Rebuilt SII Interceptor won't run smoothly and difficult to start.

After a weary long restoration of a 1969 Interceptor SII which has had the engine overhauled professionally and runs two new Amal premiers with a Boyer bransden ignition it runs very roughly and is a pig to start.
Can anybody shed light from expierience or give a run down how to get this beast running smoothly.

Speak to the pro about this. You paid after all. However, these bikes can be a right PIA. I have two and rode out on one today. It starts easily and idles but the low speed riding is poor. And this is a fresh engine. I have always thought the two cams chain drive does it no favours. Not sure which final sprocket you are running but at local road speed you are barely
using any throttle so tuning for that just off idle mix is tough. Currently available replacement silencers are straight through
with no baffles and combined with the big valves makes low speed running no fun. If you roll the power on I bet it is a lot better.
Make sure your carbs are set up correctly ie throttle cables pull equally on each side etc. Start at the beginning and check
all the basics with great care and take notes.

Any progress on this? Rode both of my bikes and sadly noticed how snappy throttle response is on one v. the other. Time
to get this attended to.

Hello Onder, thank you for asking! Unfortunately I haven't had time to get down to it yet but I will go down the road you suggest analysing the performance band.

Onder said:

combined with the big valves makes low speed running no fun.

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I know nothing about Interceptors (so here I go- haha!), but I’ve been caught out by oversized valves with fairly hot cams causing bad low speed running on a Triton. I got some improvement by increasing the inlet valve clearances. Maybe that’s feasible on an Enfield: maybe not!

Anyway, that would only be after conventional tuning of the carburettors: synchronising throttle stops and cables; idle jet cleanliness and size; throttle cutaway size; needle clip position; float level.

Test for inlet manifold air leaks by spraying the joints with WD40 (or whatever) while the engine is idling.

If it’s a Mk III or Mk IV Boyer, are you using two 12V ignition coils in series? That’s a bad idea.

In complete agreement. But really have already been there, which why I'm unhappy. It only is a pain at very small throttle openings. Ill pull the carbs and inspect AGAIN...

So I pulled both carbs, low time premiers. Both were immaculate inside including all orifices. Checked all tappets none too tight but I opened them up a thou each. Sync on the cables was decent but not great as the twist grip is likely worn after
fifty plus years. Plugs are dark, too dark. At this time of year cruise speed is low due to Our Gracious Visitors and the fact
that max cruise for them is under 40. So in high gear it is 2200 to 2600. The bike is very unhappy as the throttle opening is
often barely an eight or less. So in order to get any sort of smooth running you have to run rich. But then you have dark
plugs and unburned fuel. I do get the ever popular popping on a closed throttle downhill.
Tomorrow will have a look at timing chain adjustment, another sad compromise on the Mighty Enfield.

Hurumph ;

If you can , get some 100 Octane ' race fuel ' from the drag strip chaps , or Avgas . For Initial ' trials ' ./

BACK in the DAY , the Ign. setting was for blowing them off at the lights , 5 star 100 Oc. pump gas .
Recently seen TRIUMPH service ( factory ) info , much saying 11 / 32 b t d c . Whereas we went to great pains
to see it was exactly 3/8 th . as the book says . So , it depends which book .

THE POINT BEING theyre lumpy , grumpy & wicked on the ' more ' which is fine , out off town . As once your
underway , you dont have to worry about keeping the dfront down. Much .

Therefore & insofar , the idea is , if you pull the Ign. back a iota or two - two or three degrees , it may be better mannered .

Of Course , if it ad manual advance , you could set it 10 degrees past , with a notch for correct , and throw it ' through the gate '
for tyre smoking gettaways .
Um.
NGKs in the car , after a year or two , yesterday looked like old fashioned PLUG READINGS . Brown & Tan & other things . o.k. even .
Might leave em in a bit longer .

IF your BEDDING THE ENGINE IN , you should be ' running free ' and through the gears - initially . NOT holding a plodding lugging
barge towing pace , in a high gear .Sounds like you need to ' get out of town ' . Dont forget the TOOL KIT .

How was the timing set?

Tool kit in 2023: telephone number of the Recovery service....:-(

Woody850 said:

After a weary long restoration of a 1969 Interceptor SII which has had the engine overhauled professionally and runs two new Amal premiers with a Boyer bransden ignition it runs very roughly and is a pig to start.
Can anybody shed light from expierience or give a run down how to get this beast running smoothly.

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What plugs?
What plug caps?

N4 Champs...NGK 5k resistors...I was out today on the Norton so no time to dick with the boat anchor.

Onder said:

N4 Champs...NGK 5k resistors...I was out today on the Norton so no time to dick with the boat anchor.

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Well said Onder, I think of it asif somebody put my feet in two buckets and poured them full with quick setting concrete.