Author Topic: royal enfield 355 1929  (Read 1329 times)

Offline geoff.godwin

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royal enfield 355 1929
« on: November 30, 2023, 05:13:49 PM »
I have owned the bike for 40 years and have finally  tried to get it on the road [last used in 1940] It is the twin port ohv model .with AMAC carb and Sturmy archer gbox. I have set the cam timing such that the valve overlap is equidistant either side of tdc. Set the mag to spark at about  tdc. I get it to fire but not for more than about 5 seconds. The carb is 2 lever [big lever goes to big slide .little lever to little slide. I have not had a bike with two slides and am not sure of basic setting for starting .If I ever get it running properly riding will be a challenge with lever throttle and hand change! Is there any body on this forum with knowledge of model 355 or some basic settings to get it to run properly. cheers Geoff

Offline R

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Re: royal enfield 355 1929
« Reply #1 on: November 30, 2023, 10:25:00 PM »
If you can get it to run for ~5 secs Geoff, then your basic settings must all be in the ballpark, as they say.

Without knowing this exact model, in the slightest, my advice would be to tickle it and tickle it and tickle it
some more, esp once it fires, see if that makes a difference. ?

And/or drop the air slide down some more - it will likely need a good dollop of choke for a cold start.
Esp after 80+ years of hibernation !
Might even need the air slide down to its maximum, for a short time anyway.

We assume you have inspected and thoroughly cleaned the carb at some previous point.
Any gummy deposits or traces of corrosion inside need to be banished, forthwith !

Have fun !
We look forward to a pic of its 1st outing ...

Offline 33d6

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Re: royal enfield 355 1929
« Reply #2 on: December 01, 2023, 12:12:27 AM »
Solid advice from R to which I will add a few comments.
1929 was the last gasp of the AMAC name. By then it was close to the then new Amal carb and was well past the continual two lever juggling of the veteran era. You may use the little lever for a cold start and warming up but will mostly ride on the big lever alone. That will come with practice.
Starting commonly needs the big lever cracked open a little.
As you need to take your hands off the bars to both give hand signals as well as change gear you will soon appreciate how practical and effective a lever throttle is. This is not the place for a self closing twist grip.
Regardless of what you ride now you will find your 1929 bike requires an entirely different technique. Not better, not worse, just different. You are starting afresh in a different world.
What are the engine lubrication arrangements? That may require discussion as well.

Welcome to the club. It’s like putting on “L” plates again. All new and exciting.

Offline john.k

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Re: royal enfield 355 1929
« Reply #3 on: December 02, 2023, 02:16:00 PM »
A bit more spark advance?.........generally the 2 lever carbs needed the choke set fully on with the long and short  lever closed ,and then both levers are opened together until the engine is hot ,when the choke (short) lever can be open  until rapid acceleration is needed ,then the short lever can be closed slightly .

Offline geoff.godwin

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Re: royal enfield 355 1929
« Reply #4 on: December 02, 2023, 06:48:24 PM »
Many thanks for the replies, The oil system seems to be total loss with an adjustable output pump mounted on the magneto chain case. It sounds as if I may be on the right track anyway. I should just mention that its not just the bike thats been off the road for a long time , I sold my velo mac when I went to uni in 1966!! and yes I know the roads are busy and yes MUM I will be careful .Geoff

Offline geoff.godwin

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Re: royal enfield 355 1929
« Reply #5 on: February 04, 2024, 05:17:26 PM »
Bit of an update, I can now get it to run for longer periods But only at very fast idle or more . Any attempt to reduce and it dies ,I have tried the pilot jet screw [recommended 1/2---3/4 turn open] it affects the idle speed but not a lot, the engine runs fine at the higher speeds but as the speed reduces it hunts all over the place. I am now wondering if my valve overlap  set equidistant from tdc is correct. The only possible cam settings are about  15btdc inlet/15atdc ex     5btc inlet/ 25atdc ex      or25btc  inlet/5atdc ex   With quite a gentle cam I would expect the idle to be much slower and consistant . The other thing I find a bit odd is the size of the  AMAC  ita a !inch bore on a 350cc single  which seems big to me . I am starting to get better at starting but still have bother trying to catch it when it fires  . Geoff

Offline R

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Re: royal enfield 355 1929
« Reply #6 on: February 04, 2024, 08:44:11 PM »
Have you explored the float height setting and fuel delivery system ?

Or tried that tickle it and tickle it suggestion.
Especially when it sounds like it is starving for fuel at low rpms...

Checking that the pilot jet system is clear and unobstructed would be #1 on my suggestion list.
Carbs left standing often need much cleaning to be put back into service.
Or is that MUCH cleaning.

Offline geoff.godwin

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Re: royal enfield 355 1929
« Reply #7 on: February 04, 2024, 09:02:29 PM »
The fuel level in the carb is fixed [the valve stem has only one circlip position] I have checked the fuel level is at the top of the main jet ,which is as Amac paperwork .I have cleaned the carb several times and checked the pilot jet ways . Geoff

Offline cardan

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Re: royal enfield 355 1929
« Reply #8 on: February 05, 2024, 02:31:57 AM »
Hi Geoff,

I've re-read the above, but still not sure where you're up to. Is everything OK at higher speeds - will it rev, ride down the road, accelerate etc? If so that rules out lots of things. If not, that's a better place to start than getting a good low idle.

