either work or not work?

I just took the carb off, I can blow through the idle adjustment screw hole, everything there seems to be in order.

This bike I've owned for 25 years, my third Commando and I've rebuilt it a couple of times.

This one has me stumped.

On another matter, just saw One Week yesterday, great new Canadian flick co-starring an 850.

peckster said:

1) My first post!

2) I just can't get a nice even idle like I used to have.

3) I just took the carb off, I can blow through the idle adjustment screw hole, everything there seems to be in order.

4) On another matter, just saw One Week yesterday, great new Canadian flick co-starring an 850.

Click to expand...

1st. WELCOME to the forum!

2nd. what did you do to it since.

3rd. Sounds like you are running a single mikuni?

4th. Gonna have to catch that flic! Thanks![/url]

850 idle

hi, make sure your float heights are adjusted if you have amals check wiring all grounds and battery. I think i read on here 90 precent of carb problems electrical !!!!!!!! M.c.

Thanks for the fast responses.

I have stock amals, new bodies. Not sure how to check float levels, never had that problem.

The movie site is here: http://www.oneweek.ca/

Mate ~

Have you checked your balance tube between the carbs..
I have been caught out a few times over the years with this one ~ no idea why it should come off ~ but

Could just be as simple as that ~ :wink:

I have NEVER had issues with float levels on Animals ~ since my first concentric bearing BSA A65L in 1969 ~ never!

Aside from the very good advice above, check your mounting screws.
If one of the manifold mounting bolts is even a half-turn loose, it will cause a vacuum leak at the head. Balance tube coming loose usually effects both carbs, having a slightly loose screw on the manifold only effects one.

I balance my carbs and throttle cables with a carb stick - multiple tube vacuum gauge that lets you synchronize up to four carbs. It would show a vacuum leak.

Also, check to make sure your idle circuit is clear of any blockage using a twist tie wire or a #78 drill.

Check the air screw on that side....it might need to be screwed in a little if it's weak on that side, especially at tickover/low down

Check the head bolts and nuts are tight. This happened to me...

idle

New bodies but old slides? I would replace slides with chrome ones fron RGM to go with new bodies.
Idle drilling can be suspect on new bodies. They are not like the monoblocks with an idle adjustment.. It comes 'preset'.
It may be possible to tempory swap carbs over to see if problem transfers to other pot.
I do not suspect boyer personally, and you have swapped the coils, so I suspect the carbs

New bodies and slides. It runs fine at highway speeds, but I get a lot of carbon on the plugs in the city, I think they are just fowling, hence the erratic d idle.

I went back to the stock air filter, but I doubt that's a factor. Maybve I'll replace the NGKs with N7Ys and see if that makes a dif. Cheap and easy at least .

I took it to a shop last week, it runs better but he couldn't find anything obvious like leaks, so still searching.