Newbie here - starting help on a 74 850 needed!

Hey guys -

I looked through the forum - lurked for a bit - and I'd like to get an expert opinion. I'm helping a friend with a 74 Commando 850 (could be 73). Previous problem was that you could get it started, but you had to hold the throttle open way past 1/4 turn and even after it was warmed you couldn't get it to idle.

What I did: read the manual, for one! Adjusted and synced the carbs according to the manual. (FYI - the throttle stop screws were WAY out of adjustment). Part of the syncing procedure involves having it running, which I was able to do because it was still plenty warm. Then I took her for a test ride. Idle and up to 1/8(ish) throttle were awesome. Then it lost all power until I upshifted. Again, great to around 1/8 throttle, then no power, almost dying.

I took apart the twin Amals and cleaned. Everything looked pretty darn clean already. Based on the lugging after 1/8 power, the heavy smoking out the tail pipe and the blackened plugs, I figure she's running rich. I moved the throttle needle clip to it's top spot to lean it out (again according to the manual).

Followed the starting procedure. Now I just cannot get 'er to fire up. I've kicked until I was about to have a heart attack, and have some lovely bruises to match as I started to get tired and slipped off the kickstarter. I would appreciate any thoughts on how I can get this thing started up, and whether or not the changes I made were in the right direction! I'm good wrenching on bikes, but older bikes aren't my specialty... Thanks in advance!

Is the ignition timing right?

Welcome. For starters check the timing. If the throttle stops were badly out of adjustment I'm betting everything else needs a closer look.

We've all been there :wink: I would get new needle jets and make sure air jets cleaned (info on web) after making sure timing correct. Then there's always checking for air leaks and on, and on and on :roll:

Hmmm.. .solid concensus on ignition timing. I'll look at it. I did not check that. I forgot to mention that I did clean and re-gap the plugs.

I was prepared to replace the needles but my friend let me know that they were just replaced, so I'm hesitant to think they need replacing again. He got the bike from him father in law who said that he'd put "hours and hours" into the carbs to get them right. But we both kinda did a "huh??" to each other on that, since the throttle stops were so outta whack and there's that pesky lack of idling ability.

Checked for air leaks, but as always, I'll check again!

Okay, timing check tonight - and I'm stretching out my right leg in preparation of another kickfest. Thanks for the assistance!

Hi

Put it back to the original settings before you couldn't start.

Fit Boyer Brandsen Ignition.

Fit the ignition- so easy and no need to touch again I've run mine for twenty years.

Did you take out a plug to balance carbs? Possibly buy new jets all round as they aren't much money and if the last owner was a dork he might have cleaned them with a pin or something.

Check no play in the slides on the carbs.

Good luck

Before you make any further changes, I'd suggest trying a set of new plugs (not just cleaned and gapped. These bikes are notorious for fouling plugs, particularly if it ran rich for a while (which yours evidently did) and if left idling for any length of time. If it ran well a short time ago, I'll bet your timing is at least reasonable.

Paul

phsDommie said:

Before you make any further changes, I'd suggest trying a set of new plugs (not just cleaned and gapped. These bikes are notorious for fouling plugs, particularly if it ran rich for a while (which yours evidently did) and if left idling for any length of time. If it ran well a short time ago, I'll bet your timing is at least reasonable.

Paul

Click to expand...

You think new plugs? I thought I might be okay because I was for sure getting spark when I cranked the kick start around. Pulled each one and had a buddy watch them when I cranked. There was plenty of spark...

Similar symptoms to the thread below -

what-going-valve-job-t7239.html

Sounds quite a lot like clogged pilot jets to me...

Is the choke being operated correctly? Some people call it backwards but it must be some mental thing. Rotate lever so that the inner cable is visible winding around the narrow spool to raise the chokes for normal running. This happened to a friend of mine when he first got his Norton.