The 1" AMAC carb is presumably a T25MDY (or X if its top feed). This is usually stamped on the body somewhere, maybe near the mounting flange. If so this is the standard touring carb, with the air adjustment with the little slide on the side of the mixing chamber. Royal Enfield went to AMAL carburettors in 1930, and the 350 ohv used 6/004 body, 15/16" bore, 130 jet, 6/5 slide, needle position 3, and 14/079 float chamber. So the 1" size is about right, if a bit on the large side. Re jet: 130 AMAL = 36 AMAC = 0.038"

Don't forget that the needle in your throttle slide may or may not be the correct needle or at the correct height. AT least check that the needle is well clear of the needle jet at full throttle.

Leon

Offline 33d6

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Re: royal enfield 355 1929
« Reply #9 on: February 05, 2024, 07:01:26 AM »
I would be giving the ignition system a closer look. The old remark about so many fuel problems being ignition has a lot of truth.
You wrote earlier the bike has been off the road for 40 years, old electric equipment doesn’t age well. To me it is all suspect , magneto, HT lead, etc, etc. You also wrote you had set it to fire about tdc. I think that’s far too late. Somewhere about 3/8” at full advance is a better starting point.
Resurrecting an old beast can be a quite an exercise as you are finding out. But satisfying.

Offline geoff.godwin

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Re: royal enfield 355 1929
« Reply #10 on: February 05, 2024, 08:23:59 AM »
The carb is a 15mdy  the jet needle is unmarked but set to mid groove . The mag is non original mo1 but gives a good 5mm spark spun by hand or drill. After the earlier advice I started to use about half range on advance,about 10/15deg . The other slightly odd symptom is that I have good compression with throttle closed but less with it cracked open?  Geoff

Offline cardan

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Re: royal enfield 355 1929
« Reply #11 on: February 05, 2024, 12:59:05 PM »
Hi Geoff,

Yes T15MDY sounds good - 1 1/8" throttle valve, and presumably 1" choke. The T25 I mentioned would be too small...

The compression thing is weird.

Re the ignition timing: The bike might run with all manner of timings, but it will only run properly if the spark is set at something like 35-40 degrees (probably 3/8" or so) BTDC fully advanced. There's no need to experiment.

The valve timing sounds OK at 15/15.

But is the engine in good order? It should have good compression - hard to move over TDC with the ks lever when the throttle is open. Maybe it has a burned valve? Or worn-out valve guides? Or worn out cylinder/rings? Or no valve clearance? Or no oil?

The last one worries me. Not sure how the oiling system works on a 1929 Model 355 (still total loss? or is there a scavenge pump to put the oil back in the tank? By 1929 most bikes had gone dry sump) but hope you've got it sussed out. I'd say the most important part of recommissioning any bike is to make sure nothing bad has got inside (like a wasp nest), that the oil tank is drained, cleaned and filled with new oil, and that the oil pipes and pump are clean and functioning. No compression can be a symptom of a very dry motor; maybe try a squirt of oil down the plug hole and see if the compression comes back. If the motor is still total loss, there should be at least an eggcup of petrol in the crankcase anytime it is running. If it's dry sump, make sure the oil is returning to the oil tank is a steady stream within 10-20-30 sec of the engine starting.

Leon

Offline cardan

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Re: royal enfield 355 1929
« Reply #12 on: February 05, 2024, 01:19:38 PM »
I just had a look. Nice bike, but no dry sump until 1930, so do be careful it's feeding enough oil into the engine. Funny in this era when there's no hand pump to help out... Interesting that the spec says AMAL but the drawing shows AMAC MDY - 1929 was the change over period and lots of bike still used AMAC even though the AMAL was said to be available.

Once you've got compression and checked the ignition timing, it would be worth cheching for air leaks around the carb and inlet manifold as it won't idle if it leaks.

Good luck.

Leon

Edit: Or maybe a valve is sticking at low speed - make sure they're not rusty and give them a squirt of something
« Last Edit: February 05, 2024, 01:23:42 PM by cardan »

Offline geoff.godwin

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Re: royal enfield 355 1929
« Reply #13 on: February 05, 2024, 04:13:55 PM »
Thanks for the sound advice fellas, The engine is in reasonable nick, the piston/rings are fairly worn ,but from memory it is out at +40 .I toyed with the idea of a rebore or resleeve BUT ive heard horror stories of old cast iron pots cracking as a result . Looking around there are not a lot of 1929  355 barrels about . The reason for the one month delay on this update was a buggered calf muscle from when I forgot to retard the mag on starting ,boy that hurt!! Cardan I just picked up on your earlier post about the main jet  .038  is 1mm as near as the main jet  fitted is unmarked  but I think less than 38thou  Geoff
« Last Edit: February 05, 2024, 04:26:47 PM by geoff.godwin »

Offline R

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Re: royal enfield 355 1929
« Reply #14 on: February 05, 2024, 09:29:31 PM »
The main jet has very little effect, except at or near full throttle !!!
You still haven't said if you have actually ridden it on the road.

Nor said if you have tried tickling it to get a better idle.
Thats a good quick-n-dirty test to see if its suffering fuel starvation
Otherwise, that suggestion of exploring the ignition is a good un ....
Even if it does throw a good spark - outside the combustion chamber.

P.S. Getting a good idle is also generally dependent on getting the engine up to temp.
If its coughing and spluttering or hunting with the engine stone cold,
then all  bets are off.  Thats when it needs some choke - or extra tickling  !!