Electrex timing for a 350 narrow case Sebring

[Dave354]

Good evening,
I’m very pleased to say that after over 20 years in a shed and then a full rebuild I have the old girl running again. She actually started second kick and even idled reasonably. There was quite a bit of spitting from the exhaust when revved so I shut her down, dialled back the ignition timing a tad and kicked her over again, starting first kick. This seemed to have cured the issue. Very pleased with my success and doing a lap running around the garage, I checked for leaks…. None. So far so good, so I shut her down.
However when trying to restart, it is kicking back on the kickstart with a fair bit of violence! In fact it was so hard, the end of the kickstart flew off and landed about 30 yards away the other side of the road! ( new circlip, spring and ball now needed).
My question is, what timing do you suggest? I’m running a 30mm Amal mk1 with pretty moderate jetting. When it ran it seemed to pick up fine, so I think my issue is with the ignition timing?

Regards

Dave
https://share.icloud.com/photos/041wK_j ... s5oU8epqww

[themoudie]

Aye Dave,

Flinging the end of your kickstart across the workshop is a serious problem! Get that in the kisser and you'll no be enjoying the riding!

If you are running the Electrex Hall effect ignition, then you need to read these instructions that are with the kit:

Electrex_STK-169D_timing_instructions

You will note from the link below that is taken from the Motoscrubs Information section that whilst static timing, when using points and an AAU, is 5° to 8° and the AAU gives a further advance of 28°, therebye giving a total advance between 33° and 36° BTDC, with engine running at 3,000rpm.

Ducati_supplementary_table_of_ignition_timings_for_Narrow_case_singles

The Electrex ignition only provides an electrical advance of the ignition spark of 20° and you need to adjust the pulsar ring you fitted in the timing chest. Copied from the STK-169D instructions: "Step 6 The timing can be easily set with the piston at TDC (Top Dead Centre), then by rotating the pulser ring, align the correct full advance setting, as engraved on the ring, with either line on the rotor." With the 350 Sebring, I think that this would be the 38° mark?

Rather than relying on my assumptions, I would advise that you contact Nigel Lacey for his advise, sooner rather than later and certainly before you try to launch your napper through the garage roof!

Good health, Bill

[Duccout]

I think (from memory) that Nigel recommended 34 degrees for a 350 engine. Kick backs should happen rarely, so I'd guess that the timing is slightly advanced.


Cheers,

Colin

[mrkprsn]

I have a 1966 Sebring NC that I am also putting back on the road after 20 years. I have the original carb, stator, flywheel and RR. It all works as it should except for the hard starting when warm. When it is warm the bike kicks like a mule. So much so that it will kick you up off the bike with force when starting it. It kicks at the top, middle, bottom and anywhere in between of the kick start stroke.

I checked the timing and statically it was at 12 degrees so I reduced the advance 2 degrees at a time (10, 8, 6, 4, 2). At the last setting (2 + 28 = 30) it stilled kicked just as hard. You would think that retarding the spark would help diminish the kick back but it didn't so I set the bike at 5 degrees (+28 auto advance = 33).

I know there is a compression release for a reason and I don't have it on my NC 250 and 200 or WC 350. Has anyone ever gotten their NC Sebring to start warm without kicking back so hard?

[IanHood]

I've sometimes seen violent kickbacks when the mixture was too lean. Might be worth checking.

Ian

[blethermaskite]

Are you on points ignition? sounds like your auto advance retard unit is stuck on full advance? or is at least sticky.
Cheers,
George

[Dave354]

Thank you all, I think I have resolved the timing issue. It is the electrex electronic ignition system STK161 for the narrowcase. I have reset it to 34 degrees (or as close as I can). With the right technique she fires up fine and now after adjusting the carb she idles. When revved she still spits out of the exhaust so some fine tuning to do.

Just a small weep from the shaft tunnel oil line banjo and then re torque the head bolts…

Then just the paint, wiring loom, lights, mudguards and seat to sort out…. Oh and the pinhole leak I have found in the tank!!

Best Dave

[Boxprod]

Well done, Dave!
From one Cornishman to another, congratulations indeed.
Pete.

[themoudie]

Aye Dave,

Glad to read that the re-timing appears to have settled things down.

As for the spitting back, my '74 450 MKIII, with a AMAL 32mm MKII carb, was prone to this and it happens as the slide just starts to take over from the pilot jet. Whether this is due to Efuels or not I'm not sure? By richening up the pilot circuit, I have been able to "almost" eliminate it, there is certainly no more "spit" when going up through the box. However, occasionaly there is a wee "spit" when blipping the throttle to come down through the box and ambient temperature seems to affect this, the higher the temperature, the more prone it appears to be. Indicating that I could still be a wee bit on the lean side, with my adjustment.

All the best, Bill

[mrkprsn]

In addition to getting the timing right, I've found it really comes down to finding the sweet spot with the decompression release. Being able to get the bike just past the compression stroke but not so far as to not let you get a full kick in before the next compression firing stroke. If you're a little off it will kick (hard